diff --git a/compiler/frontend.java/src/org/jetbrains/kotlin/resolve/jvm/diagnostics/DefaultErrorMessagesJvm.java b/compiler/frontend.java/src/org/jetbrains/kotlin/resolve/jvm/diagnostics/DefaultErrorMessagesJvm.java
index 65c979439e2..a26a03aa2c5 100644
--- a/compiler/frontend.java/src/org/jetbrains/kotlin/resolve/jvm/diagnostics/DefaultErrorMessagesJvm.java
+++ b/compiler/frontend.java/src/org/jetbrains/kotlin/resolve/jvm/diagnostics/DefaultErrorMessagesJvm.java
@@ -53,8 +53,8 @@ public class DefaultErrorMessagesJvm implements DefaultErrorMessages.Extension {
         MAP.put(ErrorsJvm.OVERLOADS_PRIVATE, "''overloads'' annotation has no effect on private and local declarations");
         MAP.put(ErrorsJvm.NATIVE_DECLARATION_CANNOT_BE_ABSTRACT, "Native declaration can not be abstract");
         MAP.put(ErrorsJvm.NATIVE_DECLARATION_CANNOT_HAVE_BODY, "Native declaration can not have a body");
-        MAP.put(ErrorsJvm.NATIVE_DECLARATION_IN_TRAIT, "Members of traits can not be native");
-        MAP.put(ErrorsJvm.NATIVE_DECLARATION_CANNOT_BE_INLINED, "Members of traits can not be inlined");
+        MAP.put(ErrorsJvm.NATIVE_DECLARATION_IN_TRAIT, "Members of interfaces can not be native");
+        MAP.put(ErrorsJvm.NATIVE_DECLARATION_CANNOT_BE_INLINED, "Members of interfaces can not be inlined");
 
         MAP.put(ErrorsJvm.POSITIONED_VALUE_ARGUMENT_FOR_JAVA_ANNOTATION, "Only named arguments are available for Java annotations");
         MAP.put(ErrorsJvm.JAVA_LANG_CLASS_ARGUMENT_IN_ANNOTATION, "Usage of `javaClass<T>()` in annotations is deprecated. Use T::class instead");
@@ -65,7 +65,7 @@ public class DefaultErrorMessagesJvm implements DefaultErrorMessages.Extension {
         MAP.put(ErrorsJvm.NULLABILITY_MISMATCH_BASED_ON_JAVA_ANNOTATIONS,
                 "Expected type does not accept nulls in {0}, but the value may be null in {1}", Renderers.TO_STRING, Renderers.TO_STRING);
 
-        MAP.put(ErrorsJvm.TRAIT_CANT_CALL_DEFAULT_METHOD_VIA_SUPER, "Traits can't call Java default methods via super");
+        MAP.put(ErrorsJvm.TRAIT_CANT_CALL_DEFAULT_METHOD_VIA_SUPER, "Interfaces can't call Java default methods via super");
     }
 
 
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java b/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java
index 54ae7f2bf7c..73d7c3894ec 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java
+++ b/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java
@@ -123,13 +123,13 @@ public class DefaultErrorMessages {
         MAP.put(INAPPLICABLE_ANNOTATION, "This annotation is only applicable to top level functions");
 
         MAP.put(REDUNDANT_MODIFIER, "Modifier ''{0}'' is redundant because ''{1}'' is present", TO_STRING, TO_STRING);
-        MAP.put(ABSTRACT_MODIFIER_IN_TRAIT, "Modifier ''abstract'' is redundant in trait");
-        MAP.put(OPEN_MODIFIER_IN_TRAIT, "Modifier ''open'' is redundant in trait");
+        MAP.put(ABSTRACT_MODIFIER_IN_TRAIT, "Modifier ''abstract'' is redundant in interface");
+        MAP.put(OPEN_MODIFIER_IN_TRAIT, "Modifier ''open'' is redundant in interface");
         MAP.put(OPEN_MODIFIER_IN_ENUM, "Modifier ''open'' is not applicable for enum class");
         MAP.put(ABSTRACT_MODIFIER_IN_ENUM, "Modifier ''abstract'' is not applicable for enum class");
         MAP.put(ILLEGAL_ENUM_ANNOTATION, "Annotation ''enum'' is only applicable for class");
         MAP.put(REDUNDANT_MODIFIER_IN_GETTER, "Visibility modifiers are redundant in getter");
-        MAP.put(TRAIT_CAN_NOT_BE_FINAL, "Trait cannot be final");
+        MAP.put(TRAIT_CAN_NOT_BE_FINAL, "Interface cannot be final");
         MAP.put(TYPE_PARAMETERS_IN_ENUM, "Enum class cannot have type parameters");
         MAP.put(TYPECHECKER_HAS_RUN_INTO_RECURSIVE_PROBLEM,
                 "Type checking has run into a recursive problem. Easiest workaround: specify types of your declarations explicitly"); // TODO: message
@@ -176,17 +176,17 @@ public class DefaultErrorMessages {
 
         MAP.put(ABSTRACT_DELEGATED_PROPERTY, "Delegated property cannot be abstract");
         MAP.put(ACCESSOR_FOR_DELEGATED_PROPERTY, "Delegated property cannot have accessors with non-default implementations");
-        MAP.put(DELEGATED_PROPERTY_IN_TRAIT, "Delegated properties are not allowed in traits");
+        MAP.put(DELEGATED_PROPERTY_IN_TRAIT, "Delegated properties are not allowed in interfaces");
         MAP.put(LOCAL_VARIABLE_WITH_DELEGATE, "Local variables are not allowed to have delegates");
 
         MAP.put(PACKAGE_MEMBER_CANNOT_BE_PROTECTED, "Package member cannot be protected");
 
         MAP.put(GETTER_VISIBILITY_DIFFERS_FROM_PROPERTY_VISIBILITY, "Getter visibility must be the same as property visibility");
-        MAP.put(BACKING_FIELD_IN_TRAIT, "Property in a trait cannot have a backing field");
+        MAP.put(BACKING_FIELD_IN_TRAIT, "Property in an interface cannot have a backing field");
         MAP.put(MUST_BE_INITIALIZED, "Property must be initialized");
         MAP.put(MUST_BE_INITIALIZED_OR_BE_ABSTRACT, "Property must be initialized or be abstract");
-        MAP.put(PROPERTY_INITIALIZER_IN_TRAIT, "Property initializers are not allowed in traits");
-        MAP.put(FINAL_PROPERTY_IN_TRAIT, "Abstract property in trait cannot be final");
+        MAP.put(PROPERTY_INITIALIZER_IN_TRAIT, "Property initializers are not allowed in interfaces");
+        MAP.put(FINAL_PROPERTY_IN_TRAIT, "Abstract property in an interface cannot be final");
         MAP.put(EXTENSION_PROPERTY_WITH_BACKING_FIELD, "Extension property cannot be initialized because it has no backing field");
         MAP.put(PROPERTY_INITIALIZER_NO_BACKING_FIELD, "Initializer is not allowed here because this property has no backing field");
         MAP.put(ABSTRACT_PROPERTY_IN_NON_ABSTRACT_CLASS, "Abstract property ''{0}'' in non-abstract class ''{1}''", STRING, NAME);
@@ -257,9 +257,9 @@ public class DefaultErrorMessages {
 
         MAP.put(LOCAL_OBJECT_NOT_ALLOWED, "Named object ''{0}'' is a singleton and cannot be local. Try to use anonymous object instead", NAME);
         MAP.put(LOCAL_ENUM_NOT_ALLOWED, "Enum class ''{0}'' cannot be local", NAME);
-        MAP.put(DELEGATION_IN_TRAIT, "Traits cannot use delegation");
-        MAP.put(DELEGATION_NOT_TO_TRAIT, "Only traits can be delegated to");
-        MAP.put(UNMET_TRAIT_REQUIREMENT, "Super trait ''{0}'' requires subclasses to extend ''{1}''", NAME, NAME);
+        MAP.put(DELEGATION_IN_TRAIT, "Interfaces cannot use delegation");
+        MAP.put(DELEGATION_NOT_TO_TRAIT, "Only interfaces can be delegated to");
+        MAP.put(UNMET_TRAIT_REQUIREMENT, "Super interface ''{0}'' requires subclasses to extend ''{1}''", NAME, NAME);
         MAP.put(NO_CONSTRUCTOR, "This class does not have a constructor");
         MAP.put(NOT_A_CLASS, "Not a class");
         MAP.put(ILLEGAL_ESCAPE_SEQUENCE, "Illegal escape sequence");
@@ -286,7 +286,7 @@ public class DefaultErrorMessages {
         MAP.put(SETTER_PARAMETER_WITH_DEFAULT_VALUE, "Setter parameters cannot have default values");
         MAP.put(NO_THIS, "'this' is not defined in this context");
         MAP.put(SUPER_NOT_AVAILABLE, "No supertypes are accessible in this context");
-        MAP.put(SUPERCLASS_NOT_ACCESSIBLE_FROM_TRAIT, "Superclass is not accessible from trait");
+        MAP.put(SUPERCLASS_NOT_ACCESSIBLE_FROM_TRAIT, "Superclass is not accessible from interface");
         MAP.put(AMBIGUOUS_SUPER, "Many supertypes available, please specify the one you mean in angle brackets, e.g. 'super<Foo>'");
         MAP.put(ABSTRACT_SUPER_CALL, "Abstract member cannot be accessed directly");
         MAP.put(NOT_A_SUPERTYPE, "Not a supertype");
@@ -308,7 +308,7 @@ public class DefaultErrorMessages {
         MAP.put(INACCESSIBLE_OUTER_CLASS_EXPRESSION, "Expression is inaccessible from a nested class ''{0}'', use ''inner'' keyword to make the class inner", NAME);
         MAP.put(NESTED_CLASS_NOT_ALLOWED, "Nested class is not allowed here, use ''inner'' keyword to make the class inner");
 
-        MAP.put(INNER_CLASS_IN_TRAIT, "Inner classes are not allowed in traits");
+        MAP.put(INNER_CLASS_IN_TRAIT, "Inner classes are not allowed in interfaces");
         MAP.put(INNER_CLASS_IN_OBJECT, "Inner classes are not allowed in objects");
 
         MAP.put(HAS_NEXT_MISSING, "hasNext() cannot be called on iterator() of type ''{0}''", RENDER_TYPE);
@@ -384,11 +384,11 @@ public class DefaultErrorMessages {
         MAP.put(CYCLIC_INHERITANCE_HIERARCHY, "There's a cycle in the inheritance hierarchy for this type");
 
         MAP.put(MANY_CLASSES_IN_SUPERTYPE_LIST, "Only one class may appear in a supertype list");
-        MAP.put(SUPERTYPE_NOT_A_CLASS_OR_TRAIT, "Only classes and traits may serve as supertypes");
-        MAP.put(SUPERTYPE_INITIALIZED_IN_TRAIT, "Traits cannot initialize supertypes");
+        MAP.put(SUPERTYPE_NOT_A_CLASS_OR_TRAIT, "Only classes and interfaces may serve as supertypes");
+        MAP.put(SUPERTYPE_INITIALIZED_IN_TRAIT, "Interfaces cannot initialize supertypes");
         MAP.put(CLASS_IN_SUPERTYPE_FOR_ENUM, "Enum class cannot inherit from classes");
-        MAP.put(CONSTRUCTOR_IN_TRAIT, "A trait may not have a constructor");
-        MAP.put(TRAIT_WITH_SUPERCLASS, "Specifying a required base class for trait implementations is deprecated");
+        MAP.put(CONSTRUCTOR_IN_TRAIT, "An interface may not have a constructor");
+        MAP.put(TRAIT_WITH_SUPERCLASS, "Specifying a required base class for interface implementations is deprecated");
         MAP.put(SUPERTYPE_APPEARS_TWICE, "A supertype appears twice");
         MAP.put(FINAL_SUPERTYPE, "This type is final, so it cannot be inherited from");
         MAP.put(SINGLETON_IN_SUPERTYPE, "Cannot inherit from a singleton");
@@ -414,7 +414,7 @@ public class DefaultErrorMessages {
         MAP.put(NOT_A_LOOP_LABEL, "The label ''{0}'' does not denote a loop", STRING);
         MAP.put(NOT_A_RETURN_LABEL, "The label ''{0}'' does not reference to a context from which we can return", STRING);
 
-        MAP.put(ANONYMOUS_INITIALIZER_IN_TRAIT, "Anonymous initializers are not allowed in traits");
+        MAP.put(ANONYMOUS_INITIALIZER_IN_TRAIT, "Anonymous initializers are not allowed in interfaces");
         MAP.put(NULLABLE_SUPERTYPE, "A supertype cannot be nullable");
         MAP.put(DYNAMIC_SUPERTYPE, "A supertype cannot be dynamic");
         MAP.put(REDUNDANT_NULLABLE, "Redundant '?'");
@@ -438,7 +438,7 @@ public class DefaultErrorMessages {
         MAP.put(SMARTCAST_IMPOSSIBLE,
                 "Smart cast to ''{0}'' is impossible, because ''{1}'' could have changed since the is-check", RENDER_TYPE, STRING);
 
-        MAP.put(VARIANCE_ON_TYPE_PARAMETER_OF_FUNCTION_OR_PROPERTY, "Variance annotations are only allowed for type parameters of classes and traits");
+        MAP.put(VARIANCE_ON_TYPE_PARAMETER_OF_FUNCTION_OR_PROPERTY, "Variance annotations are only allowed for type parameters of classes and interfaces");
         MAP.put(TYPE_VARIANCE_CONFLICT, "Type parameter {0} is declared as ''{1}'' but occurs in ''{2}'' position in type {3}",
                 new MultiRenderer<VarianceConflictDiagnosticData>() {
                     @NotNull
diff --git a/compiler/testData/builtin-classes.txt b/compiler/testData/builtin-classes.txt
index ea60f107a1a..4d301097781 100644
--- a/compiler/testData/builtin-classes.txt
+++ b/compiler/testData/builtin-classes.txt
@@ -5,7 +5,7 @@ public fun kotlin.Any?.identityEquals(/*0*/ other: kotlin.Any?): kotlin.Boolean
 public fun kotlin.String?.plus(/*0*/ other: kotlin.Any?): kotlin.String
 public fun kotlin.Any?.toString(): kotlin.String
 
-public trait Annotation {
+public interface Annotation {
 }
 
 public open class Any {
@@ -300,17 +300,17 @@ public final class CharRange : kotlin.Range<kotlin.Char>, kotlin.Progression<kot
     }
 }
 
-public trait CharSequence {
+public interface CharSequence {
     public abstract fun charAt(/*0*/ index: kotlin.Int): kotlin.Char
     public abstract fun length(): kotlin.Int
     public abstract fun subSequence(/*0*/ start: kotlin.Int, /*1*/ end: kotlin.Int): kotlin.CharSequence
 }
 
-public trait Cloneable {
+public interface Cloneable {
     protected open fun clone(): kotlin.Any
 }
 
-public trait Collection</*0*/ out E> : kotlin.Iterable<E> {
+public interface Collection</*0*/ out E> : kotlin.Iterable<E> {
     public abstract fun contains(/*0*/ o: kotlin.Any?): kotlin.Boolean
     public abstract fun containsAll(/*0*/ c: kotlin.Collection<kotlin.Any?>): kotlin.Boolean
     public abstract fun isEmpty(): kotlin.Boolean
@@ -318,7 +318,7 @@ public trait Collection</*0*/ out E> : kotlin.Iterable<E> {
     public abstract fun size(): kotlin.Int
 }
 
-public trait Comparable</*0*/ in T> {
+public interface Comparable</*0*/ in T> {
     public abstract fun compareTo(/*0*/ other: T): kotlin.Int
 }
 
@@ -468,95 +468,95 @@ public abstract class Enum</*0*/ E : kotlin.Enum<E>> : kotlin.Comparable<E> {
     }
 }
 
-public trait ExtensionFunction0</*0*/ in T, /*1*/ out R> {
+public interface ExtensionFunction0</*0*/ in T, /*1*/ out R> {
     public abstract fun T.invoke(): R
 }
 
-public trait ExtensionFunction1</*0*/ in T, /*1*/ in P1, /*2*/ out R> {
+public interface ExtensionFunction1</*0*/ in T, /*1*/ in P1, /*2*/ out R> {
     public abstract fun T.invoke(/*0*/ p1: P1): R
 }
 
-public trait ExtensionFunction10</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ out R> {
+public interface ExtensionFunction10</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ out R> {
     public abstract fun T.invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10): R
 }
 
-public trait ExtensionFunction11</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ in P11, /*12*/ out R> {
+public interface ExtensionFunction11</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ in P11, /*12*/ out R> {
     public abstract fun T.invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10, /*10*/ p11: P11): R
 }
 
-public trait ExtensionFunction12</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ in P11, /*12*/ in P12, /*13*/ out R> {
+public interface ExtensionFunction12</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ in P11, /*12*/ in P12, /*13*/ out R> {
     public abstract fun T.invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10, /*10*/ p11: P11, /*11*/ p12: P12): R
 }
 
-public trait ExtensionFunction13</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ in P11, /*12*/ in P12, /*13*/ in P13, /*14*/ out R> {
+public interface ExtensionFunction13</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ in P11, /*12*/ in P12, /*13*/ in P13, /*14*/ out R> {
     public abstract fun T.invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10, /*10*/ p11: P11, /*11*/ p12: P12, /*12*/ p13: P13): R
 }
 
-public trait ExtensionFunction14</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ in P11, /*12*/ in P12, /*13*/ in P13, /*14*/ in P14, /*15*/ out R> {
+public interface ExtensionFunction14</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ in P11, /*12*/ in P12, /*13*/ in P13, /*14*/ in P14, /*15*/ out R> {
     public abstract fun T.invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10, /*10*/ p11: P11, /*11*/ p12: P12, /*12*/ p13: P13, /*13*/ p14: P14): R
 }
 
-public trait ExtensionFunction15</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ in P11, /*12*/ in P12, /*13*/ in P13, /*14*/ in P14, /*15*/ in P15, /*16*/ out R> {
+public interface ExtensionFunction15</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ in P11, /*12*/ in P12, /*13*/ in P13, /*14*/ in P14, /*15*/ in P15, /*16*/ out R> {
     public abstract fun T.invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10, /*10*/ p11: P11, /*11*/ p12: P12, /*12*/ p13: P13, /*13*/ p14: P14, /*14*/ p15: P15): R
 }
 
-public trait ExtensionFunction16</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ in P11, /*12*/ in P12, /*13*/ in P13, /*14*/ in P14, /*15*/ in P15, /*16*/ in P16, /*17*/ out R> {
+public interface ExtensionFunction16</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ in P11, /*12*/ in P12, /*13*/ in P13, /*14*/ in P14, /*15*/ in P15, /*16*/ in P16, /*17*/ out R> {
     public abstract fun T.invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10, /*10*/ p11: P11, /*11*/ p12: P12, /*12*/ p13: P13, /*13*/ p14: P14, /*14*/ p15: P15, /*15*/ p16: P16): R
 }
 
-public trait ExtensionFunction17</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ in P11, /*12*/ in P12, /*13*/ in P13, /*14*/ in P14, /*15*/ in P15, /*16*/ in P16, /*17*/ in P17, /*18*/ out R> {
+public interface ExtensionFunction17</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ in P11, /*12*/ in P12, /*13*/ in P13, /*14*/ in P14, /*15*/ in P15, /*16*/ in P16, /*17*/ in P17, /*18*/ out R> {
     public abstract fun T.invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10, /*10*/ p11: P11, /*11*/ p12: P12, /*12*/ p13: P13, /*13*/ p14: P14, /*14*/ p15: P15, /*15*/ p16: P16, /*16*/ p17: P17): R
 }
 
-public trait ExtensionFunction18</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ in P11, /*12*/ in P12, /*13*/ in P13, /*14*/ in P14, /*15*/ in P15, /*16*/ in P16, /*17*/ in P17, /*18*/ in P18, /*19*/ out R> {
+public interface ExtensionFunction18</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ in P11, /*12*/ in P12, /*13*/ in P13, /*14*/ in P14, /*15*/ in P15, /*16*/ in P16, /*17*/ in P17, /*18*/ in P18, /*19*/ out R> {
     public abstract fun T.invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10, /*10*/ p11: P11, /*11*/ p12: P12, /*12*/ p13: P13, /*13*/ p14: P14, /*14*/ p15: P15, /*15*/ p16: P16, /*16*/ p17: P17, /*17*/ p18: P18): R
 }
 
-public trait ExtensionFunction19</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ in P11, /*12*/ in P12, /*13*/ in P13, /*14*/ in P14, /*15*/ in P15, /*16*/ in P16, /*17*/ in P17, /*18*/ in P18, /*19*/ in P19, /*20*/ out R> {
+public interface ExtensionFunction19</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ in P11, /*12*/ in P12, /*13*/ in P13, /*14*/ in P14, /*15*/ in P15, /*16*/ in P16, /*17*/ in P17, /*18*/ in P18, /*19*/ in P19, /*20*/ out R> {
     public abstract fun T.invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10, /*10*/ p11: P11, /*11*/ p12: P12, /*12*/ p13: P13, /*13*/ p14: P14, /*14*/ p15: P15, /*15*/ p16: P16, /*16*/ p17: P17, /*17*/ p18: P18, /*18*/ p19: P19): R
 }
 
-public trait ExtensionFunction2</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ out R> {
+public interface ExtensionFunction2</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ out R> {
     public abstract fun T.invoke(/*0*/ p1: P1, /*1*/ p2: P2): R
 }
 
-public trait ExtensionFunction20</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ in P11, /*12*/ in P12, /*13*/ in P13, /*14*/ in P14, /*15*/ in P15, /*16*/ in P16, /*17*/ in P17, /*18*/ in P18, /*19*/ in P19, /*20*/ in P20, /*21*/ out R> {
+public interface ExtensionFunction20</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ in P11, /*12*/ in P12, /*13*/ in P13, /*14*/ in P14, /*15*/ in P15, /*16*/ in P16, /*17*/ in P17, /*18*/ in P18, /*19*/ in P19, /*20*/ in P20, /*21*/ out R> {
     public abstract fun T.invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10, /*10*/ p11: P11, /*11*/ p12: P12, /*12*/ p13: P13, /*13*/ p14: P14, /*14*/ p15: P15, /*15*/ p16: P16, /*16*/ p17: P17, /*17*/ p18: P18, /*18*/ p19: P19, /*19*/ p20: P20): R
 }
 
-public trait ExtensionFunction21</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ in P11, /*12*/ in P12, /*13*/ in P13, /*14*/ in P14, /*15*/ in P15, /*16*/ in P16, /*17*/ in P17, /*18*/ in P18, /*19*/ in P19, /*20*/ in P20, /*21*/ in P21, /*22*/ out R> {
+public interface ExtensionFunction21</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ in P11, /*12*/ in P12, /*13*/ in P13, /*14*/ in P14, /*15*/ in P15, /*16*/ in P16, /*17*/ in P17, /*18*/ in P18, /*19*/ in P19, /*20*/ in P20, /*21*/ in P21, /*22*/ out R> {
     public abstract fun T.invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10, /*10*/ p11: P11, /*11*/ p12: P12, /*12*/ p13: P13, /*13*/ p14: P14, /*14*/ p15: P15, /*15*/ p16: P16, /*16*/ p17: P17, /*17*/ p18: P18, /*18*/ p19: P19, /*19*/ p20: P20, /*20*/ p21: P21): R
 }
 
-public trait ExtensionFunction22</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ in P11, /*12*/ in P12, /*13*/ in P13, /*14*/ in P14, /*15*/ in P15, /*16*/ in P16, /*17*/ in P17, /*18*/ in P18, /*19*/ in P19, /*20*/ in P20, /*21*/ in P21, /*22*/ in P22, /*23*/ out R> {
+public interface ExtensionFunction22</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ in P10, /*11*/ in P11, /*12*/ in P12, /*13*/ in P13, /*14*/ in P14, /*15*/ in P15, /*16*/ in P16, /*17*/ in P17, /*18*/ in P18, /*19*/ in P19, /*20*/ in P20, /*21*/ in P21, /*22*/ in P22, /*23*/ out R> {
     public abstract fun T.invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10, /*10*/ p11: P11, /*11*/ p12: P12, /*12*/ p13: P13, /*13*/ p14: P14, /*14*/ p15: P15, /*15*/ p16: P16, /*16*/ p17: P17, /*17*/ p18: P18, /*18*/ p19: P19, /*19*/ p20: P20, /*20*/ p21: P21, /*21*/ p22: P22): R
 }
 
-public trait ExtensionFunction3</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ out R> {
+public interface ExtensionFunction3</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ out R> {
     public abstract fun T.invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3): R
 }
 
-public trait ExtensionFunction4</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ out R> {
+public interface ExtensionFunction4</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ out R> {
     public abstract fun T.invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4): R
 }
 
-public trait ExtensionFunction5</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ out R> {
+public interface ExtensionFunction5</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ out R> {
     public abstract fun T.invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5): R
 }
 
-public trait ExtensionFunction6</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ out R> {
+public interface ExtensionFunction6</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ out R> {
     public abstract fun T.invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6): R
 }
 
-public trait ExtensionFunction7</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ out R> {
+public interface ExtensionFunction7</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ out R> {
     public abstract fun T.invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7): R
 }
 
-public trait ExtensionFunction8</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ out R> {
+public interface ExtensionFunction8</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ out R> {
     public abstract fun T.invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8): R
 }
 
-public trait ExtensionFunction9</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ out R> {
+public interface ExtensionFunction9</*0*/ in T, /*1*/ in P1, /*2*/ in P2, /*3*/ in P3, /*4*/ in P4, /*5*/ in P5, /*6*/ in P6, /*7*/ in P7, /*8*/ in P8, /*9*/ in P9, /*10*/ out R> {
     public abstract fun T.invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9): R
 }
 
@@ -695,7 +695,7 @@ public final class FloatRange : kotlin.Range<kotlin.Float>, kotlin.Progression<k
     }
 }
 
-public trait FloatingPointConstants</*0*/ T> {
+public interface FloatingPointConstants</*0*/ T> {
     public abstract val NEGATIVE_INFINITY: T
         public abstract fun <get-NEGATIVE_INFINITY>(): T
     public abstract val NaN: T
@@ -704,95 +704,95 @@ public trait FloatingPointConstants</*0*/ T> {
         public abstract fun <get-POSITIVE_INFINITY>(): T
 }
 
-public trait Function0</*0*/ out R> {
+public interface Function0</*0*/ out R> {
     public abstract fun invoke(): R
 }
 
-public trait Function1</*0*/ in P1, /*1*/ out R> {
+public interface Function1</*0*/ in P1, /*1*/ out R> {
     public abstract fun invoke(/*0*/ p1: P1): R
 }
 
-public trait Function10</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ out R> {
+public interface Function10</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ out R> {
     public abstract fun invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10): R
 }
 
-public trait Function11</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ in P11, /*11*/ out R> {
+public interface Function11</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ in P11, /*11*/ out R> {
     public abstract fun invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10, /*10*/ p11: P11): R
 }
 
-public trait Function12</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ in P11, /*11*/ in P12, /*12*/ out R> {
+public interface Function12</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ in P11, /*11*/ in P12, /*12*/ out R> {
     public abstract fun invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10, /*10*/ p11: P11, /*11*/ p12: P12): R
 }
 
-public trait Function13</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ in P11, /*11*/ in P12, /*12*/ in P13, /*13*/ out R> {
+public interface Function13</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ in P11, /*11*/ in P12, /*12*/ in P13, /*13*/ out R> {
     public abstract fun invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10, /*10*/ p11: P11, /*11*/ p12: P12, /*12*/ p13: P13): R
 }
 
-public trait Function14</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ in P11, /*11*/ in P12, /*12*/ in P13, /*13*/ in P14, /*14*/ out R> {
+public interface Function14</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ in P11, /*11*/ in P12, /*12*/ in P13, /*13*/ in P14, /*14*/ out R> {
     public abstract fun invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10, /*10*/ p11: P11, /*11*/ p12: P12, /*12*/ p13: P13, /*13*/ p14: P14): R
 }
 
-public trait Function15</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ in P11, /*11*/ in P12, /*12*/ in P13, /*13*/ in P14, /*14*/ in P15, /*15*/ out R> {
+public interface Function15</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ in P11, /*11*/ in P12, /*12*/ in P13, /*13*/ in P14, /*14*/ in P15, /*15*/ out R> {
     public abstract fun invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10, /*10*/ p11: P11, /*11*/ p12: P12, /*12*/ p13: P13, /*13*/ p14: P14, /*14*/ p15: P15): R
 }
 
-public trait Function16</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ in P11, /*11*/ in P12, /*12*/ in P13, /*13*/ in P14, /*14*/ in P15, /*15*/ in P16, /*16*/ out R> {
+public interface Function16</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ in P11, /*11*/ in P12, /*12*/ in P13, /*13*/ in P14, /*14*/ in P15, /*15*/ in P16, /*16*/ out R> {
     public abstract fun invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10, /*10*/ p11: P11, /*11*/ p12: P12, /*12*/ p13: P13, /*13*/ p14: P14, /*14*/ p15: P15, /*15*/ p16: P16): R
 }
 
-public trait Function17</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ in P11, /*11*/ in P12, /*12*/ in P13, /*13*/ in P14, /*14*/ in P15, /*15*/ in P16, /*16*/ in P17, /*17*/ out R> {
+public interface Function17</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ in P11, /*11*/ in P12, /*12*/ in P13, /*13*/ in P14, /*14*/ in P15, /*15*/ in P16, /*16*/ in P17, /*17*/ out R> {
     public abstract fun invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10, /*10*/ p11: P11, /*11*/ p12: P12, /*12*/ p13: P13, /*13*/ p14: P14, /*14*/ p15: P15, /*15*/ p16: P16, /*16*/ p17: P17): R
 }
 
-public trait Function18</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ in P11, /*11*/ in P12, /*12*/ in P13, /*13*/ in P14, /*14*/ in P15, /*15*/ in P16, /*16*/ in P17, /*17*/ in P18, /*18*/ out R> {
+public interface Function18</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ in P11, /*11*/ in P12, /*12*/ in P13, /*13*/ in P14, /*14*/ in P15, /*15*/ in P16, /*16*/ in P17, /*17*/ in P18, /*18*/ out R> {
     public abstract fun invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10, /*10*/ p11: P11, /*11*/ p12: P12, /*12*/ p13: P13, /*13*/ p14: P14, /*14*/ p15: P15, /*15*/ p16: P16, /*16*/ p17: P17, /*17*/ p18: P18): R
 }
 
-public trait Function19</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ in P11, /*11*/ in P12, /*12*/ in P13, /*13*/ in P14, /*14*/ in P15, /*15*/ in P16, /*16*/ in P17, /*17*/ in P18, /*18*/ in P19, /*19*/ out R> {
+public interface Function19</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ in P11, /*11*/ in P12, /*12*/ in P13, /*13*/ in P14, /*14*/ in P15, /*15*/ in P16, /*16*/ in P17, /*17*/ in P18, /*18*/ in P19, /*19*/ out R> {
     public abstract fun invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10, /*10*/ p11: P11, /*11*/ p12: P12, /*12*/ p13: P13, /*13*/ p14: P14, /*14*/ p15: P15, /*15*/ p16: P16, /*16*/ p17: P17, /*17*/ p18: P18, /*18*/ p19: P19): R
 }
 
-public trait Function2</*0*/ in P1, /*1*/ in P2, /*2*/ out R> {
+public interface Function2</*0*/ in P1, /*1*/ in P2, /*2*/ out R> {
     public abstract fun invoke(/*0*/ p1: P1, /*1*/ p2: P2): R
 }
 
-public trait Function20</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ in P11, /*11*/ in P12, /*12*/ in P13, /*13*/ in P14, /*14*/ in P15, /*15*/ in P16, /*16*/ in P17, /*17*/ in P18, /*18*/ in P19, /*19*/ in P20, /*20*/ out R> {
+public interface Function20</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ in P11, /*11*/ in P12, /*12*/ in P13, /*13*/ in P14, /*14*/ in P15, /*15*/ in P16, /*16*/ in P17, /*17*/ in P18, /*18*/ in P19, /*19*/ in P20, /*20*/ out R> {
     public abstract fun invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10, /*10*/ p11: P11, /*11*/ p12: P12, /*12*/ p13: P13, /*13*/ p14: P14, /*14*/ p15: P15, /*15*/ p16: P16, /*16*/ p17: P17, /*17*/ p18: P18, /*18*/ p19: P19, /*19*/ p20: P20): R
 }
 
-public trait Function21</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ in P11, /*11*/ in P12, /*12*/ in P13, /*13*/ in P14, /*14*/ in P15, /*15*/ in P16, /*16*/ in P17, /*17*/ in P18, /*18*/ in P19, /*19*/ in P20, /*20*/ in P21, /*21*/ out R> {
+public interface Function21</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ in P11, /*11*/ in P12, /*12*/ in P13, /*13*/ in P14, /*14*/ in P15, /*15*/ in P16, /*16*/ in P17, /*17*/ in P18, /*18*/ in P19, /*19*/ in P20, /*20*/ in P21, /*21*/ out R> {
     public abstract fun invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10, /*10*/ p11: P11, /*11*/ p12: P12, /*12*/ p13: P13, /*13*/ p14: P14, /*14*/ p15: P15, /*15*/ p16: P16, /*16*/ p17: P17, /*17*/ p18: P18, /*18*/ p19: P19, /*19*/ p20: P20, /*20*/ p21: P21): R
 }
 
-public trait Function22</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ in P11, /*11*/ in P12, /*12*/ in P13, /*13*/ in P14, /*14*/ in P15, /*15*/ in P16, /*16*/ in P17, /*17*/ in P18, /*18*/ in P19, /*19*/ in P20, /*20*/ in P21, /*21*/ in P22, /*22*/ out R> {
+public interface Function22</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ in P10, /*10*/ in P11, /*11*/ in P12, /*12*/ in P13, /*13*/ in P14, /*14*/ in P15, /*15*/ in P16, /*16*/ in P17, /*17*/ in P18, /*18*/ in P19, /*19*/ in P20, /*20*/ in P21, /*21*/ in P22, /*22*/ out R> {
     public abstract fun invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9, /*9*/ p10: P10, /*10*/ p11: P11, /*11*/ p12: P12, /*12*/ p13: P13, /*13*/ p14: P14, /*14*/ p15: P15, /*15*/ p16: P16, /*16*/ p17: P17, /*17*/ p18: P18, /*18*/ p19: P19, /*19*/ p20: P20, /*20*/ p21: P21, /*21*/ p22: P22): R
 }
 
-public trait Function3</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ out R> {
+public interface Function3</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ out R> {
     public abstract fun invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3): R
 }
 
-public trait Function4</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ out R> {
+public interface Function4</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ out R> {
     public abstract fun invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4): R
 }
 
-public trait Function5</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ out R> {
+public interface Function5</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ out R> {
     public abstract fun invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5): R
 }
 
-public trait Function6</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ out R> {
+public interface Function6</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ out R> {
     public abstract fun invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6): R
 }
 
-public trait Function7</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ out R> {
+public interface Function7</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ out R> {
     public abstract fun invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7): R
 }
 
-public trait Function8</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ out R> {
+public interface Function8</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ out R> {
     public abstract fun invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8): R
 }
 
-public trait Function9</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ out R> {
+public interface Function9</*0*/ in P1, /*1*/ in P2, /*2*/ in P3, /*3*/ in P4, /*4*/ in P5, /*5*/ in P6, /*6*/ in P7, /*7*/ in P8, /*8*/ in P9, /*9*/ out R> {
     public abstract fun invoke(/*0*/ p1: P1, /*1*/ p2: P2, /*2*/ p3: P3, /*3*/ p4: P4, /*4*/ p5: P5, /*5*/ p6: P6, /*6*/ p7: P7, /*7*/ p8: P8, /*8*/ p9: P9): R
 }
 
@@ -985,16 +985,16 @@ public final class IntRange : kotlin.Range<kotlin.Int>, kotlin.Progression<kotli
     }
 }
 
-public trait Iterable</*0*/ out T> {
+public interface Iterable</*0*/ out T> {
     public abstract fun iterator(): kotlin.Iterator<T>
 }
 
-public trait Iterator</*0*/ out T> {
+public interface Iterator</*0*/ out T> {
     public abstract fun hasNext(): kotlin.Boolean
     public abstract fun next(): T
 }
 
-public trait List</*0*/ out E> : kotlin.Collection<E> {
+public interface List</*0*/ out E> : kotlin.Collection<E> {
     public abstract override /*1*/ fun contains(/*0*/ o: kotlin.Any?): kotlin.Boolean
     public abstract override /*1*/ fun containsAll(/*0*/ c: kotlin.Collection<kotlin.Any?>): kotlin.Boolean
     public abstract fun get(/*0*/ index: kotlin.Int): E
@@ -1008,7 +1008,7 @@ public trait List</*0*/ out E> : kotlin.Collection<E> {
     public abstract fun subList(/*0*/ fromIndex: kotlin.Int, /*1*/ toIndex: kotlin.Int): kotlin.List<E>
 }
 
-public trait ListIterator</*0*/ out T> : kotlin.Iterator<T> {
+public interface ListIterator</*0*/ out T> : kotlin.Iterator<T> {
     public abstract override /*1*/ fun hasNext(): kotlin.Boolean
     public abstract fun hasPrevious(): kotlin.Boolean
     public abstract override /*1*/ fun next(): T
@@ -1156,7 +1156,7 @@ public final class LongRange : kotlin.Range<kotlin.Long>, kotlin.Progression<kot
     }
 }
 
-public trait Map</*0*/ K, /*1*/ out V> {
+public interface Map</*0*/ K, /*1*/ out V> {
     public abstract fun containsKey(/*0*/ key: kotlin.Any?): kotlin.Boolean
     public abstract fun containsValue(/*0*/ value: kotlin.Any?): kotlin.Boolean
     public abstract fun entrySet(): kotlin.Set<kotlin.Map.Entry<K, V>>
@@ -1166,13 +1166,13 @@ public trait Map</*0*/ K, /*1*/ out V> {
     public abstract fun size(): kotlin.Int
     public abstract fun values(): kotlin.Collection<V>
 
-    public trait Entry</*0*/ out K, /*1*/ out V> {
+    public interface Entry</*0*/ out K, /*1*/ out V> {
         public abstract fun getKey(): K
         public abstract fun getValue(): V
     }
 }
 
-public trait MutableCollection</*0*/ E> : kotlin.Collection<E>, kotlin.MutableIterable<E> {
+public interface MutableCollection</*0*/ E> : kotlin.Collection<E>, kotlin.MutableIterable<E> {
     public abstract fun add(/*0*/ e: E): kotlin.Boolean
     public abstract fun addAll(/*0*/ c: kotlin.Collection<E>): kotlin.Boolean
     public abstract fun clear(): kotlin.Unit
@@ -1186,17 +1186,17 @@ public trait MutableCollection</*0*/ E> : kotlin.Collection<E>, kotlin.MutableIt
     public abstract override /*1*/ /*fake_override*/ fun size(): kotlin.Int
 }
 
-public trait MutableIterable</*0*/ out T> : kotlin.Iterable<T> {
+public interface MutableIterable</*0*/ out T> : kotlin.Iterable<T> {
     public abstract override /*1*/ fun iterator(): kotlin.MutableIterator<T>
 }
 
-public trait MutableIterator</*0*/ out T> : kotlin.Iterator<T> {
+public interface MutableIterator</*0*/ out T> : kotlin.Iterator<T> {
     public abstract override /*1*/ /*fake_override*/ fun hasNext(): kotlin.Boolean
     public abstract override /*1*/ /*fake_override*/ fun next(): T
     public abstract fun remove(): kotlin.Unit
 }
 
-public trait MutableList</*0*/ E> : kotlin.List<E>, kotlin.MutableCollection<E> {
+public interface MutableList</*0*/ E> : kotlin.List<E>, kotlin.MutableCollection<E> {
     public abstract override /*1*/ fun add(/*0*/ e: E): kotlin.Boolean
     public abstract fun add(/*0*/ index: kotlin.Int, /*1*/ element: E): kotlin.Unit
     public abstract override /*1*/ fun addAll(/*0*/ c: kotlin.Collection<E>): kotlin.Boolean
@@ -1220,7 +1220,7 @@ public trait MutableList</*0*/ E> : kotlin.List<E>, kotlin.MutableCollection<E>
     public abstract override /*1*/ fun subList(/*0*/ fromIndex: kotlin.Int, /*1*/ toIndex: kotlin.Int): kotlin.MutableList<E>
 }
 
-public trait MutableListIterator</*0*/ T> : kotlin.ListIterator<T>, kotlin.MutableIterator<T> {
+public interface MutableListIterator</*0*/ T> : kotlin.ListIterator<T>, kotlin.MutableIterator<T> {
     public abstract fun add(/*0*/ e: T): kotlin.Unit
     public abstract override /*2*/ fun hasNext(): kotlin.Boolean
     public abstract override /*1*/ /*fake_override*/ fun hasPrevious(): kotlin.Boolean
@@ -1232,7 +1232,7 @@ public trait MutableListIterator</*0*/ T> : kotlin.ListIterator<T>, kotlin.Mutab
     public abstract fun set(/*0*/ e: T): kotlin.Unit
 }
 
-public trait MutableMap</*0*/ K, /*1*/ V> : kotlin.Map<K, V> {
+public interface MutableMap</*0*/ K, /*1*/ V> : kotlin.Map<K, V> {
     public abstract fun clear(): kotlin.Unit
     public abstract override /*1*/ /*fake_override*/ fun containsKey(/*0*/ key: kotlin.Any?): kotlin.Boolean
     public abstract override /*1*/ /*fake_override*/ fun containsValue(/*0*/ value: kotlin.Any?): kotlin.Boolean
@@ -1246,14 +1246,14 @@ public trait MutableMap</*0*/ K, /*1*/ V> : kotlin.Map<K, V> {
     public abstract override /*1*/ /*fake_override*/ fun size(): kotlin.Int
     public abstract override /*1*/ fun values(): kotlin.MutableCollection<V>
 
-    public trait MutableEntry</*0*/ K, /*1*/ V> : kotlin.Map.Entry<K, V> {
+    public interface MutableEntry</*0*/ K, /*1*/ V> : kotlin.Map.Entry<K, V> {
         public abstract override /*1*/ /*fake_override*/ fun getKey(): K
         public abstract override /*1*/ /*fake_override*/ fun getValue(): V
         public abstract fun setValue(/*0*/ value: V): V
     }
 }
 
-public trait MutableSet</*0*/ E> : kotlin.Set<E>, kotlin.MutableCollection<E> {
+public interface MutableSet</*0*/ E> : kotlin.Set<E>, kotlin.MutableCollection<E> {
     public abstract override /*1*/ fun add(/*0*/ e: E): kotlin.Boolean
     public abstract override /*1*/ fun addAll(/*0*/ c: kotlin.Collection<E>): kotlin.Boolean
     public abstract override /*1*/ fun clear(): kotlin.Unit
@@ -1282,7 +1282,7 @@ public abstract class Number {
     public abstract fun toShort(): kotlin.Short
 }
 
-public trait Progression</*0*/ out N : kotlin.Any> : kotlin.Iterable<N> {
+public interface Progression</*0*/ out N : kotlin.Any> : kotlin.Iterable<N> {
     public abstract val end: N
         public abstract fun <get-end>(): N
     public abstract val increment: kotlin.Number
@@ -1292,7 +1292,7 @@ public trait Progression</*0*/ out N : kotlin.Any> : kotlin.Iterable<N> {
     public abstract override /*1*/ /*fake_override*/ fun iterator(): kotlin.Iterator<N>
 }
 
-public trait PropertyMetadata {
+public interface PropertyMetadata {
     public abstract val name: kotlin.String
         public abstract fun <get-name>(): kotlin.String
 }
@@ -1303,7 +1303,7 @@ public final class PropertyMetadataImpl : kotlin.PropertyMetadata {
         public open override /*1*/ fun <get-name>(): kotlin.String
 }
 
-public trait Range</*0*/ T : kotlin.Comparable<T>> {
+public interface Range</*0*/ T : kotlin.Comparable<T>> {
     public abstract val end: T
         public abstract fun <get-end>(): T
     public abstract val start: T
@@ -1312,7 +1312,7 @@ public trait Range</*0*/ T : kotlin.Comparable<T>> {
     public open fun isEmpty(): kotlin.Boolean
 }
 
-public trait Set</*0*/ out E> : kotlin.Collection<E> {
+public interface Set</*0*/ out E> : kotlin.Collection<E> {
     public abstract override /*1*/ fun contains(/*0*/ o: kotlin.Any?): kotlin.Boolean
     public abstract override /*1*/ fun containsAll(/*0*/ c: kotlin.Collection<kotlin.Any?>): kotlin.Boolean
     public abstract override /*1*/ fun isEmpty(): kotlin.Boolean
diff --git a/compiler/testData/codegen/box/diagnostics/functions/invoke/onObjects/invokeOnClassObject2.txt b/compiler/testData/codegen/box/diagnostics/functions/invoke/onObjects/invokeOnClassObject2.txt
index 47d84eff5e8..b22d66a85aa 100644
--- a/compiler/testData/codegen/box/diagnostics/functions/invoke/onObjects/invokeOnClassObject2.txt
+++ b/compiler/testData/codegen/box/diagnostics/functions/invoke/onObjects/invokeOnClassObject2.txt
@@ -17,7 +17,7 @@ internal final class A {
     }
 }
 
-internal trait B {
+internal interface B {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/checkerTestUtil/test_with_diagnostic.txt b/compiler/testData/diagnostics/checkerTestUtil/test_with_diagnostic.txt
index b93ec997487..0dcbeb278ea 100644
--- a/compiler/testData/diagnostics/checkerTestUtil/test_with_diagnostic.txt
+++ b/compiler/testData/diagnostics/checkerTestUtil/test_with_diagnostic.txt
@@ -13,7 +13,7 @@ internal final class A {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Pa</*0*/ X, /*1*/ Y> {
+internal interface Pa</*0*/ X, /*1*/ Y> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/AbstractInTrait.txt b/compiler/testData/diagnostics/tests/AbstractInTrait.txt
index 2075c3b40b2..4d9c6d8e10c 100644
--- a/compiler/testData/diagnostics/tests/AbstractInTrait.txt
+++ b/compiler/testData/diagnostics/tests/AbstractInTrait.txt
@@ -2,7 +2,7 @@ package
 
 package abstract {
 
-    internal trait MyTrait {
+    internal interface MyTrait {
         internal abstract val a: kotlin.Int
         internal open val a1: kotlin.Int = 1
         internal abstract val a2: kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/AnonymousInitializers.txt b/compiler/testData/diagnostics/tests/AnonymousInitializers.txt
index 42633716f7c..f28ac2167e9 100644
--- a/compiler/testData/diagnostics/tests/AnonymousInitializers.txt
+++ b/compiler/testData/diagnostics/tests/AnonymousInitializers.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait NoC {
+internal interface NoC {
     internal open val a: kotlin.Int
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/BreakContinue.txt b/compiler/testData/diagnostics/tests/BreakContinue.txt
index 53a12c0c89b..2e7f8c569bc 100644
--- a/compiler/testData/diagnostics/tests/BreakContinue.txt
+++ b/compiler/testData/diagnostics/tests/BreakContinue.txt
@@ -1,4 +1,4 @@
-package 
+package
 
 internal final class C {
     public constructor C()
diff --git a/compiler/testData/diagnostics/tests/BreakContinueInWhen.txt b/compiler/testData/diagnostics/tests/BreakContinueInWhen.txt
index b29df873554..04bf6406f3c 100644
--- a/compiler/testData/diagnostics/tests/BreakContinueInWhen.txt
+++ b/compiler/testData/diagnostics/tests/BreakContinueInWhen.txt
@@ -1,4 +1,4 @@
-package 
+package
 
 internal fun breakContinueInWhen(/*0*/ i: kotlin.Int): kotlin.Unit
 internal fun breakContinueInWhenWithDoWhile(/*0*/ i: kotlin.Int, /*1*/ j: kotlin.Int): kotlin.Unit
diff --git a/compiler/testData/diagnostics/tests/Builders.txt b/compiler/testData/diagnostics/tests/Builders.txt
index 479ca3ce147..55395de038c 100644
--- a/compiler/testData/diagnostics/tests/Builders.txt
+++ b/compiler/testData/diagnostics/tests/Builders.txt
@@ -84,7 +84,7 @@ package html {
         internal final override /*1*/ /*fake_override*/ fun kotlin.String.plus(): kotlin.Unit
     }
 
-    internal trait Element {
+    internal interface Element {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         internal abstract fun render(/*0*/ builder: java.lang.StringBuilder, /*1*/ indent: kotlin.String): kotlin.Unit
diff --git a/compiler/testData/diagnostics/tests/CovariantOverrideType.txt b/compiler/testData/diagnostics/tests/CovariantOverrideType.txt
index 0f9be7c7794..1b020270a00 100644
--- a/compiler/testData/diagnostics/tests/CovariantOverrideType.txt
+++ b/compiler/testData/diagnostics/tests/CovariantOverrideType.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait A {
+internal interface A {
     internal abstract val a: kotlin.Int
     internal abstract val a1: kotlin.Int
     internal abstract val </*0*/ T> g: kotlin.Iterator<T>
diff --git a/compiler/testData/diagnostics/tests/DeferredTypes.txt b/compiler/testData/diagnostics/tests/DeferredTypes.txt
index 0cc1b7bf2c3..2aa3a9d1f99 100644
--- a/compiler/testData/diagnostics/tests/DeferredTypes.txt
+++ b/compiler/testData/diagnostics/tests/DeferredTypes.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait T {
+internal interface T {
     internal open val a: [ERROR : <ERROR FUNCTION RETURN TYPE>]
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/DiamondFunction.txt b/compiler/testData/diagnostics/tests/DiamondFunction.txt
index d54c7c27135..fcd153cd4fd 100644
--- a/compiler/testData/diagnostics/tests/DiamondFunction.txt
+++ b/compiler/testData/diagnostics/tests/DiamondFunction.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait Base {
+internal interface Base {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun f(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -23,7 +23,7 @@ internal open class Left : Base {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Right : Base {
+internal interface Right : Base {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open override /*1*/ /*fake_override*/ fun f(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/DiamondFunctionGeneric.txt b/compiler/testData/diagnostics/tests/DiamondFunctionGeneric.txt
index 9d45d89013d..d5ebcf11a23 100644
--- a/compiler/testData/diagnostics/tests/DiamondFunctionGeneric.txt
+++ b/compiler/testData/diagnostics/tests/DiamondFunctionGeneric.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait Base</*0*/ P> {
+internal interface Base</*0*/ P> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun f(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -23,7 +23,7 @@ internal open class Left</*0*/ P> : Base<P> {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Right</*0*/ P> : Base<P> {
+internal interface Right</*0*/ P> : Base<P> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open override /*1*/ /*fake_override*/ fun f(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/DiamondProperty.txt b/compiler/testData/diagnostics/tests/DiamondProperty.txt
index ba812b56e6e..1cf055e9c64 100644
--- a/compiler/testData/diagnostics/tests/DiamondProperty.txt
+++ b/compiler/testData/diagnostics/tests/DiamondProperty.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait Base {
+internal interface Base {
     internal open var v: kotlin.Int
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -23,7 +23,7 @@ internal open class Left : Base {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Right : Base {
+internal interface Right : Base {
     internal open override /*1*/ /*fake_override*/ var v: kotlin.Int
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/GenericArgumentConsistency.txt b/compiler/testData/diagnostics/tests/GenericArgumentConsistency.txt
index 63eee108b76..fc4d96d2fa3 100644
--- a/compiler/testData/diagnostics/tests/GenericArgumentConsistency.txt
+++ b/compiler/testData/diagnostics/tests/GenericArgumentConsistency.txt
@@ -1,66 +1,66 @@
 package
 
-internal trait A</*0*/ in T> {
+internal interface A</*0*/ in T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait A1</*0*/ out T> {
+internal interface A1</*0*/ out T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B</*0*/ T> : A<kotlin.Int> {
+internal interface B</*0*/ T> : A<kotlin.Int> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B1 : A1<kotlin.Int> {
+internal interface B1 : A1<kotlin.Int> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B2 : A1<kotlin.Any>, B1 {
+internal interface B2 : A1<kotlin.Any>, B1 {
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait BA1</*0*/ T> {
+internal interface BA1</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait BB1 : BA1<kotlin.Int> {
+internal interface BB1 : BA1<kotlin.Int> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait BB2 : BA1<kotlin.Any>, BB1 {
+internal interface BB2 : BA1<kotlin.Any>, BB1 {
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait C</*0*/ T> : B<T>, A<T> {
+internal interface C</*0*/ T> : B<T>, A<T> {
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait C1</*0*/ T> : B<T>, A<kotlin.Any> {
+internal interface C1</*0*/ T> : B<T>, A<kotlin.Any> {
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait D : C<kotlin.Boolean>, B<kotlin.Double> {
+internal interface D : C<kotlin.Boolean>, B<kotlin.Double> {
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
@@ -68,25 +68,25 @@ internal trait D : C<kotlin.Boolean>, B<kotlin.Double> {
 
 package sx2 {
 
-    internal trait AA1</*0*/ in T> {
+    internal interface AA1</*0*/ in T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait AB1 : sx2.AA1<kotlin.Int> {
+    internal interface AB1 : sx2.AA1<kotlin.Int> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait AB2 : sx2.AA1<kotlin.Number>, sx2.AB1, sx2.AB3 {
+    internal interface AB2 : sx2.AA1<kotlin.Number>, sx2.AB1, sx2.AB3 {
         public open override /*3*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*3*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*3*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait AB3 : sx2.AA1<kotlin.Comparable<kotlin.Int>> {
+    internal interface AB3 : sx2.AA1<kotlin.Comparable<kotlin.Int>> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -95,25 +95,25 @@ package sx2 {
 
 package x {
 
-    internal trait AA1</*0*/ out T> {
+    internal interface AA1</*0*/ out T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait AB1 : x.AA1<kotlin.Int> {
+    internal interface AB1 : x.AA1<kotlin.Int> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait AB2 : x.AA1<kotlin.Number>, x.AB1, x.AB3 {
+    internal interface AB2 : x.AA1<kotlin.Number>, x.AB1, x.AB3 {
         public open override /*3*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*3*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*3*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait AB3 : x.AA1<kotlin.Comparable<kotlin.Int>> {
+    internal interface AB3 : x.AA1<kotlin.Comparable<kotlin.Int>> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -122,25 +122,25 @@ package x {
 
 package x2 {
 
-    internal trait AA1</*0*/ out T> {
+    internal interface AA1</*0*/ out T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait AB1 : x2.AA1<kotlin.Any> {
+    internal interface AB1 : x2.AA1<kotlin.Any> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait AB2 : x2.AA1<kotlin.Number>, x2.AB1, x2.AB3 {
+    internal interface AB2 : x2.AA1<kotlin.Number>, x2.AB1, x2.AB3 {
         public open override /*3*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*3*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*3*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait AB3 : x2.AA1<kotlin.Comparable<kotlin.Int>> {
+    internal interface AB3 : x2.AA1<kotlin.Comparable<kotlin.Int>> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -149,25 +149,25 @@ package x2 {
 
 package x3 {
 
-    internal trait AA1</*0*/ in T> {
+    internal interface AA1</*0*/ in T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait AB1 : x3.AA1<kotlin.Any> {
+    internal interface AB1 : x3.AA1<kotlin.Any> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait AB2 : x3.AA1<kotlin.Number>, x3.AB1, x3.AB3 {
+    internal interface AB2 : x3.AA1<kotlin.Number>, x3.AB1, x3.AB3 {
         public open override /*3*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*3*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*3*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait AB3 : x3.AA1<kotlin.Comparable<kotlin.Int>> {
+    internal interface AB3 : x3.AA1<kotlin.Comparable<kotlin.Int>> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/MultipleBounds.txt b/compiler/testData/diagnostics/tests/MultipleBounds.txt
index e50ab3723e2..5beaf807460 100644
--- a/compiler/testData/diagnostics/tests/MultipleBounds.txt
+++ b/compiler/testData/diagnostics/tests/MultipleBounds.txt
@@ -16,7 +16,7 @@ package Jet87 {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait B {
+    internal interface B {
         internal open fun bar(): kotlin.Double
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -69,7 +69,7 @@ package Jet87 {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait G</*0*/ X> {
+    internal interface G</*0*/ X> {
         internal abstract val </*0*/ A : Jet87.B> bal: kotlin.Double
         internal abstract val </*0*/ Y : Jet87.B> bas: kotlin.Double
         internal abstract val </*0*/ X : Jet87.A> boo: kotlin.Double where X : Jet87.B
diff --git a/compiler/testData/diagnostics/tests/OverridenFunctionAndSpecifiedTypeParameter.txt b/compiler/testData/diagnostics/tests/OverridenFunctionAndSpecifiedTypeParameter.txt
index 30c25a88ccd..ba834eb0a3e 100644
--- a/compiler/testData/diagnostics/tests/OverridenFunctionAndSpecifiedTypeParameter.txt
+++ b/compiler/testData/diagnostics/tests/OverridenFunctionAndSpecifiedTypeParameter.txt
@@ -2,7 +2,7 @@ package
 
 internal fun foo(): kotlin.Unit
 
-internal trait Aaa</*0*/ T> {
+internal interface Aaa</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/OverridingVarByVal.txt b/compiler/testData/diagnostics/tests/OverridingVarByVal.txt
index df553f770bf..4a16abdf98d 100644
--- a/compiler/testData/diagnostics/tests/OverridingVarByVal.txt
+++ b/compiler/testData/diagnostics/tests/OverridingVarByVal.txt
@@ -24,7 +24,7 @@ internal final class Var2 : Var {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait VarT {
+internal interface VarT {
     internal abstract var v: kotlin.Int
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/ProjectionsInSupertypes.txt b/compiler/testData/diagnostics/tests/ProjectionsInSupertypes.txt
index 4d49c875065..2a901e4984e 100644
--- a/compiler/testData/diagnostics/tests/ProjectionsInSupertypes.txt
+++ b/compiler/testData/diagnostics/tests/ProjectionsInSupertypes.txt
@@ -1,30 +1,30 @@
 package
 
-internal trait A</*0*/ T> {
+internal interface A</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B</*0*/ T> {
+internal interface B</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait C</*0*/ T> {
+internal interface C</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait D</*0*/ T> {
+internal interface D</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Test : A<in kotlin.Int>, B<out kotlin.Int>, C<*>?, D<kotlin.Int> {
+internal interface Test : A<in kotlin.Int>, B<out kotlin.Int>, C<*>?, D<kotlin.Int> {
     public open override /*4*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*4*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*4*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/ReflectionTypesNotLoaded.txt b/compiler/testData/diagnostics/tests/ReflectionTypesNotLoaded.txt
index a125d91f8ec..a335638f39a 100644
--- a/compiler/testData/diagnostics/tests/ReflectionTypesNotLoaded.txt
+++ b/compiler/testData/diagnostics/tests/ReflectionTypesNotLoaded.txt
@@ -1,4 +1,4 @@
-package 
+package
 
 internal val classLiteral: [ERROR : Unresolved class]
 internal val memberFun: [ERROR : Type for A::baz]
diff --git a/compiler/testData/diagnostics/tests/SelfTypesUnsupported.txt b/compiler/testData/diagnostics/tests/SelfTypesUnsupported.txt
index 8252ab0e333..7c9b6967c01 100644
--- a/compiler/testData/diagnostics/tests/SelfTypesUnsupported.txt
+++ b/compiler/testData/diagnostics/tests/SelfTypesUnsupported.txt
@@ -2,7 +2,7 @@ package
 
 internal fun foo(/*0*/ f: [ERROR : This]): kotlin.Unit
 
-internal trait C</*0*/ T : C<[ERROR : This]>> {
+internal interface C</*0*/ T : C<[ERROR : This]>> {
     internal abstract val x: [ERROR : This]
     internal abstract val y: [ERROR : This]?
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
diff --git a/compiler/testData/diagnostics/tests/SupertypeListChecks.txt b/compiler/testData/diagnostics/tests/SupertypeListChecks.txt
index d6f027322da..b4b45748e86 100644
--- a/compiler/testData/diagnostics/tests/SupertypeListChecks.txt
+++ b/compiler/testData/diagnostics/tests/SupertypeListChecks.txt
@@ -70,55 +70,55 @@ internal open class OC1 {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T1 {
+internal interface T1 {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T2</*0*/ T> {
+internal interface T2</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Test {
+internal interface Test {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Test1 : C2 {
+internal interface Test1 : C2 {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Test2 : C2 {
+internal interface Test2 : C2 {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Test3 : C2, C3 {
+internal interface Test3 : C2, C3 {
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Test4 : T1 {
+internal interface Test4 : T1 {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Test5 : T1, T1 {
+internal interface Test5 : T1, T1 {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Test6 : C1 {
+internal interface Test6 : C1 {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/TraitOverrideObjectMethods.txt b/compiler/testData/diagnostics/tests/TraitOverrideObjectMethods.txt
index b181b275c66..6cd3c885d45 100644
--- a/compiler/testData/diagnostics/tests/TraitOverrideObjectMethods.txt
+++ b/compiler/testData/diagnostics/tests/TraitOverrideObjectMethods.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait MyTrait : java.lang.Object {
+internal interface MyTrait : java.lang.Object {
     protected/*protected and package*/ open override /*1*/ /*fake_override*/ fun clone(): kotlin.Any!
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any!): kotlin.Boolean
     public abstract override /*1*/ fun finalize(): kotlin.Unit
diff --git a/compiler/testData/diagnostics/tests/TraitWithConstructor.txt b/compiler/testData/diagnostics/tests/TraitWithConstructor.txt
index 22acca81b30..8acdbf59e4b 100644
--- a/compiler/testData/diagnostics/tests/TraitWithConstructor.txt
+++ b/compiler/testData/diagnostics/tests/TraitWithConstructor.txt
@@ -8,7 +8,7 @@ internal final class C {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T1 {
+internal interface T1 {
     public constructor T1(/*0*/ x: kotlin.String)
     internal final val x: kotlin.String
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
@@ -16,20 +16,20 @@ internal trait T1 {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T2 {
+internal interface T2 {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T3 {
+internal interface T3 {
     public constructor T3(/*0*/ a: kotlin.Int)
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T4 {
+internal interface T4 {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/UnusedVariables.txt b/compiler/testData/diagnostics/tests/UnusedVariables.txt
index 041ab839687..4eb2b4892b8 100644
--- a/compiler/testData/diagnostics/tests/UnusedVariables.txt
+++ b/compiler/testData/diagnostics/tests/UnusedVariables.txt
@@ -32,7 +32,7 @@ package unused_variables {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait Trait {
+    internal interface Trait {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal abstract fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/annotations/annotationInheritance.txt b/compiler/testData/diagnostics/tests/annotations/annotationInheritance.txt
index 026b23c4106..f65d2209b73 100644
--- a/compiler/testData/diagnostics/tests/annotations/annotationInheritance.txt
+++ b/compiler/testData/diagnostics/tests/annotations/annotationInheritance.txt
@@ -37,7 +37,7 @@ internal open class C {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T {
+internal interface T {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/annotations/annotationModifier.txt b/compiler/testData/diagnostics/tests/annotations/annotationModifier.txt
index cb5eeb91023..6add9458f6f 100644
--- a/compiler/testData/diagnostics/tests/annotations/annotationModifier.txt
+++ b/compiler/testData/diagnostics/tests/annotations/annotationModifier.txt
@@ -32,7 +32,7 @@ internal object O {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T : kotlin.Annotation {
+internal interface T : kotlin.Annotation {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/annotations/bracketsDeprecation.txt b/compiler/testData/diagnostics/tests/annotations/bracketsDeprecation.txt
index cc0eebc5d4c..105be364059 100644
--- a/compiler/testData/diagnostics/tests/annotations/bracketsDeprecation.txt
+++ b/compiler/testData/diagnostics/tests/annotations/bracketsDeprecation.txt
@@ -24,13 +24,13 @@ internal final annotation class Ann : kotlin.Annotation {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B {
+internal interface B {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait D : B {
+internal interface D : B {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/annotations/onInitializer.txt b/compiler/testData/diagnostics/tests/annotations/onInitializer.txt
index 21aa1c45578..56ed2530a13 100644
--- a/compiler/testData/diagnostics/tests/annotations/onInitializer.txt
+++ b/compiler/testData/diagnostics/tests/annotations/onInitializer.txt
@@ -7,7 +7,7 @@ internal final class A {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T {
+internal interface T {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/annotations/typeAnnotations.txt b/compiler/testData/diagnostics/tests/annotations/typeAnnotations.txt
index fd97850b6c7..6ad58164eef 100644
--- a/compiler/testData/diagnostics/tests/annotations/typeAnnotations.txt
+++ b/compiler/testData/diagnostics/tests/annotations/typeAnnotations.txt
@@ -1,4 +1,4 @@
-package 
+package
 
 internal fun [[ERROR : x]()] A.foo(/*0*/ a: [[ERROR : x]()] kotlin.Int): kotlin.Unit
 
diff --git a/compiler/testData/diagnostics/tests/cast/DowncastMap.txt b/compiler/testData/diagnostics/tests/cast/DowncastMap.txt
index 3ba4cd675fb..f172a82c3ad 100644
--- a/compiler/testData/diagnostics/tests/cast/DowncastMap.txt
+++ b/compiler/testData/diagnostics/tests/cast/DowncastMap.txt
@@ -2,13 +2,13 @@ package
 
 internal fun p(/*0*/ p: Map<kotlin.String, kotlin.Int>): kotlin.Unit
 
-internal trait Map</*0*/ K, /*1*/ out V> {
+internal interface Map</*0*/ K, /*1*/ out V> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait MutableMap</*0*/ K, /*1*/ V> : Map<K, V> {
+internal interface MutableMap</*0*/ K, /*1*/ V> : Map<K, V> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     internal abstract fun set(/*0*/ k: K, /*1*/ v: V): kotlin.Unit
diff --git a/compiler/testData/diagnostics/tests/cast/IsErasedAllowForTypeWithIrrelevantMixin.txt b/compiler/testData/diagnostics/tests/cast/IsErasedAllowForTypeWithIrrelevantMixin.txt
index 9a8dcf8a036..2fb1c6ef427 100644
--- a/compiler/testData/diagnostics/tests/cast/IsErasedAllowForTypeWithIrrelevantMixin.txt
+++ b/compiler/testData/diagnostics/tests/cast/IsErasedAllowForTypeWithIrrelevantMixin.txt
@@ -2,37 +2,37 @@ package
 
 internal fun test(/*0*/ t: BaseSuper<B>): kotlin.Boolean
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B : A {
+internal interface B : A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait BaseImpl : BaseSuper<D> {
+internal interface BaseImpl : BaseSuper<D> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait BaseSuper</*0*/ out T> {
+internal interface BaseSuper</*0*/ out T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait D {
+internal interface D {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait DerivedSuper</*0*/ out S> : BaseSuper<S>, BaseImpl {
+internal interface DerivedSuper</*0*/ out S> : BaseSuper<S>, BaseImpl {
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/cast/IsErasedDisallowForTypeWithConstraints.txt b/compiler/testData/diagnostics/tests/cast/IsErasedDisallowForTypeWithConstraints.txt
index afcc2ebb38b..88982ee419c 100644
--- a/compiler/testData/diagnostics/tests/cast/IsErasedDisallowForTypeWithConstraints.txt
+++ b/compiler/testData/diagnostics/tests/cast/IsErasedDisallowForTypeWithConstraints.txt
@@ -2,19 +2,19 @@ package
 
 internal fun </*0*/ T : Base<A>> test(/*0*/ a: Base<B>): kotlin.Boolean
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B : A {
+internal interface B : A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Base</*0*/ T> {
+internal interface Base</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/cast/IsErasedNonGeneric.txt b/compiler/testData/diagnostics/tests/cast/IsErasedNonGeneric.txt
index 6fcf83516d2..a91483bb2d6 100644
--- a/compiler/testData/diagnostics/tests/cast/IsErasedNonGeneric.txt
+++ b/compiler/testData/diagnostics/tests/cast/IsErasedNonGeneric.txt
@@ -2,13 +2,13 @@ package
 
 internal fun testing(/*0*/ a: A): B
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B {
+internal interface B {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/cast/IsTraits.txt b/compiler/testData/diagnostics/tests/cast/IsTraits.txt
index a2ecec31f14..5558badb241 100644
--- a/compiler/testData/diagnostics/tests/cast/IsTraits.txt
+++ b/compiler/testData/diagnostics/tests/cast/IsTraits.txt
@@ -2,13 +2,13 @@ package
 
 internal fun f(/*0*/ a: Aaa): kotlin.Boolean
 
-internal trait Aaa {
+internal interface Aaa {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Bbb {
+internal interface Bbb {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/cast/bare/AsNestedBare.txt b/compiler/testData/diagnostics/tests/cast/bare/AsNestedBare.txt
index b8e550f76bf..740366e64d9 100644
--- a/compiler/testData/diagnostics/tests/cast/bare/AsNestedBare.txt
+++ b/compiler/testData/diagnostics/tests/cast/bare/AsNestedBare.txt
@@ -3,13 +3,13 @@ package
 internal fun test(/*0*/ tr: Tr): kotlin.Any
 internal fun test1(/*0*/ tr: Tr): kotlin.Any
 
-internal trait G</*0*/ T> {
+internal interface G</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Tr {
+internal interface Tr {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/cast/bare/AsNullable.txt b/compiler/testData/diagnostics/tests/cast/bare/AsNullable.txt
index 297e1575aa9..4ce6a068b22 100644
--- a/compiler/testData/diagnostics/tests/cast/bare/AsNullable.txt
+++ b/compiler/testData/diagnostics/tests/cast/bare/AsNullable.txt
@@ -2,13 +2,13 @@ package
 
 internal fun test(/*0*/ tr: Tr<kotlin.String>): kotlin.Unit
 
-internal trait G</*0*/ T> : Tr<T> {
+internal interface G</*0*/ T> : Tr<T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Tr</*0*/ T> {
+internal interface Tr</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/cast/bare/AsNullableNotEnough.txt b/compiler/testData/diagnostics/tests/cast/bare/AsNullableNotEnough.txt
index be315b60848..eff3864b1f6 100644
--- a/compiler/testData/diagnostics/tests/cast/bare/AsNullableNotEnough.txt
+++ b/compiler/testData/diagnostics/tests/cast/bare/AsNullableNotEnough.txt
@@ -2,13 +2,13 @@ package
 
 internal fun test(/*0*/ tr: Tr): kotlin.Unit
 
-internal trait G</*0*/ T> {
+internal interface G</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Tr {
+internal interface Tr {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/cast/bare/EitherAs.txt b/compiler/testData/diagnostics/tests/cast/bare/EitherAs.txt
index bd49783cbe7..e6996affc45 100644
--- a/compiler/testData/diagnostics/tests/cast/bare/EitherAs.txt
+++ b/compiler/testData/diagnostics/tests/cast/bare/EitherAs.txt
@@ -19,19 +19,19 @@ internal final class C2 {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Either</*0*/ out A, /*1*/ out B> {
+internal interface Either</*0*/ out A, /*1*/ out B> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Left</*0*/ out A> : Either<A, kotlin.Nothing> {
+internal interface Left</*0*/ out A> : Either<A, kotlin.Nothing> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Right</*0*/ out B> : Either<kotlin.Nothing, B> {
+internal interface Right</*0*/ out B> : Either<kotlin.Nothing, B> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/cast/bare/EitherIs.txt b/compiler/testData/diagnostics/tests/cast/bare/EitherIs.txt
index 09d35156197..8bad14cac15 100644
--- a/compiler/testData/diagnostics/tests/cast/bare/EitherIs.txt
+++ b/compiler/testData/diagnostics/tests/cast/bare/EitherIs.txt
@@ -19,20 +19,20 @@ internal final class C2 {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Either</*0*/ out A, /*1*/ out B> {
+internal interface Either</*0*/ out A, /*1*/ out B> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Left</*0*/ out A> : Either<A, kotlin.Nothing> {
+internal interface Left</*0*/ out A> : Either<A, kotlin.Nothing> {
     internal abstract val value: A
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Right</*0*/ out B> : Either<kotlin.Nothing, B> {
+internal interface Right</*0*/ out B> : Either<kotlin.Nothing, B> {
     internal abstract val value: B
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/cast/bare/EitherNotIs.txt b/compiler/testData/diagnostics/tests/cast/bare/EitherNotIs.txt
index 09d35156197..8bad14cac15 100644
--- a/compiler/testData/diagnostics/tests/cast/bare/EitherNotIs.txt
+++ b/compiler/testData/diagnostics/tests/cast/bare/EitherNotIs.txt
@@ -19,20 +19,20 @@ internal final class C2 {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Either</*0*/ out A, /*1*/ out B> {
+internal interface Either</*0*/ out A, /*1*/ out B> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Left</*0*/ out A> : Either<A, kotlin.Nothing> {
+internal interface Left</*0*/ out A> : Either<A, kotlin.Nothing> {
     internal abstract val value: A
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Right</*0*/ out B> : Either<kotlin.Nothing, B> {
+internal interface Right</*0*/ out B> : Either<kotlin.Nothing, B> {
     internal abstract val value: B
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/cast/bare/EitherSafeAs.txt b/compiler/testData/diagnostics/tests/cast/bare/EitherSafeAs.txt
index efb7a7a0819..ff73d77756e 100644
--- a/compiler/testData/diagnostics/tests/cast/bare/EitherSafeAs.txt
+++ b/compiler/testData/diagnostics/tests/cast/bare/EitherSafeAs.txt
@@ -19,19 +19,19 @@ internal final class C2 {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Either</*0*/ out A, /*1*/ out B> {
+internal interface Either</*0*/ out A, /*1*/ out B> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Left</*0*/ out A> : Either<A, kotlin.Nothing> {
+internal interface Left</*0*/ out A> : Either<A, kotlin.Nothing> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Right</*0*/ out B> : Either<kotlin.Nothing, B> {
+internal interface Right</*0*/ out B> : Either<kotlin.Nothing, B> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/cast/bare/EitherWhen.txt b/compiler/testData/diagnostics/tests/cast/bare/EitherWhen.txt
index 6b7d768ba06..d4a0a09378a 100644
--- a/compiler/testData/diagnostics/tests/cast/bare/EitherWhen.txt
+++ b/compiler/testData/diagnostics/tests/cast/bare/EitherWhen.txt
@@ -18,20 +18,20 @@ internal final class C2 {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Either</*0*/ out A, /*1*/ out B> {
+internal interface Either</*0*/ out A, /*1*/ out B> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Left</*0*/ out A> : Either<A, kotlin.Nothing> {
+internal interface Left</*0*/ out A> : Either<A, kotlin.Nothing> {
     internal abstract val value: A
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Right</*0*/ out B> : Either<kotlin.Nothing, B> {
+internal interface Right</*0*/ out B> : Either<kotlin.Nothing, B> {
     internal abstract val value: B
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/cast/bare/ErrorsInSubstitution.txt b/compiler/testData/diagnostics/tests/cast/bare/ErrorsInSubstitution.txt
index d5d4d93c399..f7ab5ce0205 100644
--- a/compiler/testData/diagnostics/tests/cast/bare/ErrorsInSubstitution.txt
+++ b/compiler/testData/diagnostics/tests/cast/bare/ErrorsInSubstitution.txt
@@ -2,13 +2,13 @@ package
 
 internal fun f(/*0*/ p: B<[ERROR : Foo]>): kotlin.Any
 
-internal trait B</*0*/ T> {
+internal interface B</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait G</*0*/ T> : B<T> {
+internal interface G</*0*/ T> : B<T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/cast/bare/NullableAs.txt b/compiler/testData/diagnostics/tests/cast/bare/NullableAs.txt
index ccc5f723387..160a0945f89 100644
--- a/compiler/testData/diagnostics/tests/cast/bare/NullableAs.txt
+++ b/compiler/testData/diagnostics/tests/cast/bare/NullableAs.txt
@@ -2,13 +2,13 @@ package
 
 internal fun test(/*0*/ tr: Tr<kotlin.String>?): kotlin.Unit
 
-internal trait G</*0*/ T> : Tr<T> {
+internal interface G</*0*/ T> : Tr<T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Tr</*0*/ T> {
+internal interface Tr</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/cast/bare/NullableAsNotEnough.txt b/compiler/testData/diagnostics/tests/cast/bare/NullableAsNotEnough.txt
index 57d43c51c91..2cdd182c404 100644
--- a/compiler/testData/diagnostics/tests/cast/bare/NullableAsNotEnough.txt
+++ b/compiler/testData/diagnostics/tests/cast/bare/NullableAsNotEnough.txt
@@ -2,13 +2,13 @@ package
 
 internal fun test(/*0*/ tr: Tr?): kotlin.Unit
 
-internal trait G</*0*/ T> {
+internal interface G</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Tr {
+internal interface Tr {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/cast/bare/NullableAsNullable.txt b/compiler/testData/diagnostics/tests/cast/bare/NullableAsNullable.txt
index ccc5f723387..160a0945f89 100644
--- a/compiler/testData/diagnostics/tests/cast/bare/NullableAsNullable.txt
+++ b/compiler/testData/diagnostics/tests/cast/bare/NullableAsNullable.txt
@@ -2,13 +2,13 @@ package
 
 internal fun test(/*0*/ tr: Tr<kotlin.String>?): kotlin.Unit
 
-internal trait G</*0*/ T> : Tr<T> {
+internal interface G</*0*/ T> : Tr<T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Tr</*0*/ T> {
+internal interface Tr</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/cast/bare/NullableAsNullableNotEnough.txt b/compiler/testData/diagnostics/tests/cast/bare/NullableAsNullableNotEnough.txt
index 57d43c51c91..2cdd182c404 100644
--- a/compiler/testData/diagnostics/tests/cast/bare/NullableAsNullableNotEnough.txt
+++ b/compiler/testData/diagnostics/tests/cast/bare/NullableAsNullableNotEnough.txt
@@ -2,13 +2,13 @@ package
 
 internal fun test(/*0*/ tr: Tr?): kotlin.Unit
 
-internal trait G</*0*/ T> {
+internal interface G</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Tr {
+internal interface Tr {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/cast/bare/RedundantNullable.txt b/compiler/testData/diagnostics/tests/cast/bare/RedundantNullable.txt
index a1deaa18187..36ba3d00edc 100644
--- a/compiler/testData/diagnostics/tests/cast/bare/RedundantNullable.txt
+++ b/compiler/testData/diagnostics/tests/cast/bare/RedundantNullable.txt
@@ -2,7 +2,7 @@ package
 
 internal fun f(/*0*/ b: B<kotlin.String>?): kotlin.Boolean
 
-internal trait B</*0*/ T> {
+internal interface B</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/cast/bare/UnrelatedAs.txt b/compiler/testData/diagnostics/tests/cast/bare/UnrelatedAs.txt
index be315b60848..eff3864b1f6 100644
--- a/compiler/testData/diagnostics/tests/cast/bare/UnrelatedAs.txt
+++ b/compiler/testData/diagnostics/tests/cast/bare/UnrelatedAs.txt
@@ -2,13 +2,13 @@ package
 
 internal fun test(/*0*/ tr: Tr): kotlin.Unit
 
-internal trait G</*0*/ T> {
+internal interface G</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Tr {
+internal interface Tr {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/cast/bare/UnrelatedColon.txt b/compiler/testData/diagnostics/tests/cast/bare/UnrelatedColon.txt
index a626c98472f..f619a3f8a95 100644
--- a/compiler/testData/diagnostics/tests/cast/bare/UnrelatedColon.txt
+++ b/compiler/testData/diagnostics/tests/cast/bare/UnrelatedColon.txt
@@ -2,13 +2,13 @@ package
 
 internal fun test(/*0*/ tr: Tr): [ERROR : G]
 
-internal trait G</*0*/ T> {
+internal interface G</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Tr {
+internal interface Tr {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/cast/bare/UnrelatedIs.txt b/compiler/testData/diagnostics/tests/cast/bare/UnrelatedIs.txt
index 60c674461bc..a4e942fd8e3 100644
--- a/compiler/testData/diagnostics/tests/cast/bare/UnrelatedIs.txt
+++ b/compiler/testData/diagnostics/tests/cast/bare/UnrelatedIs.txt
@@ -2,13 +2,13 @@ package
 
 internal fun test(/*0*/ tr: Tr): kotlin.Boolean
 
-internal trait G</*0*/ T> {
+internal interface G</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Tr {
+internal interface Tr {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/cast/isErasedUnrelatedAndStarred.txt b/compiler/testData/diagnostics/tests/cast/isErasedUnrelatedAndStarred.txt
index 3eb85aa5ba8..66951cd1901 100644
--- a/compiler/testData/diagnostics/tests/cast/isErasedUnrelatedAndStarred.txt
+++ b/compiler/testData/diagnostics/tests/cast/isErasedUnrelatedAndStarred.txt
@@ -9,7 +9,7 @@ internal final class G</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Tr {
+internal interface Tr {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/cast/neverSucceeds/NoGenericsRelated.txt b/compiler/testData/diagnostics/tests/cast/neverSucceeds/NoGenericsRelated.txt
index 2f63d556582..288059ed994 100644
--- a/compiler/testData/diagnostics/tests/cast/neverSucceeds/NoGenericsRelated.txt
+++ b/compiler/testData/diagnostics/tests/cast/neverSucceeds/NoGenericsRelated.txt
@@ -23,31 +23,31 @@ internal open class OC2 : OC1, T2 {
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T1 {
+internal interface T1 {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T2 {
+internal interface T2 {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T3 {
+internal interface T3 {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T4 : OC1 {
+internal interface T4 : OC1 {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T5 : T2 {
+internal interface T5 : T2 {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/cast/neverSucceeds/NoGenericsUnrelated.txt b/compiler/testData/diagnostics/tests/cast/neverSucceeds/NoGenericsUnrelated.txt
index 21c06adf5cb..e2d0435c040 100644
--- a/compiler/testData/diagnostics/tests/cast/neverSucceeds/NoGenericsUnrelated.txt
+++ b/compiler/testData/diagnostics/tests/cast/neverSucceeds/NoGenericsUnrelated.txt
@@ -30,13 +30,13 @@ internal open class OClass2 {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Trait1 {
+internal interface Trait1 {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Trait2 {
+internal interface Trait2 {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/checkType.txt b/compiler/testData/diagnostics/tests/checkType.txt
index c06fb64d219..87835c03217 100644
--- a/compiler/testData/diagnostics/tests/checkType.txt
+++ b/compiler/testData/diagnostics/tests/checkType.txt
@@ -2,19 +2,19 @@ package
 
 internal fun test(/*0*/ b: B): kotlin.Unit
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B : A {
+internal interface B : A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait C : B {
+internal interface C : B {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/controlFlowAnalysis/definiteReturn/ReturnFromFunctionInObject.txt b/compiler/testData/diagnostics/tests/controlFlowAnalysis/definiteReturn/ReturnFromFunctionInObject.txt
index 22c2a97c8e0..e7e525ed3a6 100644
--- a/compiler/testData/diagnostics/tests/controlFlowAnalysis/definiteReturn/ReturnFromFunctionInObject.txt
+++ b/compiler/testData/diagnostics/tests/controlFlowAnalysis/definiteReturn/ReturnFromFunctionInObject.txt
@@ -2,7 +2,7 @@ package
 
 internal val m: X
 
-internal trait X {
+internal interface X {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun f(): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/controlFlowAnalysis/definiteReturn/kt4034.txt b/compiler/testData/diagnostics/tests/controlFlowAnalysis/definiteReturn/kt4034.txt
index e1b5c5aceee..c0497d21839 100644
--- a/compiler/testData/diagnostics/tests/controlFlowAnalysis/definiteReturn/kt4034.txt
+++ b/compiler/testData/diagnostics/tests/controlFlowAnalysis/definiteReturn/kt4034.txt
@@ -2,19 +2,19 @@ package
 
 private fun transformClassifierType(/*0*/ classifierType: JavaClassifierType, /*1*/ howThisTypeIsUsed: TypeUsage): JetType?
 
-internal trait JavaClassifierType {
+internal interface JavaClassifierType {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait JetType {
+internal interface JetType {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait TypeUsage {
+internal interface TypeUsage {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/controlFlowAnalysis/kt1191.txt b/compiler/testData/diagnostics/tests/controlFlowAnalysis/kt1191.txt
index 1b200f614fc..181f0327f91 100644
--- a/compiler/testData/diagnostics/tests/controlFlowAnalysis/kt1191.txt
+++ b/compiler/testData/diagnostics/tests/controlFlowAnalysis/kt1191.txt
@@ -4,7 +4,7 @@ package kt1191 {
     internal fun foo(/*0*/ unused: kotlin.Int): kotlin.Any
     internal fun </*0*/ T> kt1191.FunctionalList<T>.plus(/*0*/ element: T): kt1191.FunctionalList<T>
 
-    internal trait FunctionalList</*0*/ T> {
+    internal interface FunctionalList</*0*/ T> {
         internal abstract val head: T
         internal abstract val size: kotlin.Int
         internal abstract val tail: kt1191.FunctionalList<T>
diff --git a/compiler/testData/diagnostics/tests/controlFlowAnalysis/kt2226.txt b/compiler/testData/diagnostics/tests/controlFlowAnalysis/kt2226.txt
index 94efad452b8..5cb4f126761 100644
--- a/compiler/testData/diagnostics/tests/controlFlowAnalysis/kt2226.txt
+++ b/compiler/testData/diagnostics/tests/controlFlowAnalysis/kt2226.txt
@@ -3,7 +3,7 @@ package
 package a {
     internal fun foo(/*0*/ b: a.B): kotlin.Int
 
-    internal trait A {
+    internal interface A {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal abstract fun foo(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/controlFlowAnalysis/kt3444.txt b/compiler/testData/diagnostics/tests/controlFlowAnalysis/kt3444.txt
index 71b23925146..ae73a20bc7f 100644
--- a/compiler/testData/diagnostics/tests/controlFlowAnalysis/kt3444.txt
+++ b/compiler/testData/diagnostics/tests/controlFlowAnalysis/kt3444.txt
@@ -3,7 +3,7 @@ package
 internal val m: X
 internal fun box(): kotlin.Unit
 
-internal trait X {
+internal interface X {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun f(): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/controlStructures/commonSupertypeOfT.txt b/compiler/testData/diagnostics/tests/controlStructures/commonSupertypeOfT.txt
index 8e5d48a2bab..52255422681 100644
--- a/compiler/testData/diagnostics/tests/controlStructures/commonSupertypeOfT.txt
+++ b/compiler/testData/diagnostics/tests/controlStructures/commonSupertypeOfT.txt
@@ -3,7 +3,7 @@ package
 internal fun </*0*/ T : Tr> fn(/*0*/ t1: T, /*1*/ t2: T?): kotlin.Unit
 internal fun </*0*/ T : kotlin.Any> fn(/*0*/ t1: T, /*1*/ t2: T?): kotlin.Unit
 
-internal trait Tr {
+internal interface Tr {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/cyclicHierarchy/cyclicHierarchy.txt b/compiler/testData/diagnostics/tests/cyclicHierarchy/cyclicHierarchy.txt
index 4903576ab4f..1d503d58c9d 100644
--- a/compiler/testData/diagnostics/tests/cyclicHierarchy/cyclicHierarchy.txt
+++ b/compiler/testData/diagnostics/tests/cyclicHierarchy/cyclicHierarchy.txt
@@ -10,34 +10,34 @@ internal val g: G? = null
 internal val h: H? = null
 internal fun test(): kotlin.Unit
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B : A {
+internal interface B : A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open override /*1*/ /*fake_override*/ fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait C {
+internal interface C {
 }
 
-internal trait D {
+internal interface D {
 }
 
-internal trait E {
+internal interface E {
 }
 
-internal trait F {
+internal interface F {
 }
 
-internal trait G : F {
+internal interface G : F {
 }
 
-internal trait H : F {
+internal interface H : F {
 }
diff --git a/compiler/testData/diagnostics/tests/cyclicHierarchy/javaKotlinJavaCycle.txt b/compiler/testData/diagnostics/tests/cyclicHierarchy/javaKotlinJavaCycle.txt
index 14ba1dc3eed..2b6026287e6 100644
--- a/compiler/testData/diagnostics/tests/cyclicHierarchy/javaKotlinJavaCycle.txt
+++ b/compiler/testData/diagnostics/tests/cyclicHierarchy/javaKotlinJavaCycle.txt
@@ -1,16 +1,16 @@
 package
 
-public/*package*/ trait A : C {
+public/*package*/ interface A : C {
     internal abstract override /*1*/ /*fake_override*/ fun bar(): kotlin.Unit
     public abstract override /*1*/ /*fake_override*/ fun baz(): kotlin.Unit
     public abstract fun foo(): kotlin.Unit
 }
 
-internal trait B {
+internal interface B {
     internal abstract fun bar(): kotlin.Unit
 }
 
-public/*package*/ trait C : B {
+public/*package*/ interface C : B {
     internal abstract override /*1*/ /*fake_override*/ fun bar(): kotlin.Unit
     public abstract fun baz(): kotlin.Unit
 }
diff --git a/compiler/testData/diagnostics/tests/cyclicHierarchy/kotlinJavaNestedCycle.txt b/compiler/testData/diagnostics/tests/cyclicHierarchy/kotlinJavaNestedCycle.txt
index dd6f2c9a269..4e328541b65 100644
--- a/compiler/testData/diagnostics/tests/cyclicHierarchy/kotlinJavaNestedCycle.txt
+++ b/compiler/testData/diagnostics/tests/cyclicHierarchy/kotlinJavaNestedCycle.txt
@@ -1,13 +1,13 @@
 package
 
-internal trait ExceptionTracker {
+internal interface ExceptionTracker {
 }
 
 public/*package*/ open class LockBasedStorageManager : StorageManager {
     public/*package*/ constructor LockBasedStorageManager()
     java.lang.Override() public/*package*/ open override /*1*/ fun foo(): kotlin.Unit
 
-    public/*package*/ trait ExceptionHandlingStrategy {
+    public/*package*/ interface ExceptionHandlingStrategy {
         public abstract fun bar(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -18,6 +18,6 @@ public/*package*/ open class LockBasedStorageManager : StorageManager {
     public/*package*/ final /*synthesized*/ fun ExceptionHandlingStrategy(/*0*/ function: () -> kotlin.Unit): LockBasedStorageManager.ExceptionHandlingStrategy
 }
 
-internal trait StorageManager {
+internal interface StorageManager {
     internal abstract fun foo(): kotlin.Unit
 }
diff --git a/compiler/testData/diagnostics/tests/dataClasses/implementTraitWhichHasComponent1.txt b/compiler/testData/diagnostics/tests/dataClasses/implementTraitWhichHasComponent1.txt
index 3a9d8458078..dd7e19cb84e 100644
--- a/compiler/testData/diagnostics/tests/dataClasses/implementTraitWhichHasComponent1.txt
+++ b/compiler/testData/diagnostics/tests/dataClasses/implementTraitWhichHasComponent1.txt
@@ -10,7 +10,7 @@ kotlin.data() internal final class A : T {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T {
+internal interface T {
     internal abstract fun component1(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/dataClasses/implementTraitWhichHasFinalComponent1.txt b/compiler/testData/diagnostics/tests/dataClasses/implementTraitWhichHasFinalComponent1.txt
index 9d64802d140..e34130f32ca 100644
--- a/compiler/testData/diagnostics/tests/dataClasses/implementTraitWhichHasFinalComponent1.txt
+++ b/compiler/testData/diagnostics/tests/dataClasses/implementTraitWhichHasFinalComponent1.txt
@@ -10,7 +10,7 @@ kotlin.data() internal final class A : T {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T {
+internal interface T {
     internal final fun component1(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/dataFlow/WhenSubject.txt b/compiler/testData/diagnostics/tests/dataFlow/WhenSubject.txt
index 61d1e3af6a2..af3ee9090f6 100644
--- a/compiler/testData/diagnostics/tests/dataFlow/WhenSubject.txt
+++ b/compiler/testData/diagnostics/tests/dataFlow/WhenSubject.txt
@@ -10,7 +10,7 @@ internal final class BinOp : Expr {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Expr {
+internal interface Expr {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/dataFlow/local/LocalClassDelegation.txt b/compiler/testData/diagnostics/tests/dataFlow/local/LocalClassDelegation.txt
index f4043ce40e9..68aa9a3e138 100644
--- a/compiler/testData/diagnostics/tests/dataFlow/local/LocalClassDelegation.txt
+++ b/compiler/testData/diagnostics/tests/dataFlow/local/LocalClassDelegation.txt
@@ -2,7 +2,7 @@ package
 
 internal fun test(/*0*/ d: kotlin.Any?): kotlin.Unit
 
-internal trait D {
+internal interface D {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/dataFlow/local/LocalClassFunctions.txt b/compiler/testData/diagnostics/tests/dataFlow/local/LocalClassFunctions.txt
index 0e107d51978..dc7334eebe3 100644
--- a/compiler/testData/diagnostics/tests/dataFlow/local/LocalClassFunctions.txt
+++ b/compiler/testData/diagnostics/tests/dataFlow/local/LocalClassFunctions.txt
@@ -2,7 +2,7 @@ package
 
 internal fun test(/*0*/ d: kotlin.Any?): kotlin.Unit
 
-internal trait D {
+internal interface D {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun foo(): kotlin.String
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/dataFlow/local/LocalClassInitializer.txt b/compiler/testData/diagnostics/tests/dataFlow/local/LocalClassInitializer.txt
index 1a7e2e5082b..60c9a74a2d0 100644
--- a/compiler/testData/diagnostics/tests/dataFlow/local/LocalClassInitializer.txt
+++ b/compiler/testData/diagnostics/tests/dataFlow/local/LocalClassInitializer.txt
@@ -2,7 +2,7 @@ package
 
 internal fun f(/*0*/ a: kotlin.Any?): kotlin.Unit
 
-internal trait B {
+internal interface B {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/dataFlow/local/LocalObjectDelegation.txt b/compiler/testData/diagnostics/tests/dataFlow/local/LocalObjectDelegation.txt
index 55289608651..9b74d7424db 100644
--- a/compiler/testData/diagnostics/tests/dataFlow/local/LocalObjectDelegation.txt
+++ b/compiler/testData/diagnostics/tests/dataFlow/local/LocalObjectDelegation.txt
@@ -2,7 +2,7 @@ package
 
 internal fun foo(/*0*/ b: B?): kotlin.Int
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/ArrayGetSetConvention.txt b/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/ArrayGetSetConvention.txt
index dbfb37f10c7..59d70b95ca3 100644
--- a/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/ArrayGetSetConvention.txt
+++ b/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/ArrayGetSetConvention.txt
@@ -5,7 +5,7 @@ internal fun foo2(/*0*/ a: kotlin.Int?, /*1*/ b: G): kotlin.Unit
 internal fun foo3(/*0*/ a: kotlin.Int?, /*1*/ b: G): kotlin.Unit
 internal fun foo4(/*0*/ a: kotlin.Int?, /*1*/ b: G): kotlin.Unit
 
-internal trait G {
+internal interface G {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun get(/*0*/ x: kotlin.Int, /*1*/ y: kotlin.Int): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/Assignment.txt b/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/Assignment.txt
index 842ea8c664a..5172223145c 100644
--- a/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/Assignment.txt
+++ b/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/Assignment.txt
@@ -4,13 +4,13 @@ internal fun bar1(/*0*/ a: A): kotlin.Unit
 internal fun bar2(/*0*/ a: A): kotlin.Unit
 internal fun id(/*0*/ b: B): B
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B : A {
+internal interface B : A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/AssignmentInInitializer.txt b/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/AssignmentInInitializer.txt
index efc8b2fb175..5df479bf66d 100644
--- a/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/AssignmentInInitializer.txt
+++ b/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/AssignmentInInitializer.txt
@@ -4,13 +4,13 @@ internal fun bar1(/*0*/ a: A): kotlin.Unit
 internal fun bar2(/*0*/ a: A): kotlin.Unit
 internal fun baz(/*0*/ b: B): B
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B : A {
+internal interface B : A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/BinaryExpressionCompareToConvention.txt b/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/BinaryExpressionCompareToConvention.txt
index fe28675ae16..037cbf821b2 100644
--- a/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/BinaryExpressionCompareToConvention.txt
+++ b/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/BinaryExpressionCompareToConvention.txt
@@ -4,13 +4,13 @@ internal fun bar(/*0*/ a: A, /*1*/ b: B): kotlin.Boolean
 internal fun foo(/*0*/ a: A): kotlin.Boolean
 internal fun B.compareTo(/*0*/ b: B): kotlin.Int
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B : A {
+internal interface B : A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/BinaryExpressionEqualsConvention.txt b/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/BinaryExpressionEqualsConvention.txt
index 4623a10f624..1ae5baa5b31 100644
--- a/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/BinaryExpressionEqualsConvention.txt
+++ b/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/BinaryExpressionEqualsConvention.txt
@@ -3,13 +3,13 @@ package
 internal fun foo1(/*0*/ a: A, /*1*/ b: B): kotlin.Boolean
 internal fun foo2(/*0*/ a: A, /*1*/ b: B): kotlin.Boolean
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B : A {
+internal interface B : A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/BinaryExpressionPlusConvention.txt b/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/BinaryExpressionPlusConvention.txt
index 9918c367d69..e25ce934a7f 100644
--- a/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/BinaryExpressionPlusConvention.txt
+++ b/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/BinaryExpressionPlusConvention.txt
@@ -4,13 +4,13 @@ internal fun bar(/*0*/ a: A, /*1*/ b: B): B
 internal fun foo(/*0*/ a: A): B
 internal fun B.plus(/*0*/ b: B): B
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B : A {
+internal interface B : A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/smartcasts/SmartcastAmbiguitites.txt b/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/smartcasts/SmartcastAmbiguitites.txt
index 2ab28b7a67e..0b3bc8942fd 100644
--- a/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/smartcasts/SmartcastAmbiguitites.txt
+++ b/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/smartcasts/SmartcastAmbiguitites.txt
@@ -2,7 +2,7 @@ package
 
 internal fun test(/*0*/ a: kotlin.Any?): kotlin.Unit
 
-internal trait B {
+internal interface B {
     internal open fun bar(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/smartcasts/SmartcastsForStableIdentifiers.txt b/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/smartcasts/SmartcastsForStableIdentifiers.txt
index 3a763b2f2a2..b0b8ed0a4f5 100644
--- a/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/smartcasts/SmartcastsForStableIdentifiers.txt
+++ b/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/smartcasts/SmartcastsForStableIdentifiers.txt
@@ -36,7 +36,7 @@ package example {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait T {
+    internal interface T {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/declarationChecks/FunctionWithMissingNames.txt b/compiler/testData/diagnostics/tests/declarationChecks/FunctionWithMissingNames.txt
index 23271620703..bd50e068af9 100644
--- a/compiler/testData/diagnostics/tests/declarationChecks/FunctionWithMissingNames.txt
+++ b/compiler/testData/diagnostics/tests/declarationChecks/FunctionWithMissingNames.txt
@@ -1,4 +1,4 @@
-package 
+package
 
 a() internal fun <no name provided>(): kotlin.Unit
 internal fun <no name provided>(): kotlin.Unit
@@ -6,13 +6,13 @@ internal fun outerFun(): kotlin.Unit
 internal fun A.<no name provided>(): kotlin.Unit
 internal fun [a()] A.<no name provided>(): kotlin.Unit
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B {
+internal interface B {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/declarationChecks/ambiguousObjectExpressionType.txt b/compiler/testData/diagnostics/tests/declarationChecks/ambiguousObjectExpressionType.txt
index 0eb34a7d1cd..4986df4db66 100644
--- a/compiler/testData/diagnostics/tests/declarationChecks/ambiguousObjectExpressionType.txt
+++ b/compiler/testData/diagnostics/tests/declarationChecks/ambiguousObjectExpressionType.txt
@@ -54,7 +54,7 @@ internal open class MyClass {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait MyTrait {
+internal interface MyTrait {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun f1(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/declarationChecks/illegalModifiersOnClass.txt b/compiler/testData/diagnostics/tests/declarationChecks/illegalModifiersOnClass.txt
index 2988193d0a1..6ea75415478 100644
--- a/compiler/testData/diagnostics/tests/declarationChecks/illegalModifiersOnClass.txt
+++ b/compiler/testData/diagnostics/tests/declarationChecks/illegalModifiersOnClass.txt
@@ -77,7 +77,7 @@ internal open enum class C : kotlin.Enum<C> {
     public final /*synthesized*/ fun values(): kotlin.Array<C>
 }
 
-internal trait D {
+internal interface D {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/declarationChecks/kt1141.txt b/compiler/testData/diagnostics/tests/declarationChecks/kt1141.txt
index 68993ee061f..c4591b5e69b 100644
--- a/compiler/testData/diagnostics/tests/declarationChecks/kt1141.txt
+++ b/compiler/testData/diagnostics/tests/declarationChecks/kt1141.txt
@@ -20,7 +20,7 @@ package kt1141 {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait SomeTrait {
+    public interface SomeTrait {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal abstract fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/declarationChecks/kt2397.txt b/compiler/testData/diagnostics/tests/declarationChecks/kt2397.txt
index 7a1f76a8fd0..7cc60a16f05 100644
--- a/compiler/testData/diagnostics/tests/declarationChecks/kt2397.txt
+++ b/compiler/testData/diagnostics/tests/declarationChecks/kt2397.txt
@@ -10,7 +10,7 @@ package a {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait T {
+    internal interface T {
         internal final val b: kotlin.Int
         internal final val c: kotlin.Int
         internal final val d: kotlin.Int = 1
diff --git a/compiler/testData/diagnostics/tests/delegatedProperty/delegatedPropertyOverridedInTrait.txt b/compiler/testData/diagnostics/tests/delegatedProperty/delegatedPropertyOverridedInTrait.txt
index 3ab955108c1..1e2bd7cb7f5 100644
--- a/compiler/testData/diagnostics/tests/delegatedProperty/delegatedPropertyOverridedInTrait.txt
+++ b/compiler/testData/diagnostics/tests/delegatedProperty/delegatedPropertyOverridedInTrait.txt
@@ -2,7 +2,7 @@ package
 
 internal fun foo(): kotlin.Unit
 
-internal trait A {
+internal interface A {
     internal abstract val prop: kotlin.Int
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/delegatedProperty/delegatedPropertyOverridedInTraitTypeMismatch.txt b/compiler/testData/diagnostics/tests/delegatedProperty/delegatedPropertyOverridedInTraitTypeMismatch.txt
index 5d283762f81..bb00e9bfdea 100644
--- a/compiler/testData/diagnostics/tests/delegatedProperty/delegatedPropertyOverridedInTraitTypeMismatch.txt
+++ b/compiler/testData/diagnostics/tests/delegatedProperty/delegatedPropertyOverridedInTraitTypeMismatch.txt
@@ -2,7 +2,7 @@ package
 
 internal fun foo(): kotlin.Unit
 
-internal trait A {
+internal interface A {
     internal abstract val prop: kotlin.Int
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/delegatedProperty/inTrait.txt b/compiler/testData/diagnostics/tests/delegatedProperty/inTrait.txt
index 99dfd293e8b..3d01fc35342 100644
--- a/compiler/testData/diagnostics/tests/delegatedProperty/inTrait.txt
+++ b/compiler/testData/diagnostics/tests/delegatedProperty/inTrait.txt
@@ -8,7 +8,7 @@ internal final class Delegate {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T {
+internal interface T {
     internal open val a: kotlin.Int
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/delegatedProperty/inference/differentDelegatedExpressions.txt b/compiler/testData/diagnostics/tests/delegatedProperty/inference/differentDelegatedExpressions.txt
index 4d5c96e887d..fbe5d4535f9 100644
--- a/compiler/testData/diagnostics/tests/delegatedProperty/inference/differentDelegatedExpressions.txt
+++ b/compiler/testData/diagnostics/tests/delegatedProperty/inference/differentDelegatedExpressions.txt
@@ -32,7 +32,7 @@ package baz {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait MyPropertyContainer {
+    internal interface MyPropertyContainer {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal abstract fun </*0*/ R, /*1*/ T> getMyProperty(): baz.MyProperty<R, T>
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -47,7 +47,7 @@ package baz {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait Outer {
+    internal interface Outer {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal abstract fun getContainer(): baz.MyPropertyContainer
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/delegation/DelegationAndOverriding.txt b/compiler/testData/diagnostics/tests/delegation/DelegationAndOverriding.txt
index 763727d9383..1e1fa224aad 100644
--- a/compiler/testData/diagnostics/tests/delegation/DelegationAndOverriding.txt
+++ b/compiler/testData/diagnostics/tests/delegation/DelegationAndOverriding.txt
@@ -38,7 +38,7 @@ package override {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait G</*0*/ T> {
+    internal interface G</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal abstract fun foo(/*0*/ t: T): T
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -69,7 +69,7 @@ package override {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait T {
+    internal interface T {
         internal abstract val v: kotlin.Int
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal abstract fun foo(): kotlin.Unit
diff --git a/compiler/testData/diagnostics/tests/delegation/DelegationExpectedType.txt b/compiler/testData/diagnostics/tests/delegation/DelegationExpectedType.txt
index 1c589435fb2..6ae73bba72c 100644
--- a/compiler/testData/diagnostics/tests/delegation/DelegationExpectedType.txt
+++ b/compiler/testData/diagnostics/tests/delegation/DelegationExpectedType.txt
@@ -4,7 +4,7 @@ internal fun </*0*/ T> bar(): A<T>
 internal fun </*0*/ T> baz(/*0*/ f: (T) -> T): A<T>
 internal fun </*0*/ T> boo(/*0*/ t: T): A<T>
 
-internal trait A</*0*/ T> {
+internal interface A</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/delegation/DelegationNotTotrait.txt b/compiler/testData/diagnostics/tests/delegation/DelegationNotTotrait.txt
index 3522efa04c7..b0ddc03766f 100644
--- a/compiler/testData/diagnostics/tests/delegation/DelegationNotTotrait.txt
+++ b/compiler/testData/diagnostics/tests/delegation/DelegationNotTotrait.txt
@@ -45,7 +45,7 @@ internal open class Foo {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T {
+internal interface T {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/delegation/Delegation_ClashingFunctions.txt b/compiler/testData/diagnostics/tests/delegation/Delegation_ClashingFunctions.txt
index 043cfe78e79..227db243442 100644
--- a/compiler/testData/diagnostics/tests/delegation/Delegation_ClashingFunctions.txt
+++ b/compiler/testData/diagnostics/tests/delegation/Delegation_ClashingFunctions.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait One {
+internal interface One {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public abstract fun foo(): kotlin.Any?
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -73,14 +73,14 @@ internal final class Test321 : Three, Two, One {
     public open override /*3*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Three {
+internal interface Three {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public abstract fun foo(): kotlin.String
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Two {
+internal interface Two {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public abstract fun foo(): kotlin.String?
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/delegation/Delegation_Hierarchy.txt b/compiler/testData/diagnostics/tests/delegation/Delegation_Hierarchy.txt
index 7fcc52d613b..b33fd140e9a 100644
--- a/compiler/testData/diagnostics/tests/delegation/Delegation_Hierarchy.txt
+++ b/compiler/testData/diagnostics/tests/delegation/Delegation_Hierarchy.txt
@@ -2,7 +2,7 @@ package
 
 internal fun b(/*0*/ c: C): kotlin.Unit
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/delegation/Delegation_MultipleDelegates.txt b/compiler/testData/diagnostics/tests/delegation/Delegation_MultipleDelegates.txt
index 089d7936b81..6f2247d2b29 100644
--- a/compiler/testData/diagnostics/tests/delegation/Delegation_MultipleDelegates.txt
+++ b/compiler/testData/diagnostics/tests/delegation/Delegation_MultipleDelegates.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait One {
+internal interface One {
     private final fun boo(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public abstract fun foo(): kotlin.Int
@@ -8,7 +8,7 @@ internal trait One {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait OneImpl : One {
+internal interface OneImpl : One {
     invisible_fake final override /*1*/ /*fake_override*/ fun boo(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ fun foo(): kotlin.Int
@@ -43,14 +43,14 @@ internal final class Test3 : Two, One {
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Two {
+internal interface Two {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public abstract fun foo(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait TwoImpl : Two {
+internal interface TwoImpl : Two {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ fun foo(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/delegation/Delegation_ScopeInitializationOrder.txt b/compiler/testData/diagnostics/tests/delegation/Delegation_ScopeInitializationOrder.txt
index a29ec06d794..d6f3c58c41d 100644
--- a/compiler/testData/diagnostics/tests/delegation/Delegation_ScopeInitializationOrder.txt
+++ b/compiler/testData/diagnostics/tests/delegation/Delegation_ScopeInitializationOrder.txt
@@ -1,13 +1,13 @@
 package
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B : A {
+internal interface B : A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open override /*1*/ /*fake_override*/ fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/deprecated/typeUsage.txt b/compiler/testData/diagnostics/tests/deprecated/typeUsage.txt
index 05823c4d785..7bcbcef0228 100644
--- a/compiler/testData/diagnostics/tests/deprecated/typeUsage.txt
+++ b/compiler/testData/diagnostics/tests/deprecated/typeUsage.txt
@@ -25,7 +25,7 @@ internal final class Derived2 : Derived {
     internal final override /*1*/ /*fake_override*/ fun use(): kotlin.Unit
 }
 
-internal trait Generic</*0*/ T> {
+internal interface Generic</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/delegatedFunctionOverriddenByProperty.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/delegatedFunctionOverriddenByProperty.txt
index 83a53e2d2fa..64bc124d685 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/delegatedFunctionOverriddenByProperty.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/delegatedFunctionOverriddenByProperty.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait B {
+internal interface B {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun getX(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -16,7 +16,7 @@ internal final class C : D, B {
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait D {
+internal interface D {
     internal abstract val x: kotlin.Int
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/overridesNothing.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/overridesNothing.txt
index d247c8f6587..8fb374e9721 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/overridesNothing.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/overridesNothing.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait B {
+internal interface B {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun getX(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/require.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/require.txt
index 69fed4981c4..5db625f3c0d 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/require.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/require.txt
@@ -8,7 +8,7 @@ internal open class C {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Tr : C {
+internal interface Tr : C {
     internal final override /*1*/ /*fake_override*/ val x: kotlin.Int
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun getX(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/traitFunctionOverriddenByProperty.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/traitFunctionOverriddenByProperty.txt
index 5ebaf63af51..22b960c9bc1 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/traitFunctionOverriddenByProperty.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/traitFunctionOverriddenByProperty.txt
@@ -9,7 +9,7 @@ internal final class C : T {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T {
+internal interface T {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun getX(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/traitFunctionOverriddenByPropertyInTrait.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/traitFunctionOverriddenByPropertyInTrait.txt
index fa67cc8fcad..a91733fa421 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/traitFunctionOverriddenByPropertyInTrait.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/traitFunctionOverriddenByPropertyInTrait.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait C : T {
+internal interface C : T {
     internal open val x: kotlin.Int
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open override /*1*/ /*fake_override*/ fun getX(): kotlin.Int
@@ -8,7 +8,7 @@ internal trait C : T {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T {
+internal interface T {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun getX(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/traitFunctionOverriddenByPropertyNoImpl.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/traitFunctionOverriddenByPropertyNoImpl.txt
index f7256a8dda0..64a544deba0 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/traitFunctionOverriddenByPropertyNoImpl.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/traitFunctionOverriddenByPropertyNoImpl.txt
@@ -9,7 +9,7 @@ internal abstract class C : T {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T {
+internal interface T {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun getX(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/traitPropertyOverriddenByFunction.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/traitPropertyOverriddenByFunction.txt
index 48ce5271aed..6370ae4534d 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/traitPropertyOverriddenByFunction.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/traitPropertyOverriddenByFunction.txt
@@ -9,7 +9,7 @@ internal final class C : T {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T {
+internal interface T {
     internal open val x: kotlin.Int
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/traitPropertyOverriddenByFunctionInTrait.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/traitPropertyOverriddenByFunctionInTrait.txt
index da6abfe142d..8a03242b915 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/traitPropertyOverriddenByFunctionInTrait.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/traitPropertyOverriddenByFunctionInTrait.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait C : T {
+internal interface C : T {
     internal open override /*1*/ /*fake_override*/ val x: kotlin.Int
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun getX(): kotlin.Int
@@ -8,7 +8,7 @@ internal trait C : T {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T {
+internal interface T {
     internal open val x: kotlin.Int
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/traitPropertyOverriddenByFunctionNoImpl.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/traitPropertyOverriddenByFunctionNoImpl.txt
index 0ec9468dc4a..326d174e31d 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/traitPropertyOverriddenByFunctionNoImpl.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/accidentalOverrides/traitPropertyOverriddenByFunctionNoImpl.txt
@@ -9,7 +9,7 @@ internal abstract class C : T {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T {
+internal interface T {
     internal abstract val x: kotlin.Int
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/bridges/fakeOverrideTrait.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/bridges/fakeOverrideTrait.txt
index a84c3ae15f6..d688c718a49 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/bridges/fakeOverrideTrait.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/bridges/fakeOverrideTrait.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait B</*0*/ T> {
+internal interface B</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun foo(/*0*/ t: T): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/bridges/trait.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/bridges/trait.txt
index d2659ce9f05..a4357986168 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/bridges/trait.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/bridges/trait.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait B</*0*/ T> {
+internal interface B</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun foo(/*0*/ t: T): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/delegateToTwoTraits.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/delegateToTwoTraits.txt
index 9704055fa5f..58b9e8543ed 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/delegateToTwoTraits.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/delegateToTwoTraits.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait Bar</*0*/ T> {
+internal interface Bar</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(/*0*/ l: kotlin.List<T>): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -16,7 +16,7 @@ internal final class Baz : Foo<kotlin.String>, Bar<kotlin.Int> {
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Foo</*0*/ T> {
+internal interface Foo</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(/*0*/ l: kotlin.List<T>): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/delegationAndOwnMethod.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/delegationAndOwnMethod.txt
index 6b936d7468a..94cd92524d5 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/delegationAndOwnMethod.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/delegationAndOwnMethod.txt
@@ -9,7 +9,7 @@ internal final class Bar : Foo<kotlin.String> {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Foo</*0*/ T> {
+internal interface Foo</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(/*0*/ l: kotlin.List<T>): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/delegationToTraitImplAndOwnMethod.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/delegationToTraitImplAndOwnMethod.txt
index 40c421f8fe8..4881824a781 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/delegationToTraitImplAndOwnMethod.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/delegationToTraitImplAndOwnMethod.txt
@@ -17,7 +17,7 @@ internal final class BarOther : Foo<kotlin.String> {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Foo</*0*/ T> {
+internal interface Foo</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun foo(/*0*/ l: kotlin.List<T>): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/inheritFromTwoTraits.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/inheritFromTwoTraits.txt
index ca56305600b..443f148941d 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/inheritFromTwoTraits.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/inheritFromTwoTraits.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait Bar</*0*/ T> {
+internal interface Bar</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun foo(/*0*/ l: kotlin.List<T>): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -16,7 +16,7 @@ internal final class Baz : Foo<kotlin.String>, Bar<kotlin.Int> {
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Foo</*0*/ T> {
+internal interface Foo</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun foo(/*0*/ l: kotlin.List<T>): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/superTraitAndDelegationToTraitImpl.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/superTraitAndDelegationToTraitImpl.txt
index 81b3b883547..fca2e044486 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/superTraitAndDelegationToTraitImpl.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/superTraitAndDelegationToTraitImpl.txt
@@ -1,13 +1,13 @@
 package
 
-internal trait A</*0*/ T> {
+internal interface A</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(/*0*/ l: kotlin.List<T>): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B {
+internal interface B {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun foo(/*0*/ l: kotlin.List<kotlin.Int>): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/twoTraitsAndOwnFunction.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/twoTraitsAndOwnFunction.txt
index bed15a18203..0d6f2adc8a6 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/twoTraitsAndOwnFunction.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/twoTraitsAndOwnFunction.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait Bar</*0*/ T> {
+internal interface Bar</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun foo(/*0*/ l: kotlin.List<T>): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -17,7 +17,7 @@ internal final class Baz : Foo<kotlin.String>, Bar<kotlin.Int> {
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Foo</*0*/ T> {
+internal interface Foo</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun foo(/*0*/ l: kotlin.List<T>): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/typeParameterWithBound.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/typeParameterWithBound.txt
index ebd69ecebac..7f02ea6d750 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/typeParameterWithBound.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/typeParameterWithBound.txt
@@ -3,7 +3,7 @@ package
 internal fun foo(/*0*/ x: Foo): Foo
 internal fun </*0*/ T : Foo> foo(/*0*/ x: T): T
 
-internal trait Foo {
+internal interface Foo {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/typeParameterWithTwoBounds.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/typeParameterWithTwoBounds.txt
index 643786fc71d..c4d2a23c705 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/typeParameterWithTwoBounds.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/typeParameterWithTwoBounds.txt
@@ -4,13 +4,13 @@ internal fun foo(/*0*/ x: Bar): Bar
 internal fun foo(/*0*/ x: Foo): Foo
 internal fun </*0*/ T : Foo> foo(/*0*/ x: T): T where T : Bar
 
-internal trait Bar {
+internal interface Bar {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Foo {
+internal interface Foo {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/typeParameterWithTwoBoundsInWhere.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/typeParameterWithTwoBoundsInWhere.txt
index 643786fc71d..c4d2a23c705 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/typeParameterWithTwoBoundsInWhere.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/erasure/typeParameterWithTwoBoundsInWhere.txt
@@ -4,13 +4,13 @@ internal fun foo(/*0*/ x: Bar): Bar
 internal fun foo(/*0*/ x: Foo): Foo
 internal fun </*0*/ T : Foo> foo(/*0*/ x: T): T where T : Bar
 
-internal trait Bar {
+internal interface Bar {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Foo {
+internal interface Foo {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/functionAndProperty/trait.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/functionAndProperty/trait.txt
index 44aa9ca58a9..0e9bc9fcf60 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/functionAndProperty/trait.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/functionAndProperty/trait.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait T {
+internal interface T {
     internal open val x: kotlin.Int
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun getX(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/functionAndProperty/withErrorTypes.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/functionAndProperty/withErrorTypes.txt
index 92c2967f54d..db7f973c6ab 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/functionAndProperty/withErrorTypes.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/functionAndProperty/withErrorTypes.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait T {
+internal interface T {
     internal abstract val x: [ERROR : ErrorType]
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun getX(): [ERROR : ErrorType1]
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/missingNames.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/missingNames.txt
index 616013759f3..0d573d1c24f 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/missingNames.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/missingNames.txt
@@ -12,7 +12,7 @@ internal final class <no name provided> {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait <no name provided> {
+internal interface <no name provided> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -61,7 +61,7 @@ internal final class Outer {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait <no name provided> {
+    internal interface <no name provided> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/specialNames/delegationBy.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/specialNames/delegationBy.txt
index 49b5f28b78d..785d20267dc 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/specialNames/delegationBy.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/specialNames/delegationBy.txt
@@ -8,7 +8,7 @@ internal final class Bar : Foo {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Foo {
+internal interface Foo {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/traitImpl/oneTrait.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/traitImpl/oneTrait.txt
index 527faeced2d..22ea844e5bb 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/traitImpl/oneTrait.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/traitImpl/oneTrait.txt
@@ -9,7 +9,7 @@ internal final class C : T {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T {
+internal interface T {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun getX(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/duplicateJvmSignature/traitImpl/twoTraits.txt b/compiler/testData/diagnostics/tests/duplicateJvmSignature/traitImpl/twoTraits.txt
index d3b63e5d52e..132859e1762 100644
--- a/compiler/testData/diagnostics/tests/duplicateJvmSignature/traitImpl/twoTraits.txt
+++ b/compiler/testData/diagnostics/tests/duplicateJvmSignature/traitImpl/twoTraits.txt
@@ -9,14 +9,14 @@ internal final class C : T1, T2 {
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T1 {
+internal interface T1 {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun getX(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T2 {
+internal interface T2 {
     internal open val x: kotlin.Int
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/dynamicTypes/delegationBy.txt b/compiler/testData/diagnostics/tests/dynamicTypes/delegationBy.txt
index ad197003b18..858ae2fa9e5 100644
--- a/compiler/testData/diagnostics/tests/dynamicTypes/delegationBy.txt
+++ b/compiler/testData/diagnostics/tests/dynamicTypes/delegationBy.txt
@@ -8,7 +8,7 @@ internal final class C : Tr {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Tr {
+internal interface Tr {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/enum/AbstractOverrideInEnum.txt b/compiler/testData/diagnostics/tests/enum/AbstractOverrideInEnum.txt
index ce8ee9d2601..7f44f53a32a 100644
--- a/compiler/testData/diagnostics/tests/enum/AbstractOverrideInEnum.txt
+++ b/compiler/testData/diagnostics/tests/enum/AbstractOverrideInEnum.txt
@@ -26,7 +26,7 @@ internal final enum class E : kotlin.Enum<E>, T {
     public final /*synthesized*/ fun values(): kotlin.Array<E>
 }
 
-internal trait T {
+internal interface T {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun f(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/enum/enumImplementingTrait.txt b/compiler/testData/diagnostics/tests/enum/enumImplementingTrait.txt
index 7053284a669..21fd4b68a0c 100644
--- a/compiler/testData/diagnostics/tests/enum/enumImplementingTrait.txt
+++ b/compiler/testData/diagnostics/tests/enum/enumImplementingTrait.txt
@@ -74,14 +74,14 @@ internal final enum class EnumImplementingTraitWithVal : kotlin.Enum<EnumImpleme
     public final /*synthesized*/ fun values(): kotlin.Array<EnumImplementingTraitWithVal>
 }
 
-internal trait T1 {
+internal interface T1 {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T2 {
+internal interface T2 {
     internal abstract val bar: kotlin.Int
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/enum/enumInheritance.txt b/compiler/testData/diagnostics/tests/enum/enumInheritance.txt
index 786c06eda46..329a0279719 100644
--- a/compiler/testData/diagnostics/tests/enum/enumInheritance.txt
+++ b/compiler/testData/diagnostics/tests/enum/enumInheritance.txt
@@ -60,7 +60,7 @@ internal final enum class MyEnumBase : kotlin.Enum<MyEnumBase> {
     public final /*synthesized*/ fun values(): kotlin.Array<MyEnumBase>
 }
 
-internal trait MyTrait {
+internal interface MyTrait {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/enum/enumModifier.txt b/compiler/testData/diagnostics/tests/enum/enumModifier.txt
index 41c0e5e2159..1c2fcc36de6 100644
--- a/compiler/testData/diagnostics/tests/enum/enumModifier.txt
+++ b/compiler/testData/diagnostics/tests/enum/enumModifier.txt
@@ -39,7 +39,7 @@ internal object O {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T {
+internal interface T {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/enum/inner/insideTrait.txt b/compiler/testData/diagnostics/tests/enum/inner/insideTrait.txt
index 58dc7fc786c..6ac34179076 100644
--- a/compiler/testData/diagnostics/tests/enum/inner/insideTrait.txt
+++ b/compiler/testData/diagnostics/tests/enum/inner/insideTrait.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/extensions/ExtensionsCalledOnSuper.txt b/compiler/testData/diagnostics/tests/extensions/ExtensionsCalledOnSuper.txt
index 980c27a356b..0b978a9b24d 100644
--- a/compiler/testData/diagnostics/tests/extensions/ExtensionsCalledOnSuper.txt
+++ b/compiler/testData/diagnostics/tests/extensions/ExtensionsCalledOnSuper.txt
@@ -15,7 +15,7 @@ internal final class C : T {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T {
+internal interface T {
     internal open fun buzz(): kotlin.Unit
     internal open fun buzz1(/*0*/ i: kotlin.Int): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
diff --git a/compiler/testData/diagnostics/tests/extensions/GenericIterator.txt b/compiler/testData/diagnostics/tests/extensions/GenericIterator.txt
index 89397c6ee32..217052bf76b 100644
--- a/compiler/testData/diagnostics/tests/extensions/GenericIterator.txt
+++ b/compiler/testData/diagnostics/tests/extensions/GenericIterator.txt
@@ -4,7 +4,7 @@ internal fun main(/*0*/ args: kotlin.Array<kotlin.String>): kotlin.Unit
 internal fun </*0*/ T : kotlin.Any> T?.iterator(): MyIterator<T>
 internal fun </*0*/ T> java.util.Enumeration<T>.iterator(): kotlin.Iterator<T>
 
-internal trait MyIterator</*0*/ T> {
+internal interface MyIterator</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun hasNext(): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/extensions/classObject.txt b/compiler/testData/diagnostics/tests/extensions/classObject.txt
index 2c41e8e463e..3caff4d465c 100644
--- a/compiler/testData/diagnostics/tests/extensions/classObject.txt
+++ b/compiler/testData/diagnostics/tests/extensions/classObject.txt
@@ -35,7 +35,7 @@ internal final class B {
     }
 }
 
-internal trait Tr {
+internal interface Tr {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/extensions/extensionMemberInClassObject.txt b/compiler/testData/diagnostics/tests/extensions/extensionMemberInClassObject.txt
index 5f572946249..fe122ab61a4 100644
--- a/compiler/testData/diagnostics/tests/extensions/extensionMemberInClassObject.txt
+++ b/compiler/testData/diagnostics/tests/extensions/extensionMemberInClassObject.txt
@@ -18,7 +18,7 @@ internal final class Foo {
     }
 }
 
-internal trait JPAEntityClass</*0*/ D> {
+internal interface JPAEntityClass</*0*/ D> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/extensions/kt1875.txt b/compiler/testData/diagnostics/tests/extensions/kt1875.txt
index 29dfce5161a..6043c5eb76b 100644
--- a/compiler/testData/diagnostics/tests/extensions/kt1875.txt
+++ b/compiler/testData/diagnostics/tests/extensions/kt1875.txt
@@ -5,7 +5,7 @@ package kt1875 {
     internal fun test(/*0*/ t: kt1875.T): kotlin.Unit
     internal fun test1(/*0*/ t: kt1875.T?): kotlin.Unit
 
-    internal trait T {
+    internal interface T {
         internal abstract val f: ((kotlin.Int) -> kotlin.Unit)?
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/extensions/throwOutCandidatesByReceiver.txt b/compiler/testData/diagnostics/tests/extensions/throwOutCandidatesByReceiver.txt
index 87360dc1e79..f31612a82b8 100644
--- a/compiler/testData/diagnostics/tests/extensions/throwOutCandidatesByReceiver.txt
+++ b/compiler/testData/diagnostics/tests/extensions/throwOutCandidatesByReceiver.txt
@@ -15,7 +15,7 @@ package bar {
     internal fun kotlin.Int.foo(): kotlin.Unit
     internal fun </*0*/ R : kotlin.Any> R?.sure(): R
 
-    internal trait A {
+    internal interface A {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/functionAsExpression/ScopeCheck.txt b/compiler/testData/diagnostics/tests/functionAsExpression/ScopeCheck.txt
index 0aefb08664b..f6dab53c058 100644
--- a/compiler/testData/diagnostics/tests/functionAsExpression/ScopeCheck.txt
+++ b/compiler/testData/diagnostics/tests/functionAsExpression/ScopeCheck.txt
@@ -2,7 +2,7 @@ package
 
 internal fun test(/*0*/ param: kotlin.String): kotlin.Unit
 
-internal trait B {
+internal interface B {
     internal open fun b_fun(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/functionAsExpression/WithGenericParameters.txt b/compiler/testData/diagnostics/tests/functionAsExpression/WithGenericParameters.txt
index a86c9a301ea..d2840a36861 100644
--- a/compiler/testData/diagnostics/tests/functionAsExpression/WithGenericParameters.txt
+++ b/compiler/testData/diagnostics/tests/functionAsExpression/WithGenericParameters.txt
@@ -6,7 +6,7 @@ internal fun devNull(/*0*/ a: kotlin.Any?): kotlin.Unit
 internal fun fun_with_where(): T.(T) -> T
 internal fun outer(): kotlin.Unit
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/functionLiterals/ExpectedParameterTypeMismatchVariance.txt b/compiler/testData/diagnostics/tests/functionLiterals/ExpectedParameterTypeMismatchVariance.txt
index ece8894eb4c..dd4c1595b25 100644
--- a/compiler/testData/diagnostics/tests/functionLiterals/ExpectedParameterTypeMismatchVariance.txt
+++ b/compiler/testData/diagnostics/tests/functionLiterals/ExpectedParameterTypeMismatchVariance.txt
@@ -11,13 +11,13 @@ package a {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait Super {
+    internal interface Super {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait Trait : a.Super {
+    internal interface Trait : a.Super {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/functionLiterals/LabeledFunctionLiterals.txt b/compiler/testData/diagnostics/tests/functionLiterals/LabeledFunctionLiterals.txt
index 30a4dfb0f04..33d9c415793 100644
--- a/compiler/testData/diagnostics/tests/functionLiterals/LabeledFunctionLiterals.txt
+++ b/compiler/testData/diagnostics/tests/functionLiterals/LabeledFunctionLiterals.txt
@@ -5,19 +5,19 @@ package h {
     internal fun </*0*/ T> foo(/*0*/ b: h.B, /*1*/ f: () -> T): T
     internal fun test(/*0*/ c: h.C): kotlin.Unit
 
-    internal trait A {
+    internal interface A {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait B {
+    internal interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait C : h.A, h.B {
+    internal interface C : h.A, h.B {
         public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/functionLiterals/return/MixedReturnsFromLambda.txt b/compiler/testData/diagnostics/tests/functionLiterals/return/MixedReturnsFromLambda.txt
index 03432d67aa6..0a422042f10 100644
--- a/compiler/testData/diagnostics/tests/functionLiterals/return/MixedReturnsFromLambda.txt
+++ b/compiler/testData/diagnostics/tests/functionLiterals/return/MixedReturnsFromLambda.txt
@@ -3,19 +3,19 @@ package
 internal fun </*0*/ T> run(/*0*/ f: () -> T): T
 internal fun test(/*0*/ a: C, /*1*/ b: B): kotlin.Unit
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B : A {
+internal interface B : A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait C : A {
+internal interface C : A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/functionLiterals/returnNull.txt b/compiler/testData/diagnostics/tests/functionLiterals/returnNull.txt
index 8c2db7bb5db..8428fa27b3b 100644
--- a/compiler/testData/diagnostics/tests/functionLiterals/returnNull.txt
+++ b/compiler/testData/diagnostics/tests/functionLiterals/returnNull.txt
@@ -4,7 +4,7 @@ package m {
     internal fun test(/*0*/ handlers: kotlin.Map<kotlin.String, m.Element.() -> kotlin.Unit>): kotlin.Unit
     internal fun </*0*/ K, /*1*/ V> kotlin.Map<K, V>.getOrElse(/*0*/ key: K, /*1*/ defaultValue: () -> V): V
 
-    internal trait Element {
+    internal interface Element {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/functionLiterals/returnNullWithReturn.txt b/compiler/testData/diagnostics/tests/functionLiterals/returnNullWithReturn.txt
index 8c2db7bb5db..8428fa27b3b 100644
--- a/compiler/testData/diagnostics/tests/functionLiterals/returnNullWithReturn.txt
+++ b/compiler/testData/diagnostics/tests/functionLiterals/returnNullWithReturn.txt
@@ -4,7 +4,7 @@ package m {
     internal fun test(/*0*/ handlers: kotlin.Map<kotlin.String, m.Element.() -> kotlin.Unit>): kotlin.Unit
     internal fun </*0*/ K, /*1*/ V> kotlin.Map<K, V>.getOrElse(/*0*/ key: K, /*1*/ defaultValue: () -> V): V
 
-    internal trait Element {
+    internal interface Element {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/generics/argumentsForT.txt b/compiler/testData/diagnostics/tests/generics/argumentsForT.txt
index 59e77e20cf6..50069d7ee35 100644
--- a/compiler/testData/diagnostics/tests/generics/argumentsForT.txt
+++ b/compiler/testData/diagnostics/tests/generics/argumentsForT.txt
@@ -3,7 +3,7 @@ package
 internal fun </*0*/ T> foo(/*0*/ t: T): kotlin.Unit
 internal fun </*0*/ T> foo1(/*0*/ t: T): kotlin.Unit
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/generics/recursive.txt b/compiler/testData/diagnostics/tests/generics/recursive.txt
index 27a7889eaf5..07fb0ca1619 100644
--- a/compiler/testData/diagnostics/tests/generics/recursive.txt
+++ b/compiler/testData/diagnostics/tests/generics/recursive.txt
@@ -16,7 +16,7 @@ internal final class B : Rec<B> {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Rec</*0*/ T> {
+internal interface Rec</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/generics/resolveGenericBoundsBeforeSupertypes.txt b/compiler/testData/diagnostics/tests/generics/resolveGenericBoundsBeforeSupertypes.txt
index 80a2160641a..232b73dac0c 100644
--- a/compiler/testData/diagnostics/tests/generics/resolveGenericBoundsBeforeSupertypes.txt
+++ b/compiler/testData/diagnostics/tests/generics/resolveGenericBoundsBeforeSupertypes.txt
@@ -7,7 +7,7 @@ internal object O : Tr<V<*>> {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Tr</*0*/ T> {
+internal interface Tr</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/generics/varProjection/setterNotProjectedOutAssign.txt b/compiler/testData/diagnostics/tests/generics/varProjection/setterNotProjectedOutAssign.txt
index 39d7e886fdb..761aa973463 100644
--- a/compiler/testData/diagnostics/tests/generics/varProjection/setterNotProjectedOutAssign.txt
+++ b/compiler/testData/diagnostics/tests/generics/varProjection/setterNotProjectedOutAssign.txt
@@ -2,7 +2,7 @@ package
 
 internal fun test(/*0*/ t: Tr<*>): kotlin.Unit
 
-internal trait Tr</*0*/ T> {
+internal interface Tr</*0*/ T> {
     internal abstract var v: Tr<T>
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/generics/varProjection/setterProjectedOutAssign.txt b/compiler/testData/diagnostics/tests/generics/varProjection/setterProjectedOutAssign.txt
index 9262567f409..7209e2a8500 100644
--- a/compiler/testData/diagnostics/tests/generics/varProjection/setterProjectedOutAssign.txt
+++ b/compiler/testData/diagnostics/tests/generics/varProjection/setterProjectedOutAssign.txt
@@ -2,7 +2,7 @@ package
 
 internal fun test(/*0*/ t: Tr<*>): kotlin.Unit
 
-internal trait Tr</*0*/ T> {
+internal interface Tr</*0*/ T> {
     internal abstract var v: T
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/generics/varProjection/setterProjectedOutNoPlusAssign.txt b/compiler/testData/diagnostics/tests/generics/varProjection/setterProjectedOutNoPlusAssign.txt
index 62a71d2c381..1018559b44c 100644
--- a/compiler/testData/diagnostics/tests/generics/varProjection/setterProjectedOutNoPlusAssign.txt
+++ b/compiler/testData/diagnostics/tests/generics/varProjection/setterProjectedOutNoPlusAssign.txt
@@ -2,7 +2,7 @@ package
 
 internal fun test(/*0*/ t: Tr<out kotlin.String>): kotlin.Unit
 
-internal trait Tr</*0*/ T> {
+internal interface Tr</*0*/ T> {
     internal abstract var v: T
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/generics/varProjection/setterProjectedOutPlusAssignDefined.txt b/compiler/testData/diagnostics/tests/generics/varProjection/setterProjectedOutPlusAssignDefined.txt
index 7d6e5b42e71..89f7df962ab 100644
--- a/compiler/testData/diagnostics/tests/generics/varProjection/setterProjectedOutPlusAssignDefined.txt
+++ b/compiler/testData/diagnostics/tests/generics/varProjection/setterProjectedOutPlusAssignDefined.txt
@@ -10,7 +10,7 @@ internal final class C {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Tr</*0*/ T> {
+internal interface Tr</*0*/ T> {
     internal abstract var v: T
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/incompleteCode/checkNothingIsSubtype.txt b/compiler/testData/diagnostics/tests/incompleteCode/checkNothingIsSubtype.txt
index 68dc6a23815..71a893b5343 100644
--- a/compiler/testData/diagnostics/tests/incompleteCode/checkNothingIsSubtype.txt
+++ b/compiler/testData/diagnostics/tests/incompleteCode/checkNothingIsSubtype.txt
@@ -5,7 +5,7 @@ package d {
     internal fun sum(/*0*/ a: kotlin.IntArray): kotlin.Int
     internal fun test(/*0*/ nothing: kotlin.Nothing?): kotlin.Unit
 
-    internal trait A</*0*/ T> {
+    internal interface A</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/inference/constraints/equalityConstraintOnNullableType.txt b/compiler/testData/diagnostics/tests/inference/constraints/equalityConstraintOnNullableType.txt
index 3903eac7379..f90dc7b112a 100644
--- a/compiler/testData/diagnostics/tests/inference/constraints/equalityConstraintOnNullableType.txt
+++ b/compiler/testData/diagnostics/tests/inference/constraints/equalityConstraintOnNullableType.txt
@@ -4,7 +4,7 @@ internal fun </*0*/ T> doA(/*0*/ a: A<T>): T
 internal fun </*0*/ T> foo(/*0*/ a: A<T>, /*1*/ aN: A<T?>): T
 internal fun test(/*0*/ a: A<kotlin.Int>, /*1*/ aN: A<kotlin.Int?>): kotlin.Unit
 
-internal trait A</*0*/ T> {
+internal interface A</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/inference/constraints/kt7351ConstraintFromUnitExpectedType.txt b/compiler/testData/diagnostics/tests/inference/constraints/kt7351ConstraintFromUnitExpectedType.txt
index 7f91377bfa1..88c9a339390 100644
--- a/compiler/testData/diagnostics/tests/inference/constraints/kt7351ConstraintFromUnitExpectedType.txt
+++ b/compiler/testData/diagnostics/tests/inference/constraints/kt7351ConstraintFromUnitExpectedType.txt
@@ -5,13 +5,13 @@ package kt7351 {
     internal fun kt7351.Node.append(/*0*/ block: kt7351.Source<kotlin.Int>.() -> kotlin.Unit): kotlin.Unit
     internal fun </*0*/ T, /*1*/ S : kt7351.Source<T>> S.woo(): T
 
-    internal trait Node {
+    internal interface Node {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait Source</*0*/ T> {
+    internal interface Source</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal abstract fun f(): T
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/inference/constraints/notNullConstraintOnNullableType.txt b/compiler/testData/diagnostics/tests/inference/constraints/notNullConstraintOnNullableType.txt
index 1e64fea6d44..018dbe4febb 100644
--- a/compiler/testData/diagnostics/tests/inference/constraints/notNullConstraintOnNullableType.txt
+++ b/compiler/testData/diagnostics/tests/inference/constraints/notNullConstraintOnNullableType.txt
@@ -6,19 +6,19 @@ internal fun </*0*/ T : kotlin.Any> doOut(/*0*/ o: Out<T?>): T
 internal fun </*0*/ T : kotlin.Any> doT(/*0*/ t: T?): T
 internal fun test(/*0*/ out: Out<kotlin.Int>, /*1*/ i: In<kotlin.Int>, /*2*/ inv: A<kotlin.Int>): kotlin.Unit
 
-internal trait A</*0*/ T> {
+internal interface A</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait In</*0*/ in T> {
+internal interface In</*0*/ in T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Out</*0*/ out T> {
+internal interface Out</*0*/ out T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/inference/constraints/subtypeConstraintOnNullableType.txt b/compiler/testData/diagnostics/tests/inference/constraints/subtypeConstraintOnNullableType.txt
index c261d61f606..56023308ee7 100644
--- a/compiler/testData/diagnostics/tests/inference/constraints/subtypeConstraintOnNullableType.txt
+++ b/compiler/testData/diagnostics/tests/inference/constraints/subtypeConstraintOnNullableType.txt
@@ -4,13 +4,13 @@ internal fun </*0*/ T> doOut(/*0*/ o: Out<T?>): T
 internal fun </*0*/ T> foo(/*0*/ a: A<T>, /*1*/ o: Out<T?>): T
 internal fun test(/*0*/ a: A<kotlin.Int>, /*1*/ aN: A<kotlin.Int?>, /*2*/ o: Out<kotlin.Int?>): kotlin.Unit
 
-internal trait A</*0*/ T> {
+internal interface A</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Out</*0*/ out T> {
+internal interface Out</*0*/ out T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/inference/constraints/supertypeConstraintOnNullableType.txt b/compiler/testData/diagnostics/tests/inference/constraints/supertypeConstraintOnNullableType.txt
index a53f1e81a51..af23a2c2403 100644
--- a/compiler/testData/diagnostics/tests/inference/constraints/supertypeConstraintOnNullableType.txt
+++ b/compiler/testData/diagnostics/tests/inference/constraints/supertypeConstraintOnNullableType.txt
@@ -4,13 +4,13 @@ internal fun </*0*/ T> doIn(/*0*/ i: In<T?>): T
 internal fun </*0*/ T> foo(/*0*/ a: A<T>, /*1*/ i: In<T>): T
 internal fun test(/*0*/ a: A<kotlin.Int>, /*1*/ aN: A<kotlin.Int?>, /*2*/ i: In<kotlin.Int?>): kotlin.Unit
 
-internal trait A</*0*/ T> {
+internal interface A</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait In</*0*/ in T> {
+internal interface In</*0*/ in T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/inference/nestedCalls/binaryExpressions.txt b/compiler/testData/diagnostics/tests/inference/nestedCalls/binaryExpressions.txt
index be7c3efc4b5..7ae3150d33b 100644
--- a/compiler/testData/diagnostics/tests/inference/nestedCalls/binaryExpressions.txt
+++ b/compiler/testData/diagnostics/tests/inference/nestedCalls/binaryExpressions.txt
@@ -16,13 +16,13 @@ package h {
     internal fun </*0*/ T> h.Z.foo(/*0*/ a: h.A<T>): h.A<T>
     internal fun </*0*/ T> h.Z.plus(/*0*/ a: h.A<T>): h.A<T>
 
-    internal trait A</*0*/ T> {
+    internal interface A</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait Z {
+    internal interface Z {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/inference/nestedCalls/completeNestedForVariableAsFunctionCall.txt b/compiler/testData/diagnostics/tests/inference/nestedCalls/completeNestedForVariableAsFunctionCall.txt
index d961f2b40e2..e89abadb574 100644
--- a/compiler/testData/diagnostics/tests/inference/nestedCalls/completeNestedForVariableAsFunctionCall.txt
+++ b/compiler/testData/diagnostics/tests/inference/nestedCalls/completeNestedForVariableAsFunctionCall.txt
@@ -20,7 +20,7 @@ package j {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait MyFunc</*0*/ T> {
+    internal interface MyFunc</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/inference/nestedCalls/makeNullableIfSafeCall.txt b/compiler/testData/diagnostics/tests/inference/nestedCalls/makeNullableIfSafeCall.txt
index faae9dd1964..3ff7a95718c 100644
--- a/compiler/testData/diagnostics/tests/inference/nestedCalls/makeNullableIfSafeCall.txt
+++ b/compiler/testData/diagnostics/tests/inference/nestedCalls/makeNullableIfSafeCall.txt
@@ -7,7 +7,7 @@ package a {
     internal fun a.B?.bar(): kotlin.Int
     internal fun a.B?.baz(): kotlin.Int?
 
-    internal trait A {
+    internal interface A {
         internal abstract val b: a.B
         internal abstract val nb: a.B?
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
@@ -15,7 +15,7 @@ package a {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait B {
+    internal interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal abstract fun foo(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/inference/opposite.txt b/compiler/testData/diagnostics/tests/inference/opposite.txt
index 1da5357d481..8561a8aa919 100644
--- a/compiler/testData/diagnostics/tests/inference/opposite.txt
+++ b/compiler/testData/diagnostics/tests/inference/opposite.txt
@@ -2,13 +2,13 @@ package
 
 package a {
 
-    internal trait Persistent {
+    internal interface Persistent {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait PersistentFactory</*0*/ T> {
+    internal interface PersistentFactory</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/inference/regressions/kt2283.txt b/compiler/testData/diagnostics/tests/inference/regressions/kt2283.txt
index b12d5153a78..d71aaf7a988 100644
--- a/compiler/testData/diagnostics/tests/inference/regressions/kt2283.txt
+++ b/compiler/testData/diagnostics/tests/inference/regressions/kt2283.txt
@@ -4,7 +4,7 @@ package a {
     internal fun foo(): kotlin.Unit
     internal fun </*0*/ A, /*1*/ B> a.Foo<A>.map(/*0*/ f: (A) -> B): a.Foo<B>
 
-    internal trait Foo</*0*/ A> {
+    internal interface Foo</*0*/ A> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/inference/regressions/kt2320.txt b/compiler/testData/diagnostics/tests/inference/regressions/kt2320.txt
index da4685fd670..b656e919a30 100644
--- a/compiler/testData/diagnostics/tests/inference/regressions/kt2320.txt
+++ b/compiler/testData/diagnostics/tests/inference/regressions/kt2320.txt
@@ -4,14 +4,14 @@ package i {
     internal fun </*0*/ B, /*1*/ C> i.NotMap<B>.mapValuesOnly(/*0*/ f: (B) -> C): i.NotMap<C>
     internal fun </*0*/ V, /*1*/ R> i.NotMap<V>.mapValuesOriginal(/*0*/ ff: (i.Entry<V>) -> R): i.NotMap<R>
 
-    internal trait Entry</*0*/ B> {
+    internal interface Entry</*0*/ B> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal abstract fun getValue(): B
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait NotMap</*0*/ B> {
+    internal interface NotMap</*0*/ B> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/inference/regressions/kt2505.txt b/compiler/testData/diagnostics/tests/inference/regressions/kt2505.txt
index dd1da90ff21..c4dbacd6ebf 100644
--- a/compiler/testData/diagnostics/tests/inference/regressions/kt2505.txt
+++ b/compiler/testData/diagnostics/tests/inference/regressions/kt2505.txt
@@ -19,7 +19,7 @@ package a {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait MyType {
+    internal interface MyType {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/inference/regressions/kt2841.txt b/compiler/testData/diagnostics/tests/inference/regressions/kt2841.txt
index 83b644f9e0b..3fee0b23948 100644
--- a/compiler/testData/diagnostics/tests/inference/regressions/kt2841.txt
+++ b/compiler/testData/diagnostics/tests/inference/regressions/kt2841.txt
@@ -11,7 +11,7 @@ package a {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait Closeable {
+    internal interface Closeable {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/inference/regressions/kt2841_it.txt b/compiler/testData/diagnostics/tests/inference/regressions/kt2841_it.txt
index 1f4f6d09253..7f9df3dd2da 100644
--- a/compiler/testData/diagnostics/tests/inference/regressions/kt2841_it.txt
+++ b/compiler/testData/diagnostics/tests/inference/regressions/kt2841_it.txt
@@ -12,7 +12,7 @@ package a {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait Closeable {
+    internal interface Closeable {
         internal open fun close(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/inference/regressions/kt2841_it_this.txt b/compiler/testData/diagnostics/tests/inference/regressions/kt2841_it_this.txt
index 183205ee190..51067f97ec1 100644
--- a/compiler/testData/diagnostics/tests/inference/regressions/kt2841_it_this.txt
+++ b/compiler/testData/diagnostics/tests/inference/regressions/kt2841_it_this.txt
@@ -12,7 +12,7 @@ package a {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait Closeable {
+    internal interface Closeable {
         internal open fun close(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/inference/regressions/kt2841_this.txt b/compiler/testData/diagnostics/tests/inference/regressions/kt2841_this.txt
index b39ed8727fd..9f12a489831 100644
--- a/compiler/testData/diagnostics/tests/inference/regressions/kt2841_this.txt
+++ b/compiler/testData/diagnostics/tests/inference/regressions/kt2841_this.txt
@@ -12,7 +12,7 @@ package a {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait Closeable {
+    internal interface Closeable {
         internal open fun close(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/inference/regressions/kt2842.txt b/compiler/testData/diagnostics/tests/inference/regressions/kt2842.txt
index e84e9218520..6d97fdeceee 100644
--- a/compiler/testData/diagnostics/tests/inference/regressions/kt2842.txt
+++ b/compiler/testData/diagnostics/tests/inference/regressions/kt2842.txt
@@ -8,7 +8,7 @@ package c {
     internal fun </*0*/ R> c.A<R>.foo(): kotlin.Unit
     public fun </*0*/ K, /*1*/ V> kotlin.Map<K, V>.iterator(): kotlin.Iterator<kotlin.Map.Entry<K, V>>
 
-    internal trait A</*0*/ T> {
+    internal interface A</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/inference/regressions/kt3301.txt b/compiler/testData/diagnostics/tests/inference/regressions/kt3301.txt
index a85b6b8bf70..e5e2fac201d 100644
--- a/compiler/testData/diagnostics/tests/inference/regressions/kt3301.txt
+++ b/compiler/testData/diagnostics/tests/inference/regressions/kt3301.txt
@@ -5,13 +5,13 @@ package arrays {
     internal fun m(/*0*/ args: kotlin.Array<arrays.A>): kotlin.Unit
     internal fun test122(): kotlin.Unit
 
-    internal trait A {
+    internal interface A {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait B {
+    internal interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/inference/reportingImprovements/NoAmbiguityForDifferentFunctionTypes.txt b/compiler/testData/diagnostics/tests/inference/reportingImprovements/NoAmbiguityForDifferentFunctionTypes.txt
index 4febea6e544..daba8eb130b 100644
--- a/compiler/testData/diagnostics/tests/inference/reportingImprovements/NoAmbiguityForDifferentFunctionTypes.txt
+++ b/compiler/testData/diagnostics/tests/inference/reportingImprovements/NoAmbiguityForDifferentFunctionTypes.txt
@@ -12,7 +12,7 @@ package a {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait Closeable {
+    internal interface Closeable {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/inference/typeInferenceExpectedTypeMismatch.txt b/compiler/testData/diagnostics/tests/inference/typeInferenceExpectedTypeMismatch.txt
index 1f7f61ace34..3ed34de472e 100644
--- a/compiler/testData/diagnostics/tests/inference/typeInferenceExpectedTypeMismatch.txt
+++ b/compiler/testData/diagnostics/tests/inference/typeInferenceExpectedTypeMismatch.txt
@@ -9,37 +9,37 @@ package typeInferenceExpectedTypeMismatch {
     internal fun test2(/*0*/ outA: typeInferenceExpectedTypeMismatch.Out<typeInferenceExpectedTypeMismatch.A>, /*1*/ inC: typeInferenceExpectedTypeMismatch.In<typeInferenceExpectedTypeMismatch.C>): kotlin.Unit
     internal fun use(/*0*/ vararg a: kotlin.Any? /*kotlin.Array<out kotlin.Any?>*/): kotlin.Array<out kotlin.Any?>
 
-    internal trait A {
+    internal interface A {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait B : typeInferenceExpectedTypeMismatch.A {
+    internal interface B : typeInferenceExpectedTypeMismatch.A {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait C : typeInferenceExpectedTypeMismatch.A {
+    internal interface C : typeInferenceExpectedTypeMismatch.A {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait In</*0*/ in T> {
+    internal interface In</*0*/ in T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait Out</*0*/ out T> {
+    internal interface Out</*0*/ out T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait Two</*0*/ T, /*1*/ R> {
+    internal interface Two</*0*/ T, /*1*/ R> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/inference/upperBounds/doNotInferFromBoundsOnly.txt b/compiler/testData/diagnostics/tests/inference/upperBounds/doNotInferFromBoundsOnly.txt
index 4291468e27a..fc7f8024a6b 100644
--- a/compiler/testData/diagnostics/tests/inference/upperBounds/doNotInferFromBoundsOnly.txt
+++ b/compiler/testData/diagnostics/tests/inference/upperBounds/doNotInferFromBoundsOnly.txt
@@ -19,7 +19,7 @@ package a {
     internal fun test7(/*0*/ list: kotlin.MutableList<kotlin.Int>): kotlin.Unit
     internal fun test8(): kotlin.Int
 
-    internal trait A {
+    internal interface A {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/inference/upperBounds/intersectUpperBounds.txt b/compiler/testData/diagnostics/tests/inference/upperBounds/intersectUpperBounds.txt
index 19196a5c3ea..1f18dbb293f 100644
--- a/compiler/testData/diagnostics/tests/inference/upperBounds/intersectUpperBounds.txt
+++ b/compiler/testData/diagnostics/tests/inference/upperBounds/intersectUpperBounds.txt
@@ -7,25 +7,25 @@ package s {
     internal fun test(/*0*/ inA: s.In<s.A>, /*1*/ inB: s.In<s.B>, /*2*/ inC: s.In<s.C>): kotlin.Unit
     internal fun use(/*0*/ vararg a: kotlin.Any? /*kotlin.Array<out kotlin.Any?>*/): kotlin.Array<out kotlin.Any?>
 
-    internal trait A {
+    internal interface A {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait B {
+    internal interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait C : s.A, s.B {
+    internal interface C : s.A, s.B {
         public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait In</*0*/ in T> {
+    internal interface In</*0*/ in T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/inference/upperBounds/nonNullUpperBound.txt b/compiler/testData/diagnostics/tests/inference/upperBounds/nonNullUpperBound.txt
index 33e8b2b49af..5fb7090e12b 100644
--- a/compiler/testData/diagnostics/tests/inference/upperBounds/nonNullUpperBound.txt
+++ b/compiler/testData/diagnostics/tests/inference/upperBounds/nonNullUpperBound.txt
@@ -5,7 +5,7 @@ internal fun </*0*/ T : A> fooA(/*0*/ v: kotlin.Any): T?
 internal fun </*0*/ R : kotlin.Any> unescape(/*0*/ value: kotlin.Any): R?
 internal fun </*0*/ R : A> unescapeA(/*0*/ value: kotlin.Any): R?
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/inline/nonVirtualMembersWithInline.txt b/compiler/testData/diagnostics/tests/inline/nonVirtualMembersWithInline.txt
index 2c8f525c1e2..bc35ffb00e8 100644
--- a/compiler/testData/diagnostics/tests/inline/nonVirtualMembersWithInline.txt
+++ b/compiler/testData/diagnostics/tests/inline/nonVirtualMembersWithInline.txt
@@ -21,7 +21,7 @@ internal abstract class A {
     kotlin.inline() internal abstract fun wrong6(): kotlin.Unit
 }
 
-internal trait B {
+internal interface B {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     kotlin.inline() private final fun good1(): kotlin.Unit
     kotlin.inline() public final fun good2(): kotlin.Unit
diff --git a/compiler/testData/diagnostics/tests/inline/sam.txt b/compiler/testData/diagnostics/tests/inline/sam.txt
index 2a147626fe5..4ed999394bb 100644
--- a/compiler/testData/diagnostics/tests/inline/sam.txt
+++ b/compiler/testData/diagnostics/tests/inline/sam.txt
@@ -5,7 +5,7 @@ kotlin.inline() internal fun inlineFunWithInvoke(/*0*/ s: (kotlin.Int) -> kotlin
 kotlin.inline() internal fun inlineFunWithInvokeNonInline(/*0*/ kotlin.noinline() s: (kotlin.Int) -> kotlin.Unit, /*1*/ ext: kotlin.Int.(kotlin.Int) -> kotlin.Unit): kotlin.Unit
 kotlin.inline() internal fun ((kotlin.Int) -> kotlin.Unit).inlineExt(): kotlin.Unit
 
-public trait Run {
+public interface Run {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public abstract fun run(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/inner/deepInnerClass.txt b/compiler/testData/diagnostics/tests/inner/deepInnerClass.txt
index 2a9db76c7b2..bb2b2b61c83 100644
--- a/compiler/testData/diagnostics/tests/inner/deepInnerClass.txt
+++ b/compiler/testData/diagnostics/tests/inner/deepInnerClass.txt
@@ -15,7 +15,7 @@ internal final class A</*0*/ T> {
     }
 }
 
-internal trait P</*0*/ U, /*1*/ Y> {
+internal interface P</*0*/ U, /*1*/ Y> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/inner/extensionLambdaInsideNestedClass.txt b/compiler/testData/diagnostics/tests/inner/extensionLambdaInsideNestedClass.txt
index af616eee21c..45dc1bd165e 100644
--- a/compiler/testData/diagnostics/tests/inner/extensionLambdaInsideNestedClass.txt
+++ b/compiler/testData/diagnostics/tests/inner/extensionLambdaInsideNestedClass.txt
@@ -17,7 +17,7 @@ package f {
         }
     }
 
-    internal trait ActionContext {
+    internal interface ActionContext {
         internal abstract val session: kotlin.Map<kotlin.String, kotlin.String>
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/inner/illegalModifier.txt b/compiler/testData/diagnostics/tests/inner/illegalModifier.txt
index 6a0b0928288..6a8d6fa6f75 100644
--- a/compiler/testData/diagnostics/tests/inner/illegalModifier.txt
+++ b/compiler/testData/diagnostics/tests/inner/illegalModifier.txt
@@ -11,7 +11,7 @@ internal final class A {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B {
+internal interface B {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -44,7 +44,7 @@ internal final class D {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait F {
+    internal interface F {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -117,7 +117,7 @@ internal final enum class H : kotlin.Enum<H> {
     public final /*synthesized*/ fun values(): kotlin.Array<H>
 }
 
-internal trait K {
+internal interface K {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/inner/innerThisSuper.txt b/compiler/testData/diagnostics/tests/inner/innerThisSuper.txt
index 9428971c03f..ec4166d18c5 100644
--- a/compiler/testData/diagnostics/tests/inner/innerThisSuper.txt
+++ b/compiler/testData/diagnostics/tests/inner/innerThisSuper.txt
@@ -35,7 +35,7 @@ internal final class Outer : Trait {
     }
 }
 
-internal trait Trait {
+internal interface Trait {
     internal open fun bar(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/inner/localThisSuper.txt b/compiler/testData/diagnostics/tests/inner/localThisSuper.txt
index fd59900d6d4..687d4c00e9f 100644
--- a/compiler/testData/diagnostics/tests/inner/localThisSuper.txt
+++ b/compiler/testData/diagnostics/tests/inner/localThisSuper.txt
@@ -9,7 +9,7 @@ internal final class Outer : Trait {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Trait {
+internal interface Trait {
     internal open fun bar(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/inner/nestedClassAccessedViaInstanceReference.txt b/compiler/testData/diagnostics/tests/inner/nestedClassAccessedViaInstanceReference.txt
index ad4402a6a7c..bae523fcc0c 100644
--- a/compiler/testData/diagnostics/tests/inner/nestedClassAccessedViaInstanceReference.txt
+++ b/compiler/testData/diagnostics/tests/inner/nestedClassAccessedViaInstanceReference.txt
@@ -2,7 +2,7 @@ package
 
 internal fun test(/*0*/ with: WithClassObject, /*1*/ without: WithoutClassObject, /*2*/ obj: Obj): kotlin.Unit
 
-internal trait N {
+internal interface N {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun foo(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/inner/outerProtectedMember.txt b/compiler/testData/diagnostics/tests/inner/outerProtectedMember.txt
index 6e351109a8d..db46fa5c41d 100644
--- a/compiler/testData/diagnostics/tests/inner/outerProtectedMember.txt
+++ b/compiler/testData/diagnostics/tests/inner/outerProtectedMember.txt
@@ -16,7 +16,7 @@ internal final class Foo {
     }
 }
 
-internal trait I {
+internal interface I {
     internal abstract val x: kotlin.String
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/inner/traits.txt b/compiler/testData/diagnostics/tests/inner/traits.txt
index 418063bcf61..07f09cbf667 100644
--- a/compiler/testData/diagnostics/tests/inner/traits.txt
+++ b/compiler/testData/diagnostics/tests/inner/traits.txt
@@ -1,20 +1,20 @@
 package
 
-internal trait Foo {
+internal interface Foo {
     internal abstract val b: Foo.Bar
     internal abstract val b1: Foo.Bar
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 
-    internal trait Bar {
+    internal interface Bar {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 }
 
-internal trait Foo2 : Foo {
+internal interface Foo2 : Foo {
     internal abstract override /*1*/ /*fake_override*/ val b: Foo.Bar
     internal abstract override /*1*/ /*fake_override*/ val b1: Foo.Bar
     internal abstract val bb1: Foo.Bar
diff --git a/compiler/testData/diagnostics/tests/j+k/GenericsInSupertypes.txt b/compiler/testData/diagnostics/tests/j+k/GenericsInSupertypes.txt
index d4ecedb1ed5..29eb714c058 100644
--- a/compiler/testData/diagnostics/tests/j+k/GenericsInSupertypes.txt
+++ b/compiler/testData/diagnostics/tests/j+k/GenericsInSupertypes.txt
@@ -57,7 +57,7 @@ internal abstract class K : p.C<p.P> {
 
 package p {
 
-    public trait A</*0*/ TA> {
+    public interface A</*0*/ TA> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal abstract fun foo(/*0*/ p: p.A<TA>): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -80,7 +80,7 @@ package p {
         public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait G</*0*/ TG> {
+    public interface G</*0*/ TG> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/j+k/InnerClassFromJava.txt b/compiler/testData/diagnostics/tests/j+k/InnerClassFromJava.txt
index 105375fc8d0..fe578f23c23 100644
--- a/compiler/testData/diagnostics/tests/j+k/InnerClassFromJava.txt
+++ b/compiler/testData/diagnostics/tests/j+k/InnerClassFromJava.txt
@@ -6,7 +6,7 @@ public open class Bar : Foo {
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 
-    public trait I : Boo {
+    public interface I : Boo {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -20,13 +20,13 @@ public final class Baz : Bar.I {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Boo {
+internal interface Boo {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-public trait Foo {
+public interface Foo {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/j+k/inheritAbstractSamAdapter.txt b/compiler/testData/diagnostics/tests/j+k/inheritAbstractSamAdapter.txt
index d1d12858176..fd5a4d12d50 100644
--- a/compiler/testData/diagnostics/tests/j+k/inheritAbstractSamAdapter.txt
+++ b/compiler/testData/diagnostics/tests/j+k/inheritAbstractSamAdapter.txt
@@ -2,7 +2,7 @@ package
 
 public /*synthesized*/ fun A(/*0*/ function: (java.lang.Runnable!) -> kotlin.Unit): A
 
-public trait A {
+public interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public final /*synthesized*/ fun foo(/*0*/ r: (() -> kotlin.Unit)!): kotlin.Unit
     public abstract fun foo(/*0*/ r: java.lang.Runnable!): kotlin.Unit
@@ -10,7 +10,7 @@ public trait A {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-public trait B : A {
+public interface B : A {
     public final /*synthesized*/ fun bar(/*0*/ r: (() -> kotlin.Unit)!): kotlin.Unit
     public abstract fun bar(/*0*/ r: java.lang.Runnable!): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
diff --git a/compiler/testData/diagnostics/tests/j+k/kt3307.txt b/compiler/testData/diagnostics/tests/j+k/kt3307.txt
index 4579b14985d..7a4e25cd1de 100644
--- a/compiler/testData/diagnostics/tests/j+k/kt3307.txt
+++ b/compiler/testData/diagnostics/tests/j+k/kt3307.txt
@@ -2,7 +2,7 @@ package
 
 internal fun TestBug(): kotlin.Unit
 
-public trait Bug {
+public interface Bug {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public abstract fun </*0*/ RET : Bug!> save(): RET!
diff --git a/compiler/testData/diagnostics/tests/j+k/kt6720_abstractProperty.txt b/compiler/testData/diagnostics/tests/j+k/kt6720_abstractProperty.txt
index 37463fcf716..4dd693def7b 100644
--- a/compiler/testData/diagnostics/tests/j+k/kt6720_abstractProperty.txt
+++ b/compiler/testData/diagnostics/tests/j+k/kt6720_abstractProperty.txt
@@ -2,7 +2,7 @@ package
 
 internal fun main(): kotlin.Unit
 
-internal trait A {
+internal interface A {
     internal abstract val a: kotlin.Int
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/j+k/overrideRawType.txt b/compiler/testData/diagnostics/tests/j+k/overrideRawType.txt
index c8ca7cfed49..317e11460ef 100644
--- a/compiler/testData/diagnostics/tests/j+k/overrideRawType.txt
+++ b/compiler/testData/diagnostics/tests/j+k/overrideRawType.txt
@@ -2,7 +2,7 @@ package
 
 public /*synthesized*/ fun Bar(/*0*/ function: (Foo<*>!) -> kotlin.Unit): Bar
 
-public trait Bar {
+public interface Bar {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public abstract fun f(/*0*/ f: Foo<*>!): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/j+k/traitDefaultCall.txt b/compiler/testData/diagnostics/tests/j+k/traitDefaultCall.txt
index 5adc7c27c95..45faa56c9c6 100644
--- a/compiler/testData/diagnostics/tests/j+k/traitDefaultCall.txt
+++ b/compiler/testData/diagnostics/tests/j+k/traitDefaultCall.txt
@@ -10,7 +10,7 @@ internal final class A : KTrait {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait KTrait : Test {
+internal interface KTrait : Test {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     internal open fun ktest(): kotlin.Unit
@@ -18,7 +18,7 @@ internal trait KTrait : Test {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-public trait Test {
+public interface Test {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open fun test(): kotlin.String!
diff --git a/compiler/testData/diagnostics/tests/labels/labelReferencesInsideObjectExpressions.txt b/compiler/testData/diagnostics/tests/labels/labelReferencesInsideObjectExpressions.txt
index b17c67ff5e7..f8a9dafe3b1 100644
--- a/compiler/testData/diagnostics/tests/labels/labelReferencesInsideObjectExpressions.txt
+++ b/compiler/testData/diagnostics/tests/labels/labelReferencesInsideObjectExpressions.txt
@@ -3,14 +3,14 @@ package
 internal fun test(): kotlin.Unit
 internal fun B.b(): kotlin.Unit
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B {
+internal interface B {
     internal abstract fun bar(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/modifiers/IllegalModifiers.txt b/compiler/testData/diagnostics/tests/modifiers/IllegalModifiers.txt
index 3de95611e28..13b37b781eb 100644
--- a/compiler/testData/diagnostics/tests/modifiers/IllegalModifiers.txt
+++ b/compiler/testData/diagnostics/tests/modifiers/IllegalModifiers.txt
@@ -132,7 +132,7 @@ package illegal_modifiers {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal final trait T {
+    internal final interface T {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/modifiers/defaultModifier.txt b/compiler/testData/diagnostics/tests/modifiers/defaultModifier.txt
index 6c83df0f81c..a5cc2596851 100644
--- a/compiler/testData/diagnostics/tests/modifiers/defaultModifier.txt
+++ b/compiler/testData/diagnostics/tests/modifiers/defaultModifier.txt
@@ -122,7 +122,7 @@ internal object G {
     }
 }
 
-internal trait H {
+internal interface H {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/modifiers/incompatibleVarianceModifiers.txt b/compiler/testData/diagnostics/tests/modifiers/incompatibleVarianceModifiers.txt
index d09fb260fa8..056d6b0edde 100644
--- a/compiler/testData/diagnostics/tests/modifiers/incompatibleVarianceModifiers.txt
+++ b/compiler/testData/diagnostics/tests/modifiers/incompatibleVarianceModifiers.txt
@@ -13,19 +13,19 @@ internal final class A {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Foo</*0*/ T> {
+internal interface Foo</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Foo1</*0*/ out T> {
+internal interface Foo1</*0*/ out T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Foo2</*0*/ in T> {
+internal interface Foo2</*0*/ in T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateClass/duplicateSuperClass.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateClass/duplicateSuperClass.txt
index e00f4329340..5f8dcf6c6fe 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateClass/duplicateSuperClass.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateClass/duplicateSuperClass.txt
@@ -3,7 +3,7 @@ package
 
 package p {
 
-    public trait A {
+    public interface A {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -32,7 +32,7 @@ package
 package p {
     public fun foo(/*0*/ a: p.A): kotlin.Unit
 
-    public trait A {
+    public interface A {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -48,11 +48,11 @@ internal fun test(): kotlin.Unit
 package p {
     public fun foo(/*0*/ a: p.A): kotlin.Unit
 
-    public trait A {
+    public interface A {
         // -- Module: <m1> --
     }
 
-    public trait A {
+    public interface A {
         // -- Module: <m2> --
     }
 
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateClass/genericSuperClass.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateClass/genericSuperClass.txt
index 3158783cfeb..ebe27ed6846 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateClass/genericSuperClass.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateClass/genericSuperClass.txt
@@ -3,7 +3,7 @@ package
 
 package p {
 
-    public trait A</*0*/ T> {
+    public interface A</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -16,13 +16,13 @@ package p {
         public open override /*3*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait C {
+    public interface C {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait D</*0*/ T> {
+    public interface D</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -46,19 +46,19 @@ package p {
     public fun c(/*0*/ c: p.C<kotlin.Int>): kotlin.Unit
     public fun d(/*0*/ d: p.D<kotlin.Int>): kotlin.Unit
 
-    public trait A {
+    public interface A {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait C</*0*/ T> {
+    public interface C</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait D</*0*/ T> {
+    public interface D</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -76,11 +76,11 @@ package p {
     public fun c(/*0*/ c: p.C<kotlin.Int>): kotlin.Unit
     public fun d(/*0*/ d: p.D<kotlin.Int>): kotlin.Unit
 
-    public trait A {
+    public interface A {
         // -- Module: <m2> --
     }
 
-    public trait A</*0*/ T> {
+    public interface A</*0*/ T> {
         // -- Module: <m1> --
     }
 
@@ -88,19 +88,19 @@ package p {
         // -- Module: <m1> --
     }
 
-    public trait C {
+    public interface C {
         // -- Module: <m1> --
     }
 
-    public trait C</*0*/ T> {
+    public interface C</*0*/ T> {
         // -- Module: <m2> --
     }
 
-    public trait D</*0*/ T> {
+    public interface D</*0*/ T> {
         // -- Module: <m1> --
     }
 
-    public trait D</*0*/ T> {
+    public interface D</*0*/ T> {
         // -- Module: <m2> --
     }
 
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classGenericsInParams.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classGenericsInParams.txt
index 202087bd6e6..218aa32dcb1 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classGenericsInParams.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classGenericsInParams.txt
@@ -3,7 +3,7 @@ package
 
 package p {
 
-    public trait B</*0*/ T> {
+    public interface B</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun foo(/*0*/ a: T): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -17,11 +17,11 @@ package
 
 package p {
 
-    public trait B</*0*/ T> {
+    public interface B</*0*/ T> {
         // -- Module: <m1> --
     }
 
-    public trait C</*0*/ X> : p.B<X> {
+    public interface C</*0*/ X> : p.B<X> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract override /*1*/ fun foo(/*0*/ a: X): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -35,7 +35,7 @@ package
 
 package p {
 
-    public trait B</*0*/ T> {
+    public interface B</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun foo(/*0*/ a: T): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -51,11 +51,11 @@ internal fun test(/*0*/ b: p.B<kotlin.String>?): kotlin.Unit
 
 package p {
 
-    public trait B</*0*/ T> {
+    public interface B</*0*/ T> {
         // -- Module: <m3> --
     }
 
-    public trait C</*0*/ X> : p.B<X> {
+    public interface C</*0*/ X> : p.B<X> {
         // -- Module: <m2> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classGenericsInParamsBoundMismatch.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classGenericsInParamsBoundMismatch.txt
index 1b96af57aad..eedce1e24de 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classGenericsInParamsBoundMismatch.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classGenericsInParamsBoundMismatch.txt
@@ -3,7 +3,7 @@ package
 
 package p {
 
-    public trait B</*0*/ T> {
+    public interface B</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun foo(/*0*/ a: T?): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -17,11 +17,11 @@ package
 
 package p {
 
-    public trait B</*0*/ T> {
+    public interface B</*0*/ T> {
         // -- Module: <m1> --
     }
 
-    public trait C</*0*/ X> : p.B<X> {
+    public interface C</*0*/ X> : p.B<X> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract override /*1*/ fun foo(/*0*/ a: X?): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -35,14 +35,14 @@ package
 
 package p {
 
-    public trait B</*0*/ T : p.Tr?> {
+    public interface B</*0*/ T : p.Tr?> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun foo(/*0*/ a: T?): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait Tr {
+    public interface Tr {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -57,15 +57,15 @@ internal fun test(/*0*/ b: p.B<p.Tr>?): kotlin.Unit
 
 package p {
 
-    public trait B</*0*/ T : p.Tr?> {
+    public interface B</*0*/ T : p.Tr?> {
         // -- Module: <m3> --
     }
 
-    public trait C</*0*/ X> : p.B<X> {
+    public interface C</*0*/ X> : p.B<X> {
         // -- Module: <m2> --
     }
 
-    public trait Tr {
+    public interface Tr {
         // -- Module: <m3> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classGenericsInParamsIndexMismatch.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classGenericsInParamsIndexMismatch.txt
index 968c3a7ca15..9571e889fe0 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classGenericsInParamsIndexMismatch.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classGenericsInParamsIndexMismatch.txt
@@ -3,7 +3,7 @@ package
 
 package p {
 
-    public trait B</*0*/ T, /*1*/ _> {
+    public interface B</*0*/ T, /*1*/ _> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun foo(/*0*/ a: T?): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -17,11 +17,11 @@ package
 
 package p {
 
-    public trait B</*0*/ T, /*1*/ _> {
+    public interface B</*0*/ T, /*1*/ _> {
         // -- Module: <m1> --
     }
 
-    public trait C</*0*/ X, /*1*/ _> : p.B<X, _> {
+    public interface C</*0*/ X, /*1*/ _> : p.B<X, _> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract override /*1*/ fun foo(/*0*/ a: X?): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -35,7 +35,7 @@ package
 
 package p {
 
-    public trait B</*0*/ _, /*1*/ T> {
+    public interface B</*0*/ _, /*1*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun foo(/*0*/ a: T?): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -51,11 +51,11 @@ internal fun </*0*/ Y, /*1*/ Z> test(/*0*/ b: p.B<Y, Z>?): kotlin.Unit
 
 package p {
 
-    public trait B</*0*/ _, /*1*/ T> {
+    public interface B</*0*/ _, /*1*/ T> {
         // -- Module: <m3> --
     }
 
-    public trait C</*0*/ X, /*1*/ _> : p.B<X, _> {
+    public interface C</*0*/ X, /*1*/ _> : p.B<X, _> {
         // -- Module: <m2> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classGenericsInParamsNameMismatch.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classGenericsInParamsNameMismatch.txt
index d75ec30c61e..0470de41749 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classGenericsInParamsNameMismatch.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classGenericsInParamsNameMismatch.txt
@@ -3,7 +3,7 @@ package
 
 package p {
 
-    public trait B</*0*/ T> {
+    public interface B</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun foo(/*0*/ a: T): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -17,11 +17,11 @@ package
 
 package p {
 
-    public trait B</*0*/ T> {
+    public interface B</*0*/ T> {
         // -- Module: <m1> --
     }
 
-    public trait C</*0*/ X> : p.B<X> {
+    public interface C</*0*/ X> : p.B<X> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract override /*1*/ fun foo(/*0*/ a: X): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -35,7 +35,7 @@ package
 
 package p {
 
-    public trait B</*0*/ T1> {
+    public interface B</*0*/ T1> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun foo(/*0*/ a: T1): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -51,11 +51,11 @@ internal fun </*0*/ Y> test(/*0*/ b: p.B<Y>?, /*1*/ y: Y): kotlin.Unit
 
 package p {
 
-    public trait B</*0*/ T1> {
+    public interface B</*0*/ T1> {
         // -- Module: <m3> --
     }
 
-    public trait C</*0*/ X> : p.B<X> {
+    public interface C</*0*/ X> : p.B<X> {
         // -- Module: <m2> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classGenericsInReturnType.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classGenericsInReturnType.txt
index 2ee4d193029..1ebdb377dd3 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classGenericsInReturnType.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classGenericsInReturnType.txt
@@ -3,7 +3,7 @@ package
 
 package p {
 
-    public trait B</*0*/ T> {
+    public interface B</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun foo(): T
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -17,11 +17,11 @@ package
 
 package p {
 
-    public trait B</*0*/ T> {
+    public interface B</*0*/ T> {
         // -- Module: <m1> --
     }
 
-    public trait C</*0*/ X> : p.B<X> {
+    public interface C</*0*/ X> : p.B<X> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract override /*1*/ fun foo(): X
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -35,7 +35,7 @@ package
 
 package p {
 
-    public trait B</*0*/ T> {
+    public interface B</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun foo(): T
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -51,11 +51,11 @@ internal fun test(/*0*/ b: p.B<kotlin.String>?): kotlin.Unit
 
 package p {
 
-    public trait B</*0*/ T> {
+    public interface B</*0*/ T> {
         // -- Module: <m3> --
     }
 
-    public trait C</*0*/ X> : p.B<X> {
+    public interface C</*0*/ X> : p.B<X> {
         // -- Module: <m2> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classVsFunctionGenericsInParamsMismatch.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classVsFunctionGenericsInParamsMismatch.txt
index c653c9e3a30..a3fe73253fa 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classVsFunctionGenericsInParamsMismatch.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classVsFunctionGenericsInParamsMismatch.txt
@@ -3,7 +3,7 @@ package
 
 package p {
 
-    public trait B</*0*/ T> {
+    public interface B</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun </*0*/ R> foo(/*0*/ a: T, /*1*/ b: R): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -17,11 +17,11 @@ package
 
 package p {
 
-    public trait B</*0*/ T> {
+    public interface B</*0*/ T> {
         // -- Module: <m1> --
     }
 
-    public trait C : p.B<kotlin.Any?> {
+    public interface C : p.B<kotlin.Any?> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract override /*1*/ fun </*0*/ R> foo(/*0*/ a: kotlin.Any?, /*1*/ b: R): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -35,7 +35,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun </*0*/ T, /*1*/ R> foo(/*0*/ a: T, /*1*/ b: R): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -51,11 +51,11 @@ internal fun test(/*0*/ b: p.B?, /*1*/ c: p.C): kotlin.Unit
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m3> --
     }
 
-    public trait C : p.B<kotlin.Any?> {
+    public interface C : p.B<kotlin.Any?> {
         // -- Module: <m2> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/covariantReturnTypes.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/covariantReturnTypes.txt
index 5d3c8a9f263..7230d9f3432 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/covariantReturnTypes.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/covariantReturnTypes.txt
@@ -3,7 +3,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun getParent(): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -17,11 +17,11 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m1> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract override /*1*/ fun getParent(): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -35,7 +35,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun getParent(): kotlin.Any?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -51,11 +51,11 @@ internal fun test(/*0*/ b: p.B?): kotlin.Unit
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m3> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         // -- Module: <m2> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/differenceInParamNames.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/differenceInParamNames.txt
index f62e313c7b2..b58a9610706 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/differenceInParamNames.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/differenceInParamNames.txt
@@ -3,7 +3,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun foo(/*0*/ a: kotlin.Int, /*1*/ b: kotlin.String): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -17,11 +17,11 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m1> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract override /*1*/ fun foo(/*0*/ a: kotlin.Int, /*1*/ b: kotlin.String): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -35,7 +35,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun foo(/*0*/ a1: kotlin.Int, /*1*/ b1: kotlin.String): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -51,11 +51,11 @@ internal fun test(/*0*/ b: p.B?): kotlin.Unit
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m3> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         // -- Module: <m2> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/differentGenericsInParams.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/differentGenericsInParams.txt
index 2f124b2d037..8ebedf8113c 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/differentGenericsInParams.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/differentGenericsInParams.txt
@@ -3,13 +3,13 @@ package
 
 package p {
 
-    public trait G1</*0*/ T> {
+    public interface G1</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait G2</*0*/ A, /*1*/ B> {
+    public interface G2</*0*/ A, /*1*/ B> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -22,18 +22,18 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun foo(/*0*/ a: p.G1<kotlin.Int>?, /*1*/ b: p.G2<p.B, kotlin.String>?): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait G1</*0*/ T> {
+    public interface G1</*0*/ T> {
         // -- Module: <m0> --
     }
 
-    public trait G2</*0*/ A, /*1*/ B> {
+    public interface G2</*0*/ A, /*1*/ B> {
         // -- Module: <m0> --
     }
 }
@@ -44,22 +44,22 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m1> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract override /*1*/ fun foo(/*0*/ a: p.G1<kotlin.Int>?, /*1*/ b: p.G2<p.B, kotlin.String>?): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait G1</*0*/ T> {
+    public interface G1</*0*/ T> {
         // -- Module: <m0> --
     }
 
-    public trait G2</*0*/ A, /*1*/ B> {
+    public interface G2</*0*/ A, /*1*/ B> {
         // -- Module: <m0> --
     }
 }
@@ -70,18 +70,18 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun foo(/*0*/ a: p.G1<out kotlin.Any?>?, /*1*/ b: p.G2<kotlin.Int, out kotlin.Any?>?): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait G1</*0*/ T> {
+    public interface G1</*0*/ T> {
         // -- Module: <m0> --
     }
 
-    public trait G2</*0*/ A, /*1*/ B> {
+    public interface G2</*0*/ A, /*1*/ B> {
         // -- Module: <m0> --
     }
 }
@@ -94,19 +94,19 @@ internal fun test(/*0*/ b: p.B?): kotlin.Unit
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m3> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         // -- Module: <m2> --
     }
 
-    public trait G1</*0*/ T> {
+    public interface G1</*0*/ T> {
         // -- Module: <m0> --
     }
 
-    public trait G2</*0*/ A, /*1*/ B> {
+    public interface G2</*0*/ A, /*1*/ B> {
         // -- Module: <m0> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/differentNumberOfParams.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/differentNumberOfParams.txt
index 8d2dbaec4e7..3060dbbadae 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/differentNumberOfParams.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/differentNumberOfParams.txt
@@ -3,7 +3,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun foo(/*0*/ a: kotlin.Int, /*1*/ b: kotlin.String): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -17,11 +17,11 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m1> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract override /*1*/ fun foo(/*0*/ a: kotlin.Int, /*1*/ b: kotlin.String): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -35,7 +35,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun foo(/*0*/ a: kotlin.Int, /*1*/ b: kotlin.String, /*2*/ c: kotlin.Int = ...): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -51,11 +51,11 @@ internal fun test(/*0*/ b: p.B?): kotlin.Unit
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m3> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         // -- Module: <m2> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/differentReturnTypes.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/differentReturnTypes.txt
index 4f344295ef5..530ab9eec90 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/differentReturnTypes.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/differentReturnTypes.txt
@@ -3,7 +3,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun getParent(): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -17,11 +17,11 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m1> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract override /*1*/ fun getParent(): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -35,7 +35,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun getParent(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -51,11 +51,11 @@ internal fun test(/*0*/ b: p.B?): kotlin.Unit
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m3> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         // -- Module: <m2> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/extensionMatch.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/extensionMatch.txt
index c59450bf5c5..f4f2c7c41ea 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/extensionMatch.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/extensionMatch.txt
@@ -3,7 +3,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -17,7 +17,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m1> --
     }
 
@@ -36,7 +36,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -52,7 +52,7 @@ internal fun p.B.test(): kotlin.Unit
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m3> --
     }
 
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/functionGenericsInParams.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/functionGenericsInParams.txt
index 45a3c403e1f..461b1d249a1 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/functionGenericsInParams.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/functionGenericsInParams.txt
@@ -3,7 +3,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun </*0*/ T> foo(/*0*/ a: T): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -17,11 +17,11 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m1> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract override /*1*/ fun </*0*/ T> foo(/*0*/ a: T): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -35,7 +35,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun </*0*/ T> foo(/*0*/ a: T): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -52,11 +52,11 @@ internal fun test1(/*0*/ b: p.B?): kotlin.Unit
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m3> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         // -- Module: <m2> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/functionGenericsInParamsBoundsMismatch.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/functionGenericsInParamsBoundsMismatch.txt
index 33270180596..e5fce455112 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/functionGenericsInParamsBoundsMismatch.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/functionGenericsInParamsBoundsMismatch.txt
@@ -3,7 +3,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun </*0*/ T> foo(/*0*/ a: T): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -17,11 +17,11 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m1> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract override /*1*/ fun </*0*/ T> foo(/*0*/ a: T): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -35,14 +35,14 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun </*0*/ T : p.Tr?> foo(/*0*/ a: T): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait Tr {
+    public interface Tr {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -57,15 +57,15 @@ internal fun test(/*0*/ b: p.B?): kotlin.Unit
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m3> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         // -- Module: <m2> --
     }
 
-    public trait Tr {
+    public interface Tr {
         // -- Module: <m3> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/functionGenericsInParamsEqNull.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/functionGenericsInParamsEqNull.txt
index 34ccc58ae0e..59a3ccacbb9 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/functionGenericsInParamsEqNull.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/functionGenericsInParamsEqNull.txt
@@ -3,7 +3,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun </*0*/ T> foo(/*0*/ a: T): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -17,11 +17,11 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m1> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract override /*1*/ fun </*0*/ T> foo(/*0*/ a: T): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -35,7 +35,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun </*0*/ T> foo(/*0*/ a: T): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -54,11 +54,11 @@ internal fun test3(/*0*/ b: p.B?): kotlin.Unit
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m3> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         // -- Module: <m2> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/functionGenericsInParamsNotIs.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/functionGenericsInParamsNotIs.txt
index 45a3c403e1f..461b1d249a1 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/functionGenericsInParamsNotIs.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/functionGenericsInParamsNotIs.txt
@@ -3,7 +3,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun </*0*/ T> foo(/*0*/ a: T): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -17,11 +17,11 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m1> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract override /*1*/ fun </*0*/ T> foo(/*0*/ a: T): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -35,7 +35,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun </*0*/ T> foo(/*0*/ a: T): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -52,11 +52,11 @@ internal fun test1(/*0*/ b: p.B?): kotlin.Unit
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m3> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         // -- Module: <m2> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/functionGenericsInParamsReturnFooT.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/functionGenericsInParamsReturnFooT.txt
index 31e15e3d6ed..4e19e1abd3b 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/functionGenericsInParamsReturnFooT.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/functionGenericsInParamsReturnFooT.txt
@@ -3,14 +3,14 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun </*0*/ T> foo(/*0*/ a: T): p.Foo<T>
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait Foo</*0*/ T> {
+    public interface Foo</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -23,18 +23,18 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m1> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract override /*1*/ fun </*0*/ T> foo(/*0*/ a: T): p.Foo<T>
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait Foo</*0*/ T> {
+    public interface Foo</*0*/ T> {
         // -- Module: <m1> --
     }
 }
@@ -45,14 +45,14 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun </*0*/ T> foo(/*0*/ a: T): p.Foo<T>
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait Foo</*0*/ T> {
+    public interface Foo</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -68,15 +68,15 @@ internal fun test1(/*0*/ b: p.B?): kotlin.Unit
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m3> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         // -- Module: <m2> --
     }
 
-    public trait Foo</*0*/ T> {
+    public interface Foo</*0*/ T> {
         // -- Module: <m3> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/functionGenericsInParamsReturnT.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/functionGenericsInParamsReturnT.txt
index 31b587f6fd6..29da48b9c2e 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/functionGenericsInParamsReturnT.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/functionGenericsInParamsReturnT.txt
@@ -3,7 +3,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun </*0*/ T> foo(/*0*/ a: T): T
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -17,11 +17,11 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m1> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract override /*1*/ fun </*0*/ T> foo(/*0*/ a: T): T
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -35,7 +35,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun </*0*/ T> foo(/*0*/ a: T): T
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -52,11 +52,11 @@ internal fun test1(/*0*/ b: p.B?): kotlin.Unit
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m3> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         // -- Module: <m2> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/noGenericsInParams.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/noGenericsInParams.txt
index e7023ce34bc..21a70e06a01 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/noGenericsInParams.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/noGenericsInParams.txt
@@ -3,7 +3,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun foo(/*0*/ a: kotlin.Int, /*1*/ b: kotlin.String): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -17,11 +17,11 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m1> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract override /*1*/ fun foo(/*0*/ a: kotlin.Int, /*1*/ b: kotlin.String): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -35,7 +35,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun foo(/*0*/ a: kotlin.Int, /*1*/ b: kotlin.String): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -51,11 +51,11 @@ internal fun test(/*0*/ b: p.B?): kotlin.Unit
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m3> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         // -- Module: <m2> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/noParams.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/noParams.txt
index 2de87a81be5..e700eaaf5bf 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/noParams.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/noParams.txt
@@ -3,7 +3,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun getParent(): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -17,7 +17,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m1> --
     }
 
@@ -36,7 +36,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun getParent(): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -52,7 +52,7 @@ internal fun test(/*0*/ b: p.B?): kotlin.Unit
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m3> --
     }
 
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/sameGenericsInParams.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/sameGenericsInParams.txt
index 74a311e8212..3ca2ed1667d 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/sameGenericsInParams.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/sameGenericsInParams.txt
@@ -3,13 +3,13 @@ package
 
 package p {
 
-    public trait G1</*0*/ T> {
+    public interface G1</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait G2</*0*/ A, /*1*/ B> {
+    public interface G2</*0*/ A, /*1*/ B> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -22,18 +22,18 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun foo(/*0*/ a: p.G1<kotlin.Int>, /*1*/ b: p.G2<p.B, kotlin.String>): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait G1</*0*/ T> {
+    public interface G1</*0*/ T> {
         // -- Module: <m0> --
     }
 
-    public trait G2</*0*/ A, /*1*/ B> {
+    public interface G2</*0*/ A, /*1*/ B> {
         // -- Module: <m0> --
     }
 }
@@ -44,22 +44,22 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m1> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract override /*1*/ fun foo(/*0*/ a: p.G1<kotlin.Int>, /*1*/ b: p.G2<p.B, kotlin.String>): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait G1</*0*/ T> {
+    public interface G1</*0*/ T> {
         // -- Module: <m0> --
     }
 
-    public trait G2</*0*/ A, /*1*/ B> {
+    public interface G2</*0*/ A, /*1*/ B> {
         // -- Module: <m0> --
     }
 }
@@ -70,18 +70,18 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun foo(/*0*/ a: p.G1<kotlin.Int>, /*1*/ b: p.G2<p.B, kotlin.String>): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait G1</*0*/ T> {
+    public interface G1</*0*/ T> {
         // -- Module: <m0> --
     }
 
-    public trait G2</*0*/ A, /*1*/ B> {
+    public interface G2</*0*/ A, /*1*/ B> {
         // -- Module: <m0> --
     }
 }
@@ -94,19 +94,19 @@ internal fun test(/*0*/ b: p.B?, /*1*/ a: p.G1<kotlin.Int>, /*2*/ b1: p.G2<p.B,
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m3> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         // -- Module: <m2> --
     }
 
-    public trait G1</*0*/ T> {
+    public interface G1</*0*/ T> {
         // -- Module: <m0> --
     }
 
-    public trait G2</*0*/ A, /*1*/ B> {
+    public interface G2</*0*/ A, /*1*/ B> {
         // -- Module: <m0> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/simpleWithInheritance.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/simpleWithInheritance.txt
index 89ec91a183e..63a0a7cc709 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/simpleWithInheritance.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/simpleWithInheritance.txt
@@ -3,7 +3,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun getParent(): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -17,11 +17,11 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m1> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract override /*1*/ fun getParent(): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -35,14 +35,14 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun getParent(): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait D : p.B {
+    public interface D : p.B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract override /*1*/ fun getParent(): p.B?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -58,15 +58,15 @@ internal fun test(/*0*/ b: p.B?): kotlin.Unit
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m3> --
     }
 
-    public trait C : p.B {
+    public interface C : p.B {
         // -- Module: <m2> --
     }
 
-    public trait D : p.B {
+    public interface D : p.B {
         // -- Module: <m3> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/substitutedGenericInParams.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/substitutedGenericInParams.txt
index b011c7f6916..6665c4656a8 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/substitutedGenericInParams.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateMethod/substitutedGenericInParams.txt
@@ -3,7 +3,7 @@ package
 
 package p {
 
-    public trait B</*0*/ T> {
+    public interface B</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun foo(/*0*/ a: T): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -17,11 +17,11 @@ package
 
 package p {
 
-    public trait B</*0*/ T> {
+    public interface B</*0*/ T> {
         // -- Module: <m1> --
     }
 
-    public trait C : p.B<kotlin.String> {
+    public interface C : p.B<kotlin.String> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract override /*1*/ fun foo(/*0*/ a: kotlin.String): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -35,7 +35,7 @@ package
 
 package p {
 
-    public trait B {
+    public interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public abstract fun foo(/*0*/ a: kotlin.String): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -51,11 +51,11 @@ internal fun test(/*0*/ b: p.B?): kotlin.Unit
 
 package p {
 
-    public trait B {
+    public interface B {
         // -- Module: <m3> --
     }
 
-    public trait C : p.B<kotlin.String> {
+    public interface C : p.B<kotlin.String> {
         // -- Module: <m2> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateSuper/differentSuperTraits.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateSuper/differentSuperTraits.txt
index 66816a179e2..6df6b645a1e 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateSuper/differentSuperTraits.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateSuper/differentSuperTraits.txt
@@ -3,21 +3,21 @@ package
 
 package p {
 
-    public trait A : p.Base {
+    public interface A : p.Base {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait Base {
+    public interface Base {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait C : p.A {
+    public interface C : p.A {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -31,14 +31,14 @@ package
 
 package p {
 
-    public trait B : p.Base {
+    public interface B : p.Base {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait Base {
+    public interface Base {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -60,23 +60,23 @@ internal final class Foo : p.C, p.B {
 
 package p {
 
-    public trait A : p.Base {
+    public interface A : p.Base {
         // -- Module: <m1> --
     }
 
-    public trait B : p.Base {
+    public interface B : p.Base {
         // -- Module: <m2> --
     }
 
-    public trait Base {
+    public interface Base {
         // -- Module: <m1> --
     }
 
-    public trait Base {
+    public interface Base {
         // -- Module: <m2> --
     }
 
-    public trait C : p.A {
+    public interface C : p.A {
         // -- Module: <m1> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateSuper/sameSuperTrait.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateSuper/sameSuperTrait.txt
index ddba39619a8..8611e118c4b 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateSuper/sameSuperTrait.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateSuper/sameSuperTrait.txt
@@ -3,14 +3,14 @@ package
 
 package p {
 
-    public trait A : p.Base {
+    public interface A : p.Base {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait Base {
+    public interface Base {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -24,14 +24,14 @@ package
 
 package p {
 
-    public trait B : p.Base {
+    public interface B : p.Base {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait Base {
+    public interface Base {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -53,19 +53,19 @@ internal final class Foo : p.A, p.B {
 
 package p {
 
-    public trait A : p.Base {
+    public interface A : p.Base {
         // -- Module: <m1> --
     }
 
-    public trait B : p.Base {
+    public interface B : p.Base {
         // -- Module: <m2> --
     }
 
-    public trait Base {
+    public interface Base {
         // -- Module: <m1> --
     }
 
-    public trait Base {
+    public interface Base {
         // -- Module: <m2> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateSuper/sameSuperTraitDifferentBounds.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateSuper/sameSuperTraitDifferentBounds.txt
index 0240c7f2973..3f6c9b69aa1 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateSuper/sameSuperTraitDifferentBounds.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateSuper/sameSuperTraitDifferentBounds.txt
@@ -3,14 +3,14 @@ package
 
 package p {
 
-    public trait A : p.Base {
+    public interface A : p.Base {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun </*0*/ T> foo(/*0*/ t: kotlin.Array<T>): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait Base {
+    public interface Base {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open fun </*0*/ T> foo(/*0*/ t: kotlin.Array<T>): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -24,14 +24,14 @@ package
 
 package p {
 
-    public trait B : p.Base {
+    public interface B : p.Base {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun </*0*/ T : p.Base> foo(/*0*/ t: kotlin.Array<T>): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait Base {
+    public interface Base {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open fun </*0*/ T : p.Base> foo(/*0*/ t: kotlin.Array<T>): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -54,19 +54,19 @@ internal final class Foo : p.A, p.B {
 
 package p {
 
-    public trait A : p.Base {
+    public interface A : p.Base {
         // -- Module: <m1> --
     }
 
-    public trait B : p.Base {
+    public interface B : p.Base {
         // -- Module: <m2> --
     }
 
-    public trait Base {
+    public interface Base {
         // -- Module: <m1> --
     }
 
-    public trait Base {
+    public interface Base {
         // -- Module: <m2> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/multimodule/duplicateSuper/sameSuperTraitGenerics.txt b/compiler/testData/diagnostics/tests/multimodule/duplicateSuper/sameSuperTraitGenerics.txt
index 6bcc44c4d91..ab7164be4f5 100644
--- a/compiler/testData/diagnostics/tests/multimodule/duplicateSuper/sameSuperTraitGenerics.txt
+++ b/compiler/testData/diagnostics/tests/multimodule/duplicateSuper/sameSuperTraitGenerics.txt
@@ -3,14 +3,14 @@ package
 
 package p {
 
-    public trait A</*0*/ T> : p.Base<T> {
+    public interface A</*0*/ T> : p.Base<T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun foo(/*0*/ t: T): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait Base</*0*/ T> {
+    public interface Base</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open fun foo(/*0*/ t: T): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -24,14 +24,14 @@ package
 
 package p {
 
-    public trait B : p.Base<kotlin.String> {
+    public interface B : p.Base<kotlin.String> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun foo(/*0*/ t: kotlin.String): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    public trait Base</*0*/ T> {
+    public interface Base</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open fun foo(/*0*/ t: T): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -53,19 +53,19 @@ internal final class Foo : p.A<kotlin.String>, p.B {
 
 package p {
 
-    public trait A</*0*/ T> : p.Base<T> {
+    public interface A</*0*/ T> : p.Base<T> {
         // -- Module: <m1> --
     }
 
-    public trait B : p.Base<kotlin.String> {
+    public interface B : p.Base<kotlin.String> {
         // -- Module: <m2> --
     }
 
-    public trait Base</*0*/ T> {
+    public interface Base</*0*/ T> {
         // -- Module: <m1> --
     }
 
-    public trait Base</*0*/ T> {
+    public interface Base</*0*/ T> {
         // -- Module: <m2> --
     }
 }
diff --git a/compiler/testData/diagnostics/tests/nullableTypes/redundantNullableInSupertype.txt b/compiler/testData/diagnostics/tests/nullableTypes/redundantNullableInSupertype.txt
index 553d0ba53e3..eb5c3303b0b 100644
--- a/compiler/testData/diagnostics/tests/nullableTypes/redundantNullableInSupertype.txt
+++ b/compiler/testData/diagnostics/tests/nullableTypes/redundantNullableInSupertype.txt
@@ -2,13 +2,13 @@ package
 
 internal fun </*0*/ T> interaction(/*0*/ t: T): kotlin.Unit
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait X : A? {
+internal interface X : A? {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/numbers/numbersInSimpleConstraints.txt b/compiler/testData/diagnostics/tests/numbers/numbersInSimpleConstraints.txt
index aede32f04e4..0352ceda8f1 100644
--- a/compiler/testData/diagnostics/tests/numbers/numbersInSimpleConstraints.txt
+++ b/compiler/testData/diagnostics/tests/numbers/numbersInSimpleConstraints.txt
@@ -14,19 +14,19 @@ package a {
     internal fun </*0*/ T> upperBound(/*0*/ t: T, /*1*/ l: a.Contr<T>): T
     internal fun use(/*0*/ vararg a: kotlin.Any? /*kotlin.Array<out kotlin.Any?>*/): kotlin.Array<out kotlin.Any?>
 
-    internal trait Contr</*0*/ in T> {
+    internal interface Contr</*0*/ in T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait Cov</*0*/ out T> {
+    internal interface Cov</*0*/ out T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait Inv</*0*/ T> {
+    internal interface Inv</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/objects/objectLiteralExpressionTypeMismatch.txt b/compiler/testData/diagnostics/tests/objects/objectLiteralExpressionTypeMismatch.txt
index 4d4a5e8df76..3877e658067 100644
--- a/compiler/testData/diagnostics/tests/objects/objectLiteralExpressionTypeMismatch.txt
+++ b/compiler/testData/diagnostics/tests/objects/objectLiteralExpressionTypeMismatch.txt
@@ -3,13 +3,13 @@ package
 internal fun test1(): B
 internal fun test2(): B
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B {
+internal interface B {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/objects/upperBoundViolated.txt b/compiler/testData/diagnostics/tests/objects/upperBoundViolated.txt
index f49c77fc807..73fbc66bd2f 100644
--- a/compiler/testData/diagnostics/tests/objects/upperBoundViolated.txt
+++ b/compiler/testData/diagnostics/tests/objects/upperBoundViolated.txt
@@ -28,7 +28,7 @@ internal object O2 : Trait<kotlin.String> {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Trait</*0*/ N : kotlin.Number> {
+internal interface Trait</*0*/ N : kotlin.Number> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/operatorsOverloading/IteratorAmbiguity.txt b/compiler/testData/diagnostics/tests/operatorsOverloading/IteratorAmbiguity.txt
index 9488b2d1288..db1990a580c 100644
--- a/compiler/testData/diagnostics/tests/operatorsOverloading/IteratorAmbiguity.txt
+++ b/compiler/testData/diagnostics/tests/operatorsOverloading/IteratorAmbiguity.txt
@@ -4,7 +4,7 @@ internal fun test1(/*0*/ collection: MyCollection): kotlin.Unit
 internal fun MyAnotherCollectionInterface.iterator(): MyIterator
 internal fun MyCollectionInterface.iterator(): MyIterator
 
-internal trait MyAnotherCollectionInterface {
+internal interface MyAnotherCollectionInterface {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -17,7 +17,7 @@ internal final class MyCollection : MyCollectionInterface, MyAnotherCollectionIn
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait MyCollectionInterface {
+internal interface MyCollectionInterface {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/overload/kt2493.txt b/compiler/testData/diagnostics/tests/overload/kt2493.txt
index 35eb7886c1c..a4e11e7fad6 100644
--- a/compiler/testData/diagnostics/tests/overload/kt2493.txt
+++ b/compiler/testData/diagnostics/tests/overload/kt2493.txt
@@ -4,7 +4,7 @@ internal fun main(/*0*/ args: kotlin.Array<kotlin.String>): kotlin.Unit
 internal fun </*0*/ R : A> R.f(): kotlin.Unit
 internal fun </*0*/ R : B> R.f(): kotlin.Unit
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -17,7 +17,7 @@ internal final class AImpl : A {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B {
+internal interface B {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/override/AllPrivateFromSuperTypes.txt b/compiler/testData/diagnostics/tests/override/AllPrivateFromSuperTypes.txt
index 0a95adc970c..071447f6106 100644
--- a/compiler/testData/diagnostics/tests/override/AllPrivateFromSuperTypes.txt
+++ b/compiler/testData/diagnostics/tests/override/AllPrivateFromSuperTypes.txt
@@ -2,7 +2,7 @@ package
 
 package test {
 
-    internal trait A {
+    internal interface A {
         private final val a: kotlin.String
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/AllProtectedFromSupertypes.txt b/compiler/testData/diagnostics/tests/override/AllProtectedFromSupertypes.txt
index 21c76d025fa..38fe4760840 100644
--- a/compiler/testData/diagnostics/tests/override/AllProtectedFromSupertypes.txt
+++ b/compiler/testData/diagnostics/tests/override/AllProtectedFromSupertypes.txt
@@ -2,7 +2,7 @@ package
 
 package test {
 
-    internal trait A {
+    internal interface A {
         protected abstract val a: kotlin.String
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/CannotInferVisibilityForProperty.txt b/compiler/testData/diagnostics/tests/override/CannotInferVisibilityForProperty.txt
index 116a25957a5..646502b2187 100644
--- a/compiler/testData/diagnostics/tests/override/CannotInferVisibilityForProperty.txt
+++ b/compiler/testData/diagnostics/tests/override/CannotInferVisibilityForProperty.txt
@@ -1,27 +1,27 @@
 package
 
-internal trait T {
+internal interface T {
     internal abstract var foo: kotlin.Long
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait U {
+internal interface U {
     protected abstract var foo: kotlin.Long
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait V : T, U {
+internal interface V : T, U {
     public abstract override /*2*/ var foo: kotlin.Long
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait W : T, U {
+internal interface W : T, U {
     public abstract override /*2*/ /*fake_override*/ var foo: kotlin.Long
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/CannotInferVisibilityForPropertySetter.txt b/compiler/testData/diagnostics/tests/override/CannotInferVisibilityForPropertySetter.txt
index a12e793ca58..1426386be24 100644
--- a/compiler/testData/diagnostics/tests/override/CannotInferVisibilityForPropertySetter.txt
+++ b/compiler/testData/diagnostics/tests/override/CannotInferVisibilityForPropertySetter.txt
@@ -1,20 +1,20 @@
 package
 
-internal trait T {
+internal interface T {
     public abstract var foo: kotlin.Short
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait U {
+internal interface U {
     public abstract var foo: kotlin.Short
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait V : T, U {
+internal interface V : T, U {
     public abstract override /*2*/ var foo: kotlin.Short
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/DefaultParameterValues-NoErrorsWhenInheritingFromOneTypeTwice.txt b/compiler/testData/diagnostics/tests/override/DefaultParameterValues-NoErrorsWhenInheritingFromOneTypeTwice.txt
index 5ea5f6297bd..e13d41228f3 100644
--- a/compiler/testData/diagnostics/tests/override/DefaultParameterValues-NoErrorsWhenInheritingFromOneTypeTwice.txt
+++ b/compiler/testData/diagnostics/tests/override/DefaultParameterValues-NoErrorsWhenInheritingFromOneTypeTwice.txt
@@ -1,13 +1,13 @@
 package
 
-internal trait Y {
+internal interface Y {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(/*0*/ a: kotlin.Int = ...): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait YSub : Y {
+internal interface YSub : Y {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ a: kotlin.Int = ...): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/Delegation.txt b/compiler/testData/diagnostics/tests/override/Delegation.txt
index 44fc8284ebb..6baf5892737 100644
--- a/compiler/testData/diagnostics/tests/override/Delegation.txt
+++ b/compiler/testData/diagnostics/tests/override/Delegation.txt
@@ -2,7 +2,7 @@ package
 
 package test {
 
-    internal trait Incompatible {
+    internal interface Incompatible {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal open fun foo(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -55,14 +55,14 @@ package test {
         public open override /*3*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait X {
+    internal interface X {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal open fun foo(): kotlin.String?
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait Y {
+    internal interface Y {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal open fun foo(): kotlin.String
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/DelegationFun.txt b/compiler/testData/diagnostics/tests/override/DelegationFun.txt
index 3837ec8cc80..e95e4397183 100644
--- a/compiler/testData/diagnostics/tests/override/DelegationFun.txt
+++ b/compiler/testData/diagnostics/tests/override/DelegationFun.txt
@@ -2,7 +2,7 @@ package
 
 package delegation {
 
-    internal trait Aaa {
+    internal interface Aaa {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal abstract fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/DelegationVal.txt b/compiler/testData/diagnostics/tests/override/DelegationVal.txt
index de12fa9fabe..19082dc5d7f 100644
--- a/compiler/testData/diagnostics/tests/override/DelegationVal.txt
+++ b/compiler/testData/diagnostics/tests/override/DelegationVal.txt
@@ -2,7 +2,7 @@ package
 
 package delegation {
 
-    internal trait Aaa {
+    internal interface Aaa {
         internal abstract val i: kotlin.Int
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/DelegationVar.txt b/compiler/testData/diagnostics/tests/override/DelegationVar.txt
index 43fb5bd208a..cc0a503e54a 100644
--- a/compiler/testData/diagnostics/tests/override/DelegationVar.txt
+++ b/compiler/testData/diagnostics/tests/override/DelegationVar.txt
@@ -2,7 +2,7 @@ package
 
 package delegation {
 
-    internal trait Aaa {
+    internal interface Aaa {
         internal abstract var i: kotlin.Int
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/DuplicateMethod.txt b/compiler/testData/diagnostics/tests/override/DuplicateMethod.txt
index 8ca1ae2b4b7..41b60e14cb3 100644
--- a/compiler/testData/diagnostics/tests/override/DuplicateMethod.txt
+++ b/compiler/testData/diagnostics/tests/override/DuplicateMethod.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait Some {
+internal interface Some {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     internal abstract fun test(): kotlin.Unit
diff --git a/compiler/testData/diagnostics/tests/override/EqualityOfIntersectionTypes.txt b/compiler/testData/diagnostics/tests/override/EqualityOfIntersectionTypes.txt
index c4319470367..cebe2e5a8f4 100644
--- a/compiler/testData/diagnostics/tests/override/EqualityOfIntersectionTypes.txt
+++ b/compiler/testData/diagnostics/tests/override/EqualityOfIntersectionTypes.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun </*0*/ T : Foo> foo(): kotlin.Unit where T : Bar
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -15,13 +15,13 @@ internal final class B : A {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Bar {
+internal interface Bar {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Foo {
+internal interface Foo {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/override/FakeOverrideAbstractAndNonAbstractFun.txt b/compiler/testData/diagnostics/tests/override/FakeOverrideAbstractAndNonAbstractFun.txt
index fe0e73ec0f9..bfe6ec51b6f 100644
--- a/compiler/testData/diagnostics/tests/override/FakeOverrideAbstractAndNonAbstractFun.txt
+++ b/compiler/testData/diagnostics/tests/override/FakeOverrideAbstractAndNonAbstractFun.txt
@@ -8,7 +8,7 @@ internal open class Ccc {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Ttt {
+internal interface Ttt {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/FakeOverrideDifferentDeclarationSignatures.txt b/compiler/testData/diagnostics/tests/override/FakeOverrideDifferentDeclarationSignatures.txt
index 55b585e8fd0..34d511200ad 100644
--- a/compiler/testData/diagnostics/tests/override/FakeOverrideDifferentDeclarationSignatures.txt
+++ b/compiler/testData/diagnostics/tests/override/FakeOverrideDifferentDeclarationSignatures.txt
@@ -2,7 +2,7 @@ package
 
 internal val obj: A
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun f(): kotlin.String
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/Generics.txt b/compiler/testData/diagnostics/tests/override/Generics.txt
index 8dc3eee6b1e..81971d8f56d 100644
--- a/compiler/testData/diagnostics/tests/override/Generics.txt
+++ b/compiler/testData/diagnostics/tests/override/Generics.txt
@@ -142,14 +142,14 @@ package override {
             public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
         }
 
-        internal trait MyProps</*0*/ T> {
+        internal interface MyProps</*0*/ T> {
             internal abstract val p: T
             public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
             public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
             public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
         }
 
-        internal trait MyTrait</*0*/ T> {
+        internal interface MyTrait</*0*/ T> {
             public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
             internal abstract fun foo(/*0*/ t: T): T
             public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/MultipleDefaultParametersInSupertypes.txt b/compiler/testData/diagnostics/tests/override/MultipleDefaultParametersInSupertypes.txt
index 4603e02d47c..531acc7768c 100644
--- a/compiler/testData/diagnostics/tests/override/MultipleDefaultParametersInSupertypes.txt
+++ b/compiler/testData/diagnostics/tests/override/MultipleDefaultParametersInSupertypes.txt
@@ -1,13 +1,13 @@
 package
 
-internal trait X {
+internal interface X {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(/*0*/ a: kotlin.Int = ...): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Y {
+internal interface Y {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(/*0*/ a: kotlin.Int = ...): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/MultipleDefaultParametersInSupertypesNoOverride.txt b/compiler/testData/diagnostics/tests/override/MultipleDefaultParametersInSupertypesNoOverride.txt
index 30fc6cf9e67..baf19f1076b 100644
--- a/compiler/testData/diagnostics/tests/override/MultipleDefaultParametersInSupertypesNoOverride.txt
+++ b/compiler/testData/diagnostics/tests/override/MultipleDefaultParametersInSupertypesNoOverride.txt
@@ -1,13 +1,13 @@
 package
 
-internal trait X {
+internal interface X {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(/*0*/ a: kotlin.Int = ...): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Y {
+internal interface Y {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(/*0*/ a: kotlin.Int = ...): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/MultipleDefaultsAndNamesInSupertypes.txt b/compiler/testData/diagnostics/tests/override/MultipleDefaultsAndNamesInSupertypes.txt
index d566e83348a..69f6f5dad12 100644
--- a/compiler/testData/diagnostics/tests/override/MultipleDefaultsAndNamesInSupertypes.txt
+++ b/compiler/testData/diagnostics/tests/override/MultipleDefaultsAndNamesInSupertypes.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(/*0*/ x: kotlin.Int = ...): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -15,7 +15,7 @@ internal open class B {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait C {
+internal interface C {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(/*0*/ y: kotlin.Int): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/MultipleDefaultsInSupertypesNoExplicitOverride.txt b/compiler/testData/diagnostics/tests/override/MultipleDefaultsInSupertypesNoExplicitOverride.txt
index 49367341768..12e044c04d7 100644
--- a/compiler/testData/diagnostics/tests/override/MultipleDefaultsInSupertypesNoExplicitOverride.txt
+++ b/compiler/testData/diagnostics/tests/override/MultipleDefaultsInSupertypesNoExplicitOverride.txt
@@ -1,13 +1,13 @@
 package
 
-internal trait X {
+internal interface X {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(/*0*/ a: kotlin.Int = ...): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Y {
+internal interface Y {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(/*0*/ a: kotlin.Int = ...): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/NonGenerics.txt b/compiler/testData/diagnostics/tests/override/NonGenerics.txt
index 6b0e70ab7d1..ab6dc9451f5 100644
--- a/compiler/testData/diagnostics/tests/override/NonGenerics.txt
+++ b/compiler/testData/diagnostics/tests/override/NonGenerics.txt
@@ -92,7 +92,7 @@ package override {
             public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
         }
 
-        internal trait MyTrait {
+        internal interface MyTrait {
             internal abstract val pr: kotlin.Unit
             public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
             internal abstract fun foo(): kotlin.Unit
diff --git a/compiler/testData/diagnostics/tests/override/ObjectDelegationManyImpl.txt b/compiler/testData/diagnostics/tests/override/ObjectDelegationManyImpl.txt
index c79f211718e..5f82d0e18b2 100644
--- a/compiler/testData/diagnostics/tests/override/ObjectDelegationManyImpl.txt
+++ b/compiler/testData/diagnostics/tests/override/ObjectDelegationManyImpl.txt
@@ -2,14 +2,14 @@ package
 
 internal val obj: D
 
-internal trait D {
+internal interface D {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait E {
+internal interface E {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/ParameterDefaultValues-DefaultValueFromOnlyOneSupertype.txt b/compiler/testData/diagnostics/tests/override/ParameterDefaultValues-DefaultValueFromOnlyOneSupertype.txt
index 48c18f0d9d9..64b328e7b16 100644
--- a/compiler/testData/diagnostics/tests/override/ParameterDefaultValues-DefaultValueFromOnlyOneSupertype.txt
+++ b/compiler/testData/diagnostics/tests/override/ParameterDefaultValues-DefaultValueFromOnlyOneSupertype.txt
@@ -1,13 +1,13 @@
 package
 
-internal trait X {
+internal interface X {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(/*0*/ a: kotlin.Int = ...): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Y {
+internal interface Y {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(/*0*/ a: kotlin.Int): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/ParentInheritsManyImplementations.txt b/compiler/testData/diagnostics/tests/override/ParentInheritsManyImplementations.txt
index 5b4c11ca279..c9788a3c1dd 100644
--- a/compiler/testData/diagnostics/tests/override/ParentInheritsManyImplementations.txt
+++ b/compiler/testData/diagnostics/tests/override/ParentInheritsManyImplementations.txt
@@ -2,14 +2,14 @@ package
 
 package d {
 
-    internal trait A {
+    internal interface A {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal open fun foo(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait B {
+    internal interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal open fun foo(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -32,7 +32,7 @@ package d {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait E {
+    internal interface E {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal abstract fun foo(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/ProtectedAndPrivateFromSupertypes.txt b/compiler/testData/diagnostics/tests/override/ProtectedAndPrivateFromSupertypes.txt
index c383e4eb2d0..5014c6a087f 100644
--- a/compiler/testData/diagnostics/tests/override/ProtectedAndPrivateFromSupertypes.txt
+++ b/compiler/testData/diagnostics/tests/override/ProtectedAndPrivateFromSupertypes.txt
@@ -2,14 +2,14 @@ package
 
 package test {
 
-    internal trait A {
+    internal interface A {
         protected abstract val a: kotlin.String
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait B {
+    internal interface B {
         protected abstract val a: kotlin.String
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/SuspiciousCase1.txt b/compiler/testData/diagnostics/tests/override/SuspiciousCase1.txt
index 5db97b226c3..749a590680b 100644
--- a/compiler/testData/diagnostics/tests/override/SuspiciousCase1.txt
+++ b/compiler/testData/diagnostics/tests/override/SuspiciousCase1.txt
@@ -2,7 +2,7 @@ package
 
 internal fun zz(/*0*/ b: Baz): kotlin.Int
 
-internal trait Bar</*0*/ Q> : Foo<Q> {
+internal interface Bar</*0*/ Q> : Foo<Q> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     internal open override /*1*/ /*fake_override*/ fun quux(/*0*/ p: Q, /*1*/ q: kotlin.Int = ...): kotlin.Int
@@ -17,7 +17,7 @@ internal abstract class Baz : Bar<kotlin.String> {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Foo</*0*/ P> {
+internal interface Foo</*0*/ P> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     internal open fun quux(/*0*/ p: P, /*1*/ q: kotlin.Int = ...): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/ToAbstractMembersFromSuper-kt1996.txt b/compiler/testData/diagnostics/tests/override/ToAbstractMembersFromSuper-kt1996.txt
index dc959dcb8d1..ee03faec4e9 100644
--- a/compiler/testData/diagnostics/tests/override/ToAbstractMembersFromSuper-kt1996.txt
+++ b/compiler/testData/diagnostics/tests/override/ToAbstractMembersFromSuper-kt1996.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait Bar {
+internal interface Bar {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -15,7 +15,7 @@ internal final class Baz : Foo, Bar {
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Foo {
+internal interface Foo {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/kt1862.txt b/compiler/testData/diagnostics/tests/override/kt1862.txt
index 3d6c7ffa6a9..ddfc35ef365 100644
--- a/compiler/testData/diagnostics/tests/override/kt1862.txt
+++ b/compiler/testData/diagnostics/tests/override/kt1862.txt
@@ -16,7 +16,7 @@ internal open class Bbb : Aaa {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Ccc : Aaa {
+internal interface Ccc : Aaa {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open override /*1*/ /*fake_override*/ fun foo(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/kt2052.txt b/compiler/testData/diagnostics/tests/override/kt2052.txt
index c8db3864bb9..77f958503cf 100644
--- a/compiler/testData/diagnostics/tests/override/kt2052.txt
+++ b/compiler/testData/diagnostics/tests/override/kt2052.txt
@@ -8,7 +8,7 @@ internal final class C {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Runnable {
+internal interface Runnable {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     internal abstract fun run(): kotlin.Unit
diff --git a/compiler/testData/diagnostics/tests/override/kt2491.txt b/compiler/testData/diagnostics/tests/override/kt2491.txt
index d66d29a8684..2793789cd6e 100644
--- a/compiler/testData/diagnostics/tests/override/kt2491.txt
+++ b/compiler/testData/diagnostics/tests/override/kt2491.txt
@@ -18,7 +18,7 @@ internal final class D : C, T {
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T {
+internal interface T {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public abstract fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/kt4763.txt b/compiler/testData/diagnostics/tests/override/kt4763.txt
index ce654ecd345..0f40be7774b 100644
--- a/compiler/testData/diagnostics/tests/override/kt4763.txt
+++ b/compiler/testData/diagnostics/tests/override/kt4763.txt
@@ -2,7 +2,7 @@ package
 
 internal val d: A
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun f(): kotlin.String
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/kt4763property.txt b/compiler/testData/diagnostics/tests/override/kt4763property.txt
index 36b8d93f2f4..33d57445f97 100644
--- a/compiler/testData/diagnostics/tests/override/kt4763property.txt
+++ b/compiler/testData/diagnostics/tests/override/kt4763property.txt
@@ -2,7 +2,7 @@ package
 
 internal val s: Q
 
-internal trait P {
+internal interface P {
     internal abstract var f: kotlin.Number
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/kt4785.txt b/compiler/testData/diagnostics/tests/override/kt4785.txt
index 671e239477a..0dac6a11855 100644
--- a/compiler/testData/diagnostics/tests/override/kt4785.txt
+++ b/compiler/testData/diagnostics/tests/override/kt4785.txt
@@ -18,7 +18,7 @@ internal final class E : C, T {
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T {
+internal interface T {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/kt4785classObject.txt b/compiler/testData/diagnostics/tests/override/kt4785classObject.txt
index d5d884b91da..f5866ccb276 100644
--- a/compiler/testData/diagnostics/tests/override/kt4785classObject.txt
+++ b/compiler/testData/diagnostics/tests/override/kt4785classObject.txt
@@ -1,13 +1,13 @@
 package
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B {
+internal interface B {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     protected open fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/kt4785delegation.txt b/compiler/testData/diagnostics/tests/override/kt4785delegation.txt
index 721028e5c6d..69456fcfed9 100644
--- a/compiler/testData/diagnostics/tests/override/kt4785delegation.txt
+++ b/compiler/testData/diagnostics/tests/override/kt4785delegation.txt
@@ -1,13 +1,13 @@
 package
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B {
+internal interface B {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     protected abstract fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/kt880.txt b/compiler/testData/diagnostics/tests/override/kt880.txt
index 8b3bcd3fb6f..3c70fef5ef5 100644
--- a/compiler/testData/diagnostics/tests/override/kt880.txt
+++ b/compiler/testData/diagnostics/tests/override/kt880.txt
@@ -8,7 +8,7 @@ public abstract class A {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-public trait I {
+public interface I {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     internal abstract fun test(): kotlin.Unit
diff --git a/compiler/testData/diagnostics/tests/override/parameterNames/changeOnOverrideDiagnostic.txt b/compiler/testData/diagnostics/tests/override/parameterNames/changeOnOverrideDiagnostic.txt
index f857c9b57f8..fc46441c6f0 100644
--- a/compiler/testData/diagnostics/tests/override/parameterNames/changeOnOverrideDiagnostic.txt
+++ b/compiler/testData/diagnostics/tests/override/parameterNames/changeOnOverrideDiagnostic.txt
@@ -1,13 +1,13 @@
 package
 
-internal trait A {
+internal interface A {
     internal abstract fun b(/*0*/ a: kotlin.Int): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B : A {
+internal interface B : A {
     internal abstract override /*1*/ /*fake_override*/ fun b(/*0*/ a: kotlin.Int): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/parameterNames/differentNamesInSupertypesDiagnostic.txt b/compiler/testData/diagnostics/tests/override/parameterNames/differentNamesInSupertypesDiagnostic.txt
index 208b29e6b35..c983a02fdd6 100644
--- a/compiler/testData/diagnostics/tests/override/parameterNames/differentNamesInSupertypesDiagnostic.txt
+++ b/compiler/testData/diagnostics/tests/override/parameterNames/differentNamesInSupertypesDiagnostic.txt
@@ -1,27 +1,27 @@
 package
 
-internal trait C {
+internal interface C {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(/*0*/ a: kotlin.Int): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait D {
+internal interface D {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(/*0*/ b: kotlin.Int): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait E : C, D {
+internal interface E : C, D {
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract override /*2*/ /*fake_override*/ fun foo(/*0*/ b: kotlin.Int): kotlin.Unit
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait F : C, D {
+internal interface F : C, D {
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open override /*2*/ fun foo(/*0*/ a: kotlin.Int): kotlin.Unit
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/parameterNames/jjkHierarchy.txt b/compiler/testData/diagnostics/tests/override/parameterNames/jjkHierarchy.txt
index 14db2a1df32..4e25b36f786 100644
--- a/compiler/testData/diagnostics/tests/override/parameterNames/jjkHierarchy.txt
+++ b/compiler/testData/diagnostics/tests/override/parameterNames/jjkHierarchy.txt
@@ -3,7 +3,7 @@ package
 public/*package*/ /*synthesized*/ fun Sub(/*0*/ function: (kotlin.Long) -> kotlin.Unit): Sub
 public/*package*/ /*synthesized*/ fun Super(/*0*/ function: (kotlin.Long) -> kotlin.Unit): Super
 
-public/*package*/ trait Sub : Super {
+public/*package*/ interface Sub : Super {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ superName: kotlin.Long): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -18,7 +18,7 @@ internal final class SubSub : Sub {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-public/*package*/ trait Super {
+public/*package*/ interface Super {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public abstract fun foo(/*0*/ superName: kotlin.Long): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/parameterNames/kjkHierarchy.txt b/compiler/testData/diagnostics/tests/override/parameterNames/kjkHierarchy.txt
index a0853a220d5..0cfa45d634b 100644
--- a/compiler/testData/diagnostics/tests/override/parameterNames/kjkHierarchy.txt
+++ b/compiler/testData/diagnostics/tests/override/parameterNames/kjkHierarchy.txt
@@ -2,7 +2,7 @@ package
 
 public/*package*/ /*synthesized*/ fun Sub(/*0*/ function: (kotlin.Int) -> kotlin.Unit): Sub
 
-public/*package*/ trait Sub : Super {
+public/*package*/ interface Sub : Super {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ superName: kotlin.Int): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -17,7 +17,7 @@ internal final class SubSub : Sub {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Super {
+internal interface Super {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(/*0*/ superName: kotlin.Int): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/parameterNames/kjkWithSeveralSupers.txt b/compiler/testData/diagnostics/tests/override/parameterNames/kjkWithSeveralSupers.txt
index a31460fdf02..5df89ae3305 100644
--- a/compiler/testData/diagnostics/tests/override/parameterNames/kjkWithSeveralSupers.txt
+++ b/compiler/testData/diagnostics/tests/override/parameterNames/kjkWithSeveralSupers.txt
@@ -6,42 +6,42 @@ public/*package*/ /*synthesized*/ fun Sub1(/*0*/ function: (kotlin.Int) -> kotli
 public/*package*/ /*synthesized*/ fun Sub2(/*0*/ function: (kotlin.Int) -> kotlin.Unit): Sub2
 public/*package*/ /*synthesized*/ fun Sub3(/*0*/ function: (kotlin.Int) -> kotlin.Unit): Sub3
 
-public/*package*/ trait JSuper1 {
+public/*package*/ interface JSuper1 {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public abstract fun foo(/*0*/ jsuper1Name: kotlin.Int): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-public/*package*/ trait JSuper2 {
+public/*package*/ interface JSuper2 {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public abstract fun foo(/*0*/ jsuper2Name: kotlin.Int): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait KSuper {
+internal interface KSuper {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(/*0*/ ksuperName: kotlin.Int): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-public/*package*/ trait Sub1 : KSuper, JSuper1, JSuper2 {
+public/*package*/ interface Sub1 : KSuper, JSuper1, JSuper2 {
     public open override /*3*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     java.lang.Override() public abstract override /*3*/ fun foo(/*0*/ ksuperName: kotlin.Int): kotlin.Unit
     public open override /*3*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*3*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-public/*package*/ trait Sub2 : JSuper1, KSuper, JSuper2 {
+public/*package*/ interface Sub2 : JSuper1, KSuper, JSuper2 {
     public open override /*3*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     java.lang.Override() public abstract override /*3*/ fun foo(/*0*/ ksuperName: kotlin.Int): kotlin.Unit
     public open override /*3*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*3*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-public/*package*/ trait Sub3 : JSuper1, JSuper2, KSuper {
+public/*package*/ interface Sub3 : JSuper1, JSuper2, KSuper {
     public open override /*3*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     java.lang.Override() public abstract override /*3*/ fun foo(/*0*/ ksuperName: kotlin.Int): kotlin.Unit
     public open override /*3*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/parameterNames/kotlinInheritsBothJavaAndKotlin.txt b/compiler/testData/diagnostics/tests/override/parameterNames/kotlinInheritsBothJavaAndKotlin.txt
index 93f10a2051e..41cea987f50 100644
--- a/compiler/testData/diagnostics/tests/override/parameterNames/kotlinInheritsBothJavaAndKotlin.txt
+++ b/compiler/testData/diagnostics/tests/override/parameterNames/kotlinInheritsBothJavaAndKotlin.txt
@@ -10,14 +10,14 @@ internal final class BothTraitsSubclass : JavaInterface, KotlinTrait {
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-public/*package*/ trait JavaInterface {
+public/*package*/ interface JavaInterface {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public abstract fun foo(/*0*/ javaName: kotlin.Int): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait KotlinTrait {
+internal interface KotlinTrait {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open fun foo(/*0*/ someOtherName: kotlin.Int): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/override/parameterNames/kotlinInheritsJava.txt b/compiler/testData/diagnostics/tests/override/parameterNames/kotlinInheritsJava.txt
index af8f4f7a731..5871585d550 100644
--- a/compiler/testData/diagnostics/tests/override/parameterNames/kotlinInheritsJava.txt
+++ b/compiler/testData/diagnostics/tests/override/parameterNames/kotlinInheritsJava.txt
@@ -2,7 +2,7 @@ package
 
 public/*package*/ /*synthesized*/ fun JavaInterface(/*0*/ function: (kotlin.Int) -> kotlin.Unit): JavaInterface
 
-public/*package*/ trait JavaInterface {
+public/*package*/ interface JavaInterface {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public abstract fun foo(/*0*/ javaName: kotlin.Int): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -25,7 +25,7 @@ internal final class Subclass : SubtraitWithFakeOverride {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait SubtraitWithFakeOverride : JavaInterface {
+internal interface SubtraitWithFakeOverride : JavaInterface {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ javaName: kotlin.Int): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/platformTypes/commonSupertype/withNothing.txt b/compiler/testData/diagnostics/tests/platformTypes/commonSupertype/withNothing.txt
index b617cd7b052..d09c0e16f55 100644
--- a/compiler/testData/diagnostics/tests/platformTypes/commonSupertype/withNothing.txt
+++ b/compiler/testData/diagnostics/tests/platformTypes/commonSupertype/withNothing.txt
@@ -4,7 +4,7 @@ internal fun </*0*/ T> f(/*0*/ a: Out<T>, /*1*/ b: Out<T>, /*2*/ c: Out<T>): T
 internal fun </*0*/ T> out(/*0*/ t: T): Out<kotlin.MutableList<T>>
 internal fun test(/*0*/ a: Out<kotlin.Nothing>, /*1*/ b: Out<kotlin.MutableList<p.J>>): kotlin.Unit
 
-internal trait Out</*0*/ out T1> {
+internal interface Out</*0*/ out T1> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/platformTypes/methodCall/multipleExactBounds.txt b/compiler/testData/diagnostics/tests/platformTypes/methodCall/multipleExactBounds.txt
index ed46359e7ee..50adfb5c153 100644
--- a/compiler/testData/diagnostics/tests/platformTypes/methodCall/multipleExactBounds.txt
+++ b/compiler/testData/diagnostics/tests/platformTypes/methodCall/multipleExactBounds.txt
@@ -2,25 +2,25 @@ package
 
 internal fun </*0*/ M2 : ModuleInfo, /*1*/ A : ResolverForModule> foo(/*0*/ delegateResolver: ResolverForProject<M2, A>): ResolverForProject<M2, A>
 
-internal trait ModuleDescriptorImpl {
+internal interface ModuleDescriptorImpl {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait ModuleInfo {
+internal interface ModuleInfo {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait ResolverForModule {
+internal interface ResolverForModule {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait ResolverForProject</*0*/ M1, /*1*/ R1> {
+internal interface ResolverForProject</*0*/ M1, /*1*/ R1> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/platformTypes/methodCall/multipleExactBoundsNullable.txt b/compiler/testData/diagnostics/tests/platformTypes/methodCall/multipleExactBoundsNullable.txt
index 9fee42620c3..dbc14f5d9b7 100644
--- a/compiler/testData/diagnostics/tests/platformTypes/methodCall/multipleExactBoundsNullable.txt
+++ b/compiler/testData/diagnostics/tests/platformTypes/methodCall/multipleExactBoundsNullable.txt
@@ -2,7 +2,7 @@ package
 
 internal fun </*0*/ M2 : WithFoo> foo(/*0*/ delegateResolver: ResolverForProject<M2?>): ResolverForProject<M2>
 
-internal trait ResolverForProject</*0*/ M1> {
+internal interface ResolverForProject</*0*/ M1> {
     internal open val exposeM: M1
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -17,7 +17,7 @@ internal final class ResolverForProjectImpl</*0*/ M> : ResolverForProject<M> {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait WithFoo {
+internal interface WithFoo {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/platformTypes/methodCall/singleton.txt b/compiler/testData/diagnostics/tests/platformTypes/methodCall/singleton.txt
index c5b95a4c6e2..d218819d107 100644
--- a/compiler/testData/diagnostics/tests/platformTypes/methodCall/singleton.txt
+++ b/compiler/testData/diagnostics/tests/platformTypes/methodCall/singleton.txt
@@ -2,7 +2,7 @@ package
 
 internal fun test(): kotlin.Unit
 
-internal trait Foo {
+internal interface Foo {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/platformTypes/supertypeArgumentsExplicit.txt b/compiler/testData/diagnostics/tests/platformTypes/supertypeArgumentsExplicit.txt
index 70f63634d3a..322805342d7 100644
--- a/compiler/testData/diagnostics/tests/platformTypes/supertypeArgumentsExplicit.txt
+++ b/compiler/testData/diagnostics/tests/platformTypes/supertypeArgumentsExplicit.txt
@@ -1,54 +1,54 @@
 package
 
-internal trait A</*0*/ T> {
+internal interface A</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B</*0*/ T> : A<T!> {
+internal interface B</*0*/ T> : A<T!> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait C : A<kotlin.String>, B<kotlin.String> {
+internal interface C : A<kotlin.String>, B<kotlin.String> {
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait D : B<kotlin.String>, A<kotlin.String> {
+internal interface D : B<kotlin.String>, A<kotlin.String> {
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait E : A<kotlin.String?>, B<kotlin.String?> {
+internal interface E : A<kotlin.String?>, B<kotlin.String?> {
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait F : A<kotlin.String?>, B<kotlin.String> {
+internal interface F : A<kotlin.String?>, B<kotlin.String> {
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait G : A<kotlin.String>, B<kotlin.String?> {
+internal interface G : A<kotlin.String>, B<kotlin.String?> {
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait H : A<kotlin.Int>, B<kotlin.String> {
+internal interface H : A<kotlin.Int>, B<kotlin.String> {
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait I : B<kotlin.Int>, A<kotlin.String> {
+internal interface I : B<kotlin.Int>, A<kotlin.String> {
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/platformTypes/supertypeTypeArguments.txt b/compiler/testData/diagnostics/tests/platformTypes/supertypeTypeArguments.txt
index 285b6562bf8..f8e286d2825 100644
--- a/compiler/testData/diagnostics/tests/platformTypes/supertypeTypeArguments.txt
+++ b/compiler/testData/diagnostics/tests/platformTypes/supertypeTypeArguments.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait ExtMap</*0*/ K, /*1*/ V> : kotlin.Map<K, V> {
+internal interface ExtMap</*0*/ K, /*1*/ V> : kotlin.Map<K, V> {
     public abstract override /*1*/ /*fake_override*/ fun containsKey(/*0*/ key: kotlin.Any?): kotlin.Boolean
     public abstract override /*1*/ /*fake_override*/ fun containsValue(/*0*/ value: kotlin.Any?): kotlin.Boolean
     public abstract override /*1*/ /*fake_override*/ fun entrySet(): kotlin.Set<kotlin.Map.Entry<K, V>>
diff --git a/compiler/testData/diagnostics/tests/recovery/namelessToplevelDeclarations.txt b/compiler/testData/diagnostics/tests/recovery/namelessToplevelDeclarations.txt
index 62dce90e842..3ab980b59b1 100644
--- a/compiler/testData/diagnostics/tests/recovery/namelessToplevelDeclarations.txt
+++ b/compiler/testData/diagnostics/tests/recovery/namelessToplevelDeclarations.txt
@@ -10,7 +10,7 @@ internal final class <no name provided> {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait <no name provided> {
+internal interface <no name provided> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/regressions/UnavaliableQualifiedThis.txt b/compiler/testData/diagnostics/tests/regressions/UnavaliableQualifiedThis.txt
index 4453e5f73c4..64aa508871d 100644
--- a/compiler/testData/diagnostics/tests/regressions/UnavaliableQualifiedThis.txt
+++ b/compiler/testData/diagnostics/tests/regressions/UnavaliableQualifiedThis.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait Iterator</*0*/ out T> {
+internal interface Iterator</*0*/ out T> {
     internal abstract val hasNext: kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/regressions/kt1489_1728.txt b/compiler/testData/diagnostics/tests/regressions/kt1489_1728.txt
index c6667356926..42558f397c9 100644
--- a/compiler/testData/diagnostics/tests/regressions/kt1489_1728.txt
+++ b/compiler/testData/diagnostics/tests/regressions/kt1489_1728.txt
@@ -4,7 +4,7 @@ package kt606_dependents {
     internal val x: kotlin.Int
     internal val kotlin.Int.ext: () -> kotlin.Int
 
-    internal trait AutoCloseable {
+    internal interface AutoCloseable {
         internal abstract fun close(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/regressions/kt174.txt b/compiler/testData/diagnostics/tests/regressions/kt174.txt
index 4cc09b34fe5..6017b2d29ad 100644
--- a/compiler/testData/diagnostics/tests/regressions/kt174.txt
+++ b/compiler/testData/diagnostics/tests/regressions/kt174.txt
@@ -2,7 +2,7 @@ package
 
 internal fun kotlin.Any?.TreeValue(): Tree
 
-internal trait Tree {
+internal interface Tree {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/regressions/kt302.txt b/compiler/testData/diagnostics/tests/regressions/kt302.txt
index 0b8d8fb17d7..63706b56eca 100644
--- a/compiler/testData/diagnostics/tests/regressions/kt302.txt
+++ b/compiler/testData/diagnostics/tests/regressions/kt302.txt
@@ -2,14 +2,14 @@ package
 
 package kt302 {
 
-    internal trait A {
+    internal interface A {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal open fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait B {
+    internal interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal open fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/regressions/kt307.txt b/compiler/testData/diagnostics/tests/regressions/kt307.txt
index 46592b3b8d7..56ff27f60f4 100644
--- a/compiler/testData/diagnostics/tests/regressions/kt307.txt
+++ b/compiler/testData/diagnostics/tests/regressions/kt307.txt
@@ -8,7 +8,7 @@ internal open class AL {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait ALE</*0*/ T> : AL {
+internal interface ALE</*0*/ T> : AL {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal final override /*1*/ /*fake_override*/ fun get(/*0*/ i: kotlin.Int): kotlin.Any?
     internal open fun getOrNull(/*0*/ index: kotlin.Int, /*1*/ value: T): T
diff --git a/compiler/testData/diagnostics/tests/regressions/kt316.txt b/compiler/testData/diagnostics/tests/regressions/kt316.txt
index b855b3cb99f..673c1fbdd4f 100644
--- a/compiler/testData/diagnostics/tests/regressions/kt316.txt
+++ b/compiler/testData/diagnostics/tests/regressions/kt316.txt
@@ -9,7 +9,7 @@ internal open class A : B {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B {
+internal interface B {
     internal open fun bar(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun foo(): kotlin.Unit
diff --git a/compiler/testData/diagnostics/tests/regressions/kt353.txt b/compiler/testData/diagnostics/tests/regressions/kt353.txt
index ae4a18f8e90..8e29e3e997a 100644
--- a/compiler/testData/diagnostics/tests/regressions/kt353.txt
+++ b/compiler/testData/diagnostics/tests/regressions/kt353.txt
@@ -2,7 +2,7 @@ package
 
 internal fun foo(/*0*/ a: A): kotlin.Unit
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun </*0*/ T> gen(): T
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/regressions/kt4827.txt b/compiler/testData/diagnostics/tests/regressions/kt4827.txt
index 3d9cd7361a1..c1c96ba4be6 100644
--- a/compiler/testData/diagnostics/tests/regressions/kt4827.txt
+++ b/compiler/testData/diagnostics/tests/regressions/kt4827.txt
@@ -16,7 +16,7 @@ internal final class C {
     }
 }
 
-public trait TestInterface {
+public interface TestInterface {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/regressions/kt604.txt b/compiler/testData/diagnostics/tests/regressions/kt604.txt
index 4c1380e8433..707bba71903 100644
--- a/compiler/testData/diagnostics/tests/regressions/kt604.txt
+++ b/compiler/testData/diagnostics/tests/regressions/kt604.txt
@@ -1,12 +1,12 @@
 package
 
-internal trait ChannelPipeline {
+internal interface ChannelPipeline {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait ChannelPipelineFactory {
+internal interface ChannelPipelineFactory {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun getPipeline(): ChannelPipeline
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/regressions/kt860.txt b/compiler/testData/diagnostics/tests/regressions/kt860.txt
index 6ee2b189e1a..8d8c9c7e1bd 100644
--- a/compiler/testData/diagnostics/tests/regressions/kt860.txt
+++ b/compiler/testData/diagnostics/tests/regressions/kt860.txt
@@ -1,4 +1,4 @@
-package 
+package
 
 package std {
 
diff --git a/compiler/testData/diagnostics/tests/resolve/invoke/invokeAsExtension.txt b/compiler/testData/diagnostics/tests/resolve/invoke/invokeAsExtension.txt
index 199059a327b..eb180d83d4c 100644
--- a/compiler/testData/diagnostics/tests/resolve/invoke/invokeAsExtension.txt
+++ b/compiler/testData/diagnostics/tests/resolve/invoke/invokeAsExtension.txt
@@ -8,26 +8,26 @@ internal fun test(/*0*/ foo: Foo): kotlin.Unit
 internal fun </*0*/ T, /*1*/ R> with(/*0*/ receiver: T, /*1*/ f: T.() -> R): R
 internal fun Foo.invoke(): kotlin.Unit
 
-internal trait A {
+internal interface A {
     internal abstract val foo: Foo
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B {
+internal interface B {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait C {
+internal interface C {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait D {
+internal interface D {
     internal abstract val C.foo: Foo
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/resolve/invoke/invokeAsMember.txt b/compiler/testData/diagnostics/tests/resolve/invoke/invokeAsMember.txt
index 9728f0aa273..146d4cd74f3 100644
--- a/compiler/testData/diagnostics/tests/resolve/invoke/invokeAsMember.txt
+++ b/compiler/testData/diagnostics/tests/resolve/invoke/invokeAsMember.txt
@@ -7,26 +7,26 @@ internal fun test(/*0*/ d: D, /*1*/ c: C): kotlin.Unit
 internal fun test(/*0*/ foo: Foo): kotlin.Unit
 internal fun </*0*/ T, /*1*/ R> with(/*0*/ receiver: T, /*1*/ f: T.() -> R): R
 
-internal trait A {
+internal interface A {
     internal abstract val foo: Foo
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B {
+internal interface B {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait C {
+internal interface C {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait D {
+internal interface D {
     internal abstract val C.foo: Foo
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/resolve/invoke/invokeAsMemberExtension.txt b/compiler/testData/diagnostics/tests/resolve/invoke/invokeAsMemberExtension.txt
index 12e0c5eeb5c..e9b8f38bd23 100644
--- a/compiler/testData/diagnostics/tests/resolve/invoke/invokeAsMemberExtension.txt
+++ b/compiler/testData/diagnostics/tests/resolve/invoke/invokeAsMemberExtension.txt
@@ -7,7 +7,7 @@ internal fun test(/*0*/ g: G, /*1*/ f: F): kotlin.Unit
 internal fun test(/*0*/ u: U, /*1*/ v: V, /*2*/ x: X): kotlin.Unit
 internal fun </*0*/ T, /*1*/ R> with(/*0*/ receiver: T, /*1*/ f: T.() -> R): R
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     internal open fun test(/*0*/ foo: Foo): kotlin.Unit
@@ -15,7 +15,7 @@ internal trait A {
     internal open fun Foo.invoke(): kotlin.Unit
 }
 
-internal trait B {
+internal interface B {
     internal abstract val foo: Foo
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -31,7 +31,7 @@ internal final class C {
     internal final fun Foo.invoke(): kotlin.Unit
 }
 
-internal trait D {
+internal interface D {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -46,7 +46,7 @@ internal final class E {
     internal final fun Foo.invoke(): kotlin.Unit
 }
 
-internal trait F {
+internal interface F {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -59,7 +59,7 @@ internal final class Foo {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait G {
+internal interface G {
     internal abstract val F.foo: Foo
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -68,14 +68,14 @@ internal trait G {
     internal abstract fun Foo.invoke(): kotlin.Unit
 }
 
-internal trait U {
+internal interface U {
     internal abstract val X.foo: Foo
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait V {
+internal interface V {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -83,7 +83,7 @@ internal trait V {
     internal open fun U.test(/*0*/ x: X): kotlin.Unit
 }
 
-internal trait X {
+internal interface X {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/resolve/invoke/invokeAsMemberExtensionToExplicitReceiver.txt b/compiler/testData/diagnostics/tests/resolve/invoke/invokeAsMemberExtensionToExplicitReceiver.txt
index dd0dda9ba11..e1dae0e18cf 100644
--- a/compiler/testData/diagnostics/tests/resolve/invoke/invokeAsMemberExtensionToExplicitReceiver.txt
+++ b/compiler/testData/diagnostics/tests/resolve/invoke/invokeAsMemberExtensionToExplicitReceiver.txt
@@ -3,13 +3,13 @@ package
 internal fun test(/*0*/ a: A, /*1*/ foo: Foo): kotlin.Unit
 internal fun test(/*0*/ a: kotlin.Int, /*1*/ foo: kotlin.Int.() -> kotlin.Unit): kotlin.Unit
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Foo {
+internal interface Foo {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/resolve/invoke/kt4321InvokeOnEnum.txt b/compiler/testData/diagnostics/tests/resolve/invoke/kt4321InvokeOnEnum.txt
index 23b2969032c..1c880290bce 100644
--- a/compiler/testData/diagnostics/tests/resolve/invoke/kt4321InvokeOnEnum.txt
+++ b/compiler/testData/diagnostics/tests/resolve/invoke/kt4321InvokeOnEnum.txt
@@ -39,7 +39,7 @@ internal final enum class DOMElementTestClasses : kotlin.Enum<DOMElementTestClas
     public final /*synthesized*/ fun values(): kotlin.Array<DOMElementTestClasses>
 }
 
-internal trait EnumStyleClass {
+internal interface EnumStyleClass {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     internal open fun invoke(): kotlin.Unit
diff --git a/compiler/testData/diagnostics/tests/resolve/invoke/valNamedInvoke.txt b/compiler/testData/diagnostics/tests/resolve/invoke/valNamedInvoke.txt
index 7ae5f4500ff..3263c7884dc 100644
--- a/compiler/testData/diagnostics/tests/resolve/invoke/valNamedInvoke.txt
+++ b/compiler/testData/diagnostics/tests/resolve/invoke/valNamedInvoke.txt
@@ -3,7 +3,7 @@ package
 internal fun bar(/*0*/ invoke: kotlin.Any.() -> kotlin.Any, /*1*/ a: kotlin.Any): kotlin.Unit
 internal fun foo(/*0*/ invoke: A.() -> kotlin.Unit, /*1*/ a: A): kotlin.Unit
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/resolve/nestedCalls/argumentsInParentheses.txt b/compiler/testData/diagnostics/tests/resolve/nestedCalls/argumentsInParentheses.txt
index 31ec6ab25da..910c1e11713 100644
--- a/compiler/testData/diagnostics/tests/resolve/nestedCalls/argumentsInParentheses.txt
+++ b/compiler/testData/diagnostics/tests/resolve/nestedCalls/argumentsInParentheses.txt
@@ -19,7 +19,7 @@ internal final class Bar {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Foo</*0*/ T> {
+internal interface Foo</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/resolve/nestedCalls/kt7597.txt b/compiler/testData/diagnostics/tests/resolve/nestedCalls/kt7597.txt
index 020040884dd..69a7b37f8b9 100644
--- a/compiler/testData/diagnostics/tests/resolve/nestedCalls/kt7597.txt
+++ b/compiler/testData/diagnostics/tests/resolve/nestedCalls/kt7597.txt
@@ -3,7 +3,7 @@ package
 internal fun test(/*0*/ a: Inv<kotlin.Int>): kotlin.Int
 internal fun </*0*/ S, /*1*/ T : S> Inv<T>.reduce2(): S
 
-internal trait Inv</*0*/ I> {
+internal interface Inv</*0*/ I> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/resolve/specialConstructions/elvisAsCall.txt b/compiler/testData/diagnostics/tests/resolve/specialConstructions/elvisAsCall.txt
index 93626401584..4e8531ebce5 100644
--- a/compiler/testData/diagnostics/tests/resolve/specialConstructions/elvisAsCall.txt
+++ b/compiler/testData/diagnostics/tests/resolve/specialConstructions/elvisAsCall.txt
@@ -11,7 +11,7 @@ package a {
     internal fun testElvis(/*0*/ a: kotlin.Int?, /*1*/ b: kotlin.Int?): kotlin.Unit
     internal fun testTypeMismatch(/*0*/ a: kotlin.String?, /*1*/ b: kotlin.Any): kotlin.Unit
 
-    internal trait A {
+    internal interface A {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/resolve/specialConstructions/exclExclAsCall.txt b/compiler/testData/diagnostics/tests/resolve/specialConstructions/exclExclAsCall.txt
index 619929191d5..b12442e2826 100644
--- a/compiler/testData/diagnostics/tests/resolve/specialConstructions/exclExclAsCall.txt
+++ b/compiler/testData/diagnostics/tests/resolve/specialConstructions/exclExclAsCall.txt
@@ -10,7 +10,7 @@ package a {
     internal fun testExclExcl(): kotlin.Unit
     internal fun testUnnecessaryExclExcl(/*0*/ a: kotlin.Int): kotlin.Unit
 
-    internal trait A {
+    internal interface A {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/resolve/specialConstructions/multipleSuperClasses.txt b/compiler/testData/diagnostics/tests/resolve/specialConstructions/multipleSuperClasses.txt
index 261a0fa388f..946068b415c 100644
--- a/compiler/testData/diagnostics/tests/resolve/specialConstructions/multipleSuperClasses.txt
+++ b/compiler/testData/diagnostics/tests/resolve/specialConstructions/multipleSuperClasses.txt
@@ -2,31 +2,31 @@ package
 
 internal fun foo(/*0*/ c: C?, /*1*/ d: D?, /*2*/ e: E?): kotlin.Unit
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B {
+internal interface B {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait C : A, B {
+internal interface C : A, B {
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait D : A, B {
+internal interface D : A, B {
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait E : A, B {
+internal interface E : A, B {
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/scopes/VisibilityInheritModifier.txt b/compiler/testData/diagnostics/tests/scopes/VisibilityInheritModifier.txt
index 63c48c54af5..b5ae8129ace 100644
--- a/compiler/testData/diagnostics/tests/scopes/VisibilityInheritModifier.txt
+++ b/compiler/testData/diagnostics/tests/scopes/VisibilityInheritModifier.txt
@@ -108,21 +108,21 @@ package b {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait P : b.R {
+    internal interface P : b.R {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal open override /*1*/ fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait Q : b.R {
+    internal interface Q : b.R {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         protected open override /*1*/ fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait R {
+    internal interface R {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         protected open fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -137,7 +137,7 @@ package b {
         public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait T {
+    internal interface T {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/scopes/kt1248.txt b/compiler/testData/diagnostics/tests/scopes/kt1248.txt
index 0251f566730..0037e47e5d9 100644
--- a/compiler/testData/diagnostics/tests/scopes/kt1248.txt
+++ b/compiler/testData/diagnostics/tests/scopes/kt1248.txt
@@ -2,7 +2,7 @@ package
 
 package kt1248 {
 
-    internal trait ParseResult</*0*/ out T> {
+    internal interface ParseResult</*0*/ out T> {
         public abstract val success: kotlin.Boolean
         public abstract val value: T
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
diff --git a/compiler/testData/diagnostics/tests/scopes/kt151.txt b/compiler/testData/diagnostics/tests/scopes/kt151.txt
index 30858a195ce..eaeb38b12bf 100644
--- a/compiler/testData/diagnostics/tests/scopes/kt151.txt
+++ b/compiler/testData/diagnostics/tests/scopes/kt151.txt
@@ -59,7 +59,7 @@ package kt151 {
         public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait T {
+    internal interface T {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         protected open fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/scopes/kt1579.txt b/compiler/testData/diagnostics/tests/scopes/kt1579.txt
index 63cd04ad532..c5146da1b76 100644
--- a/compiler/testData/diagnostics/tests/scopes/kt1579.txt
+++ b/compiler/testData/diagnostics/tests/scopes/kt1579.txt
@@ -2,12 +2,12 @@ package
 
 package lib {
 
-    internal trait WithInner {
+    internal interface WithInner {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 
-        internal trait Inner {
+        internal interface Inner {
             public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
             public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
             public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/scopes/kt1580.txt b/compiler/testData/diagnostics/tests/scopes/kt1580.txt
index ac3dbbe3e04..61a53ee8415 100644
--- a/compiler/testData/diagnostics/tests/scopes/kt1580.txt
+++ b/compiler/testData/diagnostics/tests/scopes/kt1580.txt
@@ -2,12 +2,12 @@ package
 
 package lib {
 
-    internal trait WithInner {
+    internal interface WithInner {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 
-        internal trait Inner {
+        internal interface Inner {
             public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
             public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
             public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/scopes/kt1822.txt b/compiler/testData/diagnostics/tests/scopes/kt1822.txt
index 5babb5bb050..28365b8eb76 100644
--- a/compiler/testData/diagnostics/tests/scopes/kt1822.txt
+++ b/compiler/testData/diagnostics/tests/scopes/kt1822.txt
@@ -10,7 +10,7 @@ package kt1822 {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait B {
+    internal interface B {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         protected open fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -25,7 +25,7 @@ package kt1822 {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait D {
+    internal interface D {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -48,7 +48,7 @@ package kt1822 {
         public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait T {
+    internal interface T {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         protected open fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/scopes/stopResolutionOnAmbiguity.txt b/compiler/testData/diagnostics/tests/scopes/stopResolutionOnAmbiguity.txt
index 7c91d51059f..5a5e7a83d11 100644
--- a/compiler/testData/diagnostics/tests/scopes/stopResolutionOnAmbiguity.txt
+++ b/compiler/testData/diagnostics/tests/scopes/stopResolutionOnAmbiguity.txt
@@ -4,7 +4,7 @@ package c {
     internal fun test(/*0*/ a: kotlin.Any?): kotlin.Unit
     internal fun kotlin.Any?.bar(): kotlin.Unit
 
-    internal trait B {
+    internal interface B {
         internal open fun bar(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/scopes/visibility.txt b/compiler/testData/diagnostics/tests/scopes/visibility.txt
index d7d50f11585..53072de9bd3 100644
--- a/compiler/testData/diagnostics/tests/scopes/visibility.txt
+++ b/compiler/testData/diagnostics/tests/scopes/visibility.txt
@@ -86,13 +86,13 @@ package test_visibility {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    protected trait ProtectedTrait {
+    protected interface ProtectedTrait {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait T {
+    internal interface T {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/secondaryConstructors/constructorInTrait.txt b/compiler/testData/diagnostics/tests/secondaryConstructors/constructorInTrait.txt
index a7b766c263a..d867f9e6a23 100644
--- a/compiler/testData/diagnostics/tests/secondaryConstructors/constructorInTrait.txt
+++ b/compiler/testData/diagnostics/tests/secondaryConstructors/constructorInTrait.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/secondaryConstructors/delegationByWithoutPrimary.txt b/compiler/testData/diagnostics/tests/secondaryConstructors/delegationByWithoutPrimary.txt
index ab2496e785d..247b8775cc1 100644
--- a/compiler/testData/diagnostics/tests/secondaryConstructors/delegationByWithoutPrimary.txt
+++ b/compiler/testData/diagnostics/tests/secondaryConstructors/delegationByWithoutPrimary.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/secondaryConstructors/membersInitializationWithPrimary.txt b/compiler/testData/diagnostics/tests/secondaryConstructors/membersInitializationWithPrimary.txt
deleted file mode 100644
index b0b6416fa16..00000000000
--- a/compiler/testData/diagnostics/tests/secondaryConstructors/membersInitializationWithPrimary.txt
+++ /dev/null
@@ -1,19 +0,0 @@
-package
-
-internal final class A {
-    public constructor A()
-    public constructor A(/*0*/ w: kotlin.Char)
-    public constructor A(/*0*/ a: kotlin.Int, /*1*/ b: kotlin.Int = ...)
-    internal final val overinitialized: kotlin.Int
-    internal final val uninitialized: kotlin.Int
-    internal final val useInitialized: kotlin.Int
-    internal final val useUnitialized: kotlin.Int
-    internal final val v: kotlin.Int = -1
-    internal final val w: kotlin.Char
-    internal final val x: kotlin.Int
-    internal final var y: kotlin.Int
-    internal final val z: kotlin.Int
-    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
-    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
-    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
-}
diff --git a/compiler/testData/diagnostics/tests/secondaryConstructors/membersInitializationWithoutPrimary.txt b/compiler/testData/diagnostics/tests/secondaryConstructors/membersInitializationWithoutPrimary.txt
deleted file mode 100644
index 610ca35deae..00000000000
--- a/compiler/testData/diagnostics/tests/secondaryConstructors/membersInitializationWithoutPrimary.txt
+++ /dev/null
@@ -1,20 +0,0 @@
-package
-
-internal final class A {
-    public constructor A()
-    public constructor A(/*0*/ a: kotlin.Double, /*1*/ b: kotlin.Int = ...)
-    public constructor A(/*0*/ a: kotlin.Int, /*1*/ b: kotlin.Int = ...)
-    public constructor A(/*0*/ x: kotlin.String)
-    public constructor A(/*0*/ a: kotlin.String, /*1*/ b: kotlin.Int = ...)
-    internal final val overinitialized: kotlin.Int
-    internal final val uninitialized: kotlin.Int
-    internal final val useInitialized: kotlin.Int
-    internal final val useUnitialized: kotlin.Int
-    internal final val v: kotlin.Int = -1
-    internal final val x: kotlin.Int
-    internal final var y: kotlin.Int
-    internal final val z: kotlin.Int
-    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
-    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
-    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
-}
diff --git a/compiler/testData/diagnostics/tests/secondaryConstructors/noSupertypeInitWithSecondaryConstructors.txt b/compiler/testData/diagnostics/tests/secondaryConstructors/noSupertypeInitWithSecondaryConstructors.txt
index c417f6a703e..5d5cdaa117d 100644
--- a/compiler/testData/diagnostics/tests/secondaryConstructors/noSupertypeInitWithSecondaryConstructors.txt
+++ b/compiler/testData/diagnostics/tests/secondaryConstructors/noSupertypeInitWithSecondaryConstructors.txt
@@ -14,13 +14,13 @@ internal open class B {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait C {
+internal interface C {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait D {
+internal interface D {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/secondaryConstructors/superSecondaryNonExisting.txt b/compiler/testData/diagnostics/tests/secondaryConstructors/superSecondaryNonExisting.txt
index bce2636cbdf..06eeaae5e8b 100644
--- a/compiler/testData/diagnostics/tests/secondaryConstructors/superSecondaryNonExisting.txt
+++ b/compiler/testData/diagnostics/tests/secondaryConstructors/superSecondaryNonExisting.txt
@@ -17,7 +17,7 @@ internal open class B {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait C {
+internal interface C {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/smartCasts/combineWithNoSelectorInfo.txt b/compiler/testData/diagnostics/tests/smartCasts/combineWithNoSelectorInfo.txt
index 8bc21b56776..75d241c6bb1 100644
--- a/compiler/testData/diagnostics/tests/smartCasts/combineWithNoSelectorInfo.txt
+++ b/compiler/testData/diagnostics/tests/smartCasts/combineWithNoSelectorInfo.txt
@@ -3,7 +3,7 @@ package
 package foo {
     internal fun dispatch(/*0*/ request: foo.Request): kotlin.Unit
 
-    internal trait Request {
+    internal interface Request {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal abstract fun getMethod(): kotlin.String?
         internal abstract fun getRequestURI(): kotlin.String?
diff --git a/compiler/testData/diagnostics/tests/smartCasts/inference/intersectionTypes.txt b/compiler/testData/diagnostics/tests/smartCasts/inference/intersectionTypes.txt
index 2ec397fa3e1..5907870c3c5 100644
--- a/compiler/testData/diagnostics/tests/smartCasts/inference/intersectionTypes.txt
+++ b/compiler/testData/diagnostics/tests/smartCasts/inference/intersectionTypes.txt
@@ -11,19 +11,19 @@ package a {
     internal fun </*0*/ T> two(/*0*/ u: T, /*1*/ v: T): T
     internal fun use(/*0*/ vararg a: kotlin.Any /*kotlin.Array<out kotlin.Any>*/): kotlin.Array<out kotlin.Any>
 
-    internal trait A {
+    internal interface A {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait B : a.A {
+    internal interface B : a.A {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait C : a.A {
+    internal interface C : a.A {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/smartCasts/inference/kt4009.txt b/compiler/testData/diagnostics/tests/smartCasts/inference/kt4009.txt
index f504758870d..bac4a0eb8df 100644
--- a/compiler/testData/diagnostics/tests/smartCasts/inference/kt4009.txt
+++ b/compiler/testData/diagnostics/tests/smartCasts/inference/kt4009.txt
@@ -3,7 +3,7 @@ package
 internal fun foo1(/*0*/ e: PsiElement): kotlin.Unit
 internal fun println(/*0*/ any: kotlin.Any?): kotlin.Nothing
 
-internal trait JetExpression : PsiElement {
+internal interface JetExpression : PsiElement {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract override /*1*/ /*fake_override*/ fun getParent(): PsiElement
     internal abstract override /*1*/ /*fake_override*/ fun getText(): kotlin.String
@@ -11,7 +11,7 @@ internal trait JetExpression : PsiElement {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait PsiElement {
+internal interface PsiElement {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun getParent(): PsiElement
     internal abstract fun getText(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/smartCasts/inference/kt4403.txt b/compiler/testData/diagnostics/tests/smartCasts/inference/kt4403.txt
index c5559030ca5..53c90bbbd43 100644
--- a/compiler/testData/diagnostics/tests/smartCasts/inference/kt4403.txt
+++ b/compiler/testData/diagnostics/tests/smartCasts/inference/kt4403.txt
@@ -3,13 +3,13 @@ package
 internal fun test(/*0*/ a: A): kotlin.Unit
 internal fun </*0*/ T> T.f(): T
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B : A {
+internal interface B : A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/smartCasts/inference/kt4415.txt b/compiler/testData/diagnostics/tests/smartCasts/inference/kt4415.txt
index f92aa515243..774c38f8cbf 100644
--- a/compiler/testData/diagnostics/tests/smartCasts/inference/kt4415.txt
+++ b/compiler/testData/diagnostics/tests/smartCasts/inference/kt4415.txt
@@ -11,7 +11,7 @@ internal object A {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait SelfJson {
+internal interface SelfJson {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/smartCasts/inference/smartCastOnReceiver.txt b/compiler/testData/diagnostics/tests/smartCasts/inference/smartCastOnReceiver.txt
index dc9a5e7335c..2f34b526f89 100644
--- a/compiler/testData/diagnostics/tests/smartCasts/inference/smartCastOnReceiver.txt
+++ b/compiler/testData/diagnostics/tests/smartCasts/inference/smartCastOnReceiver.txt
@@ -2,13 +2,13 @@ package
 
 internal fun </*0*/ A, /*1*/ B> A.to(/*0*/ that: B): Pair<A, B>
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B {
+internal interface B {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/smartCasts/kt3572.txt b/compiler/testData/diagnostics/tests/smartCasts/kt3572.txt
index 33cec66768f..226fc58da4e 100644
--- a/compiler/testData/diagnostics/tests/smartCasts/kt3572.txt
+++ b/compiler/testData/diagnostics/tests/smartCasts/kt3572.txt
@@ -18,7 +18,7 @@ internal final class OKPrinter : Printer {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Printer {
+internal interface Printer {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     internal abstract fun print(): kotlin.Unit
diff --git a/compiler/testData/diagnostics/tests/smartCasts/publicVals/kt4409.txt b/compiler/testData/diagnostics/tests/smartCasts/publicVals/kt4409.txt
index 0fb3ec02cb5..a821041f38a 100644
--- a/compiler/testData/diagnostics/tests/smartCasts/publicVals/kt4409.txt
+++ b/compiler/testData/diagnostics/tests/smartCasts/publicVals/kt4409.txt
@@ -1,6 +1,6 @@
 package
 
-public trait A {
+public interface A {
     public abstract val x: kotlin.Any
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/smartCasts/variables/kt7599.txt b/compiler/testData/diagnostics/tests/smartCasts/variables/kt7599.txt
index 31db881b731..0f3fa07cf8a 100644
--- a/compiler/testData/diagnostics/tests/smartCasts/variables/kt7599.txt
+++ b/compiler/testData/diagnostics/tests/smartCasts/variables/kt7599.txt
@@ -2,7 +2,7 @@ package
 
 internal fun foo(): kotlin.Boolean
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     internal abstract fun ok(): kotlin.Boolean
diff --git a/compiler/testData/diagnostics/tests/substitutions/starProjections.txt b/compiler/testData/diagnostics/tests/substitutions/starProjections.txt
index 5d2c09b8704..0a3585f83d1 100644
--- a/compiler/testData/diagnostics/tests/substitutions/starProjections.txt
+++ b/compiler/testData/diagnostics/tests/substitutions/starProjections.txt
@@ -3,7 +3,7 @@ package
 internal fun testA(/*0*/ a: A<*, *>): kotlin.Unit
 internal fun testB(/*0*/ b: B<*, *>): kotlin.Unit
 
-internal trait A</*0*/ R, /*1*/ T : A<R, T>> {
+internal interface A</*0*/ R, /*1*/ T : A<R, T>> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     internal abstract fun r(): R
@@ -11,7 +11,7 @@ internal trait A</*0*/ R, /*1*/ T : A<R, T>> {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B</*0*/ R, /*1*/ T : B<kotlin.List<R>, T>> {
+internal interface B</*0*/ R, /*1*/ T : B<kotlin.List<R>, T>> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     internal abstract fun r(): R
diff --git a/compiler/testData/diagnostics/tests/subtyping/kt2069.txt b/compiler/testData/diagnostics/tests/subtyping/kt2069.txt
index 2c550ba3ab3..2b862980475 100644
--- a/compiler/testData/diagnostics/tests/subtyping/kt2069.txt
+++ b/compiler/testData/diagnostics/tests/subtyping/kt2069.txt
@@ -18,7 +18,7 @@ package kt2069 {
         }
     }
 
-    internal trait T1 {
+    internal interface T1 {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal open fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/subtyping/kt3159.txt b/compiler/testData/diagnostics/tests/subtyping/kt3159.txt
index 37f14d79cd6..d62a8cce047 100644
--- a/compiler/testData/diagnostics/tests/subtyping/kt3159.txt
+++ b/compiler/testData/diagnostics/tests/subtyping/kt3159.txt
@@ -9,7 +9,7 @@ internal final class Sub : Super {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Super {
+internal interface Super {
     internal abstract var v: kotlin.CharSequence
     internal abstract val v2: kotlin.CharSequence
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
diff --git a/compiler/testData/diagnostics/tests/thisAndSuper/Super.txt b/compiler/testData/diagnostics/tests/thisAndSuper/Super.txt
index 21b42807ee9..70838b7ee41 100644
--- a/compiler/testData/diagnostics/tests/thisAndSuper/Super.txt
+++ b/compiler/testData/diagnostics/tests/thisAndSuper/Super.txt
@@ -46,14 +46,14 @@ package example {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait G</*0*/ T> {
+    internal interface G</*0*/ T> {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal open fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait T {
+    internal interface T {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         internal open fun foo(): kotlin.Unit
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/thisAndSuper/notAccessibleSuperInTrait.txt b/compiler/testData/diagnostics/tests/thisAndSuper/notAccessibleSuperInTrait.txt
index 902534193d2..b06aa2a0029 100644
--- a/compiler/testData/diagnostics/tests/thisAndSuper/notAccessibleSuperInTrait.txt
+++ b/compiler/testData/diagnostics/tests/thisAndSuper/notAccessibleSuperInTrait.txt
@@ -8,7 +8,7 @@ internal open class A {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait ATrait : A {
+internal interface ATrait : A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open override /*1*/ fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/thisAndSuper/thisInPropertyInitializer.txt b/compiler/testData/diagnostics/tests/thisAndSuper/thisInPropertyInitializer.txt
index 3668427372e..286304aa1ee 100644
--- a/compiler/testData/diagnostics/tests/thisAndSuper/thisInPropertyInitializer.txt
+++ b/compiler/testData/diagnostics/tests/thisAndSuper/thisInPropertyInitializer.txt
@@ -2,7 +2,7 @@ package
 
 internal val kotlin.String.test: Base
 
-internal trait Base {
+internal interface Base {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/thisAndSuper/traitSuperCall.txt b/compiler/testData/diagnostics/tests/thisAndSuper/traitSuperCall.txt
index 20d88207c5b..054def37a58 100644
--- a/compiler/testData/diagnostics/tests/thisAndSuper/traitSuperCall.txt
+++ b/compiler/testData/diagnostics/tests/thisAndSuper/traitSuperCall.txt
@@ -10,7 +10,7 @@ internal final class A : KTrait {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait KTrait : Test {
+internal interface KTrait : Test {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     internal open fun ktest(): kotlin.Unit
@@ -18,7 +18,7 @@ internal trait KTrait : Test {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-public trait Test {
+public interface Test {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     internal open fun test(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/traitWithRequired/abstractClass.txt b/compiler/testData/diagnostics/tests/traitWithRequired/abstractClass.txt
index 6f6f70c2b4a..95d5f579e9c 100644
--- a/compiler/testData/diagnostics/tests/traitWithRequired/abstractClass.txt
+++ b/compiler/testData/diagnostics/tests/traitWithRequired/abstractClass.txt
@@ -21,7 +21,7 @@ internal open class Required {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Trait : Required {
+internal interface Trait : Required {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/traitWithRequired/anonymousObjectExtendsTraitWithRequired.txt b/compiler/testData/diagnostics/tests/traitWithRequired/anonymousObjectExtendsTraitWithRequired.txt
index 89efef6566a..be0e2485e80 100644
--- a/compiler/testData/diagnostics/tests/traitWithRequired/anonymousObjectExtendsTraitWithRequired.txt
+++ b/compiler/testData/diagnostics/tests/traitWithRequired/anonymousObjectExtendsTraitWithRequired.txt
@@ -3,7 +3,7 @@ package
 internal val a: A
 internal val b: A
 
-internal trait A : Required {
+internal interface A : Required {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/traitWithRequired/differentGenericArguments.txt b/compiler/testData/diagnostics/tests/traitWithRequired/differentGenericArguments.txt
index 1d3b515110d..02273eb1cff 100644
--- a/compiler/testData/diagnostics/tests/traitWithRequired/differentGenericArguments.txt
+++ b/compiler/testData/diagnostics/tests/traitWithRequired/differentGenericArguments.txt
@@ -1,12 +1,12 @@
 package
 
-internal trait A : Generic<kotlin.Int> {
+internal interface A : Generic<kotlin.Int> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B : Generic<kotlin.String> {
+internal interface B : Generic<kotlin.String> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/traitWithRequired/kt3006.txt b/compiler/testData/diagnostics/tests/traitWithRequired/kt3006.txt
index f378089f5ec..c1b7ea9b199 100644
--- a/compiler/testData/diagnostics/tests/traitWithRequired/kt3006.txt
+++ b/compiler/testData/diagnostics/tests/traitWithRequired/kt3006.txt
@@ -9,7 +9,7 @@ internal open class Base {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Derived : Base {
+internal interface Derived : Base {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal open fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/traitWithRequired/manyRequirementsDisallowed.txt b/compiler/testData/diagnostics/tests/traitWithRequired/manyRequirementsDisallowed.txt
index 10290b5e921..7f2d5e3eedd 100644
--- a/compiler/testData/diagnostics/tests/traitWithRequired/manyRequirementsDisallowed.txt
+++ b/compiler/testData/diagnostics/tests/traitWithRequired/manyRequirementsDisallowed.txt
@@ -14,7 +14,7 @@ internal open class B {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait C : A, B {
+internal interface C : A, B {
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/traitWithRequired/manyTraitsRequireSameClass.txt b/compiler/testData/diagnostics/tests/traitWithRequired/manyTraitsRequireSameClass.txt
index abc258149b4..350b5b50b2f 100644
--- a/compiler/testData/diagnostics/tests/traitWithRequired/manyTraitsRequireSameClass.txt
+++ b/compiler/testData/diagnostics/tests/traitWithRequired/manyTraitsRequireSameClass.txt
@@ -1,24 +1,24 @@
 package
 
-internal trait A : Required {
+internal interface A : Required {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B : A, Required {
+internal interface B : A, Required {
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait C : Required {
+internal interface C : Required {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait D : B, Required {
+internal interface D : B, Required {
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/traitWithRequired/requirementFulfilledBySubclass.txt b/compiler/testData/diagnostics/tests/traitWithRequired/requirementFulfilledBySubclass.txt
index a488bc7c4a7..384a8cdec9f 100644
--- a/compiler/testData/diagnostics/tests/traitWithRequired/requirementFulfilledBySubclass.txt
+++ b/compiler/testData/diagnostics/tests/traitWithRequired/requirementFulfilledBySubclass.txt
@@ -28,7 +28,7 @@ internal open class RequiredDerived : RequiredBase {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Trait : RequiredBase {
+internal interface Trait : RequiredBase {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/traitWithRequired/traitExtendsTraitWithRequired.txt b/compiler/testData/diagnostics/tests/traitWithRequired/traitExtendsTraitWithRequired.txt
index 01a5670a157..9be8c52256c 100644
--- a/compiler/testData/diagnostics/tests/traitWithRequired/traitExtendsTraitWithRequired.txt
+++ b/compiler/testData/diagnostics/tests/traitWithRequired/traitExtendsTraitWithRequired.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait First : Required {
+internal interface First : Required {
     internal final override /*1*/ /*fake_override*/ val value: kotlin.String
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -15,7 +15,7 @@ internal open class Required {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Second : First {
+internal interface Second : First {
     internal final override /*1*/ /*fake_override*/ val value: kotlin.String
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/traitWithRequired/traitRequiresAny.txt b/compiler/testData/diagnostics/tests/traitWithRequired/traitRequiresAny.txt
index 0a63560d325..0eec9648931 100644
--- a/compiler/testData/diagnostics/tests/traitWithRequired/traitRequiresAny.txt
+++ b/compiler/testData/diagnostics/tests/traitWithRequired/traitRequiresAny.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait AnyTrait {
+internal interface AnyTrait {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/traitWithRequired/traitSupertypeList.txt b/compiler/testData/diagnostics/tests/traitWithRequired/traitSupertypeList.txt
index d6e728cda7d..451d0ab9a09 100644
--- a/compiler/testData/diagnostics/tests/traitWithRequired/traitSupertypeList.txt
+++ b/compiler/testData/diagnostics/tests/traitWithRequired/traitSupertypeList.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait Foo : bar, bar, bar {
+internal interface Foo : bar, bar, bar {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -20,7 +20,7 @@ internal open class Foo12 : bar, bar {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Foo2 : bar, Foo {
+internal interface Foo2 : bar, Foo {
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/traitWithRequired/uninheritableTraitDifferentGenericArguments.txt b/compiler/testData/diagnostics/tests/traitWithRequired/uninheritableTraitDifferentGenericArguments.txt
index 40bbbe4c50c..0ecd458ba78 100644
--- a/compiler/testData/diagnostics/tests/traitWithRequired/uninheritableTraitDifferentGenericArguments.txt
+++ b/compiler/testData/diagnostics/tests/traitWithRequired/uninheritableTraitDifferentGenericArguments.txt
@@ -1,18 +1,18 @@
 package
 
-internal trait A : Generic<kotlin.String> {
+internal interface A : Generic<kotlin.String> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B : Generic<kotlin.Int> {
+internal interface B : Generic<kotlin.Int> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait C : A, B {
+internal interface C : A, B {
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/variance/Class.txt b/compiler/testData/diagnostics/tests/variance/Class.txt
index 554bd02b7ed..30d047ea9b5 100644
--- a/compiler/testData/diagnostics/tests/variance/Class.txt
+++ b/compiler/testData/diagnostics/tests/variance/Class.txt
@@ -1,18 +1,18 @@
 package
 
-internal trait In</*0*/ in T> {
+internal interface In</*0*/ in T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Inv</*0*/ T> {
+internal interface Inv</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Out</*0*/ out T> {
+internal interface Out</*0*/ out T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -67,61 +67,61 @@ internal final class SubClass7</*0*/ in I, /*1*/ out O, /*2*/ P> : Inv<I> {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait TypeBounds1</*0*/ in I, /*1*/ out O, /*2*/ P, /*3*/ X : I> {
+internal interface TypeBounds1</*0*/ in I, /*1*/ out O, /*2*/ P, /*3*/ X : I> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait TypeBounds2</*0*/ in I, /*1*/ out O, /*2*/ P, /*3*/ X : O> {
+internal interface TypeBounds2</*0*/ in I, /*1*/ out O, /*2*/ P, /*3*/ X : O> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait TypeBounds3</*0*/ in I, /*1*/ out O, /*2*/ P, /*3*/ X : P> {
+internal interface TypeBounds3</*0*/ in I, /*1*/ out O, /*2*/ P, /*3*/ X : P> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait TypeBounds4</*0*/ in I, /*1*/ out O, /*2*/ P, /*3*/ X : In<I>> {
+internal interface TypeBounds4</*0*/ in I, /*1*/ out O, /*2*/ P, /*3*/ X : In<I>> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait TypeBounds5</*0*/ in I, /*1*/ out O, /*2*/ P, /*3*/ X : In<O>> {
+internal interface TypeBounds5</*0*/ in I, /*1*/ out O, /*2*/ P, /*3*/ X : In<O>> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait WhereTypeBounds1</*0*/ in I, /*1*/ out O, /*2*/ P, /*3*/ X : I> {
+internal interface WhereTypeBounds1</*0*/ in I, /*1*/ out O, /*2*/ P, /*3*/ X : I> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait WhereTypeBounds2</*0*/ in I, /*1*/ out O, /*2*/ P, /*3*/ X : O> {
+internal interface WhereTypeBounds2</*0*/ in I, /*1*/ out O, /*2*/ P, /*3*/ X : O> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait WhereTypeBounds3</*0*/ in I, /*1*/ out O, /*2*/ P, /*3*/ X : P> {
+internal interface WhereTypeBounds3</*0*/ in I, /*1*/ out O, /*2*/ P, /*3*/ X : P> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait WhereTypeBounds4</*0*/ in I, /*1*/ out O, /*2*/ P, /*3*/ X : In<I>> {
+internal interface WhereTypeBounds4</*0*/ in I, /*1*/ out O, /*2*/ P, /*3*/ X : In<I>> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait WhereTypeBounds5</*0*/ in I, /*1*/ out O, /*2*/ P, /*3*/ X : In<O>> {
+internal interface WhereTypeBounds5</*0*/ in I, /*1*/ out O, /*2*/ P, /*3*/ X : In<O>> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/variance/Function.txt b/compiler/testData/diagnostics/tests/variance/Function.txt
index f8dc7da4737..ff5281e3a0d 100644
--- a/compiler/testData/diagnostics/tests/variance/Function.txt
+++ b/compiler/testData/diagnostics/tests/variance/Function.txt
@@ -2,25 +2,25 @@ package
 
 internal fun </*0*/ T> getT(): T
 
-internal trait In</*0*/ in T> {
+internal interface In</*0*/ in T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Inv</*0*/ T> {
+internal interface Inv</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Out</*0*/ out T> {
+internal interface Out</*0*/ out T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Test</*0*/ in I, /*1*/ out O, /*2*/ P> {
+internal interface Test</*0*/ in I, /*1*/ out O, /*2*/ P> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun explicitReturnType1(): I
     internal abstract fun explicitReturnType2(): O
diff --git a/compiler/testData/diagnostics/tests/variance/FunctionTypes.txt b/compiler/testData/diagnostics/tests/variance/FunctionTypes.txt
index ff94d5130d1..ea8ac76be04 100644
--- a/compiler/testData/diagnostics/tests/variance/FunctionTypes.txt
+++ b/compiler/testData/diagnostics/tests/variance/FunctionTypes.txt
@@ -2,13 +2,13 @@ package
 
 internal fun </*0*/ T> getT(): T
 
-internal trait In</*0*/ in T> {
+internal interface In</*0*/ in T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Test</*0*/ in I, /*1*/ out O, /*2*/ P> {
+internal interface Test</*0*/ in I, /*1*/ out O, /*2*/ P> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     internal abstract fun neOk1(/*0*/ i: (I) -> O): (O) -> I
diff --git a/compiler/testData/diagnostics/tests/variance/InPosition.txt b/compiler/testData/diagnostics/tests/variance/InPosition.txt
index 3b26735009e..46c8dfdc098 100644
--- a/compiler/testData/diagnostics/tests/variance/InPosition.txt
+++ b/compiler/testData/diagnostics/tests/variance/InPosition.txt
@@ -1,30 +1,30 @@
 package
 
-internal trait In</*0*/ in T> {
+internal interface In</*0*/ in T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Inv</*0*/ T> {
+internal interface Inv</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Out</*0*/ out T> {
+internal interface Out</*0*/ out T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Pair</*0*/ out X, /*1*/ out Y> {
+internal interface Pair</*0*/ out X, /*1*/ out Y> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Test</*0*/ in I, /*1*/ out O, /*2*/ P> {
+internal interface Test</*0*/ in I, /*1*/ out O, /*2*/ P> {
     internal abstract fun Ok10(/*0*/ i: I): kotlin.Unit
     internal abstract fun Ok11(/*0*/ i: In<O>): kotlin.Unit
     internal abstract fun Ok12(/*0*/ i: In<In<I>>): kotlin.Unit
diff --git a/compiler/testData/diagnostics/tests/variance/InvariantPosition.txt b/compiler/testData/diagnostics/tests/variance/InvariantPosition.txt
index 8a693c7ac9d..b360a66dfc6 100644
--- a/compiler/testData/diagnostics/tests/variance/InvariantPosition.txt
+++ b/compiler/testData/diagnostics/tests/variance/InvariantPosition.txt
@@ -1,30 +1,30 @@
 package
 
-internal trait In</*0*/ in T> {
+internal interface In</*0*/ in T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Inv</*0*/ T> {
+internal interface Inv</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Out</*0*/ out T> {
+internal interface Out</*0*/ out T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Pair</*0*/ out X, /*1*/ out Y> {
+internal interface Pair</*0*/ out X, /*1*/ out Y> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Test</*0*/ in I, /*1*/ out O, /*2*/ P> {
+internal interface Test</*0*/ in I, /*1*/ out O, /*2*/ P> {
     internal abstract var neOk1: O
     internal abstract var neOk10: In<out I>
     internal abstract var neOk11: I
diff --git a/compiler/testData/diagnostics/tests/variance/NullableTypes.txt b/compiler/testData/diagnostics/tests/variance/NullableTypes.txt
index 534848de87f..7a4549a884d 100644
--- a/compiler/testData/diagnostics/tests/variance/NullableTypes.txt
+++ b/compiler/testData/diagnostics/tests/variance/NullableTypes.txt
@@ -2,25 +2,25 @@ package
 
 internal fun </*0*/ T> getT(): T
 
-internal trait In</*0*/ in I> {
+internal interface In</*0*/ in I> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Inv</*0*/ P> {
+internal interface Inv</*0*/ P> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Out</*0*/ out O> {
+internal interface Out</*0*/ out O> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Test</*0*/ in I : kotlin.Any, /*1*/ out O : kotlin.Any, /*2*/ P : kotlin.Any> {
+internal interface Test</*0*/ in I : kotlin.Any, /*1*/ out O : kotlin.Any, /*2*/ P : kotlin.Any> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     internal abstract fun neOk(/*0*/ i: Out<O?>?): In<O?>?
diff --git a/compiler/testData/diagnostics/tests/variance/OutPosition.txt b/compiler/testData/diagnostics/tests/variance/OutPosition.txt
index 5c44a5b01e3..302cdadf252 100644
--- a/compiler/testData/diagnostics/tests/variance/OutPosition.txt
+++ b/compiler/testData/diagnostics/tests/variance/OutPosition.txt
@@ -1,30 +1,30 @@
 package
 
-internal trait In</*0*/ in T> {
+internal interface In</*0*/ in T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Inv</*0*/ T> {
+internal interface Inv</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Out</*0*/ out T> {
+internal interface Out</*0*/ out T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Pair</*0*/ out X, /*1*/ out Y> {
+internal interface Pair</*0*/ out X, /*1*/ out Y> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Test</*0*/ in I, /*1*/ out O, /*2*/ P> {
+internal interface Test</*0*/ in I, /*1*/ out O, /*2*/ P> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     internal abstract fun neOk1(): I
diff --git a/compiler/testData/diagnostics/tests/variance/PrimaryConstructor.txt b/compiler/testData/diagnostics/tests/variance/PrimaryConstructor.txt
index 4d4d856242b..6a8adcc3a6a 100644
--- a/compiler/testData/diagnostics/tests/variance/PrimaryConstructor.txt
+++ b/compiler/testData/diagnostics/tests/variance/PrimaryConstructor.txt
@@ -2,19 +2,19 @@ package
 
 internal fun </*0*/ T> getT(): T
 
-internal trait In</*0*/ in T> {
+internal interface In</*0*/ in T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Inv</*0*/ T> {
+internal interface Inv</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Out</*0*/ out T> {
+internal interface Out</*0*/ out T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/variance/ValProperty.txt b/compiler/testData/diagnostics/tests/variance/ValProperty.txt
index 223f3a41f38..9de76fdf5f7 100644
--- a/compiler/testData/diagnostics/tests/variance/ValProperty.txt
+++ b/compiler/testData/diagnostics/tests/variance/ValProperty.txt
@@ -11,19 +11,19 @@ internal final class Delegate</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait In</*0*/ in T> {
+internal interface In</*0*/ in T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Inv</*0*/ T> {
+internal interface Inv</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Out</*0*/ out T> {
+internal interface Out</*0*/ out T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/variance/VarProperty.txt b/compiler/testData/diagnostics/tests/variance/VarProperty.txt
index 1447ada8c8a..5514e7f6508 100644
--- a/compiler/testData/diagnostics/tests/variance/VarProperty.txt
+++ b/compiler/testData/diagnostics/tests/variance/VarProperty.txt
@@ -11,19 +11,19 @@ internal final class Delegate</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait In</*0*/ in T> {
+internal interface In</*0*/ in T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Inv</*0*/ T> {
+internal interface Inv</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Out</*0*/ out T> {
+internal interface Out</*0*/ out T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/variance/Visibility.txt b/compiler/testData/diagnostics/tests/variance/Visibility.txt
index 8e04b04e237..02a31fbad90 100644
--- a/compiler/testData/diagnostics/tests/variance/Visibility.txt
+++ b/compiler/testData/diagnostics/tests/variance/Visibility.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait Test</*0*/ in I, /*1*/ out O> {
+internal interface Test</*0*/ in I, /*1*/ out O> {
     internal abstract var interlan_private_set: O
     internal abstract val internal_val: I
     private/*private to this*/ abstract var private_private_set: O
diff --git a/compiler/testData/diagnostics/tests/variance/privateToThis/Trait.txt b/compiler/testData/diagnostics/tests/variance/privateToThis/Trait.txt
index 3f4d06af6b9..e5d296595d1 100644
--- a/compiler/testData/diagnostics/tests/variance/privateToThis/Trait.txt
+++ b/compiler/testData/diagnostics/tests/variance/privateToThis/Trait.txt
@@ -1,6 +1,6 @@
-package 
+package
 
-internal trait Test</*0*/ in I> {
+internal interface Test</*0*/ in I> {
     private/*private to this*/ final val i: I
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     private/*private to this*/ final fun foo(): I
diff --git a/compiler/testData/diagnostics/testsWithJsStdLib/dynamicTypes/delegationBy.txt b/compiler/testData/diagnostics/testsWithJsStdLib/dynamicTypes/delegationBy.txt
index ad197003b18..858ae2fa9e5 100644
--- a/compiler/testData/diagnostics/testsWithJsStdLib/dynamicTypes/delegationBy.txt
+++ b/compiler/testData/diagnostics/testsWithJsStdLib/dynamicTypes/delegationBy.txt
@@ -8,7 +8,7 @@ internal final class C : Tr {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Tr {
+internal interface Tr {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/testsWithJsStdLib/dynamicTypes/inference.txt b/compiler/testData/diagnostics/testsWithJsStdLib/dynamicTypes/inference.txt
index 9f23d38fdf0..233a9144840 100644
--- a/compiler/testData/diagnostics/testsWithJsStdLib/dynamicTypes/inference.txt
+++ b/compiler/testData/diagnostics/testsWithJsStdLib/dynamicTypes/inference.txt
@@ -20,7 +20,7 @@ internal final class In</*0*/ in T> {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Tr {
+internal interface Tr {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/testsWithJsStdLib/dynamicTypes/overrides.txt b/compiler/testData/diagnostics/testsWithJsStdLib/dynamicTypes/overrides.txt
index 5ac77200423..67a968f0af3 100644
--- a/compiler/testData/diagnostics/testsWithJsStdLib/dynamicTypes/overrides.txt
+++ b/compiler/testData/diagnostics/testsWithJsStdLib/dynamicTypes/overrides.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait A {
+internal interface A {
     internal abstract fun dynamic(/*0*/ p: dynamic): dynamic
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(/*0*/ p: P): R
@@ -8,14 +8,14 @@ internal trait A {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait A1 {
+internal interface A1 {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(/*0*/ p: dynamic): dynamic
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait B : A {
+internal interface B : A {
     internal abstract override /*1*/ fun dynamic(/*0*/ p: P): R
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract override /*1*/ fun foo(/*0*/ p: dynamic): dynamic
@@ -23,7 +23,7 @@ internal trait B : A {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait C : A, A1 {
+internal interface C : A, A1 {
     internal abstract override /*1*/ /*fake_override*/ fun dynamic(/*0*/ p: dynamic): dynamic
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract override /*2*/ /*fake_override*/ fun foo(/*0*/ p: dynamic): dynamic
@@ -31,13 +31,13 @@ internal trait C : A, A1 {
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait P {
+internal interface P {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait R {
+internal interface R {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/testsWithJsStdLib/dynamicTypes/supertypesAndBounds.txt b/compiler/testData/diagnostics/testsWithJsStdLib/dynamicTypes/supertypesAndBounds.txt
index fa154ba21ac..58a74f3c4c9 100644
--- a/compiler/testData/diagnostics/testsWithJsStdLib/dynamicTypes/supertypesAndBounds.txt
+++ b/compiler/testData/diagnostics/testsWithJsStdLib/dynamicTypes/supertypesAndBounds.txt
@@ -9,7 +9,7 @@ internal final class C</*0*/ T : dynamic> {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Tr {
+internal interface Tr {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/testsWithJsStdLib/native/optionlBody/native.txt b/compiler/testData/diagnostics/testsWithJsStdLib/native/optionlBody/native.txt
index 8c8a4777cfb..a280b551dd0 100644
--- a/compiler/testData/diagnostics/testsWithJsStdLib/native/optionlBody/native.txt
+++ b/compiler/testData/diagnostics/testsWithJsStdLib/native/optionlBody/native.txt
@@ -42,7 +42,7 @@ kotlin.js.native() internal object O {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-kotlin.js.native() internal trait T {
+kotlin.js.native() internal interface T {
     internal abstract val baz: kotlin.Int
     internal open fun bar(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
diff --git a/compiler/testData/diagnostics/testsWithJsStdLib/native/optionlBody/nativeGetter.txt b/compiler/testData/diagnostics/testsWithJsStdLib/native/optionlBody/nativeGetter.txt
index 21f48ba82b0..aad4bb46937 100644
--- a/compiler/testData/diagnostics/testsWithJsStdLib/native/optionlBody/nativeGetter.txt
+++ b/compiler/testData/diagnostics/testsWithJsStdLib/native/optionlBody/nativeGetter.txt
@@ -3,7 +3,7 @@ package
 kotlin.js.nativeGetter() internal fun kotlin.String.bar(/*0*/ n: kotlin.Int): kotlin.Int?
 kotlin.js.nativeGetter() internal fun kotlin.String.foo(/*0*/ n: kotlin.Int): kotlin.Int?
 
-kotlin.js.native() internal trait T {
+kotlin.js.native() internal interface T {
     kotlin.js.nativeGetter() internal open fun bar(/*0*/ d: kotlin.Double): kotlin.String?
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     kotlin.js.nativeGetter() internal abstract fun foo(/*0*/ d: kotlin.Double): kotlin.String?
diff --git a/compiler/testData/diagnostics/testsWithJsStdLib/unsupportedFeatures/nestedInnerClassifier.txt b/compiler/testData/diagnostics/testsWithJsStdLib/unsupportedFeatures/nestedInnerClassifier.txt
index b26fe7edf68..2de5f46e3a8 100644
--- a/compiler/testData/diagnostics/testsWithJsStdLib/unsupportedFeatures/nestedInnerClassifier.txt
+++ b/compiler/testData/diagnostics/testsWithJsStdLib/unsupportedFeatures/nestedInnerClassifier.txt
@@ -33,12 +33,12 @@ internal final class A {
             public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
         }
 
-        internal trait T {
+        internal interface T {
             public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
             public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
             public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 
-            internal trait A {
+            internal interface A {
                 public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
                 public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
                 public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -108,12 +108,12 @@ internal final class A {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait T {
+    internal interface T {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 
-        internal trait A {
+        internal interface A {
             public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
             public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
             public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -191,12 +191,12 @@ internal final enum class E : kotlin.Enum<E> {
             public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
         }
 
-        internal trait T {
+        internal interface T {
             public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
             public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
             public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 
-            internal trait A {
+            internal interface A {
                 public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
                 public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
                 public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -266,12 +266,12 @@ internal final enum class E : kotlin.Enum<E> {
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
 
-    internal trait T {
+    internal interface T {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 
-        internal trait A {
+        internal interface A {
             public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
             public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
             public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -297,7 +297,7 @@ internal final enum class E : kotlin.Enum<E> {
     public final /*synthesized*/ fun values(): kotlin.Array<E>
 }
 
-internal trait T {
+internal interface T {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -329,12 +329,12 @@ internal trait T {
             public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
         }
 
-        internal trait T {
+        internal interface T {
             public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
             public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
             public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 
-            internal trait A {
+            internal interface A {
                 public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
                 public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
                 public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
@@ -397,12 +397,12 @@ internal trait T {
         public final /*synthesized*/ fun values(): kotlin.Array<T.E>
     }
 
-    internal trait T {
+    internal interface T {
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 
-        internal trait A {
+        internal interface A {
             public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
             public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
             public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/testsWithStdLib/annotations/jvmOverloads/JvmOverloadWithNoDefaults.txt b/compiler/testData/diagnostics/testsWithStdLib/annotations/jvmOverloads/JvmOverloadWithNoDefaults.txt
index 94744d9c0cc..51af08f81dd 100644
--- a/compiler/testData/diagnostics/testsWithStdLib/annotations/jvmOverloads/JvmOverloadWithNoDefaults.txt
+++ b/compiler/testData/diagnostics/testsWithStdLib/annotations/jvmOverloads/JvmOverloadWithNoDefaults.txt
@@ -1,4 +1,4 @@
-package 
+package
 
 internal final class C {
     kotlin.jvm.overloads() public constructor C()
diff --git a/compiler/testData/diagnostics/testsWithStdLib/annotations/jvmOverloads/jvmOverloadsOnAbstractMethods.txt b/compiler/testData/diagnostics/testsWithStdLib/annotations/jvmOverloads/jvmOverloadsOnAbstractMethods.txt
index 538ad90e3f0..11f073d545d 100644
--- a/compiler/testData/diagnostics/testsWithStdLib/annotations/jvmOverloads/jvmOverloadsOnAbstractMethods.txt
+++ b/compiler/testData/diagnostics/testsWithStdLib/annotations/jvmOverloads/jvmOverloadsOnAbstractMethods.txt
@@ -8,7 +8,7 @@ internal abstract class C {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait T {
+internal interface T {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     kotlin.jvm.overloads() internal abstract fun foo(/*0*/ s: kotlin.String = ...): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/testsWithStdLib/annotations/jvmOverloads/jvmOverloadsOnPrivate.txt b/compiler/testData/diagnostics/testsWithStdLib/annotations/jvmOverloads/jvmOverloadsOnPrivate.txt
index 445b042749e..165437ac82e 100644
--- a/compiler/testData/diagnostics/testsWithStdLib/annotations/jvmOverloads/jvmOverloadsOnPrivate.txt
+++ b/compiler/testData/diagnostics/testsWithStdLib/annotations/jvmOverloads/jvmOverloadsOnPrivate.txt
@@ -1,4 +1,4 @@
-package 
+package
 
 internal fun foo(): kotlin.Unit
 
diff --git a/compiler/testData/diagnostics/testsWithStdLib/annotations/platformStatic/functions.txt b/compiler/testData/diagnostics/testsWithStdLib/annotations/platformStatic/functions.txt
index 69bcae1df46..30a9c51cf88 100644
--- a/compiler/testData/diagnostics/testsWithStdLib/annotations/platformStatic/functions.txt
+++ b/compiler/testData/diagnostics/testsWithStdLib/annotations/platformStatic/functions.txt
@@ -25,7 +25,7 @@ internal final class A {
     }
 }
 
-internal trait B {
+internal interface B {
     kotlin.platform.platformStatic() internal open fun a4(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/testsWithStdLib/callableReference/function/abstractClassConstructors.txt b/compiler/testData/diagnostics/testsWithStdLib/callableReference/function/abstractClassConstructors.txt
index 44fc782f081..7461e6948ce 100644
--- a/compiler/testData/diagnostics/testsWithStdLib/callableReference/function/abstractClassConstructors.txt
+++ b/compiler/testData/diagnostics/testsWithStdLib/callableReference/function/abstractClassConstructors.txt
@@ -2,7 +2,7 @@ package
 
 internal fun main(): kotlin.Unit
 
-internal trait A {
+internal interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/testsWithStdLib/callableReference/property/abstractPropertyViaSubclasses.txt b/compiler/testData/diagnostics/testsWithStdLib/callableReference/property/abstractPropertyViaSubclasses.txt
index 13e10a2a077..756498f3cc4 100644
--- a/compiler/testData/diagnostics/testsWithStdLib/callableReference/property/abstractPropertyViaSubclasses.txt
+++ b/compiler/testData/diagnostics/testsWithStdLib/callableReference/property/abstractPropertyViaSubclasses.txt
@@ -18,7 +18,7 @@ internal open class B : Base {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-internal trait Base {
+internal interface Base {
     internal abstract val x: kotlin.Any
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/testsWithStdLib/classLiteral/arrays.txt b/compiler/testData/diagnostics/testsWithStdLib/classLiteral/arrays.txt
index 25db3962249..6608ab99fc8 100644
--- a/compiler/testData/diagnostics/testsWithStdLib/classLiteral/arrays.txt
+++ b/compiler/testData/diagnostics/testsWithStdLib/classLiteral/arrays.txt
@@ -1,4 +1,4 @@
-package 
+package
 
 internal val a01: [ERROR : Unresolved class]
 internal val a02: kotlin.reflect.KClass<kotlin.Array<[ERROR : Array]>>
diff --git a/compiler/testData/diagnostics/testsWithStdLib/duplicateJvmSignature/jvmOverloads.txt b/compiler/testData/diagnostics/testsWithStdLib/duplicateJvmSignature/jvmOverloads.txt
index f23d170aed0..74e6d811018 100644
--- a/compiler/testData/diagnostics/testsWithStdLib/duplicateJvmSignature/jvmOverloads.txt
+++ b/compiler/testData/diagnostics/testsWithStdLib/duplicateJvmSignature/jvmOverloads.txt
@@ -1,4 +1,4 @@
-package 
+package
 
 internal final class A {
     public constructor A()
diff --git a/compiler/testData/diagnostics/testsWithStdLib/kotlinSignature/parameterNames.txt b/compiler/testData/diagnostics/testsWithStdLib/kotlinSignature/parameterNames.txt
index f7292720f4b..46b70e5cab9 100644
--- a/compiler/testData/diagnostics/testsWithStdLib/kotlinSignature/parameterNames.txt
+++ b/compiler/testData/diagnostics/testsWithStdLib/kotlinSignature/parameterNames.txt
@@ -2,7 +2,7 @@ package
 
 public/*package*/ /*synthesized*/ fun A(/*0*/ function: (kotlin.String!) -> kotlin.Unit): A
 
-public/*package*/ trait A {
+public/*package*/ interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public abstract fun foo(/*0*/ kotlinSignatureName: kotlin.String!): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/testsWithStdLib/native/override.txt b/compiler/testData/diagnostics/testsWithStdLib/native/override.txt
index a37eed75a13..09750bfa064 100644
--- a/compiler/testData/diagnostics/testsWithStdLib/native/override.txt
+++ b/compiler/testData/diagnostics/testsWithStdLib/native/override.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait Base {
+internal interface Base {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     internal abstract fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
diff --git a/compiler/testData/diagnostics/testsWithStdLib/native/trait.txt b/compiler/testData/diagnostics/testsWithStdLib/native/trait.txt
index fa7e017e32c..bec001b6a7c 100644
--- a/compiler/testData/diagnostics/testsWithStdLib/native/trait.txt
+++ b/compiler/testData/diagnostics/testsWithStdLib/native/trait.txt
@@ -1,6 +1,6 @@
 package
 
-internal trait Tr {
+internal interface Tr {
     kotlin.jvm.native() internal open fun bar(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     kotlin.jvm.native() internal abstract fun foo(): kotlin.Unit
diff --git a/compiler/testData/loadJava/compiledJava/InheritMethodsDifferentReturnTypes.txt b/compiler/testData/loadJava/compiledJava/InheritMethodsDifferentReturnTypes.txt
index dcdd3a7083d..ee1f65496a6 100644
--- a/compiler/testData/loadJava/compiledJava/InheritMethodsDifferentReturnTypes.txt
+++ b/compiler/testData/loadJava/compiledJava/InheritMethodsDifferentReturnTypes.txt
@@ -3,17 +3,17 @@ package test
 public final class InheritMethodsDifferentReturnTypes {
     public constructor InheritMethodsDifferentReturnTypes()
 
-    public trait Sub : test.InheritMethodsDifferentReturnTypes.Super1, test.InheritMethodsDifferentReturnTypes.Super2 {
+    public interface Sub : test.InheritMethodsDifferentReturnTypes.Super1, test.InheritMethodsDifferentReturnTypes.Super2 {
         public abstract override /*2*/ /*fake_override*/ fun bar(): kotlin.String!
         public abstract override /*2*/ /*fake_override*/ fun foo(): kotlin.String!
     }
 
-    public trait Super1 {
+    public interface Super1 {
         public abstract fun bar(): kotlin.String!
         public abstract fun foo(): kotlin.CharSequence!
     }
 
-    public trait Super2 {
+    public interface Super2 {
         public abstract fun bar(): kotlin.CharSequence!
         public abstract fun foo(): kotlin.String!
     }
diff --git a/compiler/testData/loadJava/compiledJava/InheritMethodsDifferentReturnTypesGeneric.txt b/compiler/testData/loadJava/compiledJava/InheritMethodsDifferentReturnTypesGeneric.txt
index b7fa12bb112..74e027a740c 100644
--- a/compiler/testData/loadJava/compiledJava/InheritMethodsDifferentReturnTypesGeneric.txt
+++ b/compiler/testData/loadJava/compiledJava/InheritMethodsDifferentReturnTypesGeneric.txt
@@ -3,17 +3,17 @@ package test
 public final class InheritMethodsDifferentReturnTypesGeneric {
     public constructor InheritMethodsDifferentReturnTypesGeneric()
 
-    public trait Sub : test.InheritMethodsDifferentReturnTypesGeneric.Super1<kotlin.String!, kotlin.CharSequence!>, test.InheritMethodsDifferentReturnTypesGeneric.Super2<kotlin.CharSequence!, kotlin.String!> {
+    public interface Sub : test.InheritMethodsDifferentReturnTypesGeneric.Super1<kotlin.String!, kotlin.CharSequence!>, test.InheritMethodsDifferentReturnTypesGeneric.Super2<kotlin.CharSequence!, kotlin.String!> {
         public abstract override /*2*/ /*fake_override*/ fun bar(): kotlin.String!
         public abstract override /*2*/ /*fake_override*/ fun foo(): kotlin.String!
     }
 
-    public trait Super1</*0*/ F, /*1*/ B> {
+    public interface Super1</*0*/ F, /*1*/ B> {
         public abstract fun bar(): B!
         public abstract fun foo(): F!
     }
 
-    public trait Super2</*0*/ FF, /*1*/ BB> {
+    public interface Super2</*0*/ FF, /*1*/ BB> {
         public abstract fun bar(): BB!
         public abstract fun foo(): FF!
     }
diff --git a/compiler/testData/loadJava/compiledJava/IntrinsicCompanionObject.txt b/compiler/testData/loadJava/compiledJava/IntrinsicCompanionObject.txt
index e43a375f490..a73092b50eb 100644
--- a/compiler/testData/loadJava/compiledJava/IntrinsicCompanionObject.txt
+++ b/compiler/testData/loadJava/compiledJava/IntrinsicCompanionObject.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait IntrinsicCompanionObject {
+public interface IntrinsicCompanionObject {
     public abstract fun testChar(/*0*/ p0: kotlin.Char.Companion!): kotlin.Unit
     public abstract fun testEnum(/*0*/ p0: kotlin.Enum.Companion!): kotlin.Unit
     public abstract fun testInt(/*0*/ p0: kotlin.Int.Companion!): kotlin.Unit
diff --git a/compiler/testData/loadJava/compiledJava/RawTypeWithUpperBound.txt b/compiler/testData/loadJava/compiledJava/RawTypeWithUpperBound.txt
index 2da9f8050de..8708cc1e291 100644
--- a/compiler/testData/loadJava/compiledJava/RawTypeWithUpperBound.txt
+++ b/compiler/testData/loadJava/compiledJava/RawTypeWithUpperBound.txt
@@ -1,12 +1,12 @@
 package test
 
-public trait RawTypeWithUpperBound {
+public interface RawTypeWithUpperBound {
 
-    public trait Bar {
+    public interface Bar {
         public abstract fun f(/*0*/ p0: test.RawTypeWithUpperBound.Foo<*>!): kotlin.Unit
         public abstract fun g(/*0*/ p0: kotlin.(Mutable)List<test.RawTypeWithUpperBound.Foo<*>!>!): kotlin.Unit
     }
 
-    public trait Foo</*0*/ T : kotlin.CharSequence!> {
+    public interface Foo</*0*/ T : kotlin.CharSequence!> {
     }
 }
diff --git a/compiler/testData/loadJava/compiledJava/RawUpperBound.txt b/compiler/testData/loadJava/compiledJava/RawUpperBound.txt
index 65d8019851c..d42d54146bd 100644
--- a/compiler/testData/loadJava/compiledJava/RawUpperBound.txt
+++ b/compiler/testData/loadJava/compiledJava/RawUpperBound.txt
@@ -1,4 +1,4 @@
 package test
 
-public trait RawUpperBound</*0*/ T : test.RawUpperBound<out kotlin.Any?>!> {
+public interface RawUpperBound</*0*/ T : test.RawUpperBound<out kotlin.Any?>!> {
 }
diff --git a/compiler/testData/loadJava/compiledJava/RecursiveRawUpperBound.txt b/compiler/testData/loadJava/compiledJava/RecursiveRawUpperBound.txt
index ad788854a94..93327f13d33 100644
--- a/compiler/testData/loadJava/compiledJava/RecursiveRawUpperBound.txt
+++ b/compiler/testData/loadJava/compiledJava/RecursiveRawUpperBound.txt
@@ -1,4 +1,4 @@
 package test
 
-public trait RecursiveRawUpperBound</*0*/ T : test.RecursiveRawUpperBound<out kotlin.Any?>!> {
+public interface RecursiveRawUpperBound</*0*/ T : test.RecursiveRawUpperBound<out kotlin.Any?>!> {
 }
diff --git a/compiler/testData/loadJava/compiledJava/RecursiveWildcardUpperBound.txt b/compiler/testData/loadJava/compiledJava/RecursiveWildcardUpperBound.txt
index 696b42d1f99..122200567f3 100644
--- a/compiler/testData/loadJava/compiledJava/RecursiveWildcardUpperBound.txt
+++ b/compiler/testData/loadJava/compiledJava/RecursiveWildcardUpperBound.txt
@@ -1,4 +1,4 @@
 package test
 
-public trait RecursiveWildcardUpperBound</*0*/ T : test.RecursiveWildcardUpperBound<out kotlin.Any?>!> {
+public interface RecursiveWildcardUpperBound</*0*/ T : test.RecursiveWildcardUpperBound<out kotlin.Any?>!> {
 }
diff --git a/compiler/testData/loadJava/compiledJava/RemoveRedundantProjectionKind.txt b/compiler/testData/loadJava/compiledJava/RemoveRedundantProjectionKind.txt
index dc7ef424f95..e458e5d84e9 100644
--- a/compiler/testData/loadJava/compiledJava/RemoveRedundantProjectionKind.txt
+++ b/compiler/testData/loadJava/compiledJava/RemoveRedundantProjectionKind.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait RemoveRedundantProjectionKind {
+public interface RemoveRedundantProjectionKind {
     public abstract fun f(/*0*/ p0: (kotlin.MutableCollection<out kotlin.CharSequence!>..kotlin.Collection<kotlin.CharSequence!>?)): kotlin.Unit
     public abstract fun f(/*0*/ p0: kotlin.Comparable<kotlin.CharSequence!>!): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/compiledJava/SubclassFromNested.txt b/compiler/testData/loadJava/compiledJava/SubclassFromNested.txt
index 43c922aaa87..177143a605b 100644
--- a/compiler/testData/loadJava/compiledJava/SubclassFromNested.txt
+++ b/compiler/testData/loadJava/compiledJava/SubclassFromNested.txt
@@ -3,7 +3,7 @@ package test
 public/*package*/ open class B {
     public/*package*/ constructor B(/*0*/ p0: test.B.C!)
 
-    public/*package*/ trait C {
+    public/*package*/ interface C {
     }
 }
 
diff --git a/compiler/testData/loadJava/compiledJava/UnboundWildcard.txt b/compiler/testData/loadJava/compiledJava/UnboundWildcard.txt
index a35728a2b0f..0a2d629ebae 100644
--- a/compiler/testData/loadJava/compiledJava/UnboundWildcard.txt
+++ b/compiler/testData/loadJava/compiledJava/UnboundWildcard.txt
@@ -5,6 +5,6 @@ public final class UnboundWildcard {
     public final fun collection(): kotlin.(Mutable)Collection<*>!
     public final fun foo(): test.UnboundWildcard.MyClass<*>!
 
-    public trait MyClass</*0*/ T : kotlin.CharSequence!> {
+    public interface MyClass</*0*/ T : kotlin.CharSequence!> {
     }
 }
diff --git a/compiler/testData/loadJava/compiledJava/annotations/AnnotationInParam.txt b/compiler/testData/loadJava/compiledJava/annotations/AnnotationInParam.txt
index 71d732de16f..c9d26fa2fc3 100644
--- a/compiler/testData/loadJava/compiledJava/annotations/AnnotationInParam.txt
+++ b/compiler/testData/loadJava/compiledJava/annotations/AnnotationInParam.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait AnnotationInParam {
+public interface AnnotationInParam {
 
     test.AnnotationInParam.MyAnnotationWithParam(value = test.AnnotationInParam.MyAnnotation(value = "test": kotlin.String): test.AnnotationInParam.MyAnnotation) public open class A {
         public constructor A()
diff --git a/compiler/testData/loadJava/compiledJava/annotations/ArrayOfEnumInParam.txt b/compiler/testData/loadJava/compiledJava/annotations/ArrayOfEnumInParam.txt
index 0b8dd8bf81b..0fa8e21f2e9 100644
--- a/compiler/testData/loadJava/compiledJava/annotations/ArrayOfEnumInParam.txt
+++ b/compiler/testData/loadJava/compiledJava/annotations/ArrayOfEnumInParam.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait ArrayOfEnumInParam {
+public interface ArrayOfEnumInParam {
 
     java.lang.annotation.Target(value = {ElementType.FIELD, ElementType.CONSTRUCTOR}: kotlin.Array<out java.lang.annotation.ElementType>) public final annotation class targetAnnotation : kotlin.Annotation {
         public constructor targetAnnotation(/*0*/ value: kotlin.String)
diff --git a/compiler/testData/loadJava/compiledJava/annotations/ArrayOfStringInParam.txt b/compiler/testData/loadJava/compiledJava/annotations/ArrayOfStringInParam.txt
index 73146d3948d..8da86225697 100644
--- a/compiler/testData/loadJava/compiledJava/annotations/ArrayOfStringInParam.txt
+++ b/compiler/testData/loadJava/compiledJava/annotations/ArrayOfStringInParam.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait ArrayOfStringInParam {
+public interface ArrayOfStringInParam {
 
     test.ArrayOfStringInParam.MyAnnotation(value = {"a", "b", "c"}: kotlin.Array<out kotlin.String>) public open class A {
         public constructor A()
diff --git a/compiler/testData/loadJava/compiledJava/annotations/CustomAnnotation.txt b/compiler/testData/loadJava/compiledJava/annotations/CustomAnnotation.txt
index 37ece374eb3..8ecdf54a28a 100644
--- a/compiler/testData/loadJava/compiledJava/annotations/CustomAnnotation.txt
+++ b/compiler/testData/loadJava/compiledJava/annotations/CustomAnnotation.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait CustomAnnotation {
+public interface CustomAnnotation {
 
     public final annotation class MyAnnotation : kotlin.Annotation {
         public constructor MyAnnotation(/*0*/ value: test.CustomAnnotation.MyEnum)
diff --git a/compiler/testData/loadJava/compiledJava/annotations/CustomAnnotationWithDefaultParameter.txt b/compiler/testData/loadJava/compiledJava/annotations/CustomAnnotationWithDefaultParameter.txt
index 60c06bb3ed4..1ae1ba060d5 100644
--- a/compiler/testData/loadJava/compiledJava/annotations/CustomAnnotationWithDefaultParameter.txt
+++ b/compiler/testData/loadJava/compiledJava/annotations/CustomAnnotationWithDefaultParameter.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait CustomAnnotationWithDefaultParameter {
+public interface CustomAnnotationWithDefaultParameter {
 
     public final annotation class MyAnnotation : kotlin.Annotation {
         public constructor MyAnnotation(/*0*/ first: kotlin.String, /*1*/ second: kotlin.String = ...)
diff --git a/compiler/testData/loadJava/compiledJava/annotations/EmptyArrayInParam.txt b/compiler/testData/loadJava/compiledJava/annotations/EmptyArrayInParam.txt
index dd078940821..d539c8e275c 100644
--- a/compiler/testData/loadJava/compiledJava/annotations/EmptyArrayInParam.txt
+++ b/compiler/testData/loadJava/compiledJava/annotations/EmptyArrayInParam.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait EmptyArrayInParam {
+public interface EmptyArrayInParam {
 
     test.EmptyArrayInParam.MyAnnotation(value = {}: kotlin.Array<out kotlin.String>) public open class A {
         public constructor A()
diff --git a/compiler/testData/loadJava/compiledJava/annotations/EnumInParam.txt b/compiler/testData/loadJava/compiledJava/annotations/EnumInParam.txt
index 47b58c62a38..25e1e2d765c 100644
--- a/compiler/testData/loadJava/compiledJava/annotations/EnumInParam.txt
+++ b/compiler/testData/loadJava/compiledJava/annotations/EnumInParam.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait EnumInParam {
+public interface EnumInParam {
 
     public final annotation class MyRetention : kotlin.Annotation {
         public constructor MyRetention(/*0*/ value: java.lang.annotation.RetentionPolicy)
diff --git a/compiler/testData/loadJava/compiledJava/annotations/PrimitiveValueInParam.txt b/compiler/testData/loadJava/compiledJava/annotations/PrimitiveValueInParam.txt
index fc9d24e7021..77614e20c80 100644
--- a/compiler/testData/loadJava/compiledJava/annotations/PrimitiveValueInParam.txt
+++ b/compiler/testData/loadJava/compiledJava/annotations/PrimitiveValueInParam.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait PrimitiveValueInParam {
+public interface PrimitiveValueInParam {
 
     test.PrimitiveValueInParam.Ann(bool = true: kotlin.Boolean, d = 1.0.toDouble(): kotlin.Double, f = 1.0.toFloat(): kotlin.Float, i = 1: kotlin.Int, l = 1.toLong(): kotlin.Long, str = "str": kotlin.String) public open class A {
         public constructor A()
diff --git a/compiler/testData/loadJava/compiledJava/annotations/RecursiveAnnotation.txt b/compiler/testData/loadJava/compiledJava/annotations/RecursiveAnnotation.txt
index 71e0c8c8b78..ab6cb6ca9d3 100644
--- a/compiler/testData/loadJava/compiledJava/annotations/RecursiveAnnotation.txt
+++ b/compiler/testData/loadJava/compiledJava/annotations/RecursiveAnnotation.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait RecursiveAnnotation {
+public interface RecursiveAnnotation {
 
     test.RecursiveAnnotation.B(value = test.RecursiveAnnotation.A(value = "test": kotlin.String): test.RecursiveAnnotation.A) public final annotation class A : kotlin.Annotation {
         public constructor A(/*0*/ value: kotlin.String)
diff --git a/compiler/testData/loadJava/compiledJava/annotations/RecursiveAnnotation2.txt b/compiler/testData/loadJava/compiledJava/annotations/RecursiveAnnotation2.txt
index e1c43fa7d2d..1f8c7650267 100644
--- a/compiler/testData/loadJava/compiledJava/annotations/RecursiveAnnotation2.txt
+++ b/compiler/testData/loadJava/compiledJava/annotations/RecursiveAnnotation2.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait RecursiveAnnotation2 {
+public interface RecursiveAnnotation2 {
 
     public final annotation class A : kotlin.Annotation {
         public constructor A(/*0*/ value: test.RecursiveAnnotation2.B)
diff --git a/compiler/testData/loadJava/compiledJava/annotations/StringConcatenationInParam.txt b/compiler/testData/loadJava/compiledJava/annotations/StringConcatenationInParam.txt
index 20d6a1910e3..9cfbe06e644 100644
--- a/compiler/testData/loadJava/compiledJava/annotations/StringConcatenationInParam.txt
+++ b/compiler/testData/loadJava/compiledJava/annotations/StringConcatenationInParam.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait StringConcatenationInParam {
+public interface StringConcatenationInParam {
 
     public final annotation class Anno : kotlin.Annotation {
         public constructor Anno(/*0*/ value: kotlin.String)
diff --git a/compiler/testData/loadJava/compiledJava/annotations/StringConstantInParam.txt b/compiler/testData/loadJava/compiledJava/annotations/StringConstantInParam.txt
index 77305dd680b..27ef0791895 100644
--- a/compiler/testData/loadJava/compiledJava/annotations/StringConstantInParam.txt
+++ b/compiler/testData/loadJava/compiledJava/annotations/StringConstantInParam.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait StringConstantInParam {
+public interface StringConstantInParam {
 
     public final annotation class Anno : kotlin.Annotation {
         public constructor Anno(/*0*/ value: kotlin.String)
diff --git a/compiler/testData/loadJava/compiledJava/annotations/StringInParam.txt b/compiler/testData/loadJava/compiledJava/annotations/StringInParam.txt
index 2a18e3e8db7..0a660a063a6 100644
--- a/compiler/testData/loadJava/compiledJava/annotations/StringInParam.txt
+++ b/compiler/testData/loadJava/compiledJava/annotations/StringInParam.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait StringInParam {
+public interface StringInParam {
 
     public final annotation class Anno : kotlin.Annotation {
         public constructor Anno(/*0*/ value: kotlin.String)
diff --git a/compiler/testData/loadJava/compiledJava/javaBean/JavaBeanAbstractGetter.txt b/compiler/testData/loadJava/compiledJava/javaBean/JavaBeanAbstractGetter.txt
index 597adaea6c9..b6090e7f803 100644
--- a/compiler/testData/loadJava/compiledJava/javaBean/JavaBeanAbstractGetter.txt
+++ b/compiler/testData/loadJava/compiledJava/javaBean/JavaBeanAbstractGetter.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait JavaBeanAbstractGetter {
+public interface JavaBeanAbstractGetter {
     public abstract fun getBlue(): kotlin.Int
     public abstract fun getRed(): kotlin.Int
 }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/StarProjection.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/StarProjection.txt
index 8beb7b953e9..06e9256e277 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/StarProjection.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/StarProjection.txt
@@ -4,6 +4,6 @@ public final class StarProjection {
     public constructor StarProjection()
     public final fun foo(): test.StarProjection.MyClass<*>!
 
-    public trait MyClass</*0*/ T : kotlin.CharSequence!> {
+    public interface MyClass</*0*/ T : kotlin.CharSequence!> {
     }
 }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/PropagateTypeArgumentNullable.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/PropagateTypeArgumentNullable.txt
index 85f4370f23d..1bc60744e10 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/PropagateTypeArgumentNullable.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/PropagateTypeArgumentNullable.txt
@@ -1,8 +1,8 @@
 package test
 
-public trait PropagateTypeArgumentNullable {
+public interface PropagateTypeArgumentNullable {
 
-    public trait Sub : test.PropagateTypeArgumentNullable.Super {
+    public interface Sub : test.PropagateTypeArgumentNullable.Super {
         public abstract override /*1*/ fun invOutR(): kotlin.(Mutable)List<kotlin.(Mutable)List<kotlin.String!>!>!
         public abstract override /*1*/ fun invOutS(/*0*/ p: kotlin.(Mutable)List<kotlin.(Mutable)List<kotlin.String!>!>!): kotlin.Unit
         public abstract override /*1*/ fun invR(): kotlin.(Mutable)List<kotlin.String!>!
@@ -11,7 +11,7 @@ public trait PropagateTypeArgumentNullable {
         public abstract override /*1*/ fun outS(/*0*/ p: kotlin.(Mutable)List<kotlin.String!>!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun invOutR(): kotlin.(Mutable)List<kotlin.(Mutable)List<kotlin.String!>!>!
         public abstract fun invOutS(/*0*/ p: kotlin.(Mutable)List<kotlin.(Mutable)List<kotlin.String!>!>!): kotlin.Unit
         public abstract fun invR(): kotlin.(Mutable)List<kotlin.String!>!
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/ChangeProjectionKind1.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/ChangeProjectionKind1.txt
index b8b22ffd656..c546f3bffec 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/ChangeProjectionKind1.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/ChangeProjectionKind1.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait ChangeProjectionKind1 {
+public interface ChangeProjectionKind1 {
 
-    public trait Sub : test.ChangeProjectionKind1.Super {
+    public interface Sub : test.ChangeProjectionKind1.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p: kotlin.(Mutable)List<kotlin.String!>!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p: kotlin.(Mutable)List<kotlin.String!>!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/ChangeProjectionKind2.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/ChangeProjectionKind2.txt
index 85789993833..b6bb37ef78c 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/ChangeProjectionKind2.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/ChangeProjectionKind2.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait ChangeProjectionKind2 {
+public interface ChangeProjectionKind2 {
 
-    public trait Sub : test.ChangeProjectionKind2.Super {
+    public interface Sub : test.ChangeProjectionKind2.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p: kotlin.(Mutable)List<kotlin.String!>!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p: kotlin.(Mutable)List<kotlin.String!>!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/DeeplySubstitutedClassParameter.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/DeeplySubstitutedClassParameter.txt
index 3d6383c247f..e4fa9a1abf9 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/DeeplySubstitutedClassParameter.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/DeeplySubstitutedClassParameter.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait DeeplySubstitutedClassParameter {
+public interface DeeplySubstitutedClassParameter {
 
-    public trait Middle</*0*/ E> : test.DeeplySubstitutedClassParameter.Super<E!> {
+    public interface Middle</*0*/ E> : test.DeeplySubstitutedClassParameter.Super<E!> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ t: E!): kotlin.Unit
     }
 
-    public trait Sub : test.DeeplySubstitutedClassParameter.Middle<kotlin.String!> {
+    public interface Sub : test.DeeplySubstitutedClassParameter.Middle<kotlin.String!> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ t: kotlin.String!): kotlin.Unit
     }
 
-    public trait Super</*0*/ T> {
+    public interface Super</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ t: T!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/DeeplySubstitutedClassParameter2.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/DeeplySubstitutedClassParameter2.txt
index b987addc4a2..5dea6d49d80 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/DeeplySubstitutedClassParameter2.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/DeeplySubstitutedClassParameter2.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait DeeplySubstitutedClassParameter2 {
+public interface DeeplySubstitutedClassParameter2 {
 
-    public trait Middle</*0*/ E> : test.DeeplySubstitutedClassParameter2.Super<E!> {
+    public interface Middle</*0*/ E> : test.DeeplySubstitutedClassParameter2.Super<E!> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ t: E!): kotlin.Unit
     }
 
-    public trait Sub : test.DeeplySubstitutedClassParameter2.Middle<kotlin.String!> {
+    public interface Sub : test.DeeplySubstitutedClassParameter2.Middle<kotlin.String!> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ t: kotlin.String!): kotlin.Unit
     }
 
-    public trait Super</*0*/ T> {
+    public interface Super</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ t: T!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritMutability.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritMutability.txt
index d3888dedbea..c6cadbf3fb4 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritMutability.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritMutability.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritMutability {
+public interface InheritMutability {
 
-    public trait Sub : test.InheritMutability.Super {
+    public interface Sub : test.InheritMutability.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p: kotlin.(Mutable)List<kotlin.String!>!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p: kotlin.(Mutable)List<kotlin.String!>!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritNotVararg.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritNotVararg.txt
index df4050a18e0..d5c09e06b57 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritNotVararg.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritNotVararg.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritNotVararg {
+public interface InheritNotVararg {
 
-    public trait Sub : test.InheritNotVararg.Super {
+    public interface Sub : test.InheritNotVararg.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p0: (kotlin.Array<kotlin.String!>?..kotlin.Array<out kotlin.String!>?)): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p0: kotlin.Array<(out) kotlin.String!>!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritNotVarargInteger.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritNotVarargInteger.txt
index b2af95f97ce..dc659f6a6ad 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritNotVarargInteger.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritNotVarargInteger.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritNotVarargInteger {
+public interface InheritNotVarargInteger {
 
-    public trait Sub : test.InheritNotVarargInteger.Super {
+    public interface Sub : test.InheritNotVarargInteger.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p0: (kotlin.Array<kotlin.Int!>?..kotlin.Array<out kotlin.Int!>?)): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p0: kotlin.Array<(out) kotlin.Int!>!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritNotVarargNotNull.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritNotVarargNotNull.txt
index b807a78954a..fc338970c32 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritNotVarargNotNull.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritNotVarargNotNull.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritNotVarargNotNull {
+public interface InheritNotVarargNotNull {
 
-    public trait Sub : test.InheritNotVarargNotNull.Super {
+    public interface Sub : test.InheritNotVarargNotNull.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p: (kotlin.Array<kotlin.String!>?..kotlin.Array<out kotlin.String!>?)): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p: kotlin.Array<(out) kotlin.String!>!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritNotVarargPrimitive.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritNotVarargPrimitive.txt
index e557d7f332f..cf51102e37a 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritNotVarargPrimitive.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritNotVarargPrimitive.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritNotVarargPrimitive {
+public interface InheritNotVarargPrimitive {
 
-    public trait Sub : test.InheritNotVarargPrimitive.Super {
+    public interface Sub : test.InheritNotVarargPrimitive.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p0: kotlin.IntArray?): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p0: kotlin.IntArray!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritNullability.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritNullability.txt
index 3cfb7f44cf9..e1fd0fc86de 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritNullability.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritNullability.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritNullability {
+public interface InheritNullability {
 
-    public trait Sub : test.InheritNullability.Super {
+    public interface Sub : test.InheritNullability.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p0: kotlin.String!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ org.jetbrains.annotations.NotNull() p0: kotlin.String!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritProjectionKind.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritProjectionKind.txt
index a7978aee1ea..ae31c078042 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritProjectionKind.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritProjectionKind.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritProjectionKind {
+public interface InheritProjectionKind {
 
-    public trait Sub : test.InheritProjectionKind.Super {
+    public interface Sub : test.InheritProjectionKind.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p: kotlin.(Mutable)List<kotlin.String!>!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p: kotlin.(Mutable)List<kotlin.String!>!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritReadOnliness.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritReadOnliness.txt
index f86d83f538d..f06ac4d88c4 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritReadOnliness.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritReadOnliness.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritReadOnliness {
+public interface InheritReadOnliness {
 
-    public trait Sub : test.InheritReadOnliness.Super {
+    public interface Sub : test.InheritReadOnliness.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p: kotlin.(Mutable)List<kotlin.String!>!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p: kotlin.(Mutable)List<kotlin.String!>!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritVararg.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritVararg.txt
index b61a2f38ec3..c020a7d2089 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritVararg.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritVararg.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritVararg {
+public interface InheritVararg {
 
-    public trait Sub : test.InheritVararg.Super {
+    public interface Sub : test.InheritVararg.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ vararg p0: kotlin.String! /*kotlin.Array<(out) kotlin.String!>!*/): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ vararg p0: kotlin.String! /*kotlin.Array<(out) kotlin.String!>!*/): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritVarargInteger.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritVarargInteger.txt
index b32494ba99f..85b925cd3ad 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritVarargInteger.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritVarargInteger.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritVarargInteger {
+public interface InheritVarargInteger {
 
-    public trait Sub : test.InheritVarargInteger.Super {
+    public interface Sub : test.InheritVarargInteger.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ vararg p0: kotlin.Int! /*kotlin.Array<(out) kotlin.Int!>!*/): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ vararg p0: kotlin.Int! /*kotlin.Array<(out) kotlin.Int!>!*/): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritVarargNotNull.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritVarargNotNull.txt
index cc78ae8303a..ec47d07815c 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritVarargNotNull.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritVarargNotNull.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritVarargNotNull {
+public interface InheritVarargNotNull {
 
-    public trait Sub : test.InheritVarargNotNull.Super {
+    public interface Sub : test.InheritVarargNotNull.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ vararg p: kotlin.String! /*kotlin.Array<(out) kotlin.String!>!*/): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ vararg p: kotlin.String! /*kotlin.Array<(out) kotlin.String!>!*/): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritVarargPrimitive.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritVarargPrimitive.txt
index 7ab4356d05d..ee326e78995 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritVarargPrimitive.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/InheritVarargPrimitive.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritVarargPrimitive {
+public interface InheritVarargPrimitive {
 
-    public trait Sub : test.InheritVarargPrimitive.Super {
+    public interface Sub : test.InheritVarargPrimitive.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ vararg p0: kotlin.Int /*kotlin.IntArray*/): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ vararg p0: kotlin.Int /*kotlin.IntArray!*/): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/Kt3302.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/Kt3302.txt
index 56628c0c26c..ff7c0e33b6c 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/Kt3302.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/Kt3302.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait Kt3302 {
+public interface Kt3302 {
 
-    public trait BSONObject {
+    public interface BSONObject {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun put(/*0*/ org.jetbrains.annotations.NotNull() p0: kotlin.String!, /*1*/ org.jetbrains.annotations.NotNull() p1: kotlin.Any!): kotlin.Any!
     }
 
-    public trait BasicBSONObject : test.Kt3302.LinkedHashMap<kotlin.String!, kotlin.Any!>, test.Kt3302.BSONObject {
+    public interface BasicBSONObject : test.Kt3302.LinkedHashMap<kotlin.String!, kotlin.Any!>, test.Kt3302.BSONObject {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun put(/*0*/ key: kotlin.String!, /*1*/ value: kotlin.Any!): kotlin.Any!
     }
 
-    public trait LinkedHashMap</*0*/ K, /*1*/ V> {
+    public interface LinkedHashMap</*0*/ K, /*1*/ V> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun put(/*0*/ key: K!, /*1*/ value: V!): V!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/MutableToReadOnly.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/MutableToReadOnly.txt
index c77795faed5..07133902d5a 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/MutableToReadOnly.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/MutableToReadOnly.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait MutableToReadOnly {
+public interface MutableToReadOnly {
 
-    public trait Sub : test.MutableToReadOnly.Super {
+    public interface Sub : test.MutableToReadOnly.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p: kotlin.(Mutable)List<kotlin.String!>!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p: kotlin.(Mutable)List<kotlin.String!>!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/NotNullToNullable.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/NotNullToNullable.txt
index ec8605e0f4b..ea246554807 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/NotNullToNullable.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/NotNullToNullable.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait NotNullToNullable {
+public interface NotNullToNullable {
 
-    public trait Sub : test.NotNullToNullable.Super {
+    public interface Sub : test.NotNullToNullable.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p: kotlin.String!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ org.jetbrains.annotations.NotNull() p0: kotlin.String!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/NullableToNotNull.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/NullableToNotNull.txt
index 35b4106e1eb..99a6a6ef179 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/NullableToNotNull.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/NullableToNotNull.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait NullableToNotNull {
+public interface NullableToNotNull {
 
-    public trait Sub : test.NullableToNotNull.Super {
+    public interface Sub : test.NullableToNotNull.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ org.jetbrains.annotations.NotNull() p0: kotlin.String!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p0: kotlin.String!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/NullableToNotNullKotlinSignature.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/NullableToNotNullKotlinSignature.txt
index f51f28e10ea..a6da60948aa 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/NullableToNotNullKotlinSignature.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/NullableToNotNullKotlinSignature.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait NullableToNotNullKotlinSignature {
+public interface NullableToNotNullKotlinSignature {
 
-    public trait Sub : test.NullableToNotNullKotlinSignature.Super {
+    public interface Sub : test.NullableToNotNullKotlinSignature.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p: kotlin.String!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p: kotlin.String!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/OverrideWithErasedParameter.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/OverrideWithErasedParameter.txt
index 214b4e995a1..1b610a0186c 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/OverrideWithErasedParameter.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/OverrideWithErasedParameter.txt
@@ -1,14 +1,14 @@
 package test
 
-public trait OverrideWithErasedParameter {
+public interface OverrideWithErasedParameter {
 
-    public trait Sub</*0*/ T> : test.OverrideWithErasedParameter.Super<T!> {
+    public interface Sub</*0*/ T> : test.OverrideWithErasedParameter.Super<T!> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: T!): kotlin.Unit
         public abstract fun foo(/*0*/ p0: kotlin.Any!): kotlin.Unit
     }
 
-    public trait Super</*0*/ T> {
+    public interface Super</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p0: T!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/ReadOnlyToMutable.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/ReadOnlyToMutable.txt
index 4dd3d88270f..bd459ac97c0 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/ReadOnlyToMutable.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/ReadOnlyToMutable.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait ReadOnlyToMutable {
+public interface ReadOnlyToMutable {
 
-    public trait Sub : test.ReadOnlyToMutable.Super {
+    public interface Sub : test.ReadOnlyToMutable.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p: kotlin.(Mutable)List<kotlin.String!>!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p: kotlin.(Mutable)List<kotlin.String!>!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/SubclassFromGenericAndNot.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/SubclassFromGenericAndNot.txt
index 4fc5e5f8c2f..e5a07aef461 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/SubclassFromGenericAndNot.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/SubclassFromGenericAndNot.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait SubclassFromGenericAndNot {
+public interface SubclassFromGenericAndNot {
 
-    public trait Generic</*0*/ T> {
+    public interface Generic</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ key: T!): kotlin.Unit
     }
 
-    public trait NonGeneric {
+    public interface NonGeneric {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ org.jetbrains.annotations.NotNull() p0: kotlin.String!): kotlin.Unit
     }
 
-    public trait Sub : test.SubclassFromGenericAndNot.NonGeneric, test.SubclassFromGenericAndNot.Generic<kotlin.String!> {
+    public interface Sub : test.SubclassFromGenericAndNot.NonGeneric, test.SubclassFromGenericAndNot.Generic<kotlin.String!> {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun foo(/*0*/ key: kotlin.String!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/SubstitutedClassParameter.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/SubstitutedClassParameter.txt
index f4e9ce0ab02..aaf54cd7aef 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/SubstitutedClassParameter.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/SubstitutedClassParameter.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait SubstitutedClassParameter {
+public interface SubstitutedClassParameter {
 
-    public trait Sub : test.SubstitutedClassParameter.Super<kotlin.String!> {
+    public interface Sub : test.SubstitutedClassParameter.Super<kotlin.String!> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ t: kotlin.String!): kotlin.Unit
     }
 
-    public trait Super</*0*/ T> {
+    public interface Super</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ t: T!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/SubstitutedClassParameters.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/SubstitutedClassParameters.txt
index 781ccbde284..55cd379633b 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/SubstitutedClassParameters.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/parameter/SubstitutedClassParameters.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait SubstitutedClassParameters {
+public interface SubstitutedClassParameters {
 
-    public trait Sub : test.SubstitutedClassParameters.Super1<kotlin.String!>, test.SubstitutedClassParameters.Super2<kotlin.String!> {
+    public interface Sub : test.SubstitutedClassParameters.Super1<kotlin.String!>, test.SubstitutedClassParameters.Super2<kotlin.String!> {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun foo(/*0*/ t: kotlin.String!): kotlin.Unit
     }
 
-    public trait Super1</*0*/ T> {
+    public interface Super1</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ t: T!): kotlin.Unit
     }
 
-    public trait Super2</*0*/ E> {
+    public interface Super2</*0*/ E> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ t: E!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/AddNotNullJavaSubtype.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/AddNotNullJavaSubtype.txt
index c9880dd6031..b432f192568 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/AddNotNullJavaSubtype.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/AddNotNullJavaSubtype.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait AddNotNullJavaSubtype {
+public interface AddNotNullJavaSubtype {
 
-    public trait Sub : test.AddNotNullJavaSubtype.Super {
+    public interface Sub : test.AddNotNullJavaSubtype.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         org.jetbrains.annotations.NotNull() public abstract override /*1*/ fun foo(): kotlin.String!
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.CharSequence!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/AddNotNullSameJavaType.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/AddNotNullSameJavaType.txt
index 4f9b57fa7c2..16c66d601eb 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/AddNotNullSameJavaType.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/AddNotNullSameJavaType.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait AddNotNullSameJavaType {
+public interface AddNotNullSameJavaType {
 
-    public trait Sub : test.AddNotNullSameJavaType.Super {
+    public interface Sub : test.AddNotNullSameJavaType.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         org.jetbrains.annotations.NotNull() public abstract override /*1*/ fun foo(): kotlin.CharSequence!
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.CharSequence!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/AddNullabilityJavaSubtype.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/AddNullabilityJavaSubtype.txt
index 7dfa8bba352..119585dda3e 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/AddNullabilityJavaSubtype.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/AddNullabilityJavaSubtype.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait AddNullabilityJavaSubtype {
+public interface AddNullabilityJavaSubtype {
 
-    public trait Sub : test.AddNullabilityJavaSubtype.Super {
+    public interface Sub : test.AddNullabilityJavaSubtype.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.String!
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         org.jetbrains.annotations.NotNull() public abstract fun foo(): kotlin.CharSequence!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/AddNullabilitySameGenericType1.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/AddNullabilitySameGenericType1.txt
index 8b31b45875b..709e2bc70c6 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/AddNullabilitySameGenericType1.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/AddNullabilitySameGenericType1.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait AddNullabilitySameGenericType1 {
+public interface AddNullabilitySameGenericType1 {
 
-    public trait Sub : test.AddNullabilitySameGenericType1.Super {
+    public interface Sub : test.AddNullabilitySameGenericType1.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.(Mutable)List<kotlin.String!>!
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.(Mutable)List<kotlin.String!>!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/AddNullabilitySameGenericType2.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/AddNullabilitySameGenericType2.txt
index 1ac7cc97227..d09cf6521c2 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/AddNullabilitySameGenericType2.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/AddNullabilitySameGenericType2.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait AddNullabilitySameGenericType2 {
+public interface AddNullabilitySameGenericType2 {
 
-    public trait Sub : test.AddNullabilitySameGenericType2.Super {
+    public interface Sub : test.AddNullabilitySameGenericType2.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.(Mutable)List<kotlin.String!>!
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.(Mutable)List<kotlin.String!>!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/AddNullabilitySameJavaType.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/AddNullabilitySameJavaType.txt
index 5045b53186f..e314b0c1afc 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/AddNullabilitySameJavaType.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/AddNullabilitySameJavaType.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait AddNullabilitySameJavaType {
+public interface AddNullabilitySameJavaType {
 
-    public trait Sub : test.AddNullabilitySameJavaType.Super {
+    public interface Sub : test.AddNullabilitySameJavaType.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.CharSequence!
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         org.jetbrains.annotations.NotNull() public abstract fun foo(): kotlin.CharSequence!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/CantMakeImmutableInSubclass.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/CantMakeImmutableInSubclass.txt
index 936aee3587b..3914f7d3877 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/CantMakeImmutableInSubclass.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/CantMakeImmutableInSubclass.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait CantMakeImmutableInSubclass {
+public interface CantMakeImmutableInSubclass {
 
-    public trait Sub : test.CantMakeImmutableInSubclass.Super {
+    public interface Sub : test.CantMakeImmutableInSubclass.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.(Mutable)List<kotlin.String!>!
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.(Mutable)Collection<kotlin.String!>!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/DeeplySubstitutedClassParameter.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/DeeplySubstitutedClassParameter.txt
index 6723799cdae..b262cfb0644 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/DeeplySubstitutedClassParameter.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/DeeplySubstitutedClassParameter.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait DeeplySubstitutedClassParameter {
+public interface DeeplySubstitutedClassParameter {
 
-    public trait Middle</*0*/ E> : test.DeeplySubstitutedClassParameter.Super<E!> {
+    public interface Middle</*0*/ E> : test.DeeplySubstitutedClassParameter.Super<E!> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): E!
     }
 
-    public trait Sub : test.DeeplySubstitutedClassParameter.Middle<kotlin.String!> {
+    public interface Sub : test.DeeplySubstitutedClassParameter.Middle<kotlin.String!> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.String!
     }
 
-    public trait Super</*0*/ T> {
+    public interface Super</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): T!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/DeeplySubstitutedClassParameter2.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/DeeplySubstitutedClassParameter2.txt
index 5c5b1963b9c..7d84f8f99b1 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/DeeplySubstitutedClassParameter2.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/DeeplySubstitutedClassParameter2.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait DeeplySubstitutedClassParameter2 {
+public interface DeeplySubstitutedClassParameter2 {
 
-    public trait Middle</*0*/ E> : test.DeeplySubstitutedClassParameter2.Super<E!> {
+    public interface Middle</*0*/ E> : test.DeeplySubstitutedClassParameter2.Super<E!> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ /*fake_override*/ fun foo(): E!
     }
 
-    public trait Sub : test.DeeplySubstitutedClassParameter2.Middle<kotlin.String!> {
+    public interface Sub : test.DeeplySubstitutedClassParameter2.Middle<kotlin.String!> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.String!
     }
 
-    public trait Super</*0*/ T> {
+    public interface Super</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): T!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/HalfSubstitutedTypeParameters.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/HalfSubstitutedTypeParameters.txt
index 707893575c2..000cfa004d1 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/HalfSubstitutedTypeParameters.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/HalfSubstitutedTypeParameters.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait HalfSubstitutedTypeParameters {
+public interface HalfSubstitutedTypeParameters {
 
-    public trait Sub : test.HalfSubstitutedTypeParameters.Super {
+    public interface Sub : test.HalfSubstitutedTypeParameters.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): test.HalfSubstitutedTypeParameters.TrickyList<kotlin.Int!, kotlin.String!>!
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.(Mutable)List<kotlin.String!>!
     }
 
-    public trait TrickyList</*0*/ X, /*1*/ E> : kotlin.MutableList<E!> {
+    public interface TrickyList</*0*/ X, /*1*/ E> : kotlin.MutableList<E!> {
         public abstract override /*1*/ /*fake_override*/ fun add(/*0*/ e: E!): kotlin.Boolean
         public abstract override /*1*/ /*fake_override*/ fun add(/*0*/ index: kotlin.Int, /*1*/ element: E!): kotlin.Unit
         public abstract override /*1*/ /*fake_override*/ fun addAll(/*0*/ c: kotlin.Collection<E!>): kotlin.Boolean
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritNullabilityGenericSubclassSimple.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritNullabilityGenericSubclassSimple.txt
index 310abaab4e9..906b447dc9a 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritNullabilityGenericSubclassSimple.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritNullabilityGenericSubclassSimple.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritNullabilityGenericSubclassSimple {
+public interface InheritNullabilityGenericSubclassSimple {
 
-    public trait Sub : test.InheritNullabilityGenericSubclassSimple.Super {
+    public interface Sub : test.InheritNullabilityGenericSubclassSimple.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.(Mutable)List<kotlin.String!>!
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.(Mutable)Collection<kotlin.String!>!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritNullabilityJavaSubtype.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritNullabilityJavaSubtype.txt
index 6fc7a098989..3f186405d99 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritNullabilityJavaSubtype.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritNullabilityJavaSubtype.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritNullabilityJavaSubtype {
+public interface InheritNullabilityJavaSubtype {
 
-    public trait Sub : test.InheritNullabilityJavaSubtype.Super {
+    public interface Sub : test.InheritNullabilityJavaSubtype.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.String!
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         org.jetbrains.annotations.NotNull() public abstract fun foo(): kotlin.CharSequence!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritNullabilitySameGenericType.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritNullabilitySameGenericType.txt
index 8cb3aa01658..cff7231ce65 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritNullabilitySameGenericType.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritNullabilitySameGenericType.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritNullabilitySameGenericType {
+public interface InheritNullabilitySameGenericType {
 
-    public trait Sub : test.InheritNullabilitySameGenericType.Super {
+    public interface Sub : test.InheritNullabilitySameGenericType.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.(Mutable)List<kotlin.String!>!
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.(Mutable)List<kotlin.String!>!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritNullabilitySameJavaType.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritNullabilitySameJavaType.txt
index 61fec7bc2be..e0c68dc5b42 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritNullabilitySameJavaType.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritNullabilitySameJavaType.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritNullabilitySameJavaType {
+public interface InheritNullabilitySameJavaType {
 
-    public trait Sub : test.InheritNullabilitySameJavaType.Super {
+    public interface Sub : test.InheritNullabilitySameJavaType.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.CharSequence!
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         org.jetbrains.annotations.NotNull() public abstract fun foo(): kotlin.CharSequence!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritProjectionKind.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritProjectionKind.txt
index e4be2bcb948..0ee30efac20 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritProjectionKind.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritProjectionKind.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritProjectionKind {
+public interface InheritProjectionKind {
 
-    public trait Sub : test.InheritProjectionKind.Super {
+    public interface Sub : test.InheritProjectionKind.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.(Mutable)List<kotlin.Number!>!
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.(Mutable)Collection<kotlin.Number!>!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritReadOnlinessOfArgument.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritReadOnlinessOfArgument.txt
index e32da9851c0..3ab125a456b 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritReadOnlinessOfArgument.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritReadOnlinessOfArgument.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritReadOnlinessOfArgument {
+public interface InheritReadOnlinessOfArgument {
 
-    public trait Sub : test.InheritReadOnlinessOfArgument.Super {
+    public interface Sub : test.InheritReadOnlinessOfArgument.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.(Mutable)List<kotlin.(Mutable)List<kotlin.String!>!>!
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.(Mutable)List<kotlin.(Mutable)List<kotlin.String!>!>!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritReadOnlinessSameClass.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritReadOnlinessSameClass.txt
index 20e967d1960..3180699abf7 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritReadOnlinessSameClass.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritReadOnlinessSameClass.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritReadOnlinessSameClass {
+public interface InheritReadOnlinessSameClass {
 
-    public trait Sub : test.InheritReadOnlinessSameClass.Super {
+    public interface Sub : test.InheritReadOnlinessSameClass.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.(Mutable)List<kotlin.String!>!
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.(Mutable)List<kotlin.String!>!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritReadOnlinessSubclass.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritReadOnlinessSubclass.txt
index 2f6fccf2aef..9be8034126f 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritReadOnlinessSubclass.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/InheritReadOnlinessSubclass.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritReadOnlinessSubclass {
+public interface InheritReadOnlinessSubclass {
 
-    public trait Sub : test.InheritReadOnlinessSubclass.Super {
+    public interface Sub : test.InheritReadOnlinessSubclass.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.(Mutable)List<kotlin.String!>!
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.(Mutable)Collection<kotlin.String!>!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SameProjectionKind.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SameProjectionKind.txt
index 773ba286511..836f09c2661 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SameProjectionKind.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SameProjectionKind.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait SameProjectionKind {
+public interface SameProjectionKind {
 
-    public trait Sub : test.SameProjectionKind.Super {
+    public interface Sub : test.SameProjectionKind.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): (kotlin.MutableCollection<out kotlin.Number!>..kotlin.Collection<kotlin.Number!>?)
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): (kotlin.MutableCollection<out kotlin.Number!>..kotlin.Collection<kotlin.Number!>?)
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubclassFromGenericAndNot.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubclassFromGenericAndNot.txt
index 53c89e449bf..4f6be4fe5dd 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubclassFromGenericAndNot.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubclassFromGenericAndNot.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait SubclassFromGenericAndNot {
+public interface SubclassFromGenericAndNot {
 
-    public trait Generic</*0*/ T> {
+    public interface Generic</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): T!
     }
 
-    public trait NonGeneric {
+    public interface NonGeneric {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.String!
     }
 
-    public trait Sub : test.SubclassFromGenericAndNot.NonGeneric, test.SubclassFromGenericAndNot.Generic<kotlin.String!> {
+    public interface Sub : test.SubclassFromGenericAndNot.NonGeneric, test.SubclassFromGenericAndNot.Generic<kotlin.String!> {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun foo(): kotlin.String!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubclassOfCollection.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubclassOfCollection.txt
index a50442ef69e..116c51fa854 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubclassOfCollection.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubclassOfCollection.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait SubclassOfCollection</*0*/ E> : kotlin.MutableCollection<E!> {
+public interface SubclassOfCollection</*0*/ E> : kotlin.MutableCollection<E!> {
     public abstract override /*1*/ /*fake_override*/ fun add(/*0*/ e: E!): kotlin.Boolean
     public abstract override /*1*/ /*fake_override*/ fun addAll(/*0*/ c: kotlin.Collection<E!>): kotlin.Boolean
     public abstract override /*1*/ /*fake_override*/ fun clear(): kotlin.Unit
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubclassOfMapEntry.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubclassOfMapEntry.txt
index fd57826f36c..4de9be0dace 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubclassOfMapEntry.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubclassOfMapEntry.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait SubclassOfMapEntry</*0*/ K, /*1*/ V> : kotlin.MutableMap.MutableEntry<K!, V!> {
+public interface SubclassOfMapEntry</*0*/ K, /*1*/ V> : kotlin.MutableMap.MutableEntry<K!, V!> {
     public abstract override /*1*/ /*fake_override*/ fun getKey(): K!
     public abstract override /*1*/ /*fake_override*/ fun getValue(): V!
     public abstract override /*1*/ fun setValue(/*0*/ value: V!): V!
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubstitutedClassParameter.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubstitutedClassParameter.txt
index 560146ef065..4c591215096 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubstitutedClassParameter.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubstitutedClassParameter.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait SubstitutedClassParameter {
+public interface SubstitutedClassParameter {
 
-    public trait Sub : test.SubstitutedClassParameter.Super<kotlin.String!> {
+    public interface Sub : test.SubstitutedClassParameter.Super<kotlin.String!> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.String!
     }
 
-    public trait Super</*0*/ T> {
+    public interface Super</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): T!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubstitutedClassParameters.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubstitutedClassParameters.txt
index 165cfd7d630..ab840786f73 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubstitutedClassParameters.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/SubstitutedClassParameters.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait SubstitutedClassParameters {
+public interface SubstitutedClassParameters {
 
-    public trait Sub : test.SubstitutedClassParameters.Super1<kotlin.String!>, test.SubstitutedClassParameters.Super2<kotlin.String!> {
+    public interface Sub : test.SubstitutedClassParameters.Super1<kotlin.String!>, test.SubstitutedClassParameters.Super2<kotlin.String!> {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun foo(): kotlin.String!
     }
 
-    public trait Super1</*0*/ T> {
+    public interface Super1</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): T!
     }
 
-    public trait Super2</*0*/ E> {
+    public interface Super2</*0*/ E> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): E!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesConflictingProjectionKinds.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesConflictingProjectionKinds.txt
index c49ee0992a6..59880afc5a7 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesConflictingProjectionKinds.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesConflictingProjectionKinds.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait TwoSuperclassesConflictingProjectionKinds {
+public interface TwoSuperclassesConflictingProjectionKinds {
 
-    public trait Sub : test.TwoSuperclassesConflictingProjectionKinds.Super1, test.TwoSuperclassesConflictingProjectionKinds.Super2 {
+    public interface Sub : test.TwoSuperclassesConflictingProjectionKinds.Super1, test.TwoSuperclassesConflictingProjectionKinds.Super2 {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun foo(): kotlin.(Mutable)Collection<kotlin.CharSequence!>!
     }
 
-    public trait Super1 {
+    public interface Super1 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.(Mutable)Collection<kotlin.CharSequence!>!
     }
 
-    public trait Super2 {
+    public interface Super2 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.(Mutable)Collection<kotlin.CharSequence!>!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesInvariantAndCovariantInferMutability.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesInvariantAndCovariantInferMutability.txt
index cbb69eafdcd..af3f3d3c2ef 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesInvariantAndCovariantInferMutability.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesInvariantAndCovariantInferMutability.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait TwoSuperclassesInvariantAndCovariantInferMutability {
+public interface TwoSuperclassesInvariantAndCovariantInferMutability {
 
-    public trait Sub : test.TwoSuperclassesInvariantAndCovariantInferMutability.Super1, test.TwoSuperclassesInvariantAndCovariantInferMutability.Super2 {
+    public interface Sub : test.TwoSuperclassesInvariantAndCovariantInferMutability.Super1, test.TwoSuperclassesInvariantAndCovariantInferMutability.Super2 {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun foo(): kotlin.(Mutable)List<kotlin.(Mutable)List<kotlin.String!>!>!
     }
 
-    public trait Super1 {
+    public interface Super1 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.(Mutable)List<kotlin.(Mutable)List<kotlin.String!>!>!
     }
 
-    public trait Super2 {
+    public interface Super2 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.(Mutable)List<kotlin.(Mutable)List<kotlin.String!>!>!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesInvariantAndCovariantInferNullability.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesInvariantAndCovariantInferNullability.txt
index 8c2ac5e6a46..6330f9decd5 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesInvariantAndCovariantInferNullability.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesInvariantAndCovariantInferNullability.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait TwoSuperclassesInvariantAndCovariantInferNullability {
+public interface TwoSuperclassesInvariantAndCovariantInferNullability {
 
-    public trait Sub : test.TwoSuperclassesInvariantAndCovariantInferNullability.Super1, test.TwoSuperclassesInvariantAndCovariantInferNullability.Super2 {
+    public interface Sub : test.TwoSuperclassesInvariantAndCovariantInferNullability.Super1, test.TwoSuperclassesInvariantAndCovariantInferNullability.Super2 {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun foo(): kotlin.(Mutable)List<kotlin.String!>!
     }
 
-    public trait Super1 {
+    public interface Super1 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.(Mutable)List<kotlin.String!>!
     }
 
-    public trait Super2 {
+    public interface Super2 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.(Mutable)List<kotlin.String!>!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesMutableAndNot.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesMutableAndNot.txt
index 4a9bbacbf8d..35d958a1f74 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesMutableAndNot.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesMutableAndNot.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait TwoSuperclassesMutableAndNot {
+public interface TwoSuperclassesMutableAndNot {
 
-    public trait Sub : test.TwoSuperclassesMutableAndNot.Super1, test.TwoSuperclassesMutableAndNot.Super2 {
+    public interface Sub : test.TwoSuperclassesMutableAndNot.Super1, test.TwoSuperclassesMutableAndNot.Super2 {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun foo(): kotlin.(Mutable)List<kotlin.String!>!
     }
 
-    public trait Super1 {
+    public interface Super1 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.(Mutable)Collection<kotlin.String!>!
     }
 
-    public trait Super2 {
+    public interface Super2 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.(Mutable)List<kotlin.String!>!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesReturnJavaSubtype.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesReturnJavaSubtype.txt
index a0170b86e16..23c06c4bd70 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesReturnJavaSubtype.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesReturnJavaSubtype.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait TwoSuperclassesReturnJavaSubtype {
+public interface TwoSuperclassesReturnJavaSubtype {
 
-    public trait Sub : test.TwoSuperclassesReturnJavaSubtype.Super1, test.TwoSuperclassesReturnJavaSubtype.Super2 {
+    public interface Sub : test.TwoSuperclassesReturnJavaSubtype.Super1, test.TwoSuperclassesReturnJavaSubtype.Super2 {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun foo(): kotlin.String!
     }
 
-    public trait Super1 {
+    public interface Super1 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.CharSequence!
     }
 
-    public trait Super2 {
+    public interface Super2 {
         public abstract fun dummy(): kotlin.Unit
         org.jetbrains.annotations.NotNull() public abstract fun foo(): kotlin.CharSequence!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesReturnSameJavaType.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesReturnSameJavaType.txt
index 9fb0daa5679..635d8a77bd9 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesReturnSameJavaType.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesReturnSameJavaType.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait TwoSuperclassesReturnSameJavaType {
+public interface TwoSuperclassesReturnSameJavaType {
 
-    public trait Sub : test.TwoSuperclassesReturnSameJavaType.Super1, test.TwoSuperclassesReturnSameJavaType.Super2 {
+    public interface Sub : test.TwoSuperclassesReturnSameJavaType.Super1, test.TwoSuperclassesReturnSameJavaType.Super2 {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun foo(): kotlin.CharSequence!
     }
 
-    public trait Super1 {
+    public interface Super1 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.CharSequence!
     }
 
-    public trait Super2 {
+    public interface Super2 {
         public abstract fun dummy(): kotlin.Unit
         org.jetbrains.annotations.NotNull() public abstract fun foo(): kotlin.CharSequence!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesSupplementNotNull.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesSupplementNotNull.txt
index 063af5e1f53..52dcf636f7a 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesSupplementNotNull.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TwoSuperclassesSupplementNotNull.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait TwoSuperclassesSupplementNotNull {
+public interface TwoSuperclassesSupplementNotNull {
 
-    public trait Sub : test.TwoSuperclassesSupplementNotNull.Super1, test.TwoSuperclassesSupplementNotNull.Super2 {
+    public interface Sub : test.TwoSuperclassesSupplementNotNull.Super1, test.TwoSuperclassesSupplementNotNull.Super2 {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun foo(): kotlin.(Mutable)List<kotlin.String!>!
     }
 
-    public trait Super1 {
+    public interface Super1 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.(Mutable)List<kotlin.String!>!
     }
 
-    public trait Super2 {
+    public interface Super2 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.(Mutable)List<kotlin.String!>!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TypeParamOfClass.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TypeParamOfClass.txt
index 6101579e0f6..192d611dfa4 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TypeParamOfClass.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TypeParamOfClass.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait TypeParamOfClass {
+public interface TypeParamOfClass {
 
-    public trait Sub</*0*/ T> : test.TypeParamOfClass.Super<T!> {
+    public interface Sub</*0*/ T> : test.TypeParamOfClass.Super<T!> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): T!
     }
 
-    public trait Super</*0*/ T> {
+    public interface Super</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         org.jetbrains.annotations.NotNull() public abstract fun foo(): T!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TypeParamOfClassSubstituted.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TypeParamOfClassSubstituted.txt
index b13b81a0dda..1c759f64976 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TypeParamOfClassSubstituted.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TypeParamOfClassSubstituted.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait TypeParamOfClassSubstituted {
+public interface TypeParamOfClassSubstituted {
 
-    public trait Sub : test.TypeParamOfClassSubstituted.Super<kotlin.String!> {
+    public interface Sub : test.TypeParamOfClassSubstituted.Super<kotlin.String!> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.String!
     }
 
-    public trait Super</*0*/ T> {
+    public interface Super</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         org.jetbrains.annotations.NotNull() public abstract fun foo(): T!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TypeParamOfFun.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TypeParamOfFun.txt
index 98af80e8626..283136f6ebb 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TypeParamOfFun.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TypeParamOfFun.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait TypeParamOfFun {
+public interface TypeParamOfFun {
 
-    public trait Sub : test.TypeParamOfFun.Super {
+    public interface Sub : test.TypeParamOfFun.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun </*0*/ E> foo(): E!
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         org.jetbrains.annotations.NotNull() public abstract fun </*0*/ T> foo(): T!
     }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/InheritMutability.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/InheritMutability.txt
index fce85f1e366..9fc5625b49e 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/InheritMutability.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/InheritMutability.txt
@@ -1,12 +1,12 @@
 package test
 
-public trait InheritMutability {
+public interface InheritMutability {
 
-    public trait Sub : test.InheritMutability.Super {
+    public interface Sub : test.InheritMutability.Super {
         public abstract override /*1*/ fun </*0*/ B : kotlin.(Mutable)List<kotlin.String!>!> foo(/*0*/ a: B!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun </*0*/ A : kotlin.(Mutable)List<kotlin.String!>!> foo(/*0*/ a: A!): kotlin.Unit
     }
 }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/InheritNullability.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/InheritNullability.txt
index 3a26a35eb16..0bdd59e3df5 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/InheritNullability.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/InheritNullability.txt
@@ -1,12 +1,12 @@
 package test
 
-public trait InheritNullability {
+public interface InheritNullability {
 
-    public trait Sub : test.InheritNullability.Super {
+    public interface Sub : test.InheritNullability.Super {
         public abstract override /*1*/ fun </*0*/ B : kotlin.CharSequence!> foo(/*0*/ a: B!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun </*0*/ A : kotlin.CharSequence!> foo(/*0*/ a: A!): kotlin.Unit
     }
 }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/InheritReadOnliness.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/InheritReadOnliness.txt
index bf71cbb492a..b5e92d124a1 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/InheritReadOnliness.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/InheritReadOnliness.txt
@@ -1,12 +1,12 @@
 package test
 
-public trait InheritReadOnliness {
+public interface InheritReadOnliness {
 
-    public trait Sub : test.InheritReadOnliness.Super {
+    public interface Sub : test.InheritReadOnliness.Super {
         public abstract override /*1*/ fun </*0*/ B : kotlin.(Mutable)List<kotlin.String!>!> foo(/*0*/ a: B!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun </*0*/ A : kotlin.(Mutable)List<kotlin.String!>!> foo(/*0*/ a: A!): kotlin.Unit
     }
 }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/TwoBounds.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/TwoBounds.txt
index ed0a5dfce72..ac20daaa483 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/TwoBounds.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/TwoBounds.txt
@@ -1,12 +1,12 @@
 package test
 
-public trait TwoBounds {
+public interface TwoBounds {
 
-    public trait Sub : test.TwoBounds.Super {
+    public interface Sub : test.TwoBounds.Super {
         public abstract override /*1*/ fun </*0*/ B : kotlin.CharSequence!> foo(/*0*/ a: B!): kotlin.Unit where B : kotlin.Cloneable!
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun </*0*/ A : kotlin.CharSequence!> foo(/*0*/ a: A!): kotlin.Unit where A : kotlin.Cloneable!
     }
 }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/TwoSuperclasses.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/TwoSuperclasses.txt
index 4f2065abb60..62347ee676a 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/TwoSuperclasses.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/TwoSuperclasses.txt
@@ -1,16 +1,16 @@
 package test
 
-public trait TwoSuperclasses {
+public interface TwoSuperclasses {
 
-    public trait Sub : test.TwoSuperclasses.Super1, test.TwoSuperclasses.Super2 {
+    public interface Sub : test.TwoSuperclasses.Super1, test.TwoSuperclasses.Super2 {
         public abstract override /*2*/ fun </*0*/ C : kotlin.CharSequence!> foo(/*0*/ a: C!): kotlin.Unit
     }
 
-    public trait Super1 {
+    public interface Super1 {
         public abstract fun </*0*/ A : kotlin.CharSequence!> foo(/*0*/ a: A!): kotlin.Unit
     }
 
-    public trait Super2 {
+    public interface Super2 {
         public abstract fun </*0*/ B : kotlin.CharSequence!> foo(/*0*/ a: B!): kotlin.Unit
     }
 }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/TwoTypeParameters.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/TwoTypeParameters.txt
index a5c862e99df..f5ad55b524c 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/TwoTypeParameters.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/TwoTypeParameters.txt
@@ -1,12 +1,12 @@
 package test
 
-public trait TwoTypeParameters {
+public interface TwoTypeParameters {
 
-    public trait Sub : test.TwoTypeParameters.Super {
+    public interface Sub : test.TwoTypeParameters.Super {
         public abstract override /*1*/ fun </*0*/ B : kotlin.CharSequence!, /*1*/ A : kotlin.Cloneable!> foo(/*0*/ a: B!, /*1*/ b: A!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun </*0*/ A : kotlin.CharSequence!, /*1*/ B : kotlin.Cloneable!> foo(/*0*/ a: A!, /*1*/ b: B!): kotlin.Unit
     }
 }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/UseParameterAsUpperBound.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/UseParameterAsUpperBound.txt
index 9a1d8cef490..4f180b9f81e 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/UseParameterAsUpperBound.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/UseParameterAsUpperBound.txt
@@ -1,12 +1,12 @@
 package test
 
-public trait UseParameterAsUpperBound {
+public interface UseParameterAsUpperBound {
 
-    public trait Sub : test.UseParameterAsUpperBound.Super {
+    public interface Sub : test.UseParameterAsUpperBound.Super {
         public abstract override /*1*/ fun </*0*/ B, /*1*/ A : B!> foo(/*0*/ a: B!, /*1*/ b: A!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun </*0*/ A, /*1*/ B : A!> foo(/*0*/ a: A!, /*1*/ b: B!): kotlin.Unit
     }
 }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/UseParameterInUpperBound.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/UseParameterInUpperBound.txt
index f70b6357766..b418598ea9d 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/UseParameterInUpperBound.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/UseParameterInUpperBound.txt
@@ -1,12 +1,12 @@
 package test
 
-public trait UseParameterInUpperBound {
+public interface UseParameterInUpperBound {
 
-    public trait Sub : test.UseParameterInUpperBound.Super {
+    public interface Sub : test.UseParameterInUpperBound.Super {
         public abstract override /*1*/ fun </*0*/ B, /*1*/ A : kotlin.(Mutable)List<B!>!> foo(/*0*/ a: B!, /*1*/ b: A!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun </*0*/ A, /*1*/ B : kotlin.(Mutable)List<A!>!> foo(/*0*/ a: A!, /*1*/ b: B!): kotlin.Unit
     }
 }
diff --git a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/UseParameterInUpperBoundWithKotlinSignature.txt b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/UseParameterInUpperBoundWithKotlinSignature.txt
index e12c03e5d01..13c326075d4 100644
--- a/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/UseParameterInUpperBoundWithKotlinSignature.txt
+++ b/compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/typeParameter/UseParameterInUpperBoundWithKotlinSignature.txt
@@ -1,12 +1,12 @@
 package test
 
-public trait UseParameterInUpperBoundWithKotlinSignature {
+public interface UseParameterInUpperBoundWithKotlinSignature {
 
-    public trait Sub : test.UseParameterInUpperBoundWithKotlinSignature.Super {
+    public interface Sub : test.UseParameterInUpperBoundWithKotlinSignature.Super {
         public abstract override /*1*/ fun </*0*/ B, /*1*/ A : kotlin.(Mutable)List<B!>!> foo(/*0*/ b: B!, /*1*/ a: A!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun </*0*/ A, /*1*/ B : kotlin.(Mutable)List<A!>!> foo(/*0*/ a: A!, /*1*/ b: B!): kotlin.Unit
     }
 }
diff --git a/compiler/testData/loadJava/compiledJava/library/LoadIterable.txt b/compiler/testData/loadJava/compiledJava/library/LoadIterable.txt
index 60e4d7a8992..941a5697b81 100644
--- a/compiler/testData/loadJava/compiledJava/library/LoadIterable.txt
+++ b/compiler/testData/loadJava/compiledJava/library/LoadIterable.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait LoadIterable</*0*/ T> {
+public interface LoadIterable</*0*/ T> {
     public abstract fun getIterable(): kotlin.(Mutable)Iterable<T!>!
     public abstract fun setIterable(/*0*/ p0: kotlin.(Mutable)Iterable<T!>!): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/compiledJava/library/LoadIterator.txt b/compiler/testData/loadJava/compiledJava/library/LoadIterator.txt
index a0353e2a5e7..3230b977830 100644
--- a/compiler/testData/loadJava/compiledJava/library/LoadIterator.txt
+++ b/compiler/testData/loadJava/compiledJava/library/LoadIterator.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait LoadIterator</*0*/ T> {
+public interface LoadIterator</*0*/ T> {
     public abstract fun getIterator(): kotlin.(Mutable)Iterator<T!>!
     public abstract fun setIterator(/*0*/ p0: kotlin.(Mutable)Iterator<T!>!): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/compiledJava/mutability/LoadIterable.txt b/compiler/testData/loadJava/compiledJava/mutability/LoadIterable.txt
index 2e945fe6593..c380b33c65b 100644
--- a/compiler/testData/loadJava/compiledJava/mutability/LoadIterable.txt
+++ b/compiler/testData/loadJava/compiledJava/mutability/LoadIterable.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait LoadIterable</*0*/ T> {
+public interface LoadIterable</*0*/ T> {
     org.jetbrains.annotations.Mutable() public abstract fun getIterable(): kotlin.(Mutable)Iterable<T!>!
     org.jetbrains.annotations.ReadOnly() public abstract fun getReadOnlyIterable(): kotlin.(Mutable)Iterable<T!>!
     public abstract fun setIterable(/*0*/ org.jetbrains.annotations.Mutable() p0: kotlin.(Mutable)Iterable<T!>!): kotlin.Unit
diff --git a/compiler/testData/loadJava/compiledJava/mutability/LoadIterableWithConflict.txt b/compiler/testData/loadJava/compiledJava/mutability/LoadIterableWithConflict.txt
index 025cc9c0b0f..0d0b8971592 100644
--- a/compiler/testData/loadJava/compiledJava/mutability/LoadIterableWithConflict.txt
+++ b/compiler/testData/loadJava/compiledJava/mutability/LoadIterableWithConflict.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait LoadIterableWithConflict</*0*/ T> {
+public interface LoadIterableWithConflict</*0*/ T> {
     org.jetbrains.annotations.ReadOnly() org.jetbrains.annotations.Mutable() public abstract fun getIterable(): kotlin.(Mutable)Iterable<T!>!
     public abstract fun setIterable(/*0*/ org.jetbrains.annotations.ReadOnly() org.jetbrains.annotations.Mutable() p0: kotlin.(Mutable)Iterable<T!>!): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/compiledJava/mutability/LoadIterableWithNullability.txt b/compiler/testData/loadJava/compiledJava/mutability/LoadIterableWithNullability.txt
index d4cc87d6321..486bea8b4fd 100644
--- a/compiler/testData/loadJava/compiledJava/mutability/LoadIterableWithNullability.txt
+++ b/compiler/testData/loadJava/compiledJava/mutability/LoadIterableWithNullability.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait LoadIterableWithNullability</*0*/ T> {
+public interface LoadIterableWithNullability</*0*/ T> {
     org.jetbrains.annotations.NotNull() org.jetbrains.annotations.Mutable() public abstract fun getIterable(): kotlin.(Mutable)Iterable<T!>!
     org.jetbrains.annotations.NotNull() org.jetbrains.annotations.ReadOnly() public abstract fun getReadOnlyIterable(): kotlin.(Mutable)Iterable<T!>!
     public abstract fun setIterable(/*0*/ org.jetbrains.annotations.Mutable() org.jetbrains.annotations.NotNull() p0: kotlin.(Mutable)Iterable<T!>!): kotlin.Unit
diff --git a/compiler/testData/loadJava/compiledJava/mutability/LoadIterableWithPropagation.txt b/compiler/testData/loadJava/compiledJava/mutability/LoadIterableWithPropagation.txt
index 7523e927545..3e9b39c46d8 100644
--- a/compiler/testData/loadJava/compiledJava/mutability/LoadIterableWithPropagation.txt
+++ b/compiler/testData/loadJava/compiledJava/mutability/LoadIterableWithPropagation.txt
@@ -1,8 +1,8 @@
 package test
 
-public trait LoadIterableWithPropagation {
+public interface LoadIterableWithPropagation {
 
-    public trait LoadIterable</*0*/ T> {
+    public interface LoadIterable</*0*/ T> {
         org.jetbrains.annotations.Mutable() public abstract fun getIterable(): kotlin.(Mutable)Iterable<T!>!
         org.jetbrains.annotations.ReadOnly() public abstract fun getReadOnlyIterable(): kotlin.(Mutable)Iterable<T!>!
         public abstract fun setIterable(/*0*/ org.jetbrains.annotations.Mutable() p0: kotlin.(Mutable)Iterable<T!>!): kotlin.Unit
diff --git a/compiler/testData/loadJava/compiledJava/rendering/Rendering.txt b/compiler/testData/loadJava/compiledJava/rendering/Rendering.txt
index 276ee0b489a..3af117372e1 100644
--- a/compiler/testData/loadJava/compiledJava/rendering/Rendering.txt
+++ b/compiler/testData/loadJava/compiledJava/rendering/Rendering.txt
@@ -23,7 +23,7 @@ public open class Rendering {
         public/*package*/ constructor E_SubG()
     }
 
-    public/*package*/ trait F_Array {
+    public/*package*/ interface F_Array {
         public abstract fun foo1(/*0*/ p0: kotlin.Array<(out) kotlin.String!>!): kotlin.Unit
         public abstract fun foo2(/*0*/ p0: kotlin.Array<(out) kotlin.(Mutable)List<kotlin.String!>!>!): kotlin.Unit
         public abstract fun foo3(/*0*/ vararg p0: kotlin.Int! /*kotlin.Array<(out) kotlin.Int!>!*/): kotlin.Unit
@@ -31,7 +31,7 @@ public open class Rendering {
         public abstract fun foo5(/*0*/ vararg p0: kotlin.(Mutable)List<kotlin.String!>! /*kotlin.Array<(out) kotlin.(Mutable)List<kotlin.String!>!>!*/): kotlin.Unit
     }
 
-    public/*package*/ trait G_Collections {
+    public/*package*/ interface G_Collections {
         public abstract fun foo1(/*0*/ p0: kotlin.(Mutable)Iterator<kotlin.String!>!): kotlin.Unit
         public abstract fun foo2(/*0*/ p0: kotlin.(Mutable)Iterable<kotlin.String!>!): kotlin.Unit
         public abstract fun foo3(/*0*/ p0: kotlin.(Mutable)Collection<kotlin.String!>!): kotlin.Unit
@@ -41,12 +41,12 @@ public open class Rendering {
         public abstract fun foo7(/*0*/ p0: kotlin.(Mutable)Map.(Mutable)Entry<kotlin.String!, kotlin.String!>!): kotlin.Unit
     }
 
-    public/*package*/ trait H_Raw {
+    public/*package*/ interface H_Raw {
         public abstract fun foo1(/*0*/ p0: kotlin.(Mutable)List<*>!): kotlin.Unit
         public abstract fun foo2(/*0*/ p0: test.Rendering.D_SuperG<*>!): kotlin.Unit
     }
 
-    public/*package*/ trait I_Wildcard {
+    public/*package*/ interface I_Wildcard {
         public abstract fun foo1(/*0*/ p0: (kotlin.MutableList<out kotlin.String!>..kotlin.List<kotlin.String!>?)): kotlin.Unit
         public abstract fun foo2(/*0*/ p0: kotlin.(Mutable)List<in kotlin.String!>!): kotlin.Unit
         public abstract fun foo3(/*0*/ p0: kotlin.(Mutable)List<*>!): kotlin.Unit
diff --git a/compiler/testData/loadJava/compiledJava/sam/Comparator.txt b/compiler/testData/loadJava/compiledJava/sam/Comparator.txt
index 6fd478c32a4..29d15ec641b 100644
--- a/compiler/testData/loadJava/compiledJava/sam/Comparator.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/Comparator.txt
@@ -2,6 +2,6 @@ package test
 
 public /*synthesized*/ fun </*0*/ T> Comparator(/*0*/ function: (T!, T!) -> kotlin.Int): test.Comparator<T>
 
-public trait Comparator</*0*/ T> {
+public interface Comparator</*0*/ T> {
     public abstract fun compare(/*0*/ p0: T!, /*1*/ p1: T!): kotlin.Int
 }
diff --git a/compiler/testData/loadJava/compiledJava/sam/FilenameFilter.txt b/compiler/testData/loadJava/compiledJava/sam/FilenameFilter.txt
index 6085a6c4b86..795cf6add89 100644
--- a/compiler/testData/loadJava/compiledJava/sam/FilenameFilter.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/FilenameFilter.txt
@@ -2,6 +2,6 @@ package test
 
 public /*synthesized*/ fun FilenameFilter(/*0*/ function: (java.io.File!, kotlin.String!) -> kotlin.Boolean): test.FilenameFilter
 
-public trait FilenameFilter {
+public interface FilenameFilter {
     public abstract fun accept(/*0*/ p0: java.io.File!, /*1*/ p1: kotlin.String!): kotlin.Boolean
 }
diff --git a/compiler/testData/loadJava/compiledJava/sam/GenericInterfaceParameterWithSelfBound.txt b/compiler/testData/loadJava/compiledJava/sam/GenericInterfaceParameterWithSelfBound.txt
index 04c323b6459..dcb712837b8 100644
--- a/compiler/testData/loadJava/compiledJava/sam/GenericInterfaceParameterWithSelfBound.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/GenericInterfaceParameterWithSelfBound.txt
@@ -2,6 +2,6 @@ package test
 
 public /*synthesized*/ fun </*0*/ T : test.GenericInterfaceParameterWithSelfBound<T!>!> GenericInterfaceParameterWithSelfBound(/*0*/ function: (T!) -> T!): test.GenericInterfaceParameterWithSelfBound<T>
 
-public trait GenericInterfaceParameterWithSelfBound</*0*/ T : test.GenericInterfaceParameterWithSelfBound<T!>!> {
+public interface GenericInterfaceParameterWithSelfBound</*0*/ T : test.GenericInterfaceParameterWithSelfBound<T!>!> {
     public abstract fun method(/*0*/ p0: T!): T!
 }
diff --git a/compiler/testData/loadJava/compiledJava/sam/GenericInterfaceParametersWithBounds.txt b/compiler/testData/loadJava/compiledJava/sam/GenericInterfaceParametersWithBounds.txt
index ed9c8a36b6a..21a1b8812a9 100644
--- a/compiler/testData/loadJava/compiledJava/sam/GenericInterfaceParametersWithBounds.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/GenericInterfaceParametersWithBounds.txt
@@ -2,6 +2,6 @@ package test
 
 public /*synthesized*/ fun </*0*/ A : kotlin.Comparable<A!>!, /*1*/ B : kotlin.(Mutable)List<A!>!> GenericInterfaceParametersWithBounds(/*0*/ function: (kotlin.Array<(out) A!>!, B!) -> kotlin.Unit): test.GenericInterfaceParametersWithBounds<A, B> where A : kotlin.Cloneable!
 
-public trait GenericInterfaceParametersWithBounds</*0*/ A : kotlin.Comparable<A!>!, /*1*/ B : kotlin.(Mutable)List<A!>!> where A : kotlin.Cloneable! {
+public interface GenericInterfaceParametersWithBounds</*0*/ A : kotlin.Comparable<A!>!, /*1*/ B : kotlin.(Mutable)List<A!>!> where A : kotlin.Cloneable! {
     public abstract fun method(/*0*/ p0: kotlin.Array<(out) A!>!, /*1*/ p1: B!): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/compiledJava/sam/GenericMethodParameters.txt b/compiler/testData/loadJava/compiledJava/sam/GenericMethodParameters.txt
index 426b9a2fcab..ab948f42844 100644
--- a/compiler/testData/loadJava/compiledJava/sam/GenericMethodParameters.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/GenericMethodParameters.txt
@@ -1,5 +1,5 @@
 package test
 
-public trait GenericMethodParameters {
+public interface GenericMethodParameters {
     public abstract fun </*0*/ A : kotlin.CharSequence!, /*1*/ B : kotlin.(Mutable)List<A!>!> method(/*0*/ p0: kotlin.Array<(out) A!>!, /*1*/ p1: B!): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/compiledJava/sam/InterfaceWithObjectMethod.txt b/compiler/testData/loadJava/compiledJava/sam/InterfaceWithObjectMethod.txt
index 7727fe5cdbd..45ec3180131 100644
--- a/compiler/testData/loadJava/compiledJava/sam/InterfaceWithObjectMethod.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/InterfaceWithObjectMethod.txt
@@ -1,4 +1,4 @@
 package test
 
-public trait InterfaceWithObjectMethod {
+public interface InterfaceWithObjectMethod {
 }
diff --git a/compiler/testData/loadJava/compiledJava/sam/Nested.txt b/compiler/testData/loadJava/compiledJava/sam/Nested.txt
index 7ba4f81a1aa..6314d7ac2ca 100644
--- a/compiler/testData/loadJava/compiledJava/sam/Nested.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/Nested.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait Nested {
+public interface Nested {
 
-    public trait Deeper1 {
+    public interface Deeper1 {
 
-        public trait Runnable {
+        public interface Runnable {
             public abstract fun run(): kotlin.Unit
             public abstract fun run2(): kotlin.Unit
         }
     }
 
-    public trait Deeper2 {
+    public interface Deeper2 {
 
-        public trait Runnable {
+        public interface Runnable {
             public abstract fun run(): kotlin.Unit
         }
 
@@ -20,7 +20,7 @@ public trait Nested {
         public final /*synthesized*/ fun Runnable(/*0*/ function: () -> kotlin.Unit): test.Nested.Deeper2.Runnable
     }
 
-    public trait Runnable {
+    public interface Runnable {
         public abstract fun run(): kotlin.Unit
     }
 
diff --git a/compiler/testData/loadJava/compiledJava/sam/Runnable.txt b/compiler/testData/loadJava/compiledJava/sam/Runnable.txt
index 825a213b0b4..e4853e7c257 100644
--- a/compiler/testData/loadJava/compiledJava/sam/Runnable.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/Runnable.txt
@@ -2,6 +2,6 @@ package test
 
 public /*synthesized*/ fun Runnable(/*0*/ function: () -> kotlin.Unit): test.Runnable
 
-public trait Runnable {
+public interface Runnable {
     public abstract fun run(): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/compiledJava/sam/SamSubinterfaceOfTwo.txt b/compiler/testData/loadJava/compiledJava/sam/SamSubinterfaceOfTwo.txt
index 920e446803e..fb6394e17b0 100644
--- a/compiler/testData/loadJava/compiledJava/sam/SamSubinterfaceOfTwo.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/SamSubinterfaceOfTwo.txt
@@ -1,16 +1,16 @@
 package test
 
-public trait SamSubinterfaceOfTwo {
+public interface SamSubinterfaceOfTwo {
 
-    public trait Sub : test.SamSubinterfaceOfTwo.Super1, test.SamSubinterfaceOfTwo.Super2<kotlin.String!> {
+    public interface Sub : test.SamSubinterfaceOfTwo.Super1, test.SamSubinterfaceOfTwo.Super2<kotlin.String!> {
         public abstract override /*2*/ /*fake_override*/ fun f(): kotlin.String!
     }
 
-    public trait Super1 {
+    public interface Super1 {
         public abstract fun f(): kotlin.CharSequence!
     }
 
-    public trait Super2</*0*/ T> {
+    public interface Super2</*0*/ T> {
         public abstract fun f(): T!
     }
 
diff --git a/compiler/testData/loadJava/compiledJava/sam/SamSubinterfaceOverridding.txt b/compiler/testData/loadJava/compiledJava/sam/SamSubinterfaceOverridding.txt
index d30c2bf84fe..ff98fbe2474 100644
--- a/compiler/testData/loadJava/compiledJava/sam/SamSubinterfaceOverridding.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/SamSubinterfaceOverridding.txt
@@ -2,6 +2,6 @@ package test
 
 public /*synthesized*/ fun SamSubinterfaceOverridding(/*0*/ function: () -> kotlin.Unit): test.SamSubinterfaceOverridding
 
-public trait SamSubinterfaceOverridding : java.lang.Runnable {
+public interface SamSubinterfaceOverridding : java.lang.Runnable {
     public abstract override /*1*/ fun run(): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/compiledJava/sam/SubstitutedSamInterface.txt b/compiler/testData/loadJava/compiledJava/sam/SubstitutedSamInterface.txt
index 4e465e7fefa..7d67437dacf 100644
--- a/compiler/testData/loadJava/compiledJava/sam/SubstitutedSamInterface.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/SubstitutedSamInterface.txt
@@ -2,6 +2,6 @@ package test
 
 public /*synthesized*/ fun SubstitutedSamInterface(/*0*/ function: (kotlin.String!, kotlin.String!) -> kotlin.Int): test.SubstitutedSamInterface
 
-public trait SubstitutedSamInterface : java.util.Comparator<kotlin.String!> {
+public interface SubstitutedSamInterface : java.util.Comparator<kotlin.String!> {
     public abstract override /*1*/ /*fake_override*/ fun compare(/*0*/ p0: kotlin.String!, /*1*/ p1: kotlin.String!): kotlin.Int
 }
diff --git a/compiler/testData/loadJava/compiledJava/sam/SubstitutedSamInterfaceSubclassOfBuiltin.txt b/compiler/testData/loadJava/compiledJava/sam/SubstitutedSamInterfaceSubclassOfBuiltin.txt
index 7103eb80b8b..9bbc88c9ac4 100644
--- a/compiler/testData/loadJava/compiledJava/sam/SubstitutedSamInterfaceSubclassOfBuiltin.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/SubstitutedSamInterfaceSubclassOfBuiltin.txt
@@ -2,6 +2,6 @@ package test
 
 public /*synthesized*/ fun SubstitutedSamInterfaceSubclassOfBuiltin(/*0*/ function: (test.SubstitutedSamInterfaceSubclassOfBuiltin!) -> kotlin.Int): test.SubstitutedSamInterfaceSubclassOfBuiltin
 
-public trait SubstitutedSamInterfaceSubclassOfBuiltin : kotlin.Comparable<test.SubstitutedSamInterfaceSubclassOfBuiltin!> {
+public interface SubstitutedSamInterfaceSubclassOfBuiltin : kotlin.Comparable<test.SubstitutedSamInterfaceSubclassOfBuiltin!> {
     public abstract override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: test.SubstitutedSamInterfaceSubclassOfBuiltin!): kotlin.Int
 }
diff --git a/compiler/testData/loadJava/compiledJava/sam/VarargParameter.txt b/compiler/testData/loadJava/compiledJava/sam/VarargParameter.txt
index a6c513dcbad..b49c4ecdc10 100644
--- a/compiler/testData/loadJava/compiledJava/sam/VarargParameter.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/VarargParameter.txt
@@ -2,6 +2,6 @@ package test
 
 public /*synthesized*/ fun VarargParameter(/*0*/ function: (kotlin.Array<(out) kotlin.String!>!) -> kotlin.Unit): test.VarargParameter
 
-public trait VarargParameter {
+public interface VarargParameter {
     public abstract fun f(/*0*/ vararg p0: kotlin.String! /*kotlin.Array<(out) kotlin.String!>!*/): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/DeepSamLoop.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/DeepSamLoop.txt
index 8b28b6b1030..9fd6589f4b7 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/DeepSamLoop.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/DeepSamLoop.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait DeepSamLoop {
+public interface DeepSamLoop {
 
-    public trait Bar {
+    public interface Bar {
         public final /*synthesized*/ fun foo(/*0*/ p0: ((test.DeepSamLoop.Bar!) -> kotlin.Unit)!): kotlin.Unit
         public abstract fun foo(/*0*/ p0: test.DeepSamLoop.Foo!): kotlin.Unit
     }
 
-    public trait Foo {
+    public interface Foo {
         public final /*synthesized*/ fun foo(/*0*/ p0: ((test.DeepSamLoop.Foo!) -> kotlin.Unit)!): kotlin.Unit
         public abstract fun foo(/*0*/ p0: test.DeepSamLoop.Bar!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/PrivateSamAdapter.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/PrivateSamAdapter.txt
index d09eb4e9fb3..d50f28efa6c 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/PrivateSamAdapter.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/PrivateSamAdapter.txt
@@ -5,7 +5,7 @@ public open class PrivateSamAdapter {
     private final /*synthesized*/ fun samAdapter(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
     private open fun samAdapter(/*0*/ p0: test.PrivateSamAdapter.SamInterface!): kotlin.Unit
 
-    private trait SamInterface {
+    private interface SamInterface {
         public abstract fun foo(): kotlin.Unit
     }
 
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/SelfAsParameter.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/SelfAsParameter.txt
index 0167719076f..e8ecbe3e815 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/SelfAsParameter.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/SelfAsParameter.txt
@@ -2,7 +2,7 @@ package test
 
 public /*synthesized*/ fun SelfAsParameter(/*0*/ function: (test.SelfAsParameter!) -> kotlin.Unit): test.SelfAsParameter
 
-public trait SelfAsParameter {
+public interface SelfAsParameter {
     public final /*synthesized*/ fun foo(/*0*/ p0: ((test.SelfAsParameter!) -> kotlin.Unit)!): kotlin.Unit
     public abstract fun foo(/*0*/ p0: test.SelfAsParameter!): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/AdapterDoesntOverrideDeclaration.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/AdapterDoesntOverrideDeclaration.txt
index 25fa5efd545..8210fe730c3 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/AdapterDoesntOverrideDeclaration.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/AdapterDoesntOverrideDeclaration.txt
@@ -1,14 +1,14 @@
 package test
 
-public trait AdapterDoesntOverrideDeclaration {
+public interface AdapterDoesntOverrideDeclaration {
 
-    public trait Sub : test.AdapterDoesntOverrideDeclaration.Super {
+    public interface Sub : test.AdapterDoesntOverrideDeclaration.Super {
         public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: (() -> kotlin.Unit!)!): kotlin.Unit
         public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
         public abstract fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun foo(/*0*/ p0: (() -> kotlin.Unit!)!): kotlin.Unit
     }
 
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedAdapterAndDeclaration.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedAdapterAndDeclaration.txt
index d41e90271e4..c1f7ebe7644 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedAdapterAndDeclaration.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedAdapterAndDeclaration.txt
@@ -1,14 +1,14 @@
 package test
 
-public trait InheritedAdapterAndDeclaration {
+public interface InheritedAdapterAndDeclaration {
 
-    public trait Sub : test.InheritedAdapterAndDeclaration.Super {
+    public interface Sub : test.InheritedAdapterAndDeclaration.Super {
         public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: (() -> kotlin.Unit!)!): kotlin.Unit
         public final override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
         public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun foo(/*0*/ p0: (() -> kotlin.Unit!)!): kotlin.Unit
         public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
         public abstract fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedAmbiguousAdapters.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedAmbiguousAdapters.txt
index 85b21f7a92c..40f78972463 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedAmbiguousAdapters.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedAmbiguousAdapters.txt
@@ -1,15 +1,15 @@
 package test
 
-public trait InheritedAmbiguousAdapters {
+public interface InheritedAmbiguousAdapters {
 
-    public trait Sub : test.InheritedAmbiguousAdapters.Super {
+    public interface Sub : test.InheritedAmbiguousAdapters.Super {
         public final override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
         public final override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
         public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: java.io.Closeable!): kotlin.Unit
         public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
         public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
         public abstract fun foo(/*0*/ p0: java.io.Closeable!): kotlin.Unit
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedAndOverriddenAmbiguousAdapters.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedAndOverriddenAmbiguousAdapters.txt
index d26fcd92cfc..d7bde758e48 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedAndOverriddenAmbiguousAdapters.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedAndOverriddenAmbiguousAdapters.txt
@@ -1,15 +1,15 @@
 package test
 
-public trait InheritedAndOverriddenAmbiguousAdapters {
+public interface InheritedAndOverriddenAmbiguousAdapters {
 
-    public trait Sub : test.InheritedAndOverriddenAmbiguousAdapters.Super {
+    public interface Sub : test.InheritedAndOverriddenAmbiguousAdapters.Super {
         public final override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
         public final override /*1*/ /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
         public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: java.io.Closeable!): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
         public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
         public abstract fun foo(/*0*/ p0: java.io.Closeable!): kotlin.Unit
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedOverridden.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedOverridden.txt
index 56df91abef0..4959a737d04 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedOverridden.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedOverridden.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait InheritedOverridden {
+public interface InheritedOverridden {
 
     public open class Sub : test.InheritedOverridden.Super {
         public constructor Sub()
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedOverriddenAdapter.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedOverriddenAdapter.txt
index 42b12e26641..12bc206e50e 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedOverriddenAdapter.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedOverriddenAdapter.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait InheritedOverriddenAdapter {
+public interface InheritedOverriddenAdapter {
 
     public open class Sub : test.InheritedOverriddenAdapter.Super {
         public constructor Sub()
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedSameAdapters.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedSameAdapters.txt
index f76f3c96b31..2926af37f45 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedSameAdapters.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedSameAdapters.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait InheritedSameAdapters {
+public interface InheritedSameAdapters {
 
-    public trait Sub : test.InheritedSameAdapters.Super1, test.InheritedSameAdapters.Super2 {
+    public interface Sub : test.InheritedSameAdapters.Super1, test.InheritedSameAdapters.Super2 {
         public final override /*2*/ /*fake_override*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
         public abstract override /*2*/ /*fake_override*/ fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
 
-    public trait Super1 {
+    public interface Super1 {
         public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
         public abstract fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
 
-    public trait Super2 {
+    public interface Super2 {
         public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
         public abstract fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedSameAdaptersWithSubstitution.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedSameAdaptersWithSubstitution.txt
index 2b8ef835106..e57b8a18821 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedSameAdaptersWithSubstitution.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedSameAdaptersWithSubstitution.txt
@@ -1,23 +1,23 @@
 package test
 
-public trait InheritedSameAdaptersWithSubstitution {
+public interface InheritedSameAdaptersWithSubstitution {
 
-    public trait Sub : test.InheritedSameAdaptersWithSubstitution.Super1, test.InheritedSameAdaptersWithSubstitution.Super2Substituted {
+    public interface Sub : test.InheritedSameAdaptersWithSubstitution.Super1, test.InheritedSameAdaptersWithSubstitution.Super2Substituted {
         public final override /*2*/ /*fake_override*/ fun foo(/*0*/ p0: ((kotlin.String!, kotlin.String!) -> kotlin.Int)!): kotlin.Unit
         public abstract override /*2*/ /*fake_override*/ fun foo(/*0*/ p0: java.util.Comparator<kotlin.String!>!): kotlin.Unit
     }
 
-    public trait Super1 {
+    public interface Super1 {
         public final /*synthesized*/ fun foo(/*0*/ p0: ((kotlin.String!, kotlin.String!) -> kotlin.Int)!): kotlin.Unit
         public abstract fun foo(/*0*/ p0: java.util.Comparator<kotlin.String!>!): kotlin.Unit
     }
 
-    public trait Super2</*0*/ T> {
+    public interface Super2</*0*/ T> {
         public final /*synthesized*/ fun foo(/*0*/ p0: ((T!, T!) -> kotlin.Int)!): kotlin.Unit
         public abstract fun foo(/*0*/ p0: java.util.Comparator<T!>!): kotlin.Unit
     }
 
-    public trait Super2Substituted : test.InheritedSameAdaptersWithSubstitution.Super2<kotlin.String!> {
+    public interface Super2Substituted : test.InheritedSameAdaptersWithSubstitution.Super2<kotlin.String!> {
         public final override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: ((kotlin.String!, kotlin.String!) -> kotlin.Int)!): kotlin.Unit
         public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: java.util.Comparator<kotlin.String!>!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedSimple.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedSimple.txt
index eb5e0d5625b..caecdc3fd18 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedSimple.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/InheritedSimple.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritedSimple {
+public interface InheritedSimple {
 
-    public trait Sub : test.InheritedSimple.Super {
+    public interface Sub : test.InheritedSimple.Super {
         public final override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
         public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
         public abstract fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/OverriddenAmbiguousAdapters.txt b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/OverriddenAmbiguousAdapters.txt
index 153434ee896..3c14e209a7f 100644
--- a/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/OverriddenAmbiguousAdapters.txt
+++ b/compiler/testData/loadJava/compiledJava/sam/adapters/inheritance/OverriddenAmbiguousAdapters.txt
@@ -1,14 +1,14 @@
 package test
 
-public trait OverriddenAmbiguousAdapters {
+public interface OverriddenAmbiguousAdapters {
 
-    public trait Sub : test.OverriddenAmbiguousAdapters.Super {
+    public interface Sub : test.OverriddenAmbiguousAdapters.Super {
         public abstract override /*2*/ fun foo(/*0*/ p0: (() -> kotlin.Unit!)!): kotlin.Unit
         public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: java.io.Closeable!): kotlin.Unit
         public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ p0: java.lang.Runnable!): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
         public final /*synthesized*/ fun foo(/*0*/ p0: (() -> kotlin.Unit)!): kotlin.Unit
         public abstract fun foo(/*0*/ p0: java.io.Closeable!): kotlin.Unit
diff --git a/compiler/testData/loadJava/compiledJava/signaturePropagation/ArraysInSubtypes.txt b/compiler/testData/loadJava/compiledJava/signaturePropagation/ArraysInSubtypes.txt
index 126e113526c..891dc84c442 100644
--- a/compiler/testData/loadJava/compiledJava/signaturePropagation/ArraysInSubtypes.txt
+++ b/compiler/testData/loadJava/compiledJava/signaturePropagation/ArraysInSubtypes.txt
@@ -1,14 +1,14 @@
 package test
 
-public trait ArraysInSubtypes {
+public interface ArraysInSubtypes {
 
-    public trait Sub</*0*/ T> : test.ArraysInSubtypes.Super {
+    public interface Sub</*0*/ T> : test.ArraysInSubtypes.Super {
         public abstract override /*1*/ fun array(): kotlin.Array<(out) kotlin.String!>!
         public abstract override /*1*/ fun listOfArray(): (kotlin.MutableList<out kotlin.Array<(out) kotlin.String!>!>..kotlin.List<kotlin.Array<(out) kotlin.String!>!>?)
         public abstract override /*1*/ fun objArray(): kotlin.Array<(out) T!>!
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun array(): kotlin.Array<(out) kotlin.CharSequence!>!
         public abstract fun listOfArray(): (kotlin.MutableList<out kotlin.Array<(out) kotlin.CharSequence!>!>..kotlin.List<kotlin.Array<(out) kotlin.CharSequence!>!>?)
         public abstract fun objArray(): kotlin.Array<(out) kotlin.Any!>!
diff --git a/compiler/testData/loadJava/compiledJava/signaturePropagation/MethodTypeParameterErased.txt b/compiler/testData/loadJava/compiledJava/signaturePropagation/MethodTypeParameterErased.txt
index b3f8fa2a13d..4026ffe1b57 100644
--- a/compiler/testData/loadJava/compiledJava/signaturePropagation/MethodTypeParameterErased.txt
+++ b/compiler/testData/loadJava/compiledJava/signaturePropagation/MethodTypeParameterErased.txt
@@ -1,8 +1,8 @@
 package test
 
-public trait MethodTypeParameterErased {
+public interface MethodTypeParameterErased {
 
-    public trait Bug</*0*/ T> {
+    public interface Bug</*0*/ T> {
         public abstract fun </*0*/ RET : test.MethodTypeParameterErased.Bug<T!>!> save(): RET!
     }
 
diff --git a/compiler/testData/loadJava/compiledJava/signaturePropagation/RawSuperType.txt b/compiler/testData/loadJava/compiledJava/signaturePropagation/RawSuperType.txt
index 0f754af9ee5..d8aecadb676 100644
--- a/compiler/testData/loadJava/compiledJava/signaturePropagation/RawSuperType.txt
+++ b/compiler/testData/loadJava/compiledJava/signaturePropagation/RawSuperType.txt
@@ -9,7 +9,7 @@ public open class RawSuperType {
         public open override /*1*/ fun foo(/*0*/ p0: kotlin.Any!): kotlin.Unit
     }
 
-    public trait Super</*0*/ T> {
+    public interface Super</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p0: T!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/signaturePropagation/RawSuperTypeWithBound.txt b/compiler/testData/loadJava/compiledJava/signaturePropagation/RawSuperTypeWithBound.txt
index da96738ad0e..4f805869743 100644
--- a/compiler/testData/loadJava/compiledJava/signaturePropagation/RawSuperTypeWithBound.txt
+++ b/compiler/testData/loadJava/compiledJava/signaturePropagation/RawSuperTypeWithBound.txt
@@ -3,7 +3,7 @@ package test
 public open class RawSuperTypeWithBound {
     public constructor RawSuperTypeWithBound()
 
-    public trait Bound {
+    public interface Bound {
     }
 
     public open inner class Derived : test.RawSuperTypeWithBound.Super<test.RawSuperTypeWithBound.Bound!> {
@@ -13,7 +13,7 @@ public open class RawSuperTypeWithBound {
         public open override /*1*/ fun foo(/*0*/ p0: test.RawSuperTypeWithBound.Bound!): kotlin.Unit
     }
 
-    public trait Super</*0*/ T : test.RawSuperTypeWithBound.Bound!> {
+    public interface Super</*0*/ T : test.RawSuperTypeWithBound.Bound!> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p0: T!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/signaturePropagation/RawSuperTypeWithRecursiveBound.txt b/compiler/testData/loadJava/compiledJava/signaturePropagation/RawSuperTypeWithRecursiveBound.txt
index c84a856b2b5..c12c0756237 100644
--- a/compiler/testData/loadJava/compiledJava/signaturePropagation/RawSuperTypeWithRecursiveBound.txt
+++ b/compiler/testData/loadJava/compiledJava/signaturePropagation/RawSuperTypeWithRecursiveBound.txt
@@ -10,7 +10,7 @@ public open class RawSuperTypeWithRecursiveBound {
         public open override /*1*/ fun foo(/*0*/ p0: test.RawSuperTypeWithRecursiveBound.Super<*>!): kotlin.Unit
     }
 
-    public trait Super</*0*/ T : test.RawSuperTypeWithRecursiveBound.Super<T!>!> {
+    public interface Super</*0*/ T : test.RawSuperTypeWithRecursiveBound.Super<T!>!> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p0: T!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/signaturePropagation/RawSuperTypeWithRecursiveBoundMultipleParameters.txt b/compiler/testData/loadJava/compiledJava/signaturePropagation/RawSuperTypeWithRecursiveBoundMultipleParameters.txt
index f50cc14528c..f19f6f76e92 100644
--- a/compiler/testData/loadJava/compiledJava/signaturePropagation/RawSuperTypeWithRecursiveBoundMultipleParameters.txt
+++ b/compiler/testData/loadJava/compiledJava/signaturePropagation/RawSuperTypeWithRecursiveBoundMultipleParameters.txt
@@ -10,7 +10,7 @@ public open class RawSuperTypeWithRecursiveBoundMultipleParameters {
         public open override /*1*/ fun foo(/*0*/ p0: kotlin.Any!, /*1*/ p1: test.RawSuperTypeWithRecursiveBoundMultipleParameters.Super<*, *>!): kotlin.Unit
     }
 
-    public trait Super</*0*/ R, /*1*/ T : test.RawSuperTypeWithRecursiveBoundMultipleParameters.Super<R!, T!>!> {
+    public interface Super</*0*/ R, /*1*/ T : test.RawSuperTypeWithRecursiveBoundMultipleParameters.Super<R!, T!>!> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p0: R!, /*1*/ p1: T!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJava/signaturePropagation/ReturnInnerSubclassOfSupersInner.txt b/compiler/testData/loadJava/compiledJava/signaturePropagation/ReturnInnerSubclassOfSupersInner.txt
index 8d3069ac5df..1b71b6bddc0 100644
--- a/compiler/testData/loadJava/compiledJava/signaturePropagation/ReturnInnerSubclassOfSupersInner.txt
+++ b/compiler/testData/loadJava/compiledJava/signaturePropagation/ReturnInnerSubclassOfSupersInner.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait ReturnInnerSubclassOfSupersInner {
+public interface ReturnInnerSubclassOfSupersInner {
 
     public open class Sub</*0*/ B> : test.ReturnInnerSubclassOfSupersInner.Super<B!> {
         public constructor Sub</*0*/ B>()
diff --git a/compiler/testData/loadJava/compiledJava/signaturePropagation/SubclassWithRawType.txt b/compiler/testData/loadJava/compiledJava/signaturePropagation/SubclassWithRawType.txt
index ec0833f87c1..9851a9fb8b5 100644
--- a/compiler/testData/loadJava/compiledJava/signaturePropagation/SubclassWithRawType.txt
+++ b/compiler/testData/loadJava/compiledJava/signaturePropagation/SubclassWithRawType.txt
@@ -1,8 +1,8 @@
 package test
 
-public trait SubclassWithRawType {
+public interface SubclassWithRawType {
 
-    public trait Sub : test.SubclassWithRawType.Super {
+    public interface Sub : test.SubclassWithRawType.Super {
         public abstract override /*1*/ fun array1(): kotlin.Array<(out) kotlin.(Mutable)List<kotlin.String!>!>!
         public abstract override /*1*/ fun array2(): kotlin.Array<(out) kotlin.(Mutable)List<*>!>!
         public abstract override /*1*/ fun boundWildcard1(): (kotlin.MutableList<out kotlin.(Mutable)List<kotlin.String!>!>..kotlin.List<kotlin.(Mutable)List<kotlin.String!>!>?)
@@ -13,7 +13,7 @@ public trait SubclassWithRawType {
         public abstract override /*1*/ fun wildcard(): kotlin.(Mutable)List<*>!
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun array1(): kotlin.Array<(out) kotlin.(Mutable)List<*>!>!
         public abstract fun array2(): kotlin.Array<(out) kotlin.(Mutable)List<kotlin.String!>!>!
         public abstract fun boundWildcard1(): (kotlin.MutableList<out (kotlin.MutableList<out kotlin.Any?>..kotlin.List<kotlin.Any?>?)>..kotlin.List<(kotlin.MutableList<out kotlin.Any?>..kotlin.List<kotlin.Any?>?)>?)
diff --git a/compiler/testData/loadJava/compiledJava/signaturePropagation/TwoSuperclassesInconsistentGenericTypes.txt b/compiler/testData/loadJava/compiledJava/signaturePropagation/TwoSuperclassesInconsistentGenericTypes.txt
index 4c0551b5d66..245e00db8b1 100644
--- a/compiler/testData/loadJava/compiledJava/signaturePropagation/TwoSuperclassesInconsistentGenericTypes.txt
+++ b/compiler/testData/loadJava/compiledJava/signaturePropagation/TwoSuperclassesInconsistentGenericTypes.txt
@@ -1,10 +1,10 @@
 package test
 
-public trait TwoSuperclassesInconsistentGenericTypes {
+public interface TwoSuperclassesInconsistentGenericTypes {
     public abstract fun dummy(): kotlin.Unit
     public abstract fun foo(): kotlin.(Mutable)List<kotlin.String!>!
 
-    public trait Other {
+    public interface Other {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.(Mutable)List<kotlin.String!>!
     }
diff --git a/compiler/testData/loadJava/compiledJava/signaturePropagation/TwoSuperclassesVarargAndNot.txt b/compiler/testData/loadJava/compiledJava/signaturePropagation/TwoSuperclassesVarargAndNot.txt
index 3b4e3c64b87..c2dfa9e170d 100644
--- a/compiler/testData/loadJava/compiledJava/signaturePropagation/TwoSuperclassesVarargAndNot.txt
+++ b/compiler/testData/loadJava/compiledJava/signaturePropagation/TwoSuperclassesVarargAndNot.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait TwoSuperclassesVarargAndNot {
+public interface TwoSuperclassesVarargAndNot {
 
-    public trait Sub : test.TwoSuperclassesVarargAndNot.Super1, test.TwoSuperclassesVarargAndNot.Super2 {
+    public interface Sub : test.TwoSuperclassesVarargAndNot.Super1, test.TwoSuperclassesVarargAndNot.Super2 {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun foo(/*0*/ s: kotlin.Array<(out) kotlin.String!>!): kotlin.Unit
     }
 
-    public trait Super1 {
+    public interface Super1 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ vararg p0: kotlin.String! /*kotlin.Array<(out) kotlin.String!>!*/): kotlin.Unit
     }
 
-    public trait Super2 {
+    public interface Super2 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ s: kotlin.Array<(out) kotlin.String!>!): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledJavaAndKotlin/MixedPackage.txt b/compiler/testData/loadJava/compiledJavaAndKotlin/MixedPackage.txt
index 5a63392b69b..9096a739c7a 100644
--- a/compiler/testData/loadJava/compiledJavaAndKotlin/MixedPackage.txt
+++ b/compiler/testData/loadJava/compiledJavaAndKotlin/MixedPackage.txt
@@ -15,7 +15,7 @@ public final class KotlinClass {
     public constructor KotlinClass()
 }
 
-public trait SamInterface {
+public interface SamInterface {
     public abstract fun instanceMethod(): kotlin.Unit
 }
 
diff --git a/compiler/testData/loadJava/compiledJavaIncludeObjectMethods/EmptyInterface.txt b/compiler/testData/loadJava/compiledJavaIncludeObjectMethods/EmptyInterface.txt
index a4e468ce7bf..cfbb75d6394 100644
--- a/compiler/testData/loadJava/compiledJavaIncludeObjectMethods/EmptyInterface.txt
+++ b/compiler/testData/loadJava/compiledJavaIncludeObjectMethods/EmptyInterface.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait EmptyInterface {
+public interface EmptyInterface {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/loadJava/compiledJavaIncludeObjectMethods/InterfaceWithObjectMethods.txt b/compiler/testData/loadJava/compiledJavaIncludeObjectMethods/InterfaceWithObjectMethods.txt
index 441a3660465..fac31f9612d 100644
--- a/compiler/testData/loadJava/compiledJavaIncludeObjectMethods/InterfaceWithObjectMethods.txt
+++ b/compiler/testData/loadJava/compiledJavaIncludeObjectMethods/InterfaceWithObjectMethods.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait InterfaceWithObjectMethods {
+public interface InterfaceWithObjectMethods {
     public abstract fun clone(): kotlin.Any!
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public abstract fun finalize(): kotlin.Unit
diff --git a/compiler/testData/loadJava/compiledKotlin/annotations/MultiDimensionalArrayMethod.txt b/compiler/testData/loadJava/compiledKotlin/annotations/MultiDimensionalArrayMethod.txt
index f88f3de9b7b..f7bf6db8209 100644
--- a/compiler/testData/loadJava/compiledKotlin/annotations/MultiDimensionalArrayMethod.txt
+++ b/compiler/testData/loadJava/compiledKotlin/annotations/MultiDimensionalArrayMethod.txt
@@ -6,7 +6,7 @@ internal final annotation class Anno : kotlin.Annotation {
         internal final fun <get-s>(): kotlin.String
 }
 
-internal trait T {
+internal interface T {
     test.Anno(s = "bar": kotlin.String) internal abstract val bar: kotlin.Array<kotlin.Array<kotlin.BooleanArray>>
         internal abstract fun <get-bar>(): kotlin.Array<kotlin.Array<kotlin.BooleanArray>>
     test.Anno(s = "foo": kotlin.String) internal abstract fun foo(): kotlin.Array<kotlin.Array<kotlin.Array<test.T>>>
diff --git a/compiler/testData/loadJava/compiledKotlin/annotations/parameters/FunctionInTrait.txt b/compiler/testData/loadJava/compiledKotlin/annotations/parameters/FunctionInTrait.txt
index 0bb1077adbc..5c9f78e5745 100644
--- a/compiler/testData/loadJava/compiledKotlin/annotations/parameters/FunctionInTrait.txt
+++ b/compiler/testData/loadJava/compiledKotlin/annotations/parameters/FunctionInTrait.txt
@@ -4,6 +4,6 @@ internal final annotation class Anno : kotlin.Annotation {
     /*primary*/ public constructor Anno()
 }
 
-internal trait Trait {
+internal interface Trait {
     internal open fun foo(/*0*/ test.Anno() x: kotlin.String): kotlin.Int
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/annotations/propertiesWithoutBackingFields/NestedTrait.txt b/compiler/testData/loadJava/compiledKotlin/annotations/propertiesWithoutBackingFields/NestedTrait.txt
index c876918a3d6..c5983f0ac0f 100644
--- a/compiler/testData/loadJava/compiledKotlin/annotations/propertiesWithoutBackingFields/NestedTrait.txt
+++ b/compiler/testData/loadJava/compiledKotlin/annotations/propertiesWithoutBackingFields/NestedTrait.txt
@@ -7,7 +7,7 @@ internal final annotation class Anno : kotlin.Annotation {
 internal final class Class {
     /*primary*/ public constructor Class()
 
-    internal trait Trait {
+    internal interface Trait {
         test.Anno() internal abstract val property: kotlin.Int
             internal abstract fun <get-property>(): kotlin.Int
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/annotations/propertiesWithoutBackingFields/Trait.txt b/compiler/testData/loadJava/compiledKotlin/annotations/propertiesWithoutBackingFields/Trait.txt
index bc28d107c70..d4e5d39b108 100644
--- a/compiler/testData/loadJava/compiledKotlin/annotations/propertiesWithoutBackingFields/Trait.txt
+++ b/compiler/testData/loadJava/compiledKotlin/annotations/propertiesWithoutBackingFields/Trait.txt
@@ -4,7 +4,7 @@ internal final annotation class Anno : kotlin.Annotation {
     /*primary*/ public constructor Anno()
 }
 
-internal trait Trait {
+internal interface Trait {
     test.Anno() internal abstract val property: kotlin.Int
         internal abstract fun <get-property>(): kotlin.Int
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/annotations/propertiesWithoutBackingFields/TraitClassObject.txt b/compiler/testData/loadJava/compiledKotlin/annotations/propertiesWithoutBackingFields/TraitClassObject.txt
index 6446b9f670b..349e452ba0a 100644
--- a/compiler/testData/loadJava/compiledKotlin/annotations/propertiesWithoutBackingFields/TraitClassObject.txt
+++ b/compiler/testData/loadJava/compiledKotlin/annotations/propertiesWithoutBackingFields/TraitClassObject.txt
@@ -4,7 +4,7 @@ internal final annotation class Anno : kotlin.Annotation {
     /*primary*/ public constructor Anno()
 }
 
-internal trait Trait {
+internal interface Trait {
 
     internal companion object Companion {
         /*primary*/ private constructor Companion()
diff --git a/compiler/testData/loadJava/compiledKotlin/class/ClassMemberConflict.txt b/compiler/testData/loadJava/compiledKotlin/class/ClassMemberConflict.txt
index bf17b3e4335..8cd5ac7a868 100644
--- a/compiler/testData/loadJava/compiledKotlin/class/ClassMemberConflict.txt
+++ b/compiler/testData/loadJava/compiledKotlin/class/ClassMemberConflict.txt
@@ -20,7 +20,7 @@ internal final class ConstructorTypeParamClassObjectTypeConflict</*0*/ test> {
     internal companion object Companion {
         /*primary*/ private constructor Companion()
 
-        internal trait test {
+        internal interface test {
         }
     }
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/class/ClassParamReferencesSelf.txt b/compiler/testData/loadJava/compiledKotlin/class/ClassParamReferencesSelf.txt
index 79530901476..0f822247083 100644
--- a/compiler/testData/loadJava/compiledKotlin/class/ClassParamReferencesSelf.txt
+++ b/compiler/testData/loadJava/compiledKotlin/class/ClassParamReferencesSelf.txt
@@ -4,5 +4,5 @@ internal final class ClassParamReferencesSelf</*0*/ A : test.TraitWithP<A>> {
     /*primary*/ public constructor ClassParamReferencesSelf</*0*/ A : test.TraitWithP<A>>()
 }
 
-internal trait TraitWithP</*0*/ P> {
+internal interface TraitWithP</*0*/ P> {
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/class/InheritSubstitutedMethod.txt b/compiler/testData/loadJava/compiledKotlin/class/InheritSubstitutedMethod.txt
index 33532815dcc..fed75e310ee 100644
--- a/compiler/testData/loadJava/compiledKotlin/class/InheritSubstitutedMethod.txt
+++ b/compiler/testData/loadJava/compiledKotlin/class/InheritSubstitutedMethod.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait A</*0*/ T> {
+public interface A</*0*/ T> {
     internal abstract fun bar(): T
     internal open fun foo(): T
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/class/InheritTraitWithFunctionParam.txt b/compiler/testData/loadJava/compiledKotlin/class/InheritTraitWithFunctionParam.txt
index 0519ae1fdbf..1751aad9f1b 100644
--- a/compiler/testData/loadJava/compiledKotlin/class/InheritTraitWithFunctionParam.txt
+++ b/compiler/testData/loadJava/compiledKotlin/class/InheritTraitWithFunctionParam.txt
@@ -5,6 +5,6 @@ internal open class Class : test.Trait {
     internal open override /*1*/ /*fake_override*/ fun f(/*0*/ a: kotlin.String): kotlin.Unit
 }
 
-internal trait Trait {
+internal interface Trait {
     internal open fun f(/*0*/ a: kotlin.String): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/class/InheritTraitWithParam.txt b/compiler/testData/loadJava/compiledKotlin/class/InheritTraitWithParam.txt
index 868d701e9fd..aac7153bd92 100644
--- a/compiler/testData/loadJava/compiledKotlin/class/InheritTraitWithParam.txt
+++ b/compiler/testData/loadJava/compiledKotlin/class/InheritTraitWithParam.txt
@@ -1,6 +1,6 @@
 package test
 
-internal trait Aaa</*0*/ P> {
+internal interface Aaa</*0*/ P> {
 }
 
 internal final class Bbb : test.Aaa<java.util.Random> {
diff --git a/compiler/testData/loadJava/compiledKotlin/class/RecursiveGeneric.txt b/compiler/testData/loadJava/compiledKotlin/class/RecursiveGeneric.txt
index a5545ef0d66..732aa4e895a 100644
--- a/compiler/testData/loadJava/compiledKotlin/class/RecursiveGeneric.txt
+++ b/compiler/testData/loadJava/compiledKotlin/class/RecursiveGeneric.txt
@@ -1,9 +1,9 @@
 package test
 
-internal trait Rec</*0*/ R, /*1*/ out T : test.Rec<R, T>> {
+internal interface Rec</*0*/ R, /*1*/ out T : test.Rec<R, T>> {
     internal abstract fun t(): T
 }
 
-internal trait Super {
+internal interface Super {
     internal open fun foo(/*0*/ p: test.Rec<*, *>): test.Rec<*, *>
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/class/SingleAbstractMethod.txt b/compiler/testData/loadJava/compiledKotlin/class/SingleAbstractMethod.txt
index 78acb1f5ba4..045f9563fc5 100644
--- a/compiler/testData/loadJava/compiledKotlin/class/SingleAbstractMethod.txt
+++ b/compiler/testData/loadJava/compiledKotlin/class/SingleAbstractMethod.txt
@@ -1,5 +1,5 @@
 package test
 
-public trait SingleAbstractMethod {
+public interface SingleAbstractMethod {
     internal abstract fun foo(): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/class/Trait.txt b/compiler/testData/loadJava/compiledKotlin/class/Trait.txt
index fb39d0cdd2c..06427b3a57f 100644
--- a/compiler/testData/loadJava/compiledKotlin/class/Trait.txt
+++ b/compiler/testData/loadJava/compiledKotlin/class/Trait.txt
@@ -1,4 +1,4 @@
 package test
 
-internal trait Trtrtr {
+internal interface Trtrtr {
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/class/javaBean/JavaBeanAbstractGetter.txt b/compiler/testData/loadJava/compiledKotlin/class/javaBean/JavaBeanAbstractGetter.txt
index 597adaea6c9..b6090e7f803 100644
--- a/compiler/testData/loadJava/compiledKotlin/class/javaBean/JavaBeanAbstractGetter.txt
+++ b/compiler/testData/loadJava/compiledKotlin/class/javaBean/JavaBeanAbstractGetter.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait JavaBeanAbstractGetter {
+public interface JavaBeanAbstractGetter {
     public abstract fun getBlue(): kotlin.Int
     public abstract fun getRed(): kotlin.Int
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/classFun/FunDelegationToTraitImpl.txt b/compiler/testData/loadJava/compiledKotlin/classFun/FunDelegationToTraitImpl.txt
index 9ce1d8c662b..55b535e3054 100644
--- a/compiler/testData/loadJava/compiledKotlin/classFun/FunDelegationToTraitImpl.txt
+++ b/compiler/testData/loadJava/compiledKotlin/classFun/FunDelegationToTraitImpl.txt
@@ -1,6 +1,6 @@
 package test
 
-internal trait A {
+internal interface A {
     internal open fun f(): kotlin.String
 }
 
diff --git a/compiler/testData/loadJava/compiledKotlin/classFun/TraitFinalFun.txt b/compiler/testData/loadJava/compiledKotlin/classFun/TraitFinalFun.txt
index 7014130c8e1..fa4c8513171 100644
--- a/compiler/testData/loadJava/compiledKotlin/classFun/TraitFinalFun.txt
+++ b/compiler/testData/loadJava/compiledKotlin/classFun/TraitFinalFun.txt
@@ -1,5 +1,5 @@
 package test
 
-internal trait A {
+internal interface A {
     internal final fun f(): kotlin.String
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/classFun/TraitOpenFun.txt b/compiler/testData/loadJava/compiledKotlin/classFun/TraitOpenFun.txt
index 7017cf7c480..9ccab6c8aea 100644
--- a/compiler/testData/loadJava/compiledKotlin/classFun/TraitOpenFun.txt
+++ b/compiler/testData/loadJava/compiledKotlin/classFun/TraitOpenFun.txt
@@ -1,5 +1,5 @@
 package test
 
-internal trait A {
+internal interface A {
     internal open fun f(): kotlin.String
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/classObject/ClassObjectExtendsTrait.txt b/compiler/testData/loadJava/compiledKotlin/classObject/ClassObjectExtendsTrait.txt
index 73f09d0410f..e6197420caa 100644
--- a/compiler/testData/loadJava/compiledKotlin/classObject/ClassObjectExtendsTrait.txt
+++ b/compiler/testData/loadJava/compiledKotlin/classObject/ClassObjectExtendsTrait.txt
@@ -1,6 +1,6 @@
 package test
 
-internal trait Bbb {
+internal interface Bbb {
 }
 
 internal final class ClassObjectextendsTrait {
diff --git a/compiler/testData/loadJava/compiledKotlin/classObject/ClassObjectExtendsTraitWithTP.txt b/compiler/testData/loadJava/compiledKotlin/classObject/ClassObjectExtendsTraitWithTP.txt
index 8f2854a4f3d..adcd3fe6117 100644
--- a/compiler/testData/loadJava/compiledKotlin/classObject/ClassObjectExtendsTraitWithTP.txt
+++ b/compiler/testData/loadJava/compiledKotlin/classObject/ClassObjectExtendsTraitWithTP.txt
@@ -1,6 +1,6 @@
 package test
 
-internal trait Bbb</*0*/ P> {
+internal interface Bbb</*0*/ P> {
 }
 
 internal final class ClassObjectExtendsTraitWithTP {
diff --git a/compiler/testData/loadJava/compiledKotlin/classObject/Delegation.txt b/compiler/testData/loadJava/compiledKotlin/classObject/Delegation.txt
index 27b2ae84b9a..ea52cf19683 100644
--- a/compiler/testData/loadJava/compiledKotlin/classObject/Delegation.txt
+++ b/compiler/testData/loadJava/compiledKotlin/classObject/Delegation.txt
@@ -10,6 +10,6 @@ internal final class A : test.T {
     }
 }
 
-internal trait T {
+internal interface T {
     internal abstract fun foo(): kotlin.Int
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/classObject/classObjectInTraitStaticFields.txt b/compiler/testData/loadJava/compiledKotlin/classObject/classObjectInTraitStaticFields.txt
index 4ce9d34ef02..03539dfcede 100644
--- a/compiler/testData/loadJava/compiledKotlin/classObject/classObjectInTraitStaticFields.txt
+++ b/compiler/testData/loadJava/compiledKotlin/classObject/classObjectInTraitStaticFields.txt
@@ -1,6 +1,6 @@
 package test
 
-internal trait Test {
+internal interface Test {
 
     internal companion object Companion {
         /*primary*/ private constructor Companion()
diff --git a/compiler/testData/loadJava/compiledKotlin/enum/enumWithInnerClasses.txt b/compiler/testData/loadJava/compiledKotlin/enum/enumWithInnerClasses.txt
index 02e73073947..eb38b06c2c2 100644
--- a/compiler/testData/loadJava/compiledKotlin/enum/enumWithInnerClasses.txt
+++ b/compiler/testData/loadJava/compiledKotlin/enum/enumWithInnerClasses.txt
@@ -37,7 +37,7 @@ internal final enum class Enum : kotlin.Enum<test.Enum> {
         /*primary*/ public constructor Nested()
     }
 
-    internal trait Trait {
+    internal interface Trait {
     }
 
     // Static members
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/ClassObject.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/ClassObject.txt
index d81db790a29..65ef329e1af 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/ClassObject.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/ClassObject.txt
@@ -1,6 +1,6 @@
 package test
 
-internal trait TheTrait {
+internal interface TheTrait {
 
     internal companion object Companion {
         /*primary*/ private constructor Companion()
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/InheritMethodsDifferentReturnTypes.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/InheritMethodsDifferentReturnTypes.txt
index 32cd48b6141..44cd6a3e223 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/InheritMethodsDifferentReturnTypes.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/InheritMethodsDifferentReturnTypes.txt
@@ -3,17 +3,17 @@ package test
 public final class InheritMethodsDifferentReturnTypes {
     /*primary*/ public constructor InheritMethodsDifferentReturnTypes()
 
-    public trait Sub : test.InheritMethodsDifferentReturnTypes.Super1, test.InheritMethodsDifferentReturnTypes.Super2 {
+    public interface Sub : test.InheritMethodsDifferentReturnTypes.Super1, test.InheritMethodsDifferentReturnTypes.Super2 {
         public abstract override /*2*/ /*fake_override*/ fun bar(): kotlin.String?
         public abstract override /*2*/ /*fake_override*/ fun foo(): kotlin.String?
     }
 
-    public trait Super1 {
+    public interface Super1 {
         public abstract fun bar(): kotlin.String?
         public abstract fun foo(): kotlin.CharSequence?
     }
 
-    public trait Super2 {
+    public interface Super2 {
         public abstract fun bar(): kotlin.CharSequence?
         public abstract fun foo(): kotlin.String?
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/InheritMethodsDifferentReturnTypesGeneric.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/InheritMethodsDifferentReturnTypesGeneric.txt
index 72aff192aeb..7cca6705788 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/InheritMethodsDifferentReturnTypesGeneric.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/InheritMethodsDifferentReturnTypesGeneric.txt
@@ -3,17 +3,17 @@ package test
 public final class InheritMethodsDifferentReturnTypesGeneric {
     /*primary*/ public constructor InheritMethodsDifferentReturnTypesGeneric()
 
-    public trait Sub : test.InheritMethodsDifferentReturnTypesGeneric.Super1<kotlin.String, kotlin.CharSequence>, test.InheritMethodsDifferentReturnTypesGeneric.Super2<kotlin.CharSequence, kotlin.String> {
+    public interface Sub : test.InheritMethodsDifferentReturnTypesGeneric.Super1<kotlin.String, kotlin.CharSequence>, test.InheritMethodsDifferentReturnTypesGeneric.Super2<kotlin.CharSequence, kotlin.String> {
         public abstract override /*2*/ /*fake_override*/ fun bar(): kotlin.String?
         public abstract override /*2*/ /*fake_override*/ fun foo(): kotlin.String?
     }
 
-    public trait Super1</*0*/ F, /*1*/ B> {
+    public interface Super1</*0*/ F, /*1*/ B> {
         public abstract fun bar(): B?
         public abstract fun foo(): F?
     }
 
-    public trait Super2</*0*/ FF, /*1*/ BB> {
+    public interface Super2</*0*/ FF, /*1*/ BB> {
         public abstract fun bar(): BB?
         public abstract fun foo(): FF?
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/RemoveRedundantProjectionKind.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/RemoveRedundantProjectionKind.txt
index 781405bde80..d29e36e02fc 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/RemoveRedundantProjectionKind.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/RemoveRedundantProjectionKind.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait RemoveRedundantProjectionKind {
+public interface RemoveRedundantProjectionKind {
     public abstract fun f(/*0*/ p0: kotlin.Collection<kotlin.CharSequence?>?): kotlin.Unit
     public abstract fun f(/*0*/ p0: kotlin.Comparable<kotlin.CharSequence?>?): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/UnboundWildcard.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/UnboundWildcard.txt
index 5231fc80e8a..7355b582533 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/UnboundWildcard.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/UnboundWildcard.txt
@@ -4,6 +4,6 @@ public final class UnboundWildcard {
     /*primary*/ public constructor UnboundWildcard()
     public final fun foo(): test.UnboundWildcard.MyClass<*>?
 
-    public trait MyClass</*0*/ T : kotlin.CharSequence?> {
+    public interface MyClass</*0*/ T : kotlin.CharSequence?> {
     }
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/StarProjection.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/StarProjection.txt
index 2e42a18a3da..00af567a3b1 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/StarProjection.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/StarProjection.txt
@@ -4,6 +4,6 @@ public final class StarProjection {
     /*primary*/ public constructor StarProjection()
     public final fun foo(): test.StarProjection.MyClass<*>
 
-    public trait MyClass</*0*/ T : kotlin.CharSequence?> {
+    public interface MyClass</*0*/ T : kotlin.CharSequence?> {
     }
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/PropagateTypeArgumentNullable.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/PropagateTypeArgumentNullable.txt
index 38497dd0d31..f96ff4cf80e 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/PropagateTypeArgumentNullable.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/PropagateTypeArgumentNullable.txt
@@ -1,8 +1,8 @@
 package test
 
-public trait PropagateTypeArgumentNullable {
+public interface PropagateTypeArgumentNullable {
 
-    public trait Sub : test.PropagateTypeArgumentNullable.Super {
+    public interface Sub : test.PropagateTypeArgumentNullable.Super {
         public abstract override /*1*/ fun invOutR(): kotlin.MutableList<kotlin.List<kotlin.String?>>
         public abstract override /*1*/ fun invOutS(/*0*/ p: kotlin.MutableList<kotlin.List<kotlin.String?>>): kotlin.Unit
         public abstract override /*1*/ fun invR(): kotlin.MutableList<kotlin.String?>
@@ -11,7 +11,7 @@ public trait PropagateTypeArgumentNullable {
         public abstract override /*1*/ fun outS(/*0*/ p: kotlin.List<kotlin.String?>): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun invOutR(): kotlin.MutableList<kotlin.List<kotlin.String?>>
         public abstract fun invOutS(/*0*/ p: kotlin.MutableList<kotlin.List<kotlin.String?>>): kotlin.Unit
         public abstract fun invR(): kotlin.MutableList<kotlin.String?>
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/ChangeProjectionKind1.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/ChangeProjectionKind1.txt
index 496bc68f718..bfb1400b4c9 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/ChangeProjectionKind1.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/ChangeProjectionKind1.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait ChangeProjectionKind1 {
+public interface ChangeProjectionKind1 {
 
-    public trait Sub : test.ChangeProjectionKind1.Super {
+    public interface Sub : test.ChangeProjectionKind1.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p: kotlin.MutableList<in kotlin.String>): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p: kotlin.MutableList<in kotlin.String>): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/ChangeProjectionKind2.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/ChangeProjectionKind2.txt
index 66edcbd7178..47a192d4bfb 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/ChangeProjectionKind2.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/ChangeProjectionKind2.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait ChangeProjectionKind2 {
+public interface ChangeProjectionKind2 {
 
-    public trait Sub : test.ChangeProjectionKind2.Super {
+    public interface Sub : test.ChangeProjectionKind2.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p: kotlin.MutableList<kotlin.String>): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p: kotlin.MutableList<kotlin.String>): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/DeeplySubstitutedClassParameter.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/DeeplySubstitutedClassParameter.txt
index d85715b6570..4943b49139f 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/DeeplySubstitutedClassParameter.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/DeeplySubstitutedClassParameter.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait DeeplySubstitutedClassParameter {
+public interface DeeplySubstitutedClassParameter {
 
-    public trait Middle</*0*/ E> : test.DeeplySubstitutedClassParameter.Super<E> {
+    public interface Middle</*0*/ E> : test.DeeplySubstitutedClassParameter.Super<E> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ t: E): kotlin.Unit
     }
 
-    public trait Sub : test.DeeplySubstitutedClassParameter.Middle<kotlin.String> {
+    public interface Sub : test.DeeplySubstitutedClassParameter.Middle<kotlin.String> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ t: kotlin.String): kotlin.Unit
     }
 
-    public trait Super</*0*/ T> {
+    public interface Super</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ t: T): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/DeeplySubstitutedClassParameter2.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/DeeplySubstitutedClassParameter2.txt
index 23450f1a63e..137e89da1ee 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/DeeplySubstitutedClassParameter2.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/DeeplySubstitutedClassParameter2.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait DeeplySubstitutedClassParameter2 {
+public interface DeeplySubstitutedClassParameter2 {
 
-    public trait Middle</*0*/ E> : test.DeeplySubstitutedClassParameter2.Super<E> {
+    public interface Middle</*0*/ E> : test.DeeplySubstitutedClassParameter2.Super<E> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ t: E): kotlin.Unit
     }
 
-    public trait Sub : test.DeeplySubstitutedClassParameter2.Middle<kotlin.String> {
+    public interface Sub : test.DeeplySubstitutedClassParameter2.Middle<kotlin.String> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ t: kotlin.String): kotlin.Unit
     }
 
-    public trait Super</*0*/ T> {
+    public interface Super</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ t: T): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritMutability.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritMutability.txt
index b687ddd0921..3bbfc18414d 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritMutability.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritMutability.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritMutability {
+public interface InheritMutability {
 
-    public trait Sub : test.InheritMutability.Super {
+    public interface Sub : test.InheritMutability.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p: kotlin.MutableList<kotlin.String>): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p: kotlin.MutableList<kotlin.String>): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritNotVararg.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritNotVararg.txt
index 7026686254d..324ab37392c 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritNotVararg.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritNotVararg.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritNotVararg {
+public interface InheritNotVararg {
 
-    public trait Sub : test.InheritNotVararg.Super {
+    public interface Sub : test.InheritNotVararg.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p0: kotlin.Array<out kotlin.String>?): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p0: kotlin.Array<out kotlin.String>?): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritNotVarargInteger.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritNotVarargInteger.txt
index 1d4fd8a1f40..256418cbedb 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritNotVarargInteger.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritNotVarargInteger.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritNotVarargInteger {
+public interface InheritNotVarargInteger {
 
-    public trait Sub : test.InheritNotVarargInteger.Super {
+    public interface Sub : test.InheritNotVarargInteger.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p0: kotlin.Array<out kotlin.Int>?): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p0: kotlin.Array<out kotlin.Int>?): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritNotVarargNotNull.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritNotVarargNotNull.txt
index 2a2f2c66d7a..82d343111f3 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritNotVarargNotNull.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritNotVarargNotNull.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritNotVarargNotNull {
+public interface InheritNotVarargNotNull {
 
-    public trait Sub : test.InheritNotVarargNotNull.Super {
+    public interface Sub : test.InheritNotVarargNotNull.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p: kotlin.Array<out kotlin.String>): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p: kotlin.Array<out kotlin.String>): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritNotVarargPrimitive.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritNotVarargPrimitive.txt
index d8a94ad8413..d06199a3f5c 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritNotVarargPrimitive.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritNotVarargPrimitive.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritNotVarargPrimitive {
+public interface InheritNotVarargPrimitive {
 
-    public trait Sub : test.InheritNotVarargPrimitive.Super {
+    public interface Sub : test.InheritNotVarargPrimitive.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p0: kotlin.IntArray?): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p0: kotlin.IntArray?): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritNullability.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritNullability.txt
index adeae6a0fa2..0755cad951b 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritNullability.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritNullability.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritNullability {
+public interface InheritNullability {
 
-    public trait Sub : test.InheritNullability.Super {
+    public interface Sub : test.InheritNullability.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p0: kotlin.String): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p0: kotlin.String): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritProjectionKind.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritProjectionKind.txt
index bb45f37132a..3dd54c470f5 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritProjectionKind.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritProjectionKind.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritProjectionKind {
+public interface InheritProjectionKind {
 
-    public trait Sub : test.InheritProjectionKind.Super {
+    public interface Sub : test.InheritProjectionKind.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p: kotlin.MutableList<in kotlin.String>): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p: kotlin.MutableList<in kotlin.String>): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritReadOnliness.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritReadOnliness.txt
index 83491ecb0a0..cb9f02c2532 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritReadOnliness.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritReadOnliness.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritReadOnliness {
+public interface InheritReadOnliness {
 
-    public trait Sub : test.InheritReadOnliness.Super {
+    public interface Sub : test.InheritReadOnliness.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p: kotlin.List<kotlin.String>): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p: kotlin.List<kotlin.String>): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritVararg.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritVararg.txt
index b229baa0968..a284653bd56 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritVararg.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritVararg.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritVararg {
+public interface InheritVararg {
 
-    public trait Sub : test.InheritVararg.Super {
+    public interface Sub : test.InheritVararg.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ vararg p0: kotlin.String? /*kotlin.Array<out kotlin.String?>*/): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ vararg p0: kotlin.String? /*kotlin.Array<out kotlin.String?>*/): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritVarargInteger.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritVarargInteger.txt
index e0c7c1d7209..4ad64319889 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritVarargInteger.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritVarargInteger.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritVarargInteger {
+public interface InheritVarargInteger {
 
-    public trait Sub : test.InheritVarargInteger.Super {
+    public interface Sub : test.InheritVarargInteger.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ vararg p0: kotlin.Int? /*kotlin.Array<out kotlin.Int?>*/): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ vararg p0: kotlin.Int? /*kotlin.Array<out kotlin.Int?>*/): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritVarargNotNull.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritVarargNotNull.txt
index 93c4f71826c..1b196492c7e 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritVarargNotNull.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritVarargNotNull.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritVarargNotNull {
+public interface InheritVarargNotNull {
 
-    public trait Sub : test.InheritVarargNotNull.Super {
+    public interface Sub : test.InheritVarargNotNull.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ vararg p: kotlin.String /*kotlin.Array<out kotlin.String>*/): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ vararg p: kotlin.String /*kotlin.Array<out kotlin.String>*/): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritVarargPrimitive.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritVarargPrimitive.txt
index fb59836fb67..124ade53d93 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritVarargPrimitive.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/InheritVarargPrimitive.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritVarargPrimitive {
+public interface InheritVarargPrimitive {
 
-    public trait Sub : test.InheritVarargPrimitive.Super {
+    public interface Sub : test.InheritVarargPrimitive.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ vararg p0: kotlin.Int /*kotlin.IntArray*/): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ vararg p0: kotlin.Int /*kotlin.IntArray*/): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/Kt3302.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/Kt3302.txt
index 80d02cceaf8..0ade7b56be3 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/Kt3302.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/Kt3302.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait Kt3302 {
+public interface Kt3302 {
 
-    public trait BSONObject {
+    public interface BSONObject {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun put(/*0*/ p0: kotlin.String, /*1*/ p1: kotlin.Any): kotlin.Any?
     }
 
-    public trait BasicBSONObject : test.Kt3302.LinkedHashMap<kotlin.String, kotlin.Any>, test.Kt3302.BSONObject {
+    public interface BasicBSONObject : test.Kt3302.LinkedHashMap<kotlin.String, kotlin.Any>, test.Kt3302.BSONObject {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun put(/*0*/ key: kotlin.String, /*1*/ value: kotlin.Any): kotlin.Any?
     }
 
-    public trait LinkedHashMap</*0*/ K, /*1*/ V> {
+    public interface LinkedHashMap</*0*/ K, /*1*/ V> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun put(/*0*/ key: K, /*1*/ value: V): V?
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/MutableToReadOnly.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/MutableToReadOnly.txt
index 20d378dd58c..ab9d2a2e766 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/MutableToReadOnly.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/MutableToReadOnly.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait MutableToReadOnly {
+public interface MutableToReadOnly {
 
-    public trait Sub : test.MutableToReadOnly.Super {
+    public interface Sub : test.MutableToReadOnly.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p: kotlin.MutableList<kotlin.String>): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p: kotlin.MutableList<kotlin.String>): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/NotNullToNullable.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/NotNullToNullable.txt
index c91fe7f5f3c..9a8dce0b55a 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/NotNullToNullable.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/NotNullToNullable.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait NotNullToNullable {
+public interface NotNullToNullable {
 
-    public trait Sub : test.NotNullToNullable.Super {
+    public interface Sub : test.NotNullToNullable.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p0: kotlin.String): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p0: kotlin.String): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/NullableToNotNull.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/NullableToNotNull.txt
index ade5f610b00..c415c3bdeb1 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/NullableToNotNull.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/NullableToNotNull.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait NullableToNotNull {
+public interface NullableToNotNull {
 
-    public trait Sub : test.NullableToNotNull.Super {
+    public interface Sub : test.NullableToNotNull.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p0: kotlin.String?): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p0: kotlin.String?): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/NullableToNotNullKotlinSignature.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/NullableToNotNullKotlinSignature.txt
index 7a1e5819cfa..d67b5b476b4 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/NullableToNotNullKotlinSignature.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/NullableToNotNullKotlinSignature.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait NullableToNotNullKotlinSignature {
+public interface NullableToNotNullKotlinSignature {
 
-    public trait Sub : test.NullableToNotNullKotlinSignature.Super {
+    public interface Sub : test.NullableToNotNullKotlinSignature.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p: kotlin.String?): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p: kotlin.String?): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/OverrideWithErasedParameter.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/OverrideWithErasedParameter.txt
index 508434d2ca0..3ce48ce96a2 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/OverrideWithErasedParameter.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/OverrideWithErasedParameter.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait OverrideWithErasedParameter {
+public interface OverrideWithErasedParameter {
 
-    public trait Sub</*0*/ T> : test.OverrideWithErasedParameter.Super<T> {
+    public interface Sub</*0*/ T> : test.OverrideWithErasedParameter.Super<T> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p0: T?): kotlin.Unit
     }
 
-    public trait Super</*0*/ T> {
+    public interface Super</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p0: T?): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/ReadOnlyToMutable.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/ReadOnlyToMutable.txt
index b6fc1f31da6..c7196641374 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/ReadOnlyToMutable.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/ReadOnlyToMutable.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait ReadOnlyToMutable {
+public interface ReadOnlyToMutable {
 
-    public trait Sub : test.ReadOnlyToMutable.Super {
+    public interface Sub : test.ReadOnlyToMutable.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ p: kotlin.List<kotlin.String>): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p: kotlin.List<kotlin.String>): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/SubclassFromGenericAndNot.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/SubclassFromGenericAndNot.txt
index bb185d71dce..3793836ce1c 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/SubclassFromGenericAndNot.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/SubclassFromGenericAndNot.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait SubclassFromGenericAndNot {
+public interface SubclassFromGenericAndNot {
 
-    public trait Generic</*0*/ T> {
+    public interface Generic</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ key: T): kotlin.Unit
     }
 
-    public trait NonGeneric {
+    public interface NonGeneric {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ p0: kotlin.String): kotlin.Unit
     }
 
-    public trait Sub : test.SubclassFromGenericAndNot.NonGeneric, test.SubclassFromGenericAndNot.Generic<kotlin.String> {
+    public interface Sub : test.SubclassFromGenericAndNot.NonGeneric, test.SubclassFromGenericAndNot.Generic<kotlin.String> {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun foo(/*0*/ key: kotlin.String): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/SubstitutedClassParameter.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/SubstitutedClassParameter.txt
index 29b462d8d7f..893f5744df3 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/SubstitutedClassParameter.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/SubstitutedClassParameter.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait SubstitutedClassParameter {
+public interface SubstitutedClassParameter {
 
-    public trait Sub : test.SubstitutedClassParameter.Super<kotlin.String> {
+    public interface Sub : test.SubstitutedClassParameter.Super<kotlin.String> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(/*0*/ t: kotlin.String): kotlin.Unit
     }
 
-    public trait Super</*0*/ T> {
+    public interface Super</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ t: T): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/SubstitutedClassParameters.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/SubstitutedClassParameters.txt
index 24d12a57ebb..4f3ca6364fc 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/SubstitutedClassParameters.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/parameter/SubstitutedClassParameters.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait SubstitutedClassParameters {
+public interface SubstitutedClassParameters {
 
-    public trait Sub : test.SubstitutedClassParameters.Super1<kotlin.String>, test.SubstitutedClassParameters.Super2<kotlin.String> {
+    public interface Sub : test.SubstitutedClassParameters.Super1<kotlin.String>, test.SubstitutedClassParameters.Super2<kotlin.String> {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun foo(/*0*/ t: kotlin.String): kotlin.Unit
     }
 
-    public trait Super1</*0*/ T> {
+    public interface Super1</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ t: T): kotlin.Unit
     }
 
-    public trait Super2</*0*/ E> {
+    public interface Super2</*0*/ E> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(/*0*/ t: E): kotlin.Unit
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/AddNotNullJavaSubtype.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/AddNotNullJavaSubtype.txt
index b47be08e907..08a620e6cf1 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/AddNotNullJavaSubtype.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/AddNotNullJavaSubtype.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait AddNotNullJavaSubtype {
+public interface AddNotNullJavaSubtype {
 
-    public trait Sub : test.AddNotNullJavaSubtype.Super {
+    public interface Sub : test.AddNotNullJavaSubtype.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.String
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.CharSequence?
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/AddNotNullSameJavaType.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/AddNotNullSameJavaType.txt
index 9c8ac430929..7988f21fcbb 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/AddNotNullSameJavaType.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/AddNotNullSameJavaType.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait AddNotNullSameJavaType {
+public interface AddNotNullSameJavaType {
 
-    public trait Sub : test.AddNotNullSameJavaType.Super {
+    public interface Sub : test.AddNotNullSameJavaType.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.CharSequence
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.CharSequence?
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/AddNullabilityJavaSubtype.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/AddNullabilityJavaSubtype.txt
index 04aa3be6110..e6756da650c 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/AddNullabilityJavaSubtype.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/AddNullabilityJavaSubtype.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait AddNullabilityJavaSubtype {
+public interface AddNullabilityJavaSubtype {
 
-    public trait Sub : test.AddNullabilityJavaSubtype.Super {
+    public interface Sub : test.AddNullabilityJavaSubtype.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.String
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.CharSequence
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/AddNullabilitySameGenericType1.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/AddNullabilitySameGenericType1.txt
index 9d67a3e2eb2..26d34a209d8 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/AddNullabilitySameGenericType1.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/AddNullabilitySameGenericType1.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait AddNullabilitySameGenericType1 {
+public interface AddNullabilitySameGenericType1 {
 
-    public trait Sub : test.AddNullabilitySameGenericType1.Super {
+    public interface Sub : test.AddNullabilitySameGenericType1.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.MutableList<kotlin.String>
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.MutableList<kotlin.String>
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/AddNullabilitySameGenericType2.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/AddNullabilitySameGenericType2.txt
index 741a239056d..a48044ba58d 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/AddNullabilitySameGenericType2.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/AddNullabilitySameGenericType2.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait AddNullabilitySameGenericType2 {
+public interface AddNullabilitySameGenericType2 {
 
-    public trait Sub : test.AddNullabilitySameGenericType2.Super {
+    public interface Sub : test.AddNullabilitySameGenericType2.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.MutableList<kotlin.String>
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.MutableList<kotlin.String>
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/AddNullabilitySameJavaType.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/AddNullabilitySameJavaType.txt
index 7a8e6eb18f4..2b309f13632 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/AddNullabilitySameJavaType.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/AddNullabilitySameJavaType.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait AddNullabilitySameJavaType {
+public interface AddNullabilitySameJavaType {
 
-    public trait Sub : test.AddNullabilitySameJavaType.Super {
+    public interface Sub : test.AddNullabilitySameJavaType.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.CharSequence
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.CharSequence
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/CantMakeImmutableInSubclass.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/CantMakeImmutableInSubclass.txt
index d9ca0b67761..150515b5581 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/CantMakeImmutableInSubclass.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/CantMakeImmutableInSubclass.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait CantMakeImmutableInSubclass {
+public interface CantMakeImmutableInSubclass {
 
-    public trait Sub : test.CantMakeImmutableInSubclass.Super {
+    public interface Sub : test.CantMakeImmutableInSubclass.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.MutableList<kotlin.String>
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.MutableCollection<kotlin.String>
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/DeeplySubstitutedClassParameter.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/DeeplySubstitutedClassParameter.txt
index d2bd5d3c192..59eb82900db 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/DeeplySubstitutedClassParameter.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/DeeplySubstitutedClassParameter.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait DeeplySubstitutedClassParameter {
+public interface DeeplySubstitutedClassParameter {
 
-    public trait Middle</*0*/ E> : test.DeeplySubstitutedClassParameter.Super<E> {
+    public interface Middle</*0*/ E> : test.DeeplySubstitutedClassParameter.Super<E> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): E
     }
 
-    public trait Sub : test.DeeplySubstitutedClassParameter.Middle<kotlin.String> {
+    public interface Sub : test.DeeplySubstitutedClassParameter.Middle<kotlin.String> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.String
     }
 
-    public trait Super</*0*/ T> {
+    public interface Super</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): T
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/DeeplySubstitutedClassParameter2.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/DeeplySubstitutedClassParameter2.txt
index aa135b90e49..72472ed151f 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/DeeplySubstitutedClassParameter2.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/DeeplySubstitutedClassParameter2.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait DeeplySubstitutedClassParameter2 {
+public interface DeeplySubstitutedClassParameter2 {
 
-    public trait Middle</*0*/ E> : test.DeeplySubstitutedClassParameter2.Super<E> {
+    public interface Middle</*0*/ E> : test.DeeplySubstitutedClassParameter2.Super<E> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ /*fake_override*/ fun foo(): E
     }
 
-    public trait Sub : test.DeeplySubstitutedClassParameter2.Middle<kotlin.String> {
+    public interface Sub : test.DeeplySubstitutedClassParameter2.Middle<kotlin.String> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.String
     }
 
-    public trait Super</*0*/ T> {
+    public interface Super</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): T
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/HalfSubstitutedTypeParameters.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/HalfSubstitutedTypeParameters.txt
index c9a06f17937..49d21a0e829 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/HalfSubstitutedTypeParameters.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/HalfSubstitutedTypeParameters.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait HalfSubstitutedTypeParameters {
+public interface HalfSubstitutedTypeParameters {
 
-    public trait Sub : test.HalfSubstitutedTypeParameters.Super {
+    public interface Sub : test.HalfSubstitutedTypeParameters.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): test.HalfSubstitutedTypeParameters.TrickyList<kotlin.Int, kotlin.String?>
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.MutableList<kotlin.String?>
     }
 
-    public trait TrickyList</*0*/ X, /*1*/ E> : kotlin.MutableList<E> {
+    public interface TrickyList</*0*/ X, /*1*/ E> : kotlin.MutableList<E> {
         public abstract override /*1*/ /*fake_override*/ fun add(/*0*/ e: E): kotlin.Boolean
         public abstract override /*1*/ /*fake_override*/ fun add(/*0*/ index: kotlin.Int, /*1*/ element: E): kotlin.Unit
         public abstract override /*1*/ /*fake_override*/ fun addAll(/*0*/ c: kotlin.Collection<E>): kotlin.Boolean
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritNullabilityGenericSubclassSimple.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritNullabilityGenericSubclassSimple.txt
index ed2154c4687..b51d2bf4696 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritNullabilityGenericSubclassSimple.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritNullabilityGenericSubclassSimple.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritNullabilityGenericSubclassSimple {
+public interface InheritNullabilityGenericSubclassSimple {
 
-    public trait Sub : test.InheritNullabilityGenericSubclassSimple.Super {
+    public interface Sub : test.InheritNullabilityGenericSubclassSimple.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.MutableList<kotlin.String>
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.MutableCollection<kotlin.String>
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritNullabilityJavaSubtype.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritNullabilityJavaSubtype.txt
index 371d96b0fdb..df6d58df7d0 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritNullabilityJavaSubtype.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritNullabilityJavaSubtype.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritNullabilityJavaSubtype {
+public interface InheritNullabilityJavaSubtype {
 
-    public trait Sub : test.InheritNullabilityJavaSubtype.Super {
+    public interface Sub : test.InheritNullabilityJavaSubtype.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.String
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.CharSequence
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritNullabilitySameGenericType.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritNullabilitySameGenericType.txt
index 046900e4340..b2dbdc4e78f 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritNullabilitySameGenericType.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritNullabilitySameGenericType.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritNullabilitySameGenericType {
+public interface InheritNullabilitySameGenericType {
 
-    public trait Sub : test.InheritNullabilitySameGenericType.Super {
+    public interface Sub : test.InheritNullabilitySameGenericType.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.MutableList<kotlin.String>
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.MutableList<kotlin.String>
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritNullabilitySameJavaType.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritNullabilitySameJavaType.txt
index dc7f971d02c..bdf3b5739d0 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritNullabilitySameJavaType.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritNullabilitySameJavaType.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritNullabilitySameJavaType {
+public interface InheritNullabilitySameJavaType {
 
-    public trait Sub : test.InheritNullabilitySameJavaType.Super {
+    public interface Sub : test.InheritNullabilitySameJavaType.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.CharSequence
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.CharSequence
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritProjectionKind.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritProjectionKind.txt
index d5a6705f372..a937d0410a1 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritProjectionKind.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritProjectionKind.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritProjectionKind {
+public interface InheritProjectionKind {
 
-    public trait Sub : test.InheritProjectionKind.Super {
+    public interface Sub : test.InheritProjectionKind.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.MutableList<out kotlin.Number>
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.MutableCollection<out kotlin.Number>
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritReadOnlinessOfArgument.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritReadOnlinessOfArgument.txt
index 43b547c2d5c..c4959fc938a 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritReadOnlinessOfArgument.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritReadOnlinessOfArgument.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritReadOnlinessOfArgument {
+public interface InheritReadOnlinessOfArgument {
 
-    public trait Sub : test.InheritReadOnlinessOfArgument.Super {
+    public interface Sub : test.InheritReadOnlinessOfArgument.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.List<kotlin.List<kotlin.String>>
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.List<kotlin.List<kotlin.String>>
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritReadOnlinessSameClass.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritReadOnlinessSameClass.txt
index be5a6e6b3f1..493d19b9ba0 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritReadOnlinessSameClass.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritReadOnlinessSameClass.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritReadOnlinessSameClass {
+public interface InheritReadOnlinessSameClass {
 
-    public trait Sub : test.InheritReadOnlinessSameClass.Super {
+    public interface Sub : test.InheritReadOnlinessSameClass.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.List<kotlin.String>
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.List<kotlin.String>
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritReadOnlinessSubclass.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritReadOnlinessSubclass.txt
index 0976e7ae10b..56ace366700 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritReadOnlinessSubclass.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/InheritReadOnlinessSubclass.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait InheritReadOnlinessSubclass {
+public interface InheritReadOnlinessSubclass {
 
-    public trait Sub : test.InheritReadOnlinessSubclass.Super {
+    public interface Sub : test.InheritReadOnlinessSubclass.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.List<kotlin.String>
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.Collection<kotlin.String>
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/SameProjectionKind.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/SameProjectionKind.txt
index 01b9da26748..ad9579318a4 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/SameProjectionKind.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/SameProjectionKind.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait SameProjectionKind {
+public interface SameProjectionKind {
 
-    public trait Sub : test.SameProjectionKind.Super {
+    public interface Sub : test.SameProjectionKind.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.MutableCollection<out kotlin.Number?>?
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.MutableCollection<out kotlin.Number?>?
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/SubclassFromGenericAndNot.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/SubclassFromGenericAndNot.txt
index 1f4549c24df..8893f5e7a08 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/SubclassFromGenericAndNot.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/SubclassFromGenericAndNot.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait SubclassFromGenericAndNot {
+public interface SubclassFromGenericAndNot {
 
-    public trait Generic</*0*/ T> {
+    public interface Generic</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): T
     }
 
-    public trait NonGeneric {
+    public interface NonGeneric {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.String?
     }
 
-    public trait Sub : test.SubclassFromGenericAndNot.NonGeneric, test.SubclassFromGenericAndNot.Generic<kotlin.String> {
+    public interface Sub : test.SubclassFromGenericAndNot.NonGeneric, test.SubclassFromGenericAndNot.Generic<kotlin.String> {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun foo(): kotlin.String
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/SubclassOfCollection.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/SubclassOfCollection.txt
index b91eba675d8..a2c1921bd91 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/SubclassOfCollection.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/SubclassOfCollection.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait SubclassOfCollection</*0*/ E> : kotlin.MutableCollection<E> {
+public interface SubclassOfCollection</*0*/ E> : kotlin.MutableCollection<E> {
     public abstract override /*1*/ /*fake_override*/ fun add(/*0*/ e: E): kotlin.Boolean
     public abstract override /*1*/ /*fake_override*/ fun addAll(/*0*/ c: kotlin.Collection<E>): kotlin.Boolean
     public abstract override /*1*/ /*fake_override*/ fun clear(): kotlin.Unit
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/SubclassOfMapEntry.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/SubclassOfMapEntry.txt
index a97044fa8be..2e5890d2c4e 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/SubclassOfMapEntry.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/SubclassOfMapEntry.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait SubclassOfMapEntry</*0*/ K, /*1*/ V> : kotlin.MutableMap.MutableEntry<K, V> {
+public interface SubclassOfMapEntry</*0*/ K, /*1*/ V> : kotlin.MutableMap.MutableEntry<K, V> {
     public abstract override /*1*/ /*fake_override*/ fun getKey(): K
     public abstract override /*1*/ /*fake_override*/ fun getValue(): V
     public abstract override /*1*/ fun setValue(/*0*/ value: V): V
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/SubstitutedClassParameter.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/SubstitutedClassParameter.txt
index d6e78ee9766..0781e8a84bb 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/SubstitutedClassParameter.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/SubstitutedClassParameter.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait SubstitutedClassParameter {
+public interface SubstitutedClassParameter {
 
-    public trait Sub : test.SubstitutedClassParameter.Super<kotlin.String> {
+    public interface Sub : test.SubstitutedClassParameter.Super<kotlin.String> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.String
     }
 
-    public trait Super</*0*/ T> {
+    public interface Super</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): T
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/SubstitutedClassParameters.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/SubstitutedClassParameters.txt
index 177bba1d7fb..b73455032b8 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/SubstitutedClassParameters.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/SubstitutedClassParameters.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait SubstitutedClassParameters {
+public interface SubstitutedClassParameters {
 
-    public trait Sub : test.SubstitutedClassParameters.Super1<kotlin.String>, test.SubstitutedClassParameters.Super2<kotlin.String> {
+    public interface Sub : test.SubstitutedClassParameters.Super1<kotlin.String>, test.SubstitutedClassParameters.Super2<kotlin.String> {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun foo(): kotlin.String
     }
 
-    public trait Super1</*0*/ T> {
+    public interface Super1</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): T
     }
 
-    public trait Super2</*0*/ E> {
+    public interface Super2</*0*/ E> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): E
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesConflictingProjectionKinds.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesConflictingProjectionKinds.txt
index 979da14b148..2dddbd4050f 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesConflictingProjectionKinds.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesConflictingProjectionKinds.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait TwoSuperclassesConflictingProjectionKinds {
+public interface TwoSuperclassesConflictingProjectionKinds {
 
-    public trait Sub : test.TwoSuperclassesConflictingProjectionKinds.Super1, test.TwoSuperclassesConflictingProjectionKinds.Super2 {
+    public interface Sub : test.TwoSuperclassesConflictingProjectionKinds.Super1, test.TwoSuperclassesConflictingProjectionKinds.Super2 {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun foo(): kotlin.MutableCollection<kotlin.CharSequence>
     }
 
-    public trait Super1 {
+    public interface Super1 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.MutableCollection<kotlin.CharSequence>
     }
 
-    public trait Super2 {
+    public interface Super2 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.MutableCollection<out kotlin.CharSequence>
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesInvariantAndCovariantInferMutability.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesInvariantAndCovariantInferMutability.txt
index b4103e662cf..1b1916d8faf 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesInvariantAndCovariantInferMutability.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesInvariantAndCovariantInferMutability.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait TwoSuperclassesInvariantAndCovariantInferMutability {
+public interface TwoSuperclassesInvariantAndCovariantInferMutability {
 
-    public trait Sub : test.TwoSuperclassesInvariantAndCovariantInferMutability.Super1, test.TwoSuperclassesInvariantAndCovariantInferMutability.Super2 {
+    public interface Sub : test.TwoSuperclassesInvariantAndCovariantInferMutability.Super1, test.TwoSuperclassesInvariantAndCovariantInferMutability.Super2 {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun foo(): kotlin.MutableList<kotlin.MutableList<kotlin.String>>
     }
 
-    public trait Super1 {
+    public interface Super1 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.List<kotlin.List<kotlin.String>>
     }
 
-    public trait Super2 {
+    public interface Super2 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.MutableList<kotlin.MutableList<kotlin.String>>
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesInvariantAndCovariantInferNullability.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesInvariantAndCovariantInferNullability.txt
index 899b3f05d6f..64523aeb761 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesInvariantAndCovariantInferNullability.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesInvariantAndCovariantInferNullability.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait TwoSuperclassesInvariantAndCovariantInferNullability {
+public interface TwoSuperclassesInvariantAndCovariantInferNullability {
 
-    public trait Sub : test.TwoSuperclassesInvariantAndCovariantInferNullability.Super1, test.TwoSuperclassesInvariantAndCovariantInferNullability.Super2 {
+    public interface Sub : test.TwoSuperclassesInvariantAndCovariantInferNullability.Super1, test.TwoSuperclassesInvariantAndCovariantInferNullability.Super2 {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun foo(): kotlin.MutableList<kotlin.String>
     }
 
-    public trait Super1 {
+    public interface Super1 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.List<kotlin.String?>
     }
 
-    public trait Super2 {
+    public interface Super2 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.MutableList<kotlin.String>
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesMutableAndNot.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesMutableAndNot.txt
index f8766e5099b..48e38ab63a2 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesMutableAndNot.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesMutableAndNot.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait TwoSuperclassesMutableAndNot {
+public interface TwoSuperclassesMutableAndNot {
 
-    public trait Sub : test.TwoSuperclassesMutableAndNot.Super1, test.TwoSuperclassesMutableAndNot.Super2 {
+    public interface Sub : test.TwoSuperclassesMutableAndNot.Super1, test.TwoSuperclassesMutableAndNot.Super2 {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun foo(): kotlin.MutableList<kotlin.String>
     }
 
-    public trait Super1 {
+    public interface Super1 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.MutableCollection<kotlin.String>
     }
 
-    public trait Super2 {
+    public interface Super2 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.List<kotlin.String>
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesReturnJavaSubtype.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesReturnJavaSubtype.txt
index e5118ab022c..ada99eef360 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesReturnJavaSubtype.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesReturnJavaSubtype.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait TwoSuperclassesReturnJavaSubtype {
+public interface TwoSuperclassesReturnJavaSubtype {
 
-    public trait Sub : test.TwoSuperclassesReturnJavaSubtype.Super1, test.TwoSuperclassesReturnJavaSubtype.Super2 {
+    public interface Sub : test.TwoSuperclassesReturnJavaSubtype.Super1, test.TwoSuperclassesReturnJavaSubtype.Super2 {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun foo(): kotlin.String
     }
 
-    public trait Super1 {
+    public interface Super1 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.CharSequence?
     }
 
-    public trait Super2 {
+    public interface Super2 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.CharSequence
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesReturnSameJavaType.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesReturnSameJavaType.txt
index 984264eb3ab..76431c52cce 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesReturnSameJavaType.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesReturnSameJavaType.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait TwoSuperclassesReturnSameJavaType {
+public interface TwoSuperclassesReturnSameJavaType {
 
-    public trait Sub : test.TwoSuperclassesReturnSameJavaType.Super1, test.TwoSuperclassesReturnSameJavaType.Super2 {
+    public interface Sub : test.TwoSuperclassesReturnSameJavaType.Super1, test.TwoSuperclassesReturnSameJavaType.Super2 {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun foo(): kotlin.CharSequence
     }
 
-    public trait Super1 {
+    public interface Super1 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.CharSequence?
     }
 
-    public trait Super2 {
+    public interface Super2 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.CharSequence
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesSupplementNotNull.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesSupplementNotNull.txt
index 4db979aea9a..757d3c347c8 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesSupplementNotNull.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TwoSuperclassesSupplementNotNull.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait TwoSuperclassesSupplementNotNull {
+public interface TwoSuperclassesSupplementNotNull {
 
-    public trait Sub : test.TwoSuperclassesSupplementNotNull.Super1, test.TwoSuperclassesSupplementNotNull.Super2 {
+    public interface Sub : test.TwoSuperclassesSupplementNotNull.Super1, test.TwoSuperclassesSupplementNotNull.Super2 {
         public abstract override /*2*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*2*/ fun foo(): kotlin.List<kotlin.String>
     }
 
-    public trait Super1 {
+    public interface Super1 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.List<kotlin.String?>
     }
 
-    public trait Super2 {
+    public interface Super2 {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): kotlin.List<kotlin.String>?
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TypeParamOfClass.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TypeParamOfClass.txt
index a8e6056ab2e..71993b8767d 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TypeParamOfClass.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TypeParamOfClass.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait TypeParamOfClass {
+public interface TypeParamOfClass {
 
-    public trait Sub</*0*/ T> : test.TypeParamOfClass.Super<T> {
+    public interface Sub</*0*/ T> : test.TypeParamOfClass.Super<T> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): T
     }
 
-    public trait Super</*0*/ T> {
+    public interface Super</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): T
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TypeParamOfClassSubstituted.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TypeParamOfClassSubstituted.txt
index b24b4900e03..f0d9cbbe372 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TypeParamOfClassSubstituted.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TypeParamOfClassSubstituted.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait TypeParamOfClassSubstituted {
+public interface TypeParamOfClassSubstituted {
 
-    public trait Sub : test.TypeParamOfClassSubstituted.Super<kotlin.String> {
+    public interface Sub : test.TypeParamOfClassSubstituted.Super<kotlin.String> {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun foo(): kotlin.String
     }
 
-    public trait Super</*0*/ T> {
+    public interface Super</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun foo(): T
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TypeParamOfFun.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TypeParamOfFun.txt
index 93f004c529b..29f87c978b7 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TypeParamOfFun.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/return/TypeParamOfFun.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait TypeParamOfFun {
+public interface TypeParamOfFun {
 
-    public trait Sub : test.TypeParamOfFun.Super {
+    public interface Sub : test.TypeParamOfFun.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
         public abstract override /*1*/ fun </*0*/ E> foo(): E
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun dummy(): kotlin.Unit
         public abstract fun </*0*/ T> foo(): T
     }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/InheritMutability.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/InheritMutability.txt
index 3df3d6148ef..0fcaea04162 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/InheritMutability.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/InheritMutability.txt
@@ -1,12 +1,12 @@
 package test
 
-public trait InheritMutability {
+public interface InheritMutability {
 
-    public trait Sub : test.InheritMutability.Super {
+    public interface Sub : test.InheritMutability.Super {
         public abstract override /*1*/ fun </*0*/ B : kotlin.MutableList<kotlin.String>> foo(/*0*/ a: B): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun </*0*/ A : kotlin.MutableList<kotlin.String>> foo(/*0*/ a: A): kotlin.Unit
     }
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/InheritNullability.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/InheritNullability.txt
index ee84451ab09..44fcbbd3bfe 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/InheritNullability.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/InheritNullability.txt
@@ -1,12 +1,12 @@
 package test
 
-public trait InheritNullability {
+public interface InheritNullability {
 
-    public trait Sub : test.InheritNullability.Super {
+    public interface Sub : test.InheritNullability.Super {
         public abstract override /*1*/ fun </*0*/ B : kotlin.CharSequence> foo(/*0*/ a: B): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun </*0*/ A : kotlin.CharSequence> foo(/*0*/ a: A): kotlin.Unit
     }
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/InheritReadOnliness.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/InheritReadOnliness.txt
index 31fb9c78899..b8d5636f63a 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/InheritReadOnliness.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/InheritReadOnliness.txt
@@ -1,12 +1,12 @@
 package test
 
-public trait InheritReadOnliness {
+public interface InheritReadOnliness {
 
-    public trait Sub : test.InheritReadOnliness.Super {
+    public interface Sub : test.InheritReadOnliness.Super {
         public abstract override /*1*/ fun </*0*/ B : kotlin.List<kotlin.String>> foo(/*0*/ a: B): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun </*0*/ A : kotlin.List<kotlin.String>> foo(/*0*/ a: A): kotlin.Unit
     }
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/TwoBounds.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/TwoBounds.txt
index 088088c39b9..cc490a9dcdc 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/TwoBounds.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/TwoBounds.txt
@@ -1,12 +1,12 @@
 package test
 
-public trait TwoBounds {
+public interface TwoBounds {
 
-    public trait Sub : test.TwoBounds.Super {
+    public interface Sub : test.TwoBounds.Super {
         public abstract override /*1*/ fun </*0*/ B : kotlin.CharSequence> foo(/*0*/ a: B): kotlin.Unit where B : kotlin.Cloneable
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun </*0*/ A : kotlin.CharSequence> foo(/*0*/ a: A): kotlin.Unit where A : kotlin.Cloneable
     }
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/TwoSuperclasses.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/TwoSuperclasses.txt
index efba57c8f95..e2617722402 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/TwoSuperclasses.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/TwoSuperclasses.txt
@@ -1,16 +1,16 @@
 package test
 
-public trait TwoSuperclasses {
+public interface TwoSuperclasses {
 
-    public trait Sub : test.TwoSuperclasses.Super1, test.TwoSuperclasses.Super2 {
+    public interface Sub : test.TwoSuperclasses.Super1, test.TwoSuperclasses.Super2 {
         public abstract override /*2*/ fun </*0*/ C : kotlin.CharSequence> foo(/*0*/ a: C): kotlin.Unit
     }
 
-    public trait Super1 {
+    public interface Super1 {
         public abstract fun </*0*/ A : kotlin.CharSequence> foo(/*0*/ a: A): kotlin.Unit
     }
 
-    public trait Super2 {
+    public interface Super2 {
         public abstract fun </*0*/ B : kotlin.CharSequence> foo(/*0*/ a: B): kotlin.Unit
     }
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/TwoTypeParameters.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/TwoTypeParameters.txt
index 6e9f31a72a9..3c70e19cdab 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/TwoTypeParameters.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/TwoTypeParameters.txt
@@ -1,12 +1,12 @@
 package test
 
-public trait TwoTypeParameters {
+public interface TwoTypeParameters {
 
-    public trait Sub : test.TwoTypeParameters.Super {
+    public interface Sub : test.TwoTypeParameters.Super {
         public abstract override /*1*/ fun </*0*/ B : kotlin.CharSequence, /*1*/ A : kotlin.Cloneable> foo(/*0*/ a: B, /*1*/ b: A): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun </*0*/ A : kotlin.CharSequence, /*1*/ B : kotlin.Cloneable> foo(/*0*/ a: A, /*1*/ b: B): kotlin.Unit
     }
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/UseParameterAsUpperBound.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/UseParameterAsUpperBound.txt
index 3c1a244c604..ec22b20c474 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/UseParameterAsUpperBound.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/UseParameterAsUpperBound.txt
@@ -1,12 +1,12 @@
 package test
 
-public trait UseParameterAsUpperBound {
+public interface UseParameterAsUpperBound {
 
-    public trait Sub : test.UseParameterAsUpperBound.Super {
+    public interface Sub : test.UseParameterAsUpperBound.Super {
         public abstract override /*1*/ fun </*0*/ B, /*1*/ A : B> foo(/*0*/ a: B, /*1*/ b: A): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun </*0*/ A, /*1*/ B : A> foo(/*0*/ a: A, /*1*/ b: B): kotlin.Unit
     }
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/UseParameterInUpperBound.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/UseParameterInUpperBound.txt
index e84b3ad4977..0da4e5bbc11 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/UseParameterInUpperBound.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/UseParameterInUpperBound.txt
@@ -1,12 +1,12 @@
 package test
 
-public trait UseParameterInUpperBound {
+public interface UseParameterInUpperBound {
 
-    public trait Sub : test.UseParameterInUpperBound.Super {
+    public interface Sub : test.UseParameterInUpperBound.Super {
         public abstract override /*1*/ fun </*0*/ B, /*1*/ A : kotlin.List<B>> foo(/*0*/ a: B, /*1*/ b: A): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun </*0*/ A, /*1*/ B : kotlin.List<A>> foo(/*0*/ a: A, /*1*/ b: B): kotlin.Unit
     }
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/UseParameterInUpperBoundWithKotlinSignature.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/UseParameterInUpperBoundWithKotlinSignature.txt
index f1b548ae9a2..ee849d01570 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/UseParameterInUpperBoundWithKotlinSignature.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/kotlinSignature/propagation/typeParameter/UseParameterInUpperBoundWithKotlinSignature.txt
@@ -1,12 +1,12 @@
 package test
 
-public trait UseParameterInUpperBoundWithKotlinSignature {
+public interface UseParameterInUpperBoundWithKotlinSignature {
 
-    public trait Sub : test.UseParameterInUpperBoundWithKotlinSignature.Super {
+    public interface Sub : test.UseParameterInUpperBoundWithKotlinSignature.Super {
         public abstract override /*1*/ fun </*0*/ B, /*1*/ A : kotlin.List<B>> foo(/*0*/ b: B, /*1*/ a: A): kotlin.Unit
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun </*0*/ A, /*1*/ B : kotlin.List<A>> foo(/*0*/ a: A, /*1*/ b: B): kotlin.Unit
     }
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/library/LoadIterable.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/library/LoadIterable.txt
index 8bbe029a6b8..79a60866ea5 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/library/LoadIterable.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/library/LoadIterable.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait LoadIterable</*0*/ T> {
+public interface LoadIterable</*0*/ T> {
     public abstract fun getIterable(): kotlin.MutableIterable<T>?
     public abstract fun setIterable(/*0*/ p0: kotlin.Iterable<T>?): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/library/LoadIterator.txt b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/library/LoadIterator.txt
index 46ebe4d178f..23b2d683568 100644
--- a/compiler/testData/loadJava/compiledKotlin/fromLoadJava/library/LoadIterator.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fromLoadJava/library/LoadIterator.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait LoadIterator</*0*/ T> {
+public interface LoadIterator</*0*/ T> {
     public abstract fun getIterator(): kotlin.MutableIterator<T>?
     public abstract fun setIterator(/*0*/ p0: kotlin.Iterator<T>?): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/fun/DeclaredMemberOverridesDelegated.txt b/compiler/testData/loadJava/compiledKotlin/fun/DeclaredMemberOverridesDelegated.txt
index 25a1e513f53..1341022e684 100644
--- a/compiler/testData/loadJava/compiledKotlin/fun/DeclaredMemberOverridesDelegated.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fun/DeclaredMemberOverridesDelegated.txt
@@ -7,10 +7,10 @@ internal final class B : test.X, test.Y {
     internal open override /*2*/ fun foo(): kotlin.Unit
 }
 
-internal trait X {
+internal interface X {
     internal abstract fun foo(): kotlin.Unit
 }
 
-internal trait Y : test.X {
+internal interface Y : test.X {
     internal abstract override /*1*/ /*fake_override*/ fun foo(): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/fun/InheritMethodsDifferentReturnTypesAndVisibilities.txt b/compiler/testData/loadJava/compiledKotlin/fun/InheritMethodsDifferentReturnTypesAndVisibilities.txt
index 64d8cb090bb..bd668dfd827 100644
--- a/compiler/testData/loadJava/compiledKotlin/fun/InheritMethodsDifferentReturnTypesAndVisibilities.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fun/InheritMethodsDifferentReturnTypesAndVisibilities.txt
@@ -1,16 +1,16 @@
 package test
 
-public trait Sub : test.Super1, test.Super2 {
+public interface Sub : test.Super1, test.Super2 {
     public abstract override /*1*/ /*fake_override*/ fun bar(): kotlin.CharSequence
     public abstract override /*1*/ /*fake_override*/ fun foo(): kotlin.CharSequence
 }
 
-public trait Super1 {
+public interface Super1 {
     private abstract fun bar(): kotlin.String
     public abstract fun foo(): kotlin.CharSequence
 }
 
-public trait Super2 {
+public interface Super2 {
     public abstract fun bar(): kotlin.CharSequence
     private abstract fun foo(): kotlin.String
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/fun/InheritValAndVar.txt b/compiler/testData/loadJava/compiledKotlin/fun/InheritValAndVar.txt
index 2c842d6a730..e196551e4c1 100644
--- a/compiler/testData/loadJava/compiledKotlin/fun/InheritValAndVar.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fun/InheritValAndVar.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait Sub : test.Super1, test.Super2 {
+public interface Sub : test.Super1, test.Super2 {
     internal abstract override /*2*/ /*fake_override*/ var x: kotlin.String
         internal abstract override /*2*/ /*fake_override*/ fun <get-x>(): kotlin.String
         internal abstract override /*1*/ /*fake_override*/ fun <set-x>(/*0*/ <set-?>: kotlin.String): kotlin.Unit
@@ -9,7 +9,7 @@ public trait Sub : test.Super1, test.Super2 {
         internal abstract override /*1*/ /*fake_override*/ fun <set-y>(/*0*/ <set-?>: kotlin.String): kotlin.Unit
 }
 
-public trait Super1 {
+public interface Super1 {
     internal abstract val x: kotlin.String
         internal abstract fun <get-x>(): kotlin.String
     internal abstract var y: kotlin.String
@@ -17,7 +17,7 @@ public trait Super1 {
         internal abstract fun <set-y>(/*0*/ <set-?>: kotlin.String): kotlin.Unit
 }
 
-public trait Super2 {
+public interface Super2 {
     internal abstract var x: kotlin.String
         internal abstract fun <get-x>(): kotlin.String
         internal abstract fun <set-x>(/*0*/ <set-?>: kotlin.String): kotlin.Unit
diff --git a/compiler/testData/loadJava/compiledKotlin/fun/InheritValsDifferentTypes.txt b/compiler/testData/loadJava/compiledKotlin/fun/InheritValsDifferentTypes.txt
index b86d8b46863..43e999e76f6 100644
--- a/compiler/testData/loadJava/compiledKotlin/fun/InheritValsDifferentTypes.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fun/InheritValsDifferentTypes.txt
@@ -1,20 +1,20 @@
 package test
 
-public trait Sub : test.Super1, test.Super2 {
+public interface Sub : test.Super1, test.Super2 {
     internal abstract override /*2*/ /*fake_override*/ val x: kotlin.String
         internal abstract override /*2*/ /*fake_override*/ fun <get-x>(): kotlin.String
     internal abstract override /*2*/ /*fake_override*/ val y: kotlin.String
         internal abstract override /*2*/ /*fake_override*/ fun <get-y>(): kotlin.String
 }
 
-public trait Super1 {
+public interface Super1 {
     internal abstract val x: kotlin.String
         internal abstract fun <get-x>(): kotlin.String
     internal abstract val y: kotlin.CharSequence
         internal abstract fun <get-y>(): kotlin.CharSequence
 }
 
-public trait Super2 {
+public interface Super2 {
     internal abstract val x: kotlin.CharSequence
         internal abstract fun <get-x>(): kotlin.CharSequence
     internal abstract val y: kotlin.String
diff --git a/compiler/testData/loadJava/compiledKotlin/fun/NoDelegationForFunctionInheritedFromTraitSuperClass.txt b/compiler/testData/loadJava/compiledKotlin/fun/NoDelegationForFunctionInheritedFromTraitSuperClass.txt
index 42b3314eb6c..22c894c0e85 100644
--- a/compiler/testData/loadJava/compiledKotlin/fun/NoDelegationForFunctionInheritedFromTraitSuperClass.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fun/NoDelegationForFunctionInheritedFromTraitSuperClass.txt
@@ -24,7 +24,7 @@ internal final class D : test.B, test.X {
     internal open override /*2*/ /*fake_override*/ fun foo(): kotlin.Unit
 }
 
-internal trait X : test.A {
+internal interface X : test.A {
     internal open fun bar(): kotlin.Unit
     internal abstract override /*1*/ /*fake_override*/ fun foo(): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/fun/NoSamAdapter.txt b/compiler/testData/loadJava/compiledKotlin/fun/NoSamAdapter.txt
index a5d9d50c48c..ec5018040fe 100644
--- a/compiler/testData/loadJava/compiledKotlin/fun/NoSamAdapter.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fun/NoSamAdapter.txt
@@ -2,6 +2,6 @@ package test
 
 internal fun foo(/*0*/ r: java.lang.Runnable): kotlin.Unit
 
-public trait TaskObject {
+public interface TaskObject {
     internal abstract fun foo(/*0*/ r: java.lang.Runnable): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/fun/NoSamConstructor.txt b/compiler/testData/loadJava/compiledKotlin/fun/NoSamConstructor.txt
index f2ec3caae9f..b8272288dba 100644
--- a/compiler/testData/loadJava/compiledKotlin/fun/NoSamConstructor.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fun/NoSamConstructor.txt
@@ -1,5 +1,5 @@
 package test
 
-public trait Runnable {
+public interface Runnable {
     internal abstract fun run(): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/fun/PropagateDeepSubclass.txt b/compiler/testData/loadJava/compiledKotlin/fun/PropagateDeepSubclass.txt
index 2b4f66ed8ad..b7dd663d386 100644
--- a/compiler/testData/loadJava/compiledKotlin/fun/PropagateDeepSubclass.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fun/PropagateDeepSubclass.txt
@@ -1,6 +1,6 @@
 package test
 
-internal trait A {
+internal interface A {
     internal open fun bar(): kotlin.Unit
     internal open fun foo(): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/fun/genericWithTypeVariables/FunParamTwoUpperBounds.txt b/compiler/testData/loadJava/compiledKotlin/fun/genericWithTypeVariables/FunParamTwoUpperBounds.txt
index 2dfbdd2ae87..153da713a97 100644
--- a/compiler/testData/loadJava/compiledKotlin/fun/genericWithTypeVariables/FunParamTwoUpperBounds.txt
+++ b/compiler/testData/loadJava/compiledKotlin/fun/genericWithTypeVariables/FunParamTwoUpperBounds.txt
@@ -2,8 +2,8 @@ package test
 
 internal fun </*0*/ T : test.Foo> foo(): kotlin.Unit where T : test.Bar
 
-internal trait Bar {
+internal interface Bar {
 }
 
-internal trait Foo {
+internal interface Foo {
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/memberOrder/innerClasses.txt b/compiler/testData/loadJava/compiledKotlin/memberOrder/innerClasses.txt
index 325ed65af13..d5ef05c7421 100644
--- a/compiler/testData/loadJava/compiledKotlin/memberOrder/innerClasses.txt
+++ b/compiler/testData/loadJava/compiledKotlin/memberOrder/innerClasses.txt
@@ -19,9 +19,9 @@ internal final class O {
         /*primary*/ public constructor B2()
     }
 
-    internal trait C1 {
+    internal interface C1 {
     }
 
-    internal trait C2 {
+    internal interface C2 {
     }
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/prop/OverrideTraitVal.txt b/compiler/testData/loadJava/compiledKotlin/prop/OverrideTraitVal.txt
index efff9a0b32b..a5bb8ebcbdc 100644
--- a/compiler/testData/loadJava/compiledKotlin/prop/OverrideTraitVal.txt
+++ b/compiler/testData/loadJava/compiledKotlin/prop/OverrideTraitVal.txt
@@ -6,7 +6,7 @@ internal open class Subclass : test.Trait {
         internal open override /*1*/ fun <get-shape>(): kotlin.String
 }
 
-internal trait Trait {
+internal interface Trait {
     internal abstract val shape: kotlin.String
         internal abstract fun <get-shape>(): kotlin.String
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/prop/TraitFinalVar.txt b/compiler/testData/loadJava/compiledKotlin/prop/TraitFinalVar.txt
index 7eccf9eb78a..141424c4809 100644
--- a/compiler/testData/loadJava/compiledKotlin/prop/TraitFinalVar.txt
+++ b/compiler/testData/loadJava/compiledKotlin/prop/TraitFinalVar.txt
@@ -1,6 +1,6 @@
 package test
 
-internal trait A {
+internal interface A {
     internal open var v: kotlin.String
         internal open fun <get-v>(): kotlin.String
         internal open fun <set-v>(/*0*/ value: kotlin.String): kotlin.Unit
diff --git a/compiler/testData/loadJava/compiledKotlin/prop/TraitOpenVal.txt b/compiler/testData/loadJava/compiledKotlin/prop/TraitOpenVal.txt
index 4075f61435f..1a45f55a18d 100644
--- a/compiler/testData/loadJava/compiledKotlin/prop/TraitOpenVal.txt
+++ b/compiler/testData/loadJava/compiledKotlin/prop/TraitOpenVal.txt
@@ -1,6 +1,6 @@
 package test
 
-internal trait A {
+internal interface A {
     internal open val v: kotlin.String
         internal open fun <get-v>(): kotlin.String
 }
diff --git a/compiler/testData/loadJava/compiledKotlin/prop/VarDelegationToTraitImpl.txt b/compiler/testData/loadJava/compiledKotlin/prop/VarDelegationToTraitImpl.txt
index 488b06fa417..2deb9eb6a0a 100644
--- a/compiler/testData/loadJava/compiledKotlin/prop/VarDelegationToTraitImpl.txt
+++ b/compiler/testData/loadJava/compiledKotlin/prop/VarDelegationToTraitImpl.txt
@@ -1,6 +1,6 @@
 package test
 
-internal trait A {
+internal interface A {
     internal open var v: kotlin.String
         internal open fun <get-v>(): kotlin.String
         internal open fun <set-v>(/*0*/ value: kotlin.String): kotlin.Unit
diff --git a/compiler/testData/loadJava/compiledKotlin/visibility/InternalAbstractTraitMembersOverridden.txt b/compiler/testData/loadJava/compiledKotlin/visibility/InternalAbstractTraitMembersOverridden.txt
index 77eedc3d50c..cef2b2bb818 100644
--- a/compiler/testData/loadJava/compiledKotlin/visibility/InternalAbstractTraitMembersOverridden.txt
+++ b/compiler/testData/loadJava/compiledKotlin/visibility/InternalAbstractTraitMembersOverridden.txt
@@ -1,6 +1,6 @@
 package test
 
-internal trait A {
+internal interface A {
     public abstract var p: kotlin.Int
         public abstract fun <get-p>(): kotlin.Int
         public abstract fun <set-p>(/*0*/ <set-?>: kotlin.Int): kotlin.Unit
diff --git a/compiler/testData/loadJava/compiledKotlin/visibility/InternalTraitMembers.txt b/compiler/testData/loadJava/compiledKotlin/visibility/InternalTraitMembers.txt
index 935a3518428..e75c02f0713 100644
--- a/compiler/testData/loadJava/compiledKotlin/visibility/InternalTraitMembers.txt
+++ b/compiler/testData/loadJava/compiledKotlin/visibility/InternalTraitMembers.txt
@@ -1,6 +1,6 @@
 package test
 
-internal trait A {
+internal interface A {
     public abstract var p: kotlin.Int
         public abstract fun <get-p>(): kotlin.Int
         internal abstract fun <set-p>(/*0*/ <set-?>: kotlin.Int): kotlin.Unit
diff --git a/compiler/testData/loadJava/compiledKotlin/visibility/InternalTraitMembersInherited.txt b/compiler/testData/loadJava/compiledKotlin/visibility/InternalTraitMembersInherited.txt
index bf008557e73..01a99a40dd7 100644
--- a/compiler/testData/loadJava/compiledKotlin/visibility/InternalTraitMembersInherited.txt
+++ b/compiler/testData/loadJava/compiledKotlin/visibility/InternalTraitMembersInherited.txt
@@ -1,6 +1,6 @@
 package test
 
-internal trait A {
+internal interface A {
     public open var p: kotlin.Int
         public open fun <get-p>(): kotlin.Int
         internal open fun <set-p>(/*0*/ value: kotlin.Int): kotlin.Unit
diff --git a/compiler/testData/loadJava/compiledKotlinWithStdlib/mutability/LoadIterable.txt b/compiler/testData/loadJava/compiledKotlinWithStdlib/mutability/LoadIterable.txt
index 419ce0e8b5a..86fd64e4fbf 100644
--- a/compiler/testData/loadJava/compiledKotlinWithStdlib/mutability/LoadIterable.txt
+++ b/compiler/testData/loadJava/compiledKotlinWithStdlib/mutability/LoadIterable.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait LoadIterable</*0*/ T> {
+public interface LoadIterable</*0*/ T> {
     org.jetbrains.annotations.Mutable() public abstract fun getIterable(): kotlin.MutableIterable<T>?
     org.jetbrains.annotations.ReadOnly() public abstract fun getReadOnlyIterable(): kotlin.Iterable<T>?
     public abstract fun setIterable(/*0*/ org.jetbrains.annotations.Mutable() p0: kotlin.MutableIterable<T>?): kotlin.Unit
diff --git a/compiler/testData/loadJava/compiledKotlinWithStdlib/mutability/LoadIterableWithConflict.txt b/compiler/testData/loadJava/compiledKotlinWithStdlib/mutability/LoadIterableWithConflict.txt
index 24508b62f79..a7cec69c0f0 100644
--- a/compiler/testData/loadJava/compiledKotlinWithStdlib/mutability/LoadIterableWithConflict.txt
+++ b/compiler/testData/loadJava/compiledKotlinWithStdlib/mutability/LoadIterableWithConflict.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait LoadIterableWithConflict</*0*/ T> {
+public interface LoadIterableWithConflict</*0*/ T> {
     org.jetbrains.annotations.ReadOnly() org.jetbrains.annotations.Mutable() public abstract fun getIterable(): kotlin.MutableIterable<T>?
     public abstract fun setIterable(/*0*/ org.jetbrains.annotations.ReadOnly() org.jetbrains.annotations.Mutable() p0: kotlin.MutableIterable<T>?): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/compiledKotlinWithStdlib/mutability/LoadIterableWithNullability.txt b/compiler/testData/loadJava/compiledKotlinWithStdlib/mutability/LoadIterableWithNullability.txt
index 883eae2e90c..2289e9ed1e6 100644
--- a/compiler/testData/loadJava/compiledKotlinWithStdlib/mutability/LoadIterableWithNullability.txt
+++ b/compiler/testData/loadJava/compiledKotlinWithStdlib/mutability/LoadIterableWithNullability.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait LoadIterableWithNullability</*0*/ T> {
+public interface LoadIterableWithNullability</*0*/ T> {
     org.jetbrains.annotations.Mutable() public abstract fun getIterable(): kotlin.MutableIterable<T>
     org.jetbrains.annotations.ReadOnly() public abstract fun getReadOnlyIterable(): kotlin.Iterable<T>
     public abstract fun setIterable(/*0*/ org.jetbrains.annotations.Mutable() p0: kotlin.MutableIterable<T>): kotlin.Unit
diff --git a/compiler/testData/loadJava/compiledKotlinWithStdlib/mutability/LoadIterableWithPropagation.txt b/compiler/testData/loadJava/compiledKotlinWithStdlib/mutability/LoadIterableWithPropagation.txt
index bb83689b29f..e6a59aab757 100644
--- a/compiler/testData/loadJava/compiledKotlinWithStdlib/mutability/LoadIterableWithPropagation.txt
+++ b/compiler/testData/loadJava/compiledKotlinWithStdlib/mutability/LoadIterableWithPropagation.txt
@@ -1,8 +1,8 @@
 package test
 
-public trait LoadIterableWithPropagation {
+public interface LoadIterableWithPropagation {
 
-    public trait LoadIterable</*0*/ T> {
+    public interface LoadIterable</*0*/ T> {
         org.jetbrains.annotations.Mutable() public abstract fun getIterable(): kotlin.MutableIterable<T>?
         org.jetbrains.annotations.ReadOnly() public abstract fun getReadOnlyIterable(): kotlin.Iterable<T>?
         public abstract fun setIterable(/*0*/ org.jetbrains.annotations.Mutable() p0: kotlin.MutableIterable<T>?): kotlin.Unit
diff --git a/compiler/testData/loadJava/javaAgainstKotlin/signaturePropagation/InheritExtensionAndNot.txt b/compiler/testData/loadJava/javaAgainstKotlin/signaturePropagation/InheritExtensionAndNot.txt
index 36d03fcb7d9..517383458fb 100644
--- a/compiler/testData/loadJava/javaAgainstKotlin/signaturePropagation/InheritExtensionAndNot.txt
+++ b/compiler/testData/loadJava/javaAgainstKotlin/signaturePropagation/InheritExtensionAndNot.txt
@@ -1,18 +1,18 @@
 package test
 
-public trait Sub : test.Super1, test.Super2 {
+public interface Sub : test.Super1, test.Super2 {
     public abstract override /*1*/ fun bar(/*0*/ vararg p: kotlin.String! /*kotlin.Array<(out) kotlin.String!>!*/): kotlin.Unit
     public abstract override /*1*/ fun foo(/*0*/ p: kotlin.String!): kotlin.Unit
     public abstract override /*1*/ /*fake_override*/ fun kotlin.Array<kotlin.String>.bar(): kotlin.Unit
     public abstract override /*1*/ /*fake_override*/ fun kotlin.String.foo(): kotlin.Unit
 }
 
-public trait Super1 {
+public interface Super1 {
     public abstract fun kotlin.Array<kotlin.String>.bar(): kotlin.Unit
     public abstract fun kotlin.String.foo(): kotlin.Unit
 }
 
-public trait Super2 {
+public interface Super2 {
     public abstract fun bar(/*0*/ vararg p: kotlin.String /*kotlin.Array<out kotlin.String>*/): kotlin.Unit
     public abstract fun foo(/*0*/ p: kotlin.String): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/javaAgainstKotlin/signaturePropagation/SubclassFromTraitImplementation.txt b/compiler/testData/loadJava/javaAgainstKotlin/signaturePropagation/SubclassFromTraitImplementation.txt
index 4b5c4677dd5..b3ea369efd1 100644
--- a/compiler/testData/loadJava/javaAgainstKotlin/signaturePropagation/SubclassFromTraitImplementation.txt
+++ b/compiler/testData/loadJava/javaAgainstKotlin/signaturePropagation/SubclassFromTraitImplementation.txt
@@ -12,7 +12,7 @@ public open class Subclass : test.Impl {
     internal open override /*1*/ /*fake_override*/ fun foo(): kotlin.String
 }
 
-internal trait Trait {
+internal interface Trait {
     internal open fun bar(): kotlin.String
     internal open fun foo(): kotlin.String
 }
diff --git a/compiler/testData/loadJava/kotlinAgainstCompiledJavaWithKotlin/InheritParameterName.txt b/compiler/testData/loadJava/kotlinAgainstCompiledJavaWithKotlin/InheritParameterName.txt
index 08114a752ab..893f805f490 100644
--- a/compiler/testData/loadJava/kotlinAgainstCompiledJavaWithKotlin/InheritParameterName.txt
+++ b/compiler/testData/loadJava/kotlinAgainstCompiledJavaWithKotlin/InheritParameterName.txt
@@ -2,11 +2,11 @@ package test
 
 public /*synthesized*/ fun A(/*0*/ function: (kotlin.Int) -> kotlin.Unit): test.A
 
-public trait A {
+public interface A {
     public abstract fun foo(/*0*/ p0: kotlin.Int): kotlin.Unit
 }
 
-internal trait B {
+internal interface B {
     internal abstract fun foo(/*0*/ kotlinName: kotlin.Int): kotlin.Unit
 }
 
diff --git a/compiler/testData/loadJava/kotlinAgainstCompiledJavaWithKotlin/javaRefersToKotlin.txt b/compiler/testData/loadJava/kotlinAgainstCompiledJavaWithKotlin/javaRefersToKotlin.txt
index d4ee5edb09a..c872d0e5bce 100644
--- a/compiler/testData/loadJava/kotlinAgainstCompiledJavaWithKotlin/javaRefersToKotlin.txt
+++ b/compiler/testData/loadJava/kotlinAgainstCompiledJavaWithKotlin/javaRefersToKotlin.txt
@@ -2,13 +2,13 @@ package test
 
 public /*synthesized*/ fun J(/*0*/ function: (test.K!) -> kotlin.Unit): test.J
 
-public trait J {
+public interface J {
     public abstract fun foo(/*0*/ p0: test.K!): kotlin.Unit
 }
 
-internal trait K {
+internal interface K {
 }
 
-internal trait K1 : test.J {
+internal interface K1 : test.J {
     public abstract override /*1*/ fun foo(/*0*/ k: test.K?): kotlin.Unit
 }
diff --git a/compiler/testData/loadJava/kotlinAgainstCompiledJavaWithKotlin/propagationAgainstDeserializedSuperclass.txt b/compiler/testData/loadJava/kotlinAgainstCompiledJavaWithKotlin/propagationAgainstDeserializedSuperclass.txt
index 8fa5fa08b24..980f9346556 100644
--- a/compiler/testData/loadJava/kotlinAgainstCompiledJavaWithKotlin/propagationAgainstDeserializedSuperclass.txt
+++ b/compiler/testData/loadJava/kotlinAgainstCompiledJavaWithKotlin/propagationAgainstDeserializedSuperclass.txt
@@ -5,7 +5,7 @@ public open class J : test.K {
     public open override /*1*/ fun foo(/*0*/ l: kotlin.(Mutable)List<kotlin.String!>!): kotlin.String!
 }
 
-internal trait K {
+internal interface K {
     public abstract fun foo(/*0*/ l: kotlin.MutableList<kotlin.String>): kotlin.String
 }
 
diff --git a/compiler/testData/loadJava/sourceJava/ErrorTypes.txt b/compiler/testData/loadJava/sourceJava/ErrorTypes.txt
index a4b4c90be88..edcf853c392 100644
--- a/compiler/testData/loadJava/sourceJava/ErrorTypes.txt
+++ b/compiler/testData/loadJava/sourceJava/ErrorTypes.txt
@@ -1,13 +1,13 @@
 package test
 
-public trait ErrorTypes {
+public interface ErrorTypes {
 
-    public trait Sub : test.ErrorTypes.Super {
+    public interface Sub : test.ErrorTypes.Super {
         public abstract override /*1*/ fun errorTypeInParameter(/*0*/ list: kotlin.(Mutable)List<kotlin.Array<(out) [ERROR : Unresolved java classifier: T]!>!>!): kotlin.Unit
         public abstract override /*1*/ fun returnErrorType(): [ERROR : Unresolved java classifier: T]!
     }
 
-    public trait Super {
+    public interface Super {
         public abstract fun errorTypeInParameter(/*0*/ list: kotlin.(Mutable)List<kotlin.Array<(out) [ERROR : Unresolved java classifier: T]!>!>!): kotlin.Unit
         public abstract fun returnErrorType(): [ERROR : Unresolved java classifier: T]!
     }
diff --git a/compiler/testData/loadJava/sourceJava/NullInAnnotation.txt b/compiler/testData/loadJava/sourceJava/NullInAnnotation.txt
index 5d5bbe8446d..9469d92c46e 100644
--- a/compiler/testData/loadJava/sourceJava/NullInAnnotation.txt
+++ b/compiler/testData/loadJava/sourceJava/NullInAnnotation.txt
@@ -2,7 +2,7 @@ package test
 
 public /*synthesized*/ fun NullInAnnotation(/*0*/ function: () -> kotlin.Unit): test.NullInAnnotation
 
-public trait NullInAnnotation {
+public interface NullInAnnotation {
     test.NullInAnnotation.Ann(a = null: kotlin.Nothing?, b = {null}: kotlin.Array<out kotlin.String>) public abstract fun foo(): kotlin.Unit
 
     public final annotation class Ann : kotlin.Annotation {
diff --git a/compiler/testData/loadJava/sourceJava/ReturnInnerSubclassOfSupersInner.txt b/compiler/testData/loadJava/sourceJava/ReturnInnerSubclassOfSupersInner.txt
index 8d3069ac5df..1b71b6bddc0 100644
--- a/compiler/testData/loadJava/sourceJava/ReturnInnerSubclassOfSupersInner.txt
+++ b/compiler/testData/loadJava/sourceJava/ReturnInnerSubclassOfSupersInner.txt
@@ -1,6 +1,6 @@
 package test
 
-public trait ReturnInnerSubclassOfSupersInner {
+public interface ReturnInnerSubclassOfSupersInner {
 
     public open class Sub</*0*/ B> : test.ReturnInnerSubclassOfSupersInner.Super<B!> {
         public constructor Sub</*0*/ B>()
diff --git a/compiler/testData/loadJava/sourceJava/ReturnNotSubtype.txt b/compiler/testData/loadJava/sourceJava/ReturnNotSubtype.txt
index 0a1a3786015..61dc85446eb 100644
--- a/compiler/testData/loadJava/sourceJava/ReturnNotSubtype.txt
+++ b/compiler/testData/loadJava/sourceJava/ReturnNotSubtype.txt
@@ -1,8 +1,8 @@
 package test
 
-public trait ReturnNotSubtype {
+public interface ReturnNotSubtype {
 
-    public trait Sub : test.ReturnNotSubtype.Super<kotlin.Boolean!> {
+    public interface Sub : test.ReturnNotSubtype.Super<kotlin.Boolean!> {
         public abstract override /*1*/ fun _void(): kotlin.Boolean
         public abstract override /*1*/ fun array(): kotlin.Array<(out) java.lang.Void!>!
         public abstract override /*1*/ fun klass(): java.lang.Class<*>!
@@ -11,7 +11,7 @@ public trait ReturnNotSubtype {
         public abstract override /*1*/ fun t(): java.lang.Void!
     }
 
-    public trait Super</*0*/ T> {
+    public interface Super</*0*/ T> {
         public abstract fun _void(): kotlin.Unit
         public abstract fun array(): kotlin.Array<(out) T!>!
         public abstract fun klass(): java.lang.Class<out kotlin.CharSequence!>!
diff --git a/compiler/testData/loadJava/sourceJava/WrongNumberOfGenericParameters.txt b/compiler/testData/loadJava/sourceJava/WrongNumberOfGenericParameters.txt
index 81a5ab3c736..0224c07a3aa 100644
--- a/compiler/testData/loadJava/sourceJava/WrongNumberOfGenericParameters.txt
+++ b/compiler/testData/loadJava/sourceJava/WrongNumberOfGenericParameters.txt
@@ -1,17 +1,17 @@
 package test
 
-public trait WrongNumberOfGenericParameters {
+public interface WrongNumberOfGenericParameters {
     public abstract fun o0(): test.WrongNumberOfGenericParameters.One<*>!
     public abstract fun o2(): test.WrongNumberOfGenericParameters.One<[ERROR : T]>!
     public abstract fun t1(): test.WrongNumberOfGenericParameters.Two<*, *>!
     public abstract fun z(): test.WrongNumberOfGenericParameters.Zero!
 
-    public trait One</*0*/ T> {
+    public interface One</*0*/ T> {
     }
 
-    public trait Two</*0*/ P, /*1*/ Q> {
+    public interface Two</*0*/ P, /*1*/ Q> {
     }
 
-    public trait Zero {
+    public interface Zero {
     }
 }
diff --git a/compiler/testData/renderer/Classes.kt b/compiler/testData/renderer/Classes.kt
index b8843b33aa6..253f20f5042 100644
--- a/compiler/testData/renderer/Classes.kt
+++ b/compiler/testData/renderer/Classes.kt
@@ -56,7 +56,7 @@ public trait TwoUpperBounds<T> where T : Number, T : Any
 //public constructor Inner() defined in rendererTest.TheClass.Inner
 //internal final class InternalClass defined in rendererTest
 //public constructor InternalClass() defined in rendererTest.InternalClass
-//internal trait TheTrait defined in rendererTest
+//internal interface TheTrait defined in rendererTest
 //internal abstract fun abstractFun(): kotlin.Unit defined in rendererTest.TheTrait
 //internal companion object : rendererTest.TheClass<kotlin.Int, kotlin.Int> defined in rendererTest.TheTrait
 //private constructor Companion() defined in rendererTest.TheTrait.Companion
@@ -65,5 +65,5 @@ public trait TwoUpperBounds<T> where T : Number, T : Any
 //public constructor WithReified<reified A, reified out B>() defined in rendererTest.WithReified
 //<reified A> defined in rendererTest.WithReified
 //<reified out B> defined in rendererTest.WithReified
-//public trait TwoUpperBounds<T : kotlin.Number> where T : kotlin.Any defined in rendererTest
+//public interface TwoUpperBounds<T : kotlin.Number> where T : kotlin.Any defined in rendererTest
 //<T : kotlin.Number & kotlin.Any> defined in rendererTest.TwoUpperBounds
diff --git a/compiler/testData/renderer/GlobalFunctions.kt b/compiler/testData/renderer/GlobalFunctions.kt
index b7a437537be..88261778537 100644
--- a/compiler/testData/renderer/GlobalFunctions.kt
+++ b/compiler/testData/renderer/GlobalFunctions.kt
@@ -31,8 +31,8 @@ deprecated("") fun deprecatedFun()
 //public fun <out T> withTypeParam(a: kotlin.Array<T>): kotlin.Int defined in rendererTest
 //<out T> defined in rendererTest.withTypeParam
 //value-parameter val a: kotlin.Array<T> defined in rendererTest.withTypeParam
-//internal trait Foo defined in rendererTest
-//internal trait Bar defined in rendererTest
+//internal interface Foo defined in rendererTest
+//internal interface Bar defined in rendererTest
 //internal fun <P : rendererTest.Foo> funTypeParameterWithTwoUpperBounds(): kotlin.Int where P : rendererTest.Bar defined in rendererTest
 //<P : rendererTest.Foo & rendererTest.Bar> defined in rendererTest.funTypeParameterWithTwoUpperBounds
 //kotlin.deprecated internal fun deprecatedFun(): kotlin.Unit defined in rendererTest
diff --git a/compiler/testData/renderer/InheritedMembersVisibility.kt b/compiler/testData/renderer/InheritedMembersVisibility.kt
index eb90eb900c7..391a7607021 100644
--- a/compiler/testData/renderer/InheritedMembersVisibility.kt
+++ b/compiler/testData/renderer/InheritedMembersVisibility.kt
@@ -15,7 +15,7 @@ class B : A {
         get
 }
 
-//internal trait A defined in root package
+//internal interface A defined in root package
 //internal abstract val v: kotlin.Int defined in A
 //public abstract var int: kotlin.Int defined in A
 //private abstract fun <set-int>(<set-?>: kotlin.Int): kotlin.Unit defined in A
diff --git a/compiler/testData/renderer/KeywordsInNames.kt b/compiler/testData/renderer/KeywordsInNames.kt
index a47640ccc14..21e40e46ce4 100644
--- a/compiler/testData/renderer/KeywordsInNames.kt
+++ b/compiler/testData/renderer/KeywordsInNames.kt
@@ -20,7 +20,7 @@ val NOT_IS = 3
 //internal final annotation class `true` : kotlin.Annotation defined in root package
 //public constructor `true`() defined in `true`
 //internal val `val`: kotlin.Int defined in root package
-//`true` internal trait `trait` defined in root package
+//`true` internal interface `trait` defined in root package
 //internal final class `class`<`in`> defined in root package
 //<`in`> defined in `class`
 //public constructor `class`<`in`>(p: `in`?) defined in `class`
diff --git a/core/descriptors/src/org/jetbrains/kotlin/renderer/DescriptorRendererImpl.java b/core/descriptors/src/org/jetbrains/kotlin/renderer/DescriptorRendererImpl.java
index edd6e263dea..b2391b3ad4f 100644
--- a/core/descriptors/src/org/jetbrains/kotlin/renderer/DescriptorRendererImpl.java
+++ b/core/descriptors/src/org/jetbrains/kotlin/renderer/DescriptorRendererImpl.java
@@ -1057,7 +1057,7 @@ public class DescriptorRendererImpl implements DescriptorRenderer {
             case CLASS:
                 return "class";
             case INTERFACE:
-                return "trait";
+                return "interface";
             case ENUM_CLASS:
                 return "enum class";
             case OBJECT:
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/JetBundle.properties b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/JetBundle.properties
index e9eab708f07..91cfae4609c 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/JetBundle.properties
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/JetBundle.properties
@@ -136,7 +136,7 @@ livetemplate.description.void=Function returning nothing
 livetemplate.description.fun0=Function with no parameters
 livetemplate.description.fun1=Function with one parameter
 livetemplate.description.fun2=Function with two parameters
-livetemplate.description.interface=Trait
+livetemplate.description.interface=Interface
 livetemplate.description.singleton=Singleton
 livetemplate.description.closure=Closure (function without name)
 livetemplate.description.anonymous=Anonymous class
@@ -158,7 +158,6 @@ options.kotlin.attribute.descriptor.arrow=Arrow
 options.kotlin.attribute.descriptor.kdoc.comment=KDoc comment
 options.kotlin.attribute.descriptor.kdoc.tag=KDoc tag
 options.kotlin.attribute.descriptor.kdoc.value=Link in KDoc tag
-options.kotlin.attribute.descriptor.trait=Trait
 options.kotlin.attribute.descriptor.object=Object
 options.kotlin.attribute.descriptor.annotation=Annotation
 options.kotlin.attribute.descriptor.var=Var (mutable variable, parameter or property)
@@ -209,7 +208,6 @@ create.from.usage.family=Create from usage
 create.0.from.usage=Create {0}
 create.local.variable.from.usage=Create local variable ''{0}''
 create.parameter.from.usage=Create parameter ''{0}''
-choose.target.class.or.trait.title=Choose target class or trait
 surround.with=Surround with
 surround.with.string.template="${expr}"
 surround.with.when.template=when (expr) {}
@@ -368,7 +366,7 @@ usageType.packageMemberAccess = Package member access
 
 x.in.y={0} in {1}
 x.implements.y={0} in {1} implements {2} in {3}.
-x.overrides.y.in.class.list={0} in {1} overrides functions in the following classes/traits: {2} Do you want to {3} the base functions?
+x.overrides.y.in.class.list={0} in {1} overrides functions in the following classes/interfaces: {2} Do you want to {3} the base functions?
 
 unused.overriding.methods.title=Unused Overriding Members
 there.are.unused.methods.that.override.methods.you.delete=There are unused members that override methods you delete.
@@ -388,7 +386,6 @@ find.options.include.overloaded.methods.checkbox=Include o&verloaded functions a
 find.what.functions.usages.checkbox=Usages of &functions
 find.what.properties.usages.checkbox=Usages of &properties
 find.what.constructor.usages.checkbox=Usages of &constructor
-find.what.derived.traits.checkbox=&Derived traits
 find.what.derived.classes.checkbox=&Derived classes
 
 hierarchy.legend.member.is.defined.in.class=Member is defined in the class
diff --git a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/highlighter/KotlinSuppressableWarningProblemGroup.kt b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/highlighter/KotlinSuppressableWarningProblemGroup.kt
index a53cb5ffbd0..3037d924bb8 100644
--- a/idea/idea-analysis/src/org/jetbrains/kotlin/idea/highlighter/KotlinSuppressableWarningProblemGroup.kt
+++ b/idea/idea-analysis/src/org/jetbrains/kotlin/idea/highlighter/KotlinSuppressableWarningProblemGroup.kt
@@ -83,7 +83,7 @@ private object DeclarationKindDetector : JetVisitor<AnnotationHostKind?, Unit?>(
 
     override fun visitDeclaration(d: JetDeclaration, _: Unit?) = null
 
-    override fun visitClass(d: JetClass, _: Unit?) = detect(d, if (d.isInterface()) "trait" else "class")
+    override fun visitClass(d: JetClass, _: Unit?) = detect(d, if (d.isInterface()) "interface" else "class")
 
     override fun visitNamedFunction(d: JetNamedFunction, _: Unit?) = detect(d, "fun")
 
diff --git a/idea/src/META-INF/plugin.xml b/idea/src/META-INF/plugin.xml
index 8f707c98222..6e1a4ab238a 100644
--- a/idea/src/META-INF/plugin.xml
+++ b/idea/src/META-INF/plugin.xml
@@ -215,7 +215,7 @@
     <internalFileTemplate name="Kotlin File"/>
     <internalFileTemplate name="Kotlin Class"/>
     <internalFileTemplate name="Kotlin Enum"/>
-    <internalFileTemplate name="Kotlin Trait"/>
+    <internalFileTemplate name="Kotlin Interface"/>
 
     <gotoSymbolContributor implementation="org.jetbrains.kotlin.idea.caches.JetGotoSymbolContributor"/>
     <gotoClassContributor implementation="org.jetbrains.kotlin.idea.caches.JetGotoClassContributor"/>
diff --git a/idea/src/org/jetbrains/kotlin/idea/findUsages/JetElementDescriptionProvider.kt b/idea/src/org/jetbrains/kotlin/idea/findUsages/JetElementDescriptionProvider.kt
index 5df9b4e6357..b9230f505a5 100644
--- a/idea/src/org/jetbrains/kotlin/idea/findUsages/JetElementDescriptionProvider.kt
+++ b/idea/src/org/jetbrains/kotlin/idea/findUsages/JetElementDescriptionProvider.kt
@@ -36,7 +36,7 @@ public class JetElementDescriptionProvider : ElementDescriptionProvider {
         val targetElement = element.unwrapped
 
         fun elementKind() = when (targetElement) {
-            is JetClass -> if (targetElement.isInterface()) "trait" else "class"
+            is JetClass -> if (targetElement.isInterface()) "interface" else "class"
             is JetObjectDeclaration -> "object"
             is JetNamedFunction -> "function"
             is JetSecondaryConstructor -> "constructor"
diff --git a/idea/src/org/jetbrains/kotlin/idea/findUsages/dialogs/KotlinFindClassUsagesDialog.java b/idea/src/org/jetbrains/kotlin/idea/findUsages/dialogs/KotlinFindClassUsagesDialog.java
index d88847f1cd1..4fc98f68973 100644
--- a/idea/src/org/jetbrains/kotlin/idea/findUsages/dialogs/KotlinFindClassUsagesDialog.java
+++ b/idea/src/org/jetbrains/kotlin/idea/findUsages/dialogs/KotlinFindClassUsagesDialog.java
@@ -75,8 +75,7 @@ public class KotlinFindClassUsagesDialog extends FindClassUsagesDialog {
                 findWhatPanel,
                 true
         );
-        derivedTraits = addCheckboxToPanel(
-                JetBundle.message("find.what.derived.traits.checkbox"),
+        derivedTraits = addCheckboxToPanel("&Derived interfaces",
                 getFindUsagesOptions().isDerivedInterfaces,
                 findWhatPanel,
                 true
diff --git a/idea/src/org/jetbrains/kotlin/idea/highlighter/JetColorSettingsPage.java b/idea/src/org/jetbrains/kotlin/idea/highlighter/JetColorSettingsPage.java
index 76a8e913153..d4488e4d44a 100644
--- a/idea/src/org/jetbrains/kotlin/idea/highlighter/JetColorSettingsPage.java
+++ b/idea/src/org/jetbrains/kotlin/idea/highlighter/JetColorSettingsPage.java
@@ -134,7 +134,7 @@ public class JetColorSettingsPage implements ColorSettingsPage {
             new AttributesDescriptor(OptionsBundle.message("options.java.attribute.descriptor.class"), JetHighlightingColors.CLASS),
             new AttributesDescriptor(OptionsBundle.message("options.java.attribute.descriptor.type.parameter"), JetHighlightingColors.TYPE_PARAMETER),
             new AttributesDescriptor(OptionsBundle.message("options.java.attribute.descriptor.abstract.class"), JetHighlightingColors.ABSTRACT_CLASS),
-            new AttributesDescriptor(JetBundle.message("options.kotlin.attribute.descriptor.trait"), JetHighlightingColors.TRAIT),
+            new AttributesDescriptor("Interface", JetHighlightingColors.TRAIT),
             new AttributesDescriptor(JetBundle.message("options.kotlin.attribute.descriptor.annotation"), JetHighlightingColors.ANNOTATION),
             new AttributesDescriptor(JetBundle.message("options.kotlin.attribute.descriptor.object"), JetHighlightingColors.OBJECT),
 
diff --git a/idea/src/org/jetbrains/kotlin/idea/quickfix/createFromUsage/createCallable/CreateCallableFromUsageFix.kt b/idea/src/org/jetbrains/kotlin/idea/quickfix/createFromUsage/createCallable/CreateCallableFromUsageFix.kt
index c593a7b580b..ee17f4fef51 100644
--- a/idea/src/org/jetbrains/kotlin/idea/quickfix/createFromUsage/createCallable/CreateCallableFromUsageFix.kt
+++ b/idea/src/org/jetbrains/kotlin/idea/quickfix/createFromUsage/createCallable/CreateCallableFromUsageFix.kt
@@ -120,7 +120,7 @@ public class CreateCallableFromUsageFix(
             return
         }
 
-        val popupTitle = JetBundle.message("choose.target.class.or.trait.title")
+        val popupTitle = "Choose target class or interface"
         val receiverTypeCandidates = callableBuilder.computeTypeCandidates(callableInfo.receiverTypeInfo)
         if (receiverTypeCandidates.isNotEmpty()) {
             val containers = receiverTypeCandidates
diff --git a/idea/src/org/jetbrains/kotlin/idea/quickfix/createFromUsage/createClass/CreateClassFromUsageFix.kt b/idea/src/org/jetbrains/kotlin/idea/quickfix/createFromUsage/createClass/CreateClassFromUsageFix.kt
index 3ad16a04e07..2a086112b1b 100644
--- a/idea/src/org/jetbrains/kotlin/idea/quickfix/createFromUsage/createClass/CreateClassFromUsageFix.kt
+++ b/idea/src/org/jetbrains/kotlin/idea/quickfix/createFromUsage/createClass/CreateClassFromUsageFix.kt
@@ -44,7 +44,7 @@ enum class ClassKind(val keyword: String, val description: String) {
     ENUM_CLASS: ClassKind("enum class", "enum")
     ENUM_ENTRY: ClassKind("", "enum constant")
     ANNOTATION_CLASS: ClassKind("annotation class", "annotation")
-    TRAIT: ClassKind("trait", "trait")
+    TRAIT: ClassKind("interface", "interface")
     OBJECT: ClassKind("object", "object")
 }
 
diff --git a/idea/testData/decompiler/navigation/decompiled/SimpleTrait.kt b/idea/testData/decompiler/navigation/decompiled/SimpleTrait.kt
index 7d9bf553e53..0fe88452321 100644
--- a/idea/testData/decompiler/navigation/decompiled/SimpleTrait.kt
+++ b/idea/testData/decompiler/navigation/decompiled/SimpleTrait.kt
@@ -3,5 +3,5 @@
 
 package testData.libraries
 
-[public trait SimpleTrait {
+[public interface SimpleTrait {
 }]
diff --git a/idea/testData/decompiler/navigation/decompiled/WithInnerAndObject.kt b/idea/testData/decompiler/navigation/decompiled/WithInnerAndObject.kt
index 4bb3277b238..5476fe4c95e 100644
--- a/idea/testData/decompiler/navigation/decompiled/WithInnerAndObject.kt
+++ b/idea/testData/decompiler/navigation/decompiled/WithInnerAndObject.kt
@@ -9,7 +9,7 @@ package testData.libraries
     }]]
 
     [[internal final class MyInner public () {
-        [internal trait MyInnerInner {
+        [internal interface MyInnerInner {
             [internal abstract fun innerInnerMethod(): kotlin.Unit]
         }]
     }]]
diff --git a/idea/testData/quickfix/autoImports/noImportInImports.before.Main.kt b/idea/testData/quickfix/autoImports/noImportInImports.before.Main.kt
index de5cb10351f..154e620995a 100644
--- a/idea/testData/quickfix/autoImports/noImportInImports.before.Main.kt
+++ b/idea/testData/quickfix/autoImports/noImportInImports.before.Main.kt
@@ -1,9 +1,9 @@
 // "class com.intellij.codeInsight.daemon.impl.quickfix.ImportClassFixBase" "false"
 // ACTION: Create annotation 'SomeTest'
 // ACTION: Create class 'SomeTest'
+// ACTION: Create interface 'SomeTest'
 // ACTION: Create enum 'SomeTest'
 // ACTION: Create object 'SomeTest'
-// ACTION: Create trait 'SomeTest'
 // ERROR: Unresolved reference: SomeTest
 
 package testing
diff --git a/idea/testData/quickfix/autoImports/noImportInQualifiedUserTypeNotFirst.before.Main.kt b/idea/testData/quickfix/autoImports/noImportInQualifiedUserTypeNotFirst.before.Main.kt
index cde34c65f33..219cffe792e 100644
--- a/idea/testData/quickfix/autoImports/noImportInQualifiedUserTypeNotFirst.before.Main.kt
+++ b/idea/testData/quickfix/autoImports/noImportInQualifiedUserTypeNotFirst.before.Main.kt
@@ -1,5 +1,5 @@
 // "class com.intellij.codeInsight.daemon.impl.quickfix.ImportClassFixBase" "false"
-// ACTION: Create trait 'SomeTest'
+// ACTION: Create interface 'SomeTest'
 // ERROR: Unresolved reference: SomeTest
 
 package testing
diff --git a/idea/testData/quickfix/createFromUsage/createClass/delegationSpecifier/classDelegatorToSuperclass.kt b/idea/testData/quickfix/createFromUsage/createClass/delegationSpecifier/classDelegatorToSuperclass.kt
index a58d5068a41..9ff1dcb0b65 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/delegationSpecifier/classDelegatorToSuperclass.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/delegationSpecifier/classDelegatorToSuperclass.kt
@@ -1,5 +1,5 @@
 // "Create class 'A'" "false"
-// ACTION: Create trait 'A'
+// ACTION: Create interface 'A'
 // ERROR: Unresolved reference: A
 package p
 
diff --git a/idea/testData/quickfix/createFromUsage/createClass/delegationSpecifier/traitDelegatorToNestedGroovySuperclass.before.Main.kt b/idea/testData/quickfix/createFromUsage/createClass/delegationSpecifier/traitDelegatorToNestedGroovySuperclass.before.Main.kt
index 23e303cc2d1..04ffe313da2 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/delegationSpecifier/traitDelegatorToNestedGroovySuperclass.before.Main.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/delegationSpecifier/traitDelegatorToNestedGroovySuperclass.before.Main.kt
@@ -1,4 +1,4 @@
-// "Create trait 'A'" "false"
+// "Create interface 'A'" "false"
 // ERROR: Unresolved reference: A
 class Foo: J.<caret>A {
 
diff --git a/idea/testData/quickfix/createFromUsage/createClass/delegationSpecifier/traitDelegatorToNestedJavaSuperclass.after.kt b/idea/testData/quickfix/createFromUsage/createClass/delegationSpecifier/traitDelegatorToNestedJavaSuperclass.after.kt
index 721e5d294c3..edcf9c17a98 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/delegationSpecifier/traitDelegatorToNestedJavaSuperclass.after.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/delegationSpecifier/traitDelegatorToNestedJavaSuperclass.after.kt
@@ -1,4 +1,4 @@
-// "Create trait 'A'" "true"
+// "Create interface 'A'" "true"
 // ERROR: Unresolved reference: A
 class Foo: J.A {
 
diff --git a/idea/testData/quickfix/createFromUsage/createClass/delegationSpecifier/traitDelegatorToNestedJavaSuperclass.before.Main.kt b/idea/testData/quickfix/createFromUsage/createClass/delegationSpecifier/traitDelegatorToNestedJavaSuperclass.before.Main.kt
index 5695ee57183..4cfcc9ef792 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/delegationSpecifier/traitDelegatorToNestedJavaSuperclass.before.Main.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/delegationSpecifier/traitDelegatorToNestedJavaSuperclass.before.Main.kt
@@ -1,4 +1,4 @@
-// "Create trait 'A'" "true"
+// "Create interface 'A'" "true"
 // ERROR: Unresolved reference: A
 class Foo: J.<caret>A {
 
diff --git a/idea/testData/quickfix/createFromUsage/createClass/delegationSpecifier/traitDelegatorToSuperclass.kt b/idea/testData/quickfix/createFromUsage/createClass/delegationSpecifier/traitDelegatorToSuperclass.kt
index 71d715351bb..425e79ac604 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/delegationSpecifier/traitDelegatorToSuperclass.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/delegationSpecifier/traitDelegatorToSuperclass.kt
@@ -1,4 +1,4 @@
-// "Create trait 'A'" "true"
+// "Create interface 'A'" "true"
 package p
 
 class Foo: <caret>A {
diff --git a/idea/testData/quickfix/createFromUsage/createClass/delegationSpecifier/traitDelegatorToSuperclass.kt.after b/idea/testData/quickfix/createFromUsage/createClass/delegationSpecifier/traitDelegatorToSuperclass.kt.after
index d3f80be35b5..5849738faa7 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/delegationSpecifier/traitDelegatorToSuperclass.kt.after
+++ b/idea/testData/quickfix/createFromUsage/createClass/delegationSpecifier/traitDelegatorToSuperclass.kt.after
@@ -1,10 +1,10 @@
-// "Create trait 'A'" "true"
+// "Create interface 'A'" "true"
 package p
 
 class Foo: A {
 
 }
 
-trait A {
+interface A {
 
 }
diff --git a/idea/testData/quickfix/createFromUsage/createClass/importDirective/enumEntryInJavaEnum.before.Main.kt b/idea/testData/quickfix/createFromUsage/createClass/importDirective/enumEntryInJavaEnum.before.Main.kt
index a601f889899..0183cdfe912 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/importDirective/enumEntryInJavaEnum.before.Main.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/importDirective/enumEntryInJavaEnum.before.Main.kt
@@ -2,7 +2,7 @@
 // ACTION: Create annotation 'A'
 // ACTION: Create class 'A'
 // ACTION: Create enum 'A'
-// ACTION: Create trait 'A'
+// ACTION: Create interface 'A'
 // ERROR: Unresolved reference: A
 import E.<caret>A
 
diff --git a/idea/testData/quickfix/createFromUsage/createClass/importDirective/enumEntryInPackage.kt b/idea/testData/quickfix/createFromUsage/createClass/importDirective/enumEntryInPackage.kt
index 76bf8af903f..c88d76f04e4 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/importDirective/enumEntryInPackage.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/importDirective/enumEntryInPackage.kt
@@ -1,6 +1,6 @@
 // "Create enum constant 'A'" "false"
 // ACTION: Create class 'A'
-// ACTION: Create trait 'A'
+// ACTION: Create interface 'A'
 // ACTION: Create object 'A'
 // ACTION: Create enum 'A'
 // ACTION: Create annotation 'A'
diff --git a/idea/testData/quickfix/createFromUsage/createClass/importDirective/enumEntryWithQualifier.kt b/idea/testData/quickfix/createFromUsage/createClass/importDirective/enumEntryWithQualifier.kt
index 82f94fde623..072bf614c0b 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/importDirective/enumEntryWithQualifier.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/importDirective/enumEntryWithQualifier.kt
@@ -1,6 +1,6 @@
 // "Create enum constant 'A'" "false"
 // ACTION: Create class 'A'
-// ACTION: Create trait 'A'
+// ACTION: Create interface 'A'
 // ACTION: Create object 'A'
 // ACTION: Create enum 'A'
 // ACTION: Create annotation 'A'
diff --git a/idea/testData/quickfix/createFromUsage/createClass/importDirective/objectWithJavaQualifier.before.Main.kt b/idea/testData/quickfix/createFromUsage/createClass/importDirective/objectWithJavaQualifier.before.Main.kt
index f32eececa48..5082c82f15b 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/importDirective/objectWithJavaQualifier.before.Main.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/importDirective/objectWithJavaQualifier.before.Main.kt
@@ -2,8 +2,8 @@
 // ERROR: Unresolved reference: A
 // ACTION: Create annotation 'A'
 // ACTION: Create class 'A'
+// ACTION: Create interface 'A'
 // ACTION: Create enum 'A'
-// ACTION: Create trait 'A'
 import J.<caret>A
 
 class X {
diff --git a/idea/testData/quickfix/createFromUsage/createClass/importDirective/traitInPackage.kt b/idea/testData/quickfix/createFromUsage/createClass/importDirective/traitInPackage.kt
index a3198c9518f..4ac9a6840e6 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/importDirective/traitInPackage.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/importDirective/traitInPackage.kt
@@ -1,4 +1,4 @@
-// "Create trait 'A'" "true"
+// "Create interface 'A'" "true"
 package p
 
 import p.<caret>A
\ No newline at end of file
diff --git a/idea/testData/quickfix/createFromUsage/createClass/importDirective/traitInPackage.kt.after b/idea/testData/quickfix/createFromUsage/createClass/importDirective/traitInPackage.kt.after
index cca6acd26c9..707adf69a64 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/importDirective/traitInPackage.kt.after
+++ b/idea/testData/quickfix/createFromUsage/createClass/importDirective/traitInPackage.kt.after
@@ -1,8 +1,8 @@
-// "Create trait 'A'" "true"
+// "Create interface 'A'" "true"
 package p
 
 import p.A
 
-trait A {
+interface A {
 
 }
diff --git a/idea/testData/quickfix/createFromUsage/createClass/importDirective/traitWithJavaQualifier.after.kt b/idea/testData/quickfix/createFromUsage/createClass/importDirective/traitWithJavaQualifier.after.kt
index fdd8d88b5d5..75ef1c243d2 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/importDirective/traitWithJavaQualifier.after.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/importDirective/traitWithJavaQualifier.after.kt
@@ -1,4 +1,4 @@
-// "Create trait 'A'" "true"
+// "Create interface 'A'" "true"
 // ERROR: Unresolved reference: A
 import J.A
 
diff --git a/idea/testData/quickfix/createFromUsage/createClass/importDirective/traitWithJavaQualifier.before.Main.kt b/idea/testData/quickfix/createFromUsage/createClass/importDirective/traitWithJavaQualifier.before.Main.kt
index 7485adf6d5a..4626f7100e1 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/importDirective/traitWithJavaQualifier.before.Main.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/importDirective/traitWithJavaQualifier.before.Main.kt
@@ -1,4 +1,4 @@
-// "Create trait 'A'" "true"
+// "Create interface 'A'" "true"
 // ERROR: Unresolved reference: A
 import J.<caret>A
 
diff --git a/idea/testData/quickfix/createFromUsage/createClass/importDirective/traitWithQualifier.kt b/idea/testData/quickfix/createFromUsage/createClass/importDirective/traitWithQualifier.kt
index cc8f3302836..e0dac680a4b 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/importDirective/traitWithQualifier.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/importDirective/traitWithQualifier.kt
@@ -1,4 +1,4 @@
-// "Create trait 'A'" "true"
+// "Create interface 'A'" "true"
 package p
 
 import p.X.<caret>A
diff --git a/idea/testData/quickfix/createFromUsage/createClass/importDirective/traitWithQualifier.kt.after b/idea/testData/quickfix/createFromUsage/createClass/importDirective/traitWithQualifier.kt.after
index 47182fcb543..121cf151085 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/importDirective/traitWithQualifier.kt.after
+++ b/idea/testData/quickfix/createFromUsage/createClass/importDirective/traitWithQualifier.kt.after
@@ -1,10 +1,10 @@
-// "Create trait 'A'" "true"
+// "Create interface 'A'" "true"
 package p
 
 import p.X.A
 
 class X {
-    trait A {
+    interface A {
 
     }
 
diff --git a/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/traitByNestedJavaQualifier.after.kt b/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/traitByNestedJavaQualifier.after.kt
index f3442cedc89..ac51b994973 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/traitByNestedJavaQualifier.after.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/traitByNestedJavaQualifier.after.kt
@@ -1,3 +1,3 @@
-// "Create trait 'A'" "true"
+// "Create interface 'A'" "true"
 // ERROR: Unresolved reference: A
 fun foo() = J.A.B
diff --git a/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/traitByNestedJavaQualifier.before.Main.kt b/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/traitByNestedJavaQualifier.before.Main.kt
index 147321764b9..ccc051514da 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/traitByNestedJavaQualifier.before.Main.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/traitByNestedJavaQualifier.before.Main.kt
@@ -1,3 +1,3 @@
-// "Create trait 'A'" "true"
+// "Create interface 'A'" "true"
 // ERROR: Unresolved reference: A
 fun foo() = J.<caret>A.B
diff --git a/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/traitByQualifier.kt b/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/traitByQualifier.kt
index e2e61303cd3..2a5d28f1287 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/traitByQualifier.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/traitByQualifier.kt
@@ -1,4 +1,4 @@
-// "Create trait 'A'" "true"
+// "Create interface 'A'" "true"
 // ERROR: Unresolved reference: B
 package p
 
diff --git a/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/traitByQualifier.kt.after b/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/traitByQualifier.kt.after
index a763498f703..77601050953 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/traitByQualifier.kt.after
+++ b/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/traitByQualifier.kt.after
@@ -1,9 +1,9 @@
-// "Create trait 'A'" "true"
+// "Create interface 'A'" "true"
 // ERROR: Unresolved reference: B
 package p
 
 fun foo() = A.B
 
-trait A {
+interface A {
 
 }
diff --git a/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/traitNoReceiver.kt b/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/traitNoReceiver.kt
index ba093e03389..cbc1a37db1b 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/traitNoReceiver.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/traitNoReceiver.kt
@@ -1,4 +1,4 @@
-// "Create trait 'A'" "false"
+// "Create interface 'A'" "false"
 // ACTION: Create object 'A'
 // ACTION: Create local variable 'A'
 // ACTION: Create parameter 'A'
diff --git a/idea/testData/quickfix/createFromUsage/createClass/typeReference/annotationNotQualifierWithTypeArgs.kt b/idea/testData/quickfix/createFromUsage/createClass/typeReference/annotationNotQualifierWithTypeArgs.kt
index 7d7c25a0e8d..5d7a4f03ab0 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/typeReference/annotationNotQualifierWithTypeArgs.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/typeReference/annotationNotQualifierWithTypeArgs.kt
@@ -1,6 +1,6 @@
 // "Create annotation 'A'" "false"
 // ACTION: Create class 'A'
-// ACTION: Create trait 'A'
+// ACTION: Create interface 'A'
 // ACTION: Convert to block body
 // ERROR: Unresolved reference: A
 package p
diff --git a/idea/testData/quickfix/createFromUsage/createClass/typeReference/annotationQualifierNoTypeArgs.kt b/idea/testData/quickfix/createFromUsage/createClass/typeReference/annotationQualifierNoTypeArgs.kt
index e5fb554e31c..302cb1d0532 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/typeReference/annotationQualifierNoTypeArgs.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/typeReference/annotationQualifierNoTypeArgs.kt
@@ -1,7 +1,7 @@
 // "Create annotation 'A'" "false"
 // ACTION: Create class 'A'
 // ACTION: Create object 'A'
-// ACTION: Create trait 'A'
+// ACTION: Create interface 'A'
 // ACTION: Create enum 'A'
 // ACTION: Convert to block body
 // ERROR: Unresolved reference: A
diff --git a/idea/testData/quickfix/createFromUsage/createClass/typeReference/enumEntryJavaEnumReceiver.before.Main.kt b/idea/testData/quickfix/createFromUsage/createClass/typeReference/enumEntryJavaEnumReceiver.before.Main.kt
index 1e0766abbb5..e33d903dd0d 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/typeReference/enumEntryJavaEnumReceiver.before.Main.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/typeReference/enumEntryJavaEnumReceiver.before.Main.kt
@@ -3,6 +3,6 @@
 // ACTION: Create annotation 'A'
 // ACTION: Create class 'A'
 // ACTION: Create enum 'A'
-// ACTION: Create trait 'A'
+// ACTION: Create interface 'A'
 // ERROR: Unresolved reference: A
 fun foo(): J.<caret>A = throw Throwable("")
\ No newline at end of file
diff --git a/idea/testData/quickfix/createFromUsage/createClass/typeReference/enumEntryNotQualifierNoTypeArgs.kt b/idea/testData/quickfix/createFromUsage/createClass/typeReference/enumEntryNotQualifierNoTypeArgs.kt
index b3a8af91aca..2c513465470 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/typeReference/enumEntryNotQualifierNoTypeArgs.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/typeReference/enumEntryNotQualifierNoTypeArgs.kt
@@ -1,7 +1,7 @@
 // "Create enum constant 'A'" "false"
 // ACTION: Create annotation 'A'
 // ACTION: Create class 'A'
-// ACTION: Create trait 'A'
+// ACTION: Create interface 'A'
 // ACTION: Create enum 'A'
 // ACTION: Convert to block body
 // ERROR: Unresolved reference: A
diff --git a/idea/testData/quickfix/createFromUsage/createClass/typeReference/enumNotQualifierWithTypeArgs.kt b/idea/testData/quickfix/createFromUsage/createClass/typeReference/enumNotQualifierWithTypeArgs.kt
index 5a5f991bed6..d1884aba818 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/typeReference/enumNotQualifierWithTypeArgs.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/typeReference/enumNotQualifierWithTypeArgs.kt
@@ -1,6 +1,6 @@
 // "Create enum 'A'" "false"
 // ACTION: Create class 'A'
-// ACTION: Create trait 'A'
+// ACTION: Create interface 'A'
 // ACTION: Convert to block body
 // ERROR: Unresolved reference: A
 package p
diff --git a/idea/testData/quickfix/createFromUsage/createClass/typeReference/objectNotQualifierNoTypeArgs.kt b/idea/testData/quickfix/createFromUsage/createClass/typeReference/objectNotQualifierNoTypeArgs.kt
index 88eef3d2751..d25e6bb96f3 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/typeReference/objectNotQualifierNoTypeArgs.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/typeReference/objectNotQualifierNoTypeArgs.kt
@@ -1,7 +1,7 @@
 // "Create object 'A'" "false"
 // ACTION: Create annotation 'A'
 // ACTION: Create class 'A'
-// ACTION: Create trait 'A'
+// ACTION: Create interface 'A'
 // ACTION: Create enum 'A'
 // ACTION: Convert to block body
 // ERROR: Unresolved reference: A
diff --git a/idea/testData/quickfix/createFromUsage/createClass/typeReference/objectNotQualifierWithTypeArgs.kt b/idea/testData/quickfix/createFromUsage/createClass/typeReference/objectNotQualifierWithTypeArgs.kt
index 839c50f7729..8f9ce8bb3e9 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/typeReference/objectNotQualifierWithTypeArgs.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/typeReference/objectNotQualifierWithTypeArgs.kt
@@ -1,6 +1,6 @@
 // "Create object 'A'" "false"
 // ACTION: Create class 'A'
-// ACTION: Create trait 'A'
+// ACTION: Create interface 'A'
 // ACTION: Convert to block body
 // ERROR: Unresolved reference: A
 package p
diff --git a/idea/testData/quickfix/createFromUsage/createClass/typeReference/traitJavaTypeReceiver.after.kt b/idea/testData/quickfix/createFromUsage/createClass/typeReference/traitJavaTypeReceiver.after.kt
index cae3116a795..518bc6279d6 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/typeReference/traitJavaTypeReceiver.after.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/typeReference/traitJavaTypeReceiver.after.kt
@@ -1,3 +1,3 @@
-// "Create trait 'A'" "true"
+// "Create interface 'A'" "true"
 // ERROR: Unresolved reference: A
 fun foo(): J.A = throw Throwable("")
\ No newline at end of file
diff --git a/idea/testData/quickfix/createFromUsage/createClass/typeReference/traitJavaTypeReceiver.before.Main.kt b/idea/testData/quickfix/createFromUsage/createClass/typeReference/traitJavaTypeReceiver.before.Main.kt
index 328cc1328f4..9a48335c964 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/typeReference/traitJavaTypeReceiver.before.Main.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/typeReference/traitJavaTypeReceiver.before.Main.kt
@@ -1,3 +1,3 @@
-// "Create trait 'A'" "true"
+// "Create interface 'A'" "true"
 // ERROR: Unresolved reference: A
 fun foo(): J.<caret>A = throw Throwable("")
\ No newline at end of file
diff --git a/idea/testData/quickfix/createFromUsage/createClass/typeReference/traitNotQualifierNoTypeArgs.kt b/idea/testData/quickfix/createFromUsage/createClass/typeReference/traitNotQualifierNoTypeArgs.kt
index f7b91c25b56..66af9b1cd93 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/typeReference/traitNotQualifierNoTypeArgs.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/typeReference/traitNotQualifierNoTypeArgs.kt
@@ -1,4 +1,4 @@
-// "Create trait 'A'" "true"
+// "Create interface 'A'" "true"
 package p
 
 fun foo(): <caret>A = throw Throwable("")
\ No newline at end of file
diff --git a/idea/testData/quickfix/createFromUsage/createClass/typeReference/traitNotQualifierNoTypeArgs.kt.after b/idea/testData/quickfix/createFromUsage/createClass/typeReference/traitNotQualifierNoTypeArgs.kt.after
index 5a6c191a324..96f3f01de30 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/typeReference/traitNotQualifierNoTypeArgs.kt.after
+++ b/idea/testData/quickfix/createFromUsage/createClass/typeReference/traitNotQualifierNoTypeArgs.kt.after
@@ -1,8 +1,8 @@
-// "Create trait 'A'" "true"
+// "Create interface 'A'" "true"
 package p
 
 fun foo(): A = throw Throwable("")
 
-trait A {
+interface A {
 
 }
diff --git a/idea/testData/quickfix/suppress/declarationKinds/trait.kt b/idea/testData/quickfix/suppress/declarationKinds/trait.kt
index 606dd96e76e..ca9d69e2758 100644
--- a/idea/testData/quickfix/suppress/declarationKinds/trait.kt
+++ b/idea/testData/quickfix/suppress/declarationKinds/trait.kt
@@ -1,4 +1,4 @@
-// "Suppress 'REDUNDANT_NULLABLE' for trait C" "true"
+// "Suppress 'REDUNDANT_NULLABLE' for interface C" "true"
 
 trait C {
     var foo: String?<caret>?
diff --git a/idea/testData/quickfix/suppress/declarationKinds/trait.kt.after b/idea/testData/quickfix/suppress/declarationKinds/trait.kt.after
index 485f25f337c..382c8dad791 100644
--- a/idea/testData/quickfix/suppress/declarationKinds/trait.kt.after
+++ b/idea/testData/quickfix/suppress/declarationKinds/trait.kt.after
@@ -1,4 +1,4 @@
-// "Suppress 'REDUNDANT_NULLABLE' for trait C" "true"
+// "Suppress 'REDUNDANT_NULLABLE' for interface C" "true"
 
 @suppress("REDUNDANT_NULLABLE")
 trait C {
diff --git a/idea/testData/quickfix/typeMismatch/typeMismatchOnReturnedExpression/dontChangeFunctionReturnTypeToErrorType.kt b/idea/testData/quickfix/typeMismatch/typeMismatchOnReturnedExpression/dontChangeFunctionReturnTypeToErrorType.kt
index 08521457d70..57f923f963a 100644
--- a/idea/testData/quickfix/typeMismatch/typeMismatchOnReturnedExpression/dontChangeFunctionReturnTypeToErrorType.kt
+++ b/idea/testData/quickfix/typeMismatch/typeMismatchOnReturnedExpression/dontChangeFunctionReturnTypeToErrorType.kt
@@ -4,7 +4,7 @@
 // ACTION: Create annotation 'NoSuchType'
 // ACTION: Create class 'NoSuchType'
 // ACTION: Create enum 'NoSuchType'
-// ACTION: Create trait 'NoSuchType'
+// ACTION: Create interface 'NoSuchType'
 // ACTION: Remove explicit lambda parameter types (may break code)
 // ERROR: <html>Type mismatch.<table><tr><td>Required:</td><td>kotlin.Int</td></tr><tr><td>Found:</td><td>([ERROR : NoSuchType]) &rarr; kotlin.Int</td></tr></table></html>
 // ERROR: Unresolved reference: NoSuchType
diff --git a/idea/testData/safeDelete/deleteClass/kotlinClass/trait2.kt.messages b/idea/testData/safeDelete/deleteClass/kotlinClass/trait2.kt.messages
index 1d4a53dbb2e..fbc0e43ed1c 100644
--- a/idea/testData/safeDelete/deleteClass/kotlinClass/trait2.kt.messages
+++ b/idea/testData/safeDelete/deleteClass/kotlinClass/trait2.kt.messages
@@ -1 +1 @@
-trait test.A has 1 usage that is not safe to delete.
\ No newline at end of file
+interface test.A has 1 usage that is not safe to delete.
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteFunction/kotlinFunction/implement1.kt.messages b/idea/testData/safeDelete/deleteFunction/kotlinFunction/implement1.kt.messages
index 9377c061b50..c50461f9734 100644
--- a/idea/testData/safeDelete/deleteFunction/kotlinFunction/implement1.kt.messages
+++ b/idea/testData/safeDelete/deleteFunction/kotlinFunction/implement1.kt.messages
@@ -1 +1 @@
-fun foo(): kotlin.Unit in final class B : A implements fun foo(): kotlin.Unit in trait A.
\ No newline at end of file
+fun foo(): kotlin.Unit in final class B : A implements fun foo(): kotlin.Unit in interface A.
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteFunction/kotlinFunction/implement2.kt.messages b/idea/testData/safeDelete/deleteFunction/kotlinFunction/implement2.kt.messages
index f3adda2a411..9005f0b63eb 100644
--- a/idea/testData/safeDelete/deleteFunction/kotlinFunction/implement2.kt.messages
+++ b/idea/testData/safeDelete/deleteFunction/kotlinFunction/implement2.kt.messages
@@ -1,2 +1,2 @@
-fun foo(): kotlin.Unit in final class B : A, Z implements fun foo(): kotlin.Unit in trait A.
-fun foo(): kotlin.Unit in final class B : A, Z implements fun foo(): kotlin.Unit in trait Z.
\ No newline at end of file
+fun foo(): kotlin.Unit in final class B : A, Z implements fun foo(): kotlin.Unit in interface A.
+fun foo(): kotlin.Unit in final class B : A, Z implements fun foo(): kotlin.Unit in interface Z.
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteFunction/kotlinFunction/overrideAndImplement1.kt.messages b/idea/testData/safeDelete/deleteFunction/kotlinFunction/overrideAndImplement1.kt.messages
index 1f0a4a17874..00c79ceb39d 100644
--- a/idea/testData/safeDelete/deleteFunction/kotlinFunction/overrideAndImplement1.kt.messages
+++ b/idea/testData/safeDelete/deleteFunction/kotlinFunction/overrideAndImplement1.kt.messages
@@ -1 +1 @@
-fun foo(): kotlin.Unit in final class B : A, Z implements fun foo(): kotlin.Unit in trait Z.
\ No newline at end of file
+fun foo(): kotlin.Unit in final class B : A, Z implements fun foo(): kotlin.Unit in interface Z.
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement1.kt.messages b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement1.kt.messages
index b426ce6903c..0ae59da4428 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement1.kt.messages
+++ b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement1.kt.messages
@@ -1 +1 @@
-val foo: kotlin.String in final class B : A implements val foo: kotlin.String in trait A.
\ No newline at end of file
+val foo: kotlin.String in final class B : A implements val foo: kotlin.String in interface A.
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement2.kt.messages b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement2.kt.messages
index 77e535369c9..18208af839c 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement2.kt.messages
+++ b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement2.kt.messages
@@ -1,2 +1,2 @@
-val foo: kotlin.String in final class B : A, Z implements val foo: kotlin.String in trait A.
-val foo: kotlin.String in final class B : A, Z implements val foo: kotlin.String in trait Z.
\ No newline at end of file
+val foo: kotlin.String in final class B : A, Z implements val foo: kotlin.String in interface A.
+val foo: kotlin.String in final class B : A, Z implements val foo: kotlin.String in interface Z.
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement3.kt.messages b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement3.kt.messages
index c9850a839ea..cb14c1f00eb 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement3.kt.messages
+++ b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement3.kt.messages
@@ -1 +1 @@
-var foo: kotlin.String in final class B : A implements var foo: kotlin.String in trait A.
\ No newline at end of file
+var foo: kotlin.String in final class B : A implements var foo: kotlin.String in interface A.
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement4.kt.messages b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement4.kt.messages
index 3cde93936b0..5bbb687b003 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement4.kt.messages
+++ b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement4.kt.messages
@@ -1,2 +1,2 @@
-var foo: kotlin.String in final class B : A, Z implements var foo: kotlin.String in trait A.
-var foo: kotlin.String in final class B : A, Z implements var foo: kotlin.String in trait Z.
\ No newline at end of file
+var foo: kotlin.String in final class B : A, Z implements var foo: kotlin.String in interface A.
+var foo: kotlin.String in final class B : A, Z implements var foo: kotlin.String in interface Z.
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement1.kt.messages b/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement1.kt.messages
index 583204d0ba3..ede44f3a195 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement1.kt.messages
+++ b/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement1.kt.messages
@@ -1 +1 @@
-val foo: kotlin.String in final class B : A, Z implements val foo: kotlin.String in trait Z.
\ No newline at end of file
+val foo: kotlin.String in final class B : A, Z implements val foo: kotlin.String in interface Z.
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement3.kt.messages b/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement3.kt.messages
index 9c1505bdd20..04b9d670e7e 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement3.kt.messages
+++ b/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement3.kt.messages
@@ -1 +1 @@
-var foo: kotlin.String in final class B : A, Z implements var foo: kotlin.String in trait Z.
\ No newline at end of file
+var foo: kotlin.String in final class B : A, Z implements var foo: kotlin.String in interface Z.
\ No newline at end of file