diff --git a/idea/resources/liveTemplates/Kotlin.xml b/idea/resources/liveTemplates/Kotlin.xml
index 7723456dc11..5fa298bd867 100644
--- a/idea/resources/liveTemplates/Kotlin.xml
+++ b/idea/resources/liveTemplates/Kotlin.xml
@@ -114,7 +114,7 @@
     </template>
 
     <template resource-bundle="org.jetbrains.kotlin.idea.JetBundle" key="livetemplate.description.interface"
-              name="interface" toReformat="true" toShortenFQNames="true" value="trait $NAME$ {&#10;$END$&#10;}">
+              name="interface" toReformat="true" toShortenFQNames="true" value="interface $NAME$ {&#10;$END$&#10;}">
         <variable alwaysStopAt="true" defaultValue="" expression="" name="NAME" />
         <context>
             <option name="KOTLIN_STATEMENT" value="true"/>
diff --git a/idea/testData/addImport/StdlibImportsLast.dependency.kt b/idea/testData/addImport/StdlibImportsLast.dependency.kt
index 635777ad235..dae154c6664 100644
--- a/idea/testData/addImport/StdlibImportsLast.dependency.kt
+++ b/idea/testData/addImport/StdlibImportsLast.dependency.kt
@@ -1,3 +1,3 @@
 package xxx
 
-trait Dependency
\ No newline at end of file
+interface Dependency
\ No newline at end of file
diff --git a/idea/testData/checker/Abstract.kt b/idea/testData/checker/Abstract.kt
index 7112dd9a1b2..81de10d88dc 100644
--- a/idea/testData/checker/Abstract.kt
+++ b/idea/testData/checker/Abstract.kt
@@ -62,7 +62,7 @@ abstract class MyAbstractClass() {
     <error>abstract</error> fun j() {}
 }
 
-trait MyTrait {
+interface MyTrait {
     //properties
 
     val a: Int
diff --git a/idea/testData/checker/AnonymousInitializers.kt b/idea/testData/checker/AnonymousInitializers.kt
index 2fbc177d6eb..14b4d8fe654 100644
--- a/idea/testData/checker/AnonymousInitializers.kt
+++ b/idea/testData/checker/AnonymousInitializers.kt
@@ -1,4 +1,4 @@
-trait NoC {
+interface NoC {
   <error>init {
 
   }</error>
diff --git a/idea/testData/checker/Builders.kt b/idea/testData/checker/Builders.kt
index 296de8b6e68..9ee7e42b4d1 100644
--- a/idea/testData/checker/Builders.kt
+++ b/idea/testData/checker/Builders.kt
@@ -2,11 +2,11 @@ package html
 
 import java.util.*
 
-  trait Factory<T> {
+  interface Factory<T> {
     fun create() : T
   }
 
-  trait Element
+  interface Element
 
   class TextElement(val text : String) : Element
 
diff --git a/idea/testData/checker/CyclicHierarchy.kt b/idea/testData/checker/CyclicHierarchy.kt
index 24c7565d5ec..dd5d0cfaa6d 100644
--- a/idea/testData/checker/CyclicHierarchy.kt
+++ b/idea/testData/checker/CyclicHierarchy.kt
@@ -1,13 +1,13 @@
-trait A {
+interface A {
     fun foo() {}
 }
-trait B : A, <error>E</error> {}
-trait C : <error>B</error> {}
-trait D : <error>B</error> {}
-trait E : <error>F</error> {}
-trait F : <error>D</error>, <error>C</error> {}
-trait G : F {}
-trait H : F {}
+interface B : A, <error>E</error> {}
+interface C : <error>B</error> {}
+interface D : <error>B</error> {}
+interface E : <error>F</error> {}
+interface F : <error>D</error>, <error>C</error> {}
+interface G : F {}
+interface H : F {}
 
 val a : A? = null
 val b : B? = null
diff --git a/idea/testData/checker/GenericArgumentConsistency.kt b/idea/testData/checker/GenericArgumentConsistency.kt
index 650637388cd..d1ebe4294e8 100644
--- a/idea/testData/checker/GenericArgumentConsistency.kt
+++ b/idea/testData/checker/GenericArgumentConsistency.kt
@@ -1,42 +1,42 @@
-trait A<in T> {}
-trait B<T> : A<Int> {}
-trait C<T> : <error>B<T>, A<T></error> {}
-trait C1<T> : <error>B<T>, A<Any></error> {}
-trait D : <error><error>C<Boolean>, B<Double></error></error>{}
+interface A<in T> {}
+interface B<T> : A<Int> {}
+interface C<T> : <error>B<T>, A<T></error> {}
+interface C1<T> : <error>B<T>, A<Any></error> {}
+interface D : <error><error>C<Boolean>, B<Double></error></error>{}
 
-trait A1<out T> {}
-trait B1 : A1<Int> {}
-trait B2 : <error>A1<Any>, B1</error> {}
+interface A1<out T> {}
+interface B1 : A1<Int> {}
+interface B2 : <error>A1<Any>, B1</error> {}
 
-trait BA1<T> {}
-trait BB1 : BA1<Int> {}
-trait BB2 : <error>BA1<Any>, BB1</error> {}
+interface BA1<T> {}
+interface BB1 : BA1<Int> {}
+interface BB2 : <error>BA1<Any>, BB1</error> {}
 
 
 //package x {
-    trait xAA1<out T> {}
-    trait xAB1 : xAA1<Int> {}
-    trait xAB3 : xAA1<Comparable<Int>> {}
-    trait xAB2 : <error>xAA1<Number>, xAB1, xAB3</error> {}
+    interface xAA1<out T> {}
+    interface xAB1 : xAA1<Int> {}
+    interface xAB3 : xAA1<Comparable<Int>> {}
+    interface xAB2 : <error>xAA1<Number>, xAB1, xAB3</error> {}
 //}
 
 //package x2 {
-    trait x2AA1<out T> {}
-    trait x2AB1 : x2AA1<Any> {}
-    trait x2AB3 : x2AA1<Comparable<Int>> {}
-    trait x2AB2 : <error>x2AA1<Number>, x2AB1, x2AB3</error> {}
+    interface x2AA1<out T> {}
+    interface x2AB1 : x2AA1<Any> {}
+    interface x2AB3 : x2AA1<Comparable<Int>> {}
+    interface x2AB2 : <error>x2AA1<Number>, x2AB1, x2AB3</error> {}
 //}
 
 //package x3 {
-    trait x3AA1<in T> {}
-    trait x3AB1 : x3AA1<Any> {}
-    trait x3AB3 : x3AA1<Comparable<Int>> {}
-    trait x3AB2 : <error>x3AA1<Number>, x3AB1, x3AB3</error> {}
+    interface x3AA1<in T> {}
+    interface x3AB1 : x3AA1<Any> {}
+    interface x3AB3 : x3AA1<Comparable<Int>> {}
+    interface x3AB2 : <error>x3AA1<Number>, x3AB1, x3AB3</error> {}
 //}
 
 //package sx2 {
-    trait sx2AA1<in T> {}
-    trait sx2AB1 : sx2AA1<Int> {}
-    trait sx2AB3 : sx2AA1<Comparable<Int>> {}
-    trait sx2AB2 : <error>sx2AA1<Number>, sx2AB1, sx2AB3</error> {}
+    interface sx2AA1<in T> {}
+    interface sx2AB1 : sx2AA1<Int> {}
+    interface sx2AB3 : sx2AA1<Comparable<Int>> {}
+    interface sx2AB2 : <error>sx2AA1<Number>, sx2AB1, sx2AB3</error> {}
 //}
\ No newline at end of file
diff --git a/idea/testData/checker/MultipleBounds.kt b/idea/testData/checker/MultipleBounds.kt
index a2ccd56b410..6d018eabaac 100644
--- a/idea/testData/checker/MultipleBounds.kt
+++ b/idea/testData/checker/MultipleBounds.kt
@@ -4,7 +4,7 @@ open class A() {
   fun foo() : Int = 1
 }
 
-trait B {
+interface B {
   fun bar() : Double = 1.0;
 }
 
diff --git a/idea/testData/checker/Override.kt b/idea/testData/checker/Override.kt
index ac29d304646..b4a83a90178 100644
--- a/idea/testData/checker/Override.kt
+++ b/idea/testData/checker/Override.kt
@@ -1,6 +1,6 @@
 package override
 
-    trait MyTrait {
+    interface MyTrait {
         fun foo()
     }
 
diff --git a/idea/testData/checker/OverridesAndGenerics.kt b/idea/testData/checker/OverridesAndGenerics.kt
index a932dbafd72..8e8a3d0c036 100644
--- a/idea/testData/checker/OverridesAndGenerics.kt
+++ b/idea/testData/checker/OverridesAndGenerics.kt
@@ -1,4 +1,4 @@
-    trait MyTrait<T> {
+    interface MyTrait<T> {
         fun foo(t: T) : T
     }
 
diff --git a/idea/testData/checker/PlatformStaticUsagesRuntime.kt b/idea/testData/checker/PlatformStaticUsagesRuntime.kt
index aa9d49ae695..7e2ff04555d 100644
--- a/idea/testData/checker/PlatformStaticUsagesRuntime.kt
+++ b/idea/testData/checker/PlatformStaticUsagesRuntime.kt
@@ -30,7 +30,7 @@ class <error descr="[PLATFORM_STATIC_ILLEGAL_USAGE] This declaration does not su
 }
 
 platformStatic
-trait <error descr="[PLATFORM_STATIC_ILLEGAL_USAGE] This declaration does not support 'platformStatic'">B</error> {
+interface <error descr="[PLATFORM_STATIC_ILLEGAL_USAGE] This declaration does not support 'platformStatic'">B</error> {
     companion object {
         <error descr="[PLATFORM_STATIC_NOT_IN_OBJECT] Only functions in named objects and companion objects of classes can be annotated with 'platformStatic'">platformStatic fun a1()</error> {
 
diff --git a/idea/testData/checker/ProjectionsInSupertypes.kt b/idea/testData/checker/ProjectionsInSupertypes.kt
index 02d64a69469..38680fad820 100644
--- a/idea/testData/checker/ProjectionsInSupertypes.kt
+++ b/idea/testData/checker/ProjectionsInSupertypes.kt
@@ -1,6 +1,6 @@
-trait A<T> {}
-trait B<T> {}
-trait C<T> {}
-trait D<T> {}
+interface A<T> {}
+interface B<T> {}
+interface C<T> {}
+interface D<T> {}
 
-trait Test : A<<error>in</error> Int>, B<<error>out</error> Int>, C<<error>*</error>><error>?</error><warning>?</warning><warning>?</warning>, D<Int> {}
\ No newline at end of file
+interface Test : A<<error>in</error> Int>, B<<error>out</error> Int>, C<<error>*</error>><error>?</error><warning>?</warning><warning>?</warning>, D<Int> {}
\ No newline at end of file
diff --git a/idea/testData/checker/SupertypeListChecks.kt b/idea/testData/checker/SupertypeListChecks.kt
index da94dafbe48..9755d5016f9 100644
--- a/idea/testData/checker/SupertypeListChecks.kt
+++ b/idea/testData/checker/SupertypeListChecks.kt
@@ -4,7 +4,7 @@
 In a supertype list:
  Same type should not be mentioned twice
  Same type should not be indirectly mentioned with incoherent type arguments
- Every trait's required dependencies should be satisfied
+ Every interface's required dependencies should be satisfied
  No final types should appear
  Only one class is allowed
 */
@@ -17,24 +17,24 @@ open class C2 {}
 
 open class C3 {}
 
-trait T1 {}
+interface T1 {}
 
-trait T2<T> {}
+interface T2<T> {}
 
-trait Test<error>()</error> {
+interface Test<error>()</error> {
 }
 
-trait Test1 : <warning>C2</warning><error>()</error> {}
+interface Test1 : <warning>C2</warning><error>()</error> {}
 
-trait Test2 : <warning>C2</warning> {}
+interface Test2 : <warning>C2</warning> {}
 
-trait Test3 : <warning>C2</warning>, <error>C3</error> {}
+interface Test3 : <warning>C2</warning>, <error>C3</error> {}
 
-trait Test4 : T1 {}
+interface Test4 : T1 {}
 
-trait Test5 : T1, <error>T1</error> {}
+interface Test5 : T1, <error>T1</error> {}
 
-trait Test6 : <error>C1</error> {}
+interface Test6 : <error>C1</error> {}
 
 class CTest1() : OC1() {}
 
diff --git a/idea/testData/checker/TraitSupertypeList.kt b/idea/testData/checker/TraitSupertypeList.kt
index c39e318c9f6..4bc79467c92 100644
--- a/idea/testData/checker/TraitSupertypeList.kt
+++ b/idea/testData/checker/TraitSupertypeList.kt
@@ -1,9 +1,9 @@
 open class bar()
 
-trait Foo<error>()</error> : <warning>bar</warning><error>()</error>, <error><error>bar</error></error>, <error><error>bar</error></error> {
+interface Foo<error>()</error> : <warning>bar</warning><error>()</error>, <error><error>bar</error></error>, <error><error>bar</error></error> {
 }
 
-trait Foo2 : <warning>bar</warning>, Foo {
+interface Foo2 : <warning>bar</warning>, Foo {
 }
 
 open class Foo1() : bar(), <error>bar</error>, Foo, <error>Foo</error><error>()</error> {}
diff --git a/idea/testData/checker/duplicateJvmSignature/functionAndProperty/trait.kt b/idea/testData/checker/duplicateJvmSignature/functionAndProperty/trait.kt
index d4f0adf7fcf..3512f01c284 100644
--- a/idea/testData/checker/duplicateJvmSignature/functionAndProperty/trait.kt
+++ b/idea/testData/checker/duplicateJvmSignature/functionAndProperty/trait.kt
@@ -1,4 +1,4 @@
-trait T {
+interface T {
     <error descr="[CONFLICTING_JVM_DECLARATIONS] Platform declaration clash: The following declarations have the same JVM signature (foo(Ljava/util/List;)V):
     fun foo(l: kotlin.List<kotlin.String>): kotlin.Unit
     fun foo(l: kotlin.List<kotlin.Int>): kotlin.Unit">fun foo(l: List<String>)</error> {}
diff --git a/idea/testData/checker/duplicateJvmSignature/traitImpl/twoTraits.kt b/idea/testData/checker/duplicateJvmSignature/traitImpl/twoTraits.kt
index 8a0490579de..f0ecaaba1b7 100644
--- a/idea/testData/checker/duplicateJvmSignature/traitImpl/twoTraits.kt
+++ b/idea/testData/checker/duplicateJvmSignature/traitImpl/twoTraits.kt
@@ -1,8 +1,8 @@
-trait T1 {
+interface T1 {
     fun getX() = 1
 }
 
-trait T2 {
+interface T2 {
     val x: Int
         get() = 1
 }
diff --git a/idea/testData/checker/infos/CapturedConstructorParameter.kt b/idea/testData/checker/infos/CapturedConstructorParameter.kt
index 6634dc8c3d3..9a0bd10c07d 100644
--- a/idea/testData/checker/infos/CapturedConstructorParameter.kt
+++ b/idea/testData/checker/infos/CapturedConstructorParameter.kt
@@ -1,4 +1,4 @@
-trait T
+interface T
 class T1(<warning>t</warning>: Int): T
 
 inline fun <T> run(f: () -> T) = f()
diff --git a/idea/testData/checker/infos/SmartCastsWithSafeAccess.kt b/idea/testData/checker/infos/SmartCastsWithSafeAccess.kt
index 0d138659a84..19809df76c0 100644
--- a/idea/testData/checker/infos/SmartCastsWithSafeAccess.kt
+++ b/idea/testData/checker/infos/SmartCastsWithSafeAccess.kt
@@ -1,14 +1,14 @@
-trait A {
+interface A {
     fun foo()
 }
 
-trait B : A {
+interface B : A {
     fun bar()
 }
 
-trait C
+interface C
 
-trait D : A
+interface D : A
 
 fun test(a: A?) {
     if (a != null && a is B?) {
diff --git a/idea/testData/checker/recovery/namelessToplevelDeclarations.kt b/idea/testData/checker/recovery/namelessToplevelDeclarations.kt
index daf846bf54a..3bbd0384b9e 100644
--- a/idea/testData/checker/recovery/namelessToplevelDeclarations.kt
+++ b/idea/testData/checker/recovery/namelessToplevelDeclarations.kt
@@ -11,7 +11,7 @@ class<error> </error>{
 
 }
 
-trait<error> </error>{
+interface<error> </error>{
 
 }
 
diff --git a/idea/testData/checker/regression/extensionMemberInClassObject.kt b/idea/testData/checker/regression/extensionMemberInClassObject.kt
index c110c3c33b5..4e5a137e04c 100644
--- a/idea/testData/checker/regression/extensionMemberInClassObject.kt
+++ b/idea/testData/checker/regression/extensionMemberInClassObject.kt
@@ -1,4 +1,4 @@
-trait Bar {
+interface Bar {
     fun <T> T.bar() {}
 }
 
diff --git a/idea/testData/checker/unmetTraitRequirements.kt b/idea/testData/checker/unmetTraitRequirements.kt
index b692a9d41d3..9973da8408c 100644
--- a/idea/testData/checker/unmetTraitRequirements.kt
+++ b/idea/testData/checker/unmetTraitRequirements.kt
@@ -1,7 +1,7 @@
 open class Base {
 }
 
-trait Derived: <warning>Base</warning> {
+interface Derived: <warning>Base</warning> {
     fun foo() {
         f1(this@Derived)
     }
diff --git a/idea/testData/codeInsight/lineMarker/overrideImplement/BadCodeNoExceptions.kt b/idea/testData/codeInsight/lineMarker/overrideImplement/BadCodeNoExceptions.kt
index 3fa668a0c63..fbdbf7a6020 100644
--- a/idea/testData/codeInsight/lineMarker/overrideImplement/BadCodeNoExceptions.kt
+++ b/idea/testData/codeInsight/lineMarker/overrideImplement/BadCodeNoExceptions.kt
@@ -1,4 +1,4 @@
-trait Hi {
+interface Hi {
     fun foo(): Int
 }
 
diff --git a/idea/testData/codeInsight/lineMarker/overrideImplement/ClassObjectInStaticNestedClass.kt b/idea/testData/codeInsight/lineMarker/overrideImplement/ClassObjectInStaticNestedClass.kt
index 296219d9dd0..89197e9c394 100644
--- a/idea/testData/codeInsight/lineMarker/overrideImplement/ClassObjectInStaticNestedClass.kt
+++ b/idea/testData/codeInsight/lineMarker/overrideImplement/ClassObjectInStaticNestedClass.kt
@@ -1,4 +1,4 @@
-trait <lineMarker></lineMarker>TestTrait {
+interface <lineMarker></lineMarker>TestTrait {
     fun <lineMarker></lineMarker>test()
 }
 
diff --git a/idea/testData/codeInsight/lineMarker/overrideImplement/DelegatedFun.kt b/idea/testData/codeInsight/lineMarker/overrideImplement/DelegatedFun.kt
index 4364b2d0f9b..09aac6ea6cf 100644
--- a/idea/testData/codeInsight/lineMarker/overrideImplement/DelegatedFun.kt
+++ b/idea/testData/codeInsight/lineMarker/overrideImplement/DelegatedFun.kt
@@ -1,9 +1,9 @@
-trait <lineMarker></lineMarker>A {
+interface <lineMarker></lineMarker>A {
     fun <lineMarker></lineMarker>f() {
     }
 }
 
-trait <lineMarker></lineMarker>B : A
+interface <lineMarker></lineMarker>B : A
 
 open class <lineMarker></lineMarker>C(b : B) : B by b, A {
 }
diff --git a/idea/testData/codeInsight/lineMarker/overrideImplement/DelegatedProperty.kt b/idea/testData/codeInsight/lineMarker/overrideImplement/DelegatedProperty.kt
index 6bf827d6b28..f759845a674 100644
--- a/idea/testData/codeInsight/lineMarker/overrideImplement/DelegatedProperty.kt
+++ b/idea/testData/codeInsight/lineMarker/overrideImplement/DelegatedProperty.kt
@@ -1,9 +1,9 @@
-trait <lineMarker></lineMarker>A {
+interface <lineMarker></lineMarker>A {
     val <lineMarker></lineMarker>f: Int
         get() = 3
 }
 
-trait <lineMarker></lineMarker>B : A
+interface <lineMarker></lineMarker>B : A
 
 open class <lineMarker></lineMarker>C(b : B) : B by b, A {
 }
diff --git a/idea/testData/codeInsight/lineMarker/overrideImplement/FakeOverrideForClasses.kt b/idea/testData/codeInsight/lineMarker/overrideImplement/FakeOverrideForClasses.kt
index 49f35fcc94f..4b4b332b1ac 100644
--- a/idea/testData/codeInsight/lineMarker/overrideImplement/FakeOverrideForClasses.kt
+++ b/idea/testData/codeInsight/lineMarker/overrideImplement/FakeOverrideForClasses.kt
@@ -1,6 +1,6 @@
 package sample
 
-trait <lineMarker descr="*"></lineMarker>S<T> {
+interface <lineMarker descr="*"></lineMarker>S<T> {
     fun <lineMarker descr="<html><body>Is implemented in <br>&nbsp;&nbsp;&nbsp;&nbsp;sample.S2</body></html>"></lineMarker>foo(t: T): T
 
     val <lineMarker descr="<html><body>Is implemented in <br/>&nbsp;&nbsp;&nbsp;&nbsp;sample.S2</body></html>"></lineMarker>some: T? get
diff --git a/idea/testData/codeInsight/lineMarker/overrideImplement/FakeOverrideFun.kt b/idea/testData/codeInsight/lineMarker/overrideImplement/FakeOverrideFun.kt
index 1961703b7cc..2cd3c436209 100644
--- a/idea/testData/codeInsight/lineMarker/overrideImplement/FakeOverrideFun.kt
+++ b/idea/testData/codeInsight/lineMarker/overrideImplement/FakeOverrideFun.kt
@@ -1,10 +1,10 @@
-trait <lineMarker></lineMarker>A {
+interface <lineMarker></lineMarker>A {
   fun <lineMarker></lineMarker>f() {}
 }
 
-trait <lineMarker></lineMarker>B : A
+interface <lineMarker></lineMarker>B : A
 
-trait <lineMarker></lineMarker>C : B, A
+interface <lineMarker></lineMarker>C : B, A
 
 class SomeClass() : C {
   override fun <lineMarker descr="Overrides function in 'A'"></lineMarker>f() {}
diff --git a/idea/testData/codeInsight/lineMarker/overrideImplement/FakeOverrideFunWithMostRelevantImplementation.kt b/idea/testData/codeInsight/lineMarker/overrideImplement/FakeOverrideFunWithMostRelevantImplementation.kt
index 25eda5e73c4..0d071af3208 100644
--- a/idea/testData/codeInsight/lineMarker/overrideImplement/FakeOverrideFunWithMostRelevantImplementation.kt
+++ b/idea/testData/codeInsight/lineMarker/overrideImplement/FakeOverrideFunWithMostRelevantImplementation.kt
@@ -1,12 +1,12 @@
-trait <lineMarker></lineMarker>A {
+interface <lineMarker></lineMarker>A {
     fun <lineMarker></lineMarker><lineMarker></lineMarker>f() {}
 }
 
-trait <lineMarker></lineMarker>B : A {
+interface <lineMarker></lineMarker>B : A {
     override fun <lineMarker></lineMarker>f() {}
 }
 
-trait <lineMarker></lineMarker>C : B, A
+interface <lineMarker></lineMarker>C : B, A
 
 class SomeClass() : C {
     override fun <lineMarker descr="Overrides function in 'B'"></lineMarker>f() {}
diff --git a/idea/testData/codeInsight/lineMarker/overrideImplement/FakeOverrideProperty.kt b/idea/testData/codeInsight/lineMarker/overrideImplement/FakeOverrideProperty.kt
index ea81e0aaed1..e03c44a012d 100644
--- a/idea/testData/codeInsight/lineMarker/overrideImplement/FakeOverrideProperty.kt
+++ b/idea/testData/codeInsight/lineMarker/overrideImplement/FakeOverrideProperty.kt
@@ -1,11 +1,11 @@
-trait <lineMarker></lineMarker>A {
+interface <lineMarker></lineMarker>A {
     val <lineMarker></lineMarker>f: Int
         get() = 2
 }
 
-trait <lineMarker></lineMarker>B : A
+interface <lineMarker></lineMarker>B : A
 
-trait <lineMarker></lineMarker>C : B, A
+interface <lineMarker></lineMarker>C : B, A
 
 class SomeClass() : C {
     override val <lineMarker descr="Overrides property in 'A'"></lineMarker>f: Int = 4
diff --git a/idea/testData/codeInsight/lineMarker/overrideImplement/FakeOverrideToStringInTrait.kt b/idea/testData/codeInsight/lineMarker/overrideImplement/FakeOverrideToStringInTrait.kt
index 30749065d0e..5ad1f9ad91d 100644
--- a/idea/testData/codeInsight/lineMarker/overrideImplement/FakeOverrideToStringInTrait.kt
+++ b/idea/testData/codeInsight/lineMarker/overrideImplement/FakeOverrideToStringInTrait.kt
@@ -1,4 +1,4 @@
-trait <lineMarker descr="*"></lineMarker>A {
+interface <lineMarker descr="*"></lineMarker>A {
     override fun <lineMarker descr="<html><body>Is implemented in <br>&nbsp;&nbsp;&nbsp;&nbsp;C</body></html>"><lineMarker descr="*"></lineMarker></lineMarker>toString() = "A"
 }
 
diff --git a/idea/testData/codeInsight/lineMarker/overrideImplement/FakeOverridesForTraitFunWithImpl.kt b/idea/testData/codeInsight/lineMarker/overrideImplement/FakeOverridesForTraitFunWithImpl.kt
index 005b55efd75..1b71bae5fab 100644
--- a/idea/testData/codeInsight/lineMarker/overrideImplement/FakeOverridesForTraitFunWithImpl.kt
+++ b/idea/testData/codeInsight/lineMarker/overrideImplement/FakeOverridesForTraitFunWithImpl.kt
@@ -1,4 +1,4 @@
-trait <lineMarker descr="*"></lineMarker>A {
+interface <lineMarker descr="*"></lineMarker>A {
     fun <lineMarker descr="<html><body>Is implemented in <br>&nbsp;&nbsp;&nbsp;&nbsp;C</body></html>"></lineMarker>foo(): String = "A"
 
     // TODO: B shoudn't be mentioned
diff --git a/idea/testData/codeInsight/lineMarker/overrideImplement/NavigateToSeveralSuperElements.kt b/idea/testData/codeInsight/lineMarker/overrideImplement/NavigateToSeveralSuperElements.kt
index ad300b501fe..435f4c83e50 100644
--- a/idea/testData/codeInsight/lineMarker/overrideImplement/NavigateToSeveralSuperElements.kt
+++ b/idea/testData/codeInsight/lineMarker/overrideImplement/NavigateToSeveralSuperElements.kt
@@ -1,8 +1,8 @@
-trait <lineMarker></lineMarker>A1 {
+interface <lineMarker></lineMarker>A1 {
     fun <lineMarker></lineMarker>foo()
 }
 
-trait <lineMarker></lineMarker>B1 {
+interface <lineMarker></lineMarker>B1 {
     fun <lineMarker></lineMarker>foo()
 }
 
@@ -17,6 +17,6 @@ NavigateToSeveralSuperElements.kt
     fun <1>foo()
 }
 
-trait B1 {
+interface B1 {
     fun <2>foo()
 */
\ No newline at end of file
diff --git a/idea/testData/codeInsight/lineMarker/overrideImplement/NoOverridingMarkerOnDefaultTraitImpl.kt b/idea/testData/codeInsight/lineMarker/overrideImplement/NoOverridingMarkerOnDefaultTraitImpl.kt
index 93442ce008c..c3e9dd307c7 100644
--- a/idea/testData/codeInsight/lineMarker/overrideImplement/NoOverridingMarkerOnDefaultTraitImpl.kt
+++ b/idea/testData/codeInsight/lineMarker/overrideImplement/NoOverridingMarkerOnDefaultTraitImpl.kt
@@ -1,8 +1,8 @@
-trait <lineMarker descr="*"></lineMarker>SkipSupport {
+interface <lineMarker descr="*"></lineMarker>SkipSupport {
     fun <lineMarker descr="<html><body>Is implemented in <br>&nbsp;&nbsp;&nbsp;&nbsp;SkipSupportWithDefaults</body></html>"></lineMarker>skip()
 }
 
-public trait <lineMarker descr="*"></lineMarker>SkipSupportWithDefaults : SkipSupport {
+public interface <lineMarker descr="*"></lineMarker>SkipSupportWithDefaults : SkipSupport {
     override fun <lineMarker descr="Implements function in 'SkipSupport'"></lineMarker>skip() {}
 }
 
diff --git a/idea/testData/codeInsight/lineMarker/overrideImplement/Overloads.kt b/idea/testData/codeInsight/lineMarker/overrideImplement/Overloads.kt
index c988c04a619..25c02020c98 100644
--- a/idea/testData/codeInsight/lineMarker/overrideImplement/Overloads.kt
+++ b/idea/testData/codeInsight/lineMarker/overrideImplement/Overloads.kt
@@ -1,4 +1,4 @@
-trait <lineMarker descr="*"></lineMarker>A {
+interface <lineMarker descr="*"></lineMarker>A {
     fun <lineMarker descr="<html><body>Is implemented in <br>&nbsp;&nbsp;&nbsp;&nbsp;B</body></html>"></lineMarker>foo(str: String)
     fun <lineMarker descr="<html><body>Is implemented in <br>&nbsp;&nbsp;&nbsp;&nbsp;B</body></html>"></lineMarker>foo()
 }
diff --git a/idea/testData/codeInsight/lineMarker/overrideImplement/OverrideIconForOverloadMethodBug.kt b/idea/testData/codeInsight/lineMarker/overrideImplement/OverrideIconForOverloadMethodBug.kt
index a54dbdb4d5c..49df74d5fbd 100644
--- a/idea/testData/codeInsight/lineMarker/overrideImplement/OverrideIconForOverloadMethodBug.kt
+++ b/idea/testData/codeInsight/lineMarker/overrideImplement/OverrideIconForOverloadMethodBug.kt
@@ -1,9 +1,9 @@
-trait <lineMarker descr="*"></lineMarker>SkipSupport {
+interface <lineMarker descr="*"></lineMarker>SkipSupport {
     fun <lineMarker descr="<html><body>Is implemented in <br>&nbsp;&nbsp;&nbsp;&nbsp;SkipSupportImpl<br>&nbsp;&nbsp;&nbsp;&nbsp;SkipSupportWithDefaults</body></html>"></lineMarker>skip(why: String)
     fun <lineMarker descr="<html><body>Is implemented in <br>&nbsp;&nbsp;&nbsp;&nbsp;SkipSupportWithDefaults</body></html>"></lineMarker>skip()
 }
 
-public trait <lineMarker descr="*"></lineMarker>SkipSupportWithDefaults : SkipSupport {
+public interface <lineMarker descr="*"></lineMarker>SkipSupportWithDefaults : SkipSupport {
     // TODO: should be "Is overriden in SkipSupportImpl"
     override fun <lineMarker descr="<html><body>Is implemented in <br>&nbsp;&nbsp;&nbsp;&nbsp;SkipSupportImpl</body></html>"><lineMarker descr="Implements function in 'SkipSupport'"></lineMarker></lineMarker>skip(why: String) {}
 
diff --git a/idea/testData/codeInsight/lineMarker/overrideImplement/OverridenTraitDeclarations.kt b/idea/testData/codeInsight/lineMarker/overrideImplement/OverridenTraitDeclarations.kt
index a6a502a3b64..86f94cbedc8 100644
--- a/idea/testData/codeInsight/lineMarker/overrideImplement/OverridenTraitDeclarations.kt
+++ b/idea/testData/codeInsight/lineMarker/overrideImplement/OverridenTraitDeclarations.kt
@@ -1,5 +1,5 @@
 // TODO: Declarations have no implementation and should be considered as "overloaded"
-trait <lineMarker descr="*"></lineMarker>First {
+interface <lineMarker descr="*"></lineMarker>First {
     val <lineMarker descr="<html><body>Is implemented in <br/>&nbsp;&nbsp;&nbsp;&nbsp;Second</body></html>"></lineMarker>some: Int
     var <lineMarker descr="<html><body>Is implemented in <br/>&nbsp;&nbsp;&nbsp;&nbsp;Second</body></html>"></lineMarker>other: String
         get
@@ -8,7 +8,7 @@ trait <lineMarker descr="*"></lineMarker>First {
     fun <lineMarker descr="<html><body>Is implemented in <br>&nbsp;&nbsp;&nbsp;&nbsp;Second</body></html>"></lineMarker>foo()
 }
 
-trait Second : First {
+interface Second : First {
     override val <lineMarker descr="Overrides property in 'First'"></lineMarker>some: Int
     override var <lineMarker descr="Overrides property in 'First'"></lineMarker>other: String
     override fun <lineMarker descr="Overrides function in 'First'"></lineMarker>foo()
diff --git a/idea/testData/codeInsight/lineMarker/overrideImplement/OverridingTooltipOnDefaultTraitImpl.kt b/idea/testData/codeInsight/lineMarker/overrideImplement/OverridingTooltipOnDefaultTraitImpl.kt
index cc3f7f953f6..43a55a128eb 100644
--- a/idea/testData/codeInsight/lineMarker/overrideImplement/OverridingTooltipOnDefaultTraitImpl.kt
+++ b/idea/testData/codeInsight/lineMarker/overrideImplement/OverridingTooltipOnDefaultTraitImpl.kt
@@ -1,12 +1,12 @@
-trait <lineMarker descr="*"></lineMarker>SkipSupport {
+interface <lineMarker descr="*"></lineMarker>SkipSupport {
     fun <lineMarker descr="<html><body>Is implemented in <br>&nbsp;&nbsp;&nbsp;&nbsp;SkipSupportImpl1<br>&nbsp;&nbsp;&nbsp;&nbsp;SkipSupportWithDefaults</body></html>"></lineMarker>skip()
 }
 
-public trait <lineMarker descr="*"></lineMarker>SkipSupportWithDefaults : SkipSupport {
+public interface <lineMarker descr="*"></lineMarker>SkipSupportWithDefaults : SkipSupport {
     override fun <lineMarker descr="<html><body>Is implemented in <br>&nbsp;&nbsp;&nbsp;&nbsp;SkipSupportImpl1</body></html>"><lineMarker descr="Implements function in 'SkipSupport'"></lineMarker></lineMarker>skip() {}
 }
 
-public trait SkipSupportImpl1 : SkipSupportWithDefaults {
+public interface SkipSupportImpl1 : SkipSupportWithDefaults {
     override fun <lineMarker descr="Overrides function in 'SkipSupportWithDefaults'"></lineMarker>skip() {}
 }
 
diff --git a/idea/testData/codeInsight/lineMarker/overrideImplement/ToStringInTrait.kt b/idea/testData/codeInsight/lineMarker/overrideImplement/ToStringInTrait.kt
index d5968f4dc0a..2e760a6dcb9 100644
--- a/idea/testData/codeInsight/lineMarker/overrideImplement/ToStringInTrait.kt
+++ b/idea/testData/codeInsight/lineMarker/overrideImplement/ToStringInTrait.kt
@@ -1,4 +1,4 @@
-public trait Foo {
+public interface Foo {
     override fun <lineMarker descr="Overrides function in 'Any'"></lineMarker>toString() = "str"
 }
 
diff --git a/idea/testData/codeInsight/lineMarker/overrideImplement/Trait.kt b/idea/testData/codeInsight/lineMarker/overrideImplement/Trait.kt
index ac35ff5d317..2c9cfe8ac72 100644
--- a/idea/testData/codeInsight/lineMarker/overrideImplement/Trait.kt
+++ b/idea/testData/codeInsight/lineMarker/overrideImplement/Trait.kt
@@ -1,4 +1,4 @@
-trait <lineMarker></lineMarker>A {
+interface <lineMarker></lineMarker>A {
   fun <lineMarker></lineMarker>a(){
   }
 }
diff --git a/idea/testData/codeInsight/outOfBlock/InFunInPropertyInObjectLiteral.kt b/idea/testData/codeInsight/outOfBlock/InFunInPropertyInObjectLiteral.kt
index b64af660cd3..2f1f5bbded9 100644
--- a/idea/testData/codeInsight/outOfBlock/InFunInPropertyInObjectLiteral.kt
+++ b/idea/testData/codeInsight/outOfBlock/InFunInPropertyInObjectLiteral.kt
@@ -1,5 +1,5 @@
 // FALSE
-trait Some
+interface Some
 
 fun test() {
     val foo = object: Some {
diff --git a/idea/testData/codeInsight/outOfBlock/InFunObjectLiteral.kt b/idea/testData/codeInsight/outOfBlock/InFunObjectLiteral.kt
index 82d8c9c12e4..a321fed787a 100644
--- a/idea/testData/codeInsight/outOfBlock/InFunObjectLiteral.kt
+++ b/idea/testData/codeInsight/outOfBlock/InFunObjectLiteral.kt
@@ -1,5 +1,5 @@
 // FALSE
-trait Some
+interface Some
 
 fun test() {
     object : Some {
diff --git a/idea/testData/codeInsight/outOfBlock/PropNotNullType_Initializer_ObjectLiteral_Fun.kt b/idea/testData/codeInsight/outOfBlock/PropNotNullType_Initializer_ObjectLiteral_Fun.kt
index de8927a7da8..deab9da7824 100644
--- a/idea/testData/codeInsight/outOfBlock/PropNotNullType_Initializer_ObjectLiteral_Fun.kt
+++ b/idea/testData/codeInsight/outOfBlock/PropNotNullType_Initializer_ObjectLiteral_Fun.kt
@@ -1,7 +1,7 @@
 // TRUE
 
 // Problem with lazy initialization of nullable properties
-trait Some
+interface Some
 
 val test: Some = object: Some {
     fun test() {
diff --git a/idea/testData/codeInsight/outOfBlock/PropNullType_Initializer_ObjectLiteral_Fun.kt b/idea/testData/codeInsight/outOfBlock/PropNullType_Initializer_ObjectLiteral_Fun.kt
index 180d7bfd371..1882dd20b14 100644
--- a/idea/testData/codeInsight/outOfBlock/PropNullType_Initializer_ObjectLiteral_Fun.kt
+++ b/idea/testData/codeInsight/outOfBlock/PropNullType_Initializer_ObjectLiteral_Fun.kt
@@ -1,7 +1,7 @@
 // TRUE
 
 // Problem with lazy initialization of nullable properties
-trait Some
+interface Some
 
 val test: Some? = object: Some {
     fun test() {
diff --git a/idea/testData/codeInsight/overrideImplement/defaultValues.kt b/idea/testData/codeInsight/overrideImplement/defaultValues.kt
index 112bb1e7e16..2ee15a92dca 100644
--- a/idea/testData/codeInsight/overrideImplement/defaultValues.kt
+++ b/idea/testData/codeInsight/overrideImplement/defaultValues.kt
@@ -1,4 +1,4 @@
-trait T {
+interface T {
     fun foo(a:Int = 1)
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/defaultValues.kt.after b/idea/testData/codeInsight/overrideImplement/defaultValues.kt.after
index 4bad01c54d9..4daa86d7020 100644
--- a/idea/testData/codeInsight/overrideImplement/defaultValues.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/defaultValues.kt.after
@@ -1,4 +1,4 @@
-trait T {
+interface T {
     fun foo(a:Int = 1)
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/delegatedMembers.kt b/idea/testData/codeInsight/overrideImplement/delegatedMembers.kt
index e807763e8f5..9696f8659aa 100644
--- a/idea/testData/codeInsight/overrideImplement/delegatedMembers.kt
+++ b/idea/testData/codeInsight/overrideImplement/delegatedMembers.kt
@@ -1,4 +1,4 @@
-trait T {
+interface T {
     fun foo()
     fun bar()
 }
diff --git a/idea/testData/codeInsight/overrideImplement/delegatedMembers.kt.after b/idea/testData/codeInsight/overrideImplement/delegatedMembers.kt.after
index ac1fbfc7c87..bcad0d8fb1a 100644
--- a/idea/testData/codeInsight/overrideImplement/delegatedMembers.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/delegatedMembers.kt.after
@@ -1,4 +1,4 @@
-trait T {
+interface T {
     fun foo()
     fun bar()
 }
diff --git a/idea/testData/codeInsight/overrideImplement/emptyClassBodyFunctionMethod.kt b/idea/testData/codeInsight/overrideImplement/emptyClassBodyFunctionMethod.kt
index 207375dd207..f3c61ea0f14 100644
--- a/idea/testData/codeInsight/overrideImplement/emptyClassBodyFunctionMethod.kt
+++ b/idea/testData/codeInsight/overrideImplement/emptyClassBodyFunctionMethod.kt
@@ -1,5 +1,5 @@
 // From KT-1254
-trait T {
+interface T {
     fun Foo() : (String) -> Unit
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/emptyClassBodyFunctionMethod.kt.after b/idea/testData/codeInsight/overrideImplement/emptyClassBodyFunctionMethod.kt.after
index cfaf2fc8c34..25c5a63b1f7 100644
--- a/idea/testData/codeInsight/overrideImplement/emptyClassBodyFunctionMethod.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/emptyClassBodyFunctionMethod.kt.after
@@ -1,5 +1,5 @@
 // From KT-1254
-trait T {
+interface T {
     fun Foo() : (String) -> Unit
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/functionFromTraitInJava/foo/KotlinTrait.kt b/idea/testData/codeInsight/overrideImplement/functionFromTraitInJava/foo/KotlinTrait.kt
index c2f02ffe90b..b947689f5db 100644
--- a/idea/testData/codeInsight/overrideImplement/functionFromTraitInJava/foo/KotlinTrait.kt
+++ b/idea/testData/codeInsight/overrideImplement/functionFromTraitInJava/foo/KotlinTrait.kt
@@ -1,6 +1,6 @@
 package foo
 
-trait KotlinTrait {
+interface KotlinTrait {
     fun bar(price : String?)
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/functionMethod.kt b/idea/testData/codeInsight/overrideImplement/functionMethod.kt
index 34ac85eab84..b2348d5e19d 100644
--- a/idea/testData/codeInsight/overrideImplement/functionMethod.kt
+++ b/idea/testData/codeInsight/overrideImplement/functionMethod.kt
@@ -1,5 +1,5 @@
 // From KT-1254
-trait T {
+interface T {
     fun Foo() : (String) -> Unit
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/functionMethod.kt.after b/idea/testData/codeInsight/overrideImplement/functionMethod.kt.after
index cfaf2fc8c34..25c5a63b1f7 100644
--- a/idea/testData/codeInsight/overrideImplement/functionMethod.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/functionMethod.kt.after
@@ -1,5 +1,5 @@
 // From KT-1254
-trait T {
+interface T {
     fun Foo() : (String) -> Unit
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/functionProperty.kt b/idea/testData/codeInsight/overrideImplement/functionProperty.kt
index 32b3fc10ef5..69c0c9b82d0 100644
--- a/idea/testData/codeInsight/overrideImplement/functionProperty.kt
+++ b/idea/testData/codeInsight/overrideImplement/functionProperty.kt
@@ -1,5 +1,5 @@
 // From KT-1648
-trait A {
+interface A {
     val method:() -> Unit?
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/functionProperty.kt.after b/idea/testData/codeInsight/overrideImplement/functionProperty.kt.after
index 844352289c8..273792bc16e 100644
--- a/idea/testData/codeInsight/overrideImplement/functionProperty.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/functionProperty.kt.after
@@ -1,5 +1,5 @@
 // From KT-1648
-trait A {
+interface A {
     val method:() -> Unit?
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/functionWithTypeParameters.kt b/idea/testData/codeInsight/overrideImplement/functionWithTypeParameters.kt
index 5e7faae277f..67f474a828b 100644
--- a/idea/testData/codeInsight/overrideImplement/functionWithTypeParameters.kt
+++ b/idea/testData/codeInsight/overrideImplement/functionWithTypeParameters.kt
@@ -1,4 +1,4 @@
-trait Trait {
+interface Trait {
     fun <A, B : Runnable, E : Map.Entry<A, B>> foo() where B : Cloneable, B : Comparable<B>;
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/functionWithTypeParameters.kt.after b/idea/testData/codeInsight/overrideImplement/functionWithTypeParameters.kt.after
index 618c827f73f..113fbac465e 100644
--- a/idea/testData/codeInsight/overrideImplement/functionWithTypeParameters.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/functionWithTypeParameters.kt.after
@@ -1,4 +1,4 @@
-trait Trait {
+interface Trait {
     fun <A, B : Runnable, E : Map.Entry<A, B>> foo() where B : Cloneable, B : Comparable<B>;
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/generateMulti.kt b/idea/testData/codeInsight/overrideImplement/generateMulti.kt
index 6386a579032..e7604e1aa6f 100644
--- a/idea/testData/codeInsight/overrideImplement/generateMulti.kt
+++ b/idea/testData/codeInsight/overrideImplement/generateMulti.kt
@@ -1,6 +1,6 @@
 package something
 
-trait Some<T> {
+interface Some<T> {
     fun someFoo()
     fun someOtherFoo() : Int
     fun someGenericFoo() : T
diff --git a/idea/testData/codeInsight/overrideImplement/generateMulti.kt.after b/idea/testData/codeInsight/overrideImplement/generateMulti.kt.after
index ca9b68f025f..7f1ef6fa6a0 100644
--- a/idea/testData/codeInsight/overrideImplement/generateMulti.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/generateMulti.kt.after
@@ -1,6 +1,6 @@
 package something
 
-trait Some<T> {
+interface Some<T> {
     fun someFoo()
     fun someOtherFoo() : Int
     fun someGenericFoo() : T
diff --git a/idea/testData/codeInsight/overrideImplement/genericMethod.kt b/idea/testData/codeInsight/overrideImplement/genericMethod.kt
index 3c7e6d8de5b..ef2f8e80c5d 100644
--- a/idea/testData/codeInsight/overrideImplement/genericMethod.kt
+++ b/idea/testData/codeInsight/overrideImplement/genericMethod.kt
@@ -1,4 +1,4 @@
-trait G<T> {
+interface G<T> {
     fun foo(t : T) : T
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/genericMethod.kt.after b/idea/testData/codeInsight/overrideImplement/genericMethod.kt.after
index 13767de189d..c06b8ab2899 100644
--- a/idea/testData/codeInsight/overrideImplement/genericMethod.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/genericMethod.kt.after
@@ -1,4 +1,4 @@
-trait G<T> {
+interface G<T> {
     fun foo(t : T) : T
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/inheritVisibilities.kt b/idea/testData/codeInsight/overrideImplement/inheritVisibilities.kt
index 1f2c248aff6..1e422a7f8f8 100644
--- a/idea/testData/codeInsight/overrideImplement/inheritVisibilities.kt
+++ b/idea/testData/codeInsight/overrideImplement/inheritVisibilities.kt
@@ -4,7 +4,7 @@ open class A() {
     public open fun publicFun() {}
 }
 
-trait B {
+interface B {
    protected open val protectedProperty : Int
    internal open val internalProperty : Int
    public open val publicProperty : Int
diff --git a/idea/testData/codeInsight/overrideImplement/inheritVisibilities.kt.after b/idea/testData/codeInsight/overrideImplement/inheritVisibilities.kt.after
index 43fd44a8226..50a4d049947 100644
--- a/idea/testData/codeInsight/overrideImplement/inheritVisibilities.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/inheritVisibilities.kt.after
@@ -4,7 +4,7 @@ open class A() {
     public open fun publicFun() {}
 }
 
-trait B {
+interface B {
    protected open val protectedProperty : Int
    internal open val internalProperty : Int
    public open val publicProperty : Int
diff --git a/idea/testData/codeInsight/overrideImplement/multiOverride.kt b/idea/testData/codeInsight/overrideImplement/multiOverride.kt
index dfa8e828d09..7b36341464f 100644
--- a/idea/testData/codeInsight/overrideImplement/multiOverride.kt
+++ b/idea/testData/codeInsight/overrideImplement/multiOverride.kt
@@ -1,4 +1,4 @@
-trait A {
+interface A {
     fun foo(value : String) : Int = 0
     fun bar() : String = "hello"
 }
diff --git a/idea/testData/codeInsight/overrideImplement/multiOverride.kt.after b/idea/testData/codeInsight/overrideImplement/multiOverride.kt.after
index f27ffb755c3..e212affd00e 100644
--- a/idea/testData/codeInsight/overrideImplement/multiOverride.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/multiOverride.kt.after
@@ -1,4 +1,4 @@
-trait A {
+interface A {
     fun foo(value : String) : Int = 0
     fun bar() : String = "hello"
 }
diff --git a/idea/testData/codeInsight/overrideImplement/multipleSupers.kt b/idea/testData/codeInsight/overrideImplement/multipleSupers.kt
index d9d5c03fe17..998988e05db 100644
--- a/idea/testData/codeInsight/overrideImplement/multipleSupers.kt
+++ b/idea/testData/codeInsight/overrideImplement/multipleSupers.kt
@@ -2,7 +2,7 @@ open class A {
     open fun foo() {}
 }
 
-trait B {
+interface B {
     fun bar()
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/multipleSupers.kt.after b/idea/testData/codeInsight/overrideImplement/multipleSupers.kt.after
index 63d29ae522f..9bf200b5b69 100644
--- a/idea/testData/codeInsight/overrideImplement/multipleSupers.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/multipleSupers.kt.after
@@ -2,7 +2,7 @@ open class A {
     open fun foo() {}
 }
 
-trait B {
+interface B {
     fun bar()
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/overrideExplicitFunction.kt b/idea/testData/codeInsight/overrideImplement/overrideExplicitFunction.kt
index 023bac0af7f..ffe0fc271e9 100644
--- a/idea/testData/codeInsight/overrideImplement/overrideExplicitFunction.kt
+++ b/idea/testData/codeInsight/overrideImplement/overrideExplicitFunction.kt
@@ -1,4 +1,4 @@
-trait A {
+interface A {
     fun String.foo()
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/overrideExplicitFunction.kt.after b/idea/testData/codeInsight/overrideImplement/overrideExplicitFunction.kt.after
index 53963ddc39e..569e451c7e2 100644
--- a/idea/testData/codeInsight/overrideImplement/overrideExplicitFunction.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/overrideExplicitFunction.kt.after
@@ -1,4 +1,4 @@
-trait A {
+interface A {
     fun String.foo()
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/overrideExtensionProperty.kt b/idea/testData/codeInsight/overrideImplement/overrideExtensionProperty.kt
index 53f68c7cf53..41ae4e987e2 100644
--- a/idea/testData/codeInsight/overrideImplement/overrideExtensionProperty.kt
+++ b/idea/testData/codeInsight/overrideImplement/overrideExtensionProperty.kt
@@ -1,4 +1,4 @@
-trait A {
+interface A {
     val String.prop : Int
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/overrideExtensionProperty.kt.after b/idea/testData/codeInsight/overrideImplement/overrideExtensionProperty.kt.after
index 20abfb78d24..0a5a5a40168 100644
--- a/idea/testData/codeInsight/overrideImplement/overrideExtensionProperty.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/overrideExtensionProperty.kt.after
@@ -1,4 +1,4 @@
-trait A {
+interface A {
     val String.prop : Int
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/overrideFromClassName.kt b/idea/testData/codeInsight/overrideImplement/overrideFromClassName.kt
index 1365cdce0bd..ffd97d2104c 100644
--- a/idea/testData/codeInsight/overrideImplement/overrideFromClassName.kt
+++ b/idea/testData/codeInsight/overrideImplement/overrideFromClassName.kt
@@ -1,4 +1,4 @@
-trait Some {
+interface Some {
     fun foo()
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/overrideFromClassName.kt.after b/idea/testData/codeInsight/overrideImplement/overrideFromClassName.kt.after
index 379c2f435b7..d5c1c5cb39d 100644
--- a/idea/testData/codeInsight/overrideImplement/overrideFromClassName.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/overrideFromClassName.kt.after
@@ -1,4 +1,4 @@
-trait Some {
+interface Some {
     fun foo()
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/overrideFromFunctionPosition.kt b/idea/testData/codeInsight/overrideImplement/overrideFromFunctionPosition.kt
index fb34348c279..48c6f6d592e 100644
--- a/idea/testData/codeInsight/overrideImplement/overrideFromFunctionPosition.kt
+++ b/idea/testData/codeInsight/overrideImplement/overrideFromFunctionPosition.kt
@@ -1,4 +1,4 @@
-trait Some {
+interface Some {
     fun foo()
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/overrideFromFunctionPosition.kt.after b/idea/testData/codeInsight/overrideImplement/overrideFromFunctionPosition.kt.after
index 67d5b0c67fe..2697e2751b7 100644
--- a/idea/testData/codeInsight/overrideImplement/overrideFromFunctionPosition.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/overrideFromFunctionPosition.kt.after
@@ -1,4 +1,4 @@
-trait Some {
+interface Some {
     fun foo()
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/overrideFromLBrace.kt b/idea/testData/codeInsight/overrideImplement/overrideFromLBrace.kt
index 6cd00a4b6bf..dc356b17932 100644
--- a/idea/testData/codeInsight/overrideImplement/overrideFromLBrace.kt
+++ b/idea/testData/codeInsight/overrideImplement/overrideFromLBrace.kt
@@ -1,4 +1,4 @@
-trait Some {
+interface Some {
     fun foo()
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/overrideFromLBrace.kt.after b/idea/testData/codeInsight/overrideImplement/overrideFromLBrace.kt.after
index 379c2f435b7..d5c1c5cb39d 100644
--- a/idea/testData/codeInsight/overrideImplement/overrideFromLBrace.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/overrideFromLBrace.kt.after
@@ -1,4 +1,4 @@
-trait Some {
+interface Some {
     fun foo()
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/overrideGenericFunction.kt b/idea/testData/codeInsight/overrideImplement/overrideGenericFunction.kt
index b659459316a..bc9dc4eeda4 100644
--- a/idea/testData/codeInsight/overrideImplement/overrideGenericFunction.kt
+++ b/idea/testData/codeInsight/overrideImplement/overrideGenericFunction.kt
@@ -1,4 +1,4 @@
-trait A<T> {
+interface A<T> {
     fun foo(value : T) : Unit = println(value)
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/overrideGenericFunction.kt.after b/idea/testData/codeInsight/overrideImplement/overrideGenericFunction.kt.after
index d90e8bf52d4..faaaf25d70c 100644
--- a/idea/testData/codeInsight/overrideImplement/overrideGenericFunction.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/overrideGenericFunction.kt.after
@@ -1,4 +1,4 @@
-trait A<T> {
+interface A<T> {
     fun foo(value : T) : Unit = println(value)
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/overrideMutableExtensionProperty.kt b/idea/testData/codeInsight/overrideImplement/overrideMutableExtensionProperty.kt
index cce7551b75d..b054c3e1ce7 100644
--- a/idea/testData/codeInsight/overrideImplement/overrideMutableExtensionProperty.kt
+++ b/idea/testData/codeInsight/overrideImplement/overrideMutableExtensionProperty.kt
@@ -1,4 +1,4 @@
-trait A {
+interface A {
     var Int.foo : Double
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/overrideMutableExtensionProperty.kt.after b/idea/testData/codeInsight/overrideImplement/overrideMutableExtensionProperty.kt.after
index 859f2229529..ad024669fdc 100644
--- a/idea/testData/codeInsight/overrideImplement/overrideMutableExtensionProperty.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/overrideMutableExtensionProperty.kt.after
@@ -1,4 +1,4 @@
-trait A {
+interface A {
     var Int.foo : Double
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/overrideNonUnitFunction.kt b/idea/testData/codeInsight/overrideImplement/overrideNonUnitFunction.kt
index 625bea2ea7f..7f5269262b9 100644
--- a/idea/testData/codeInsight/overrideImplement/overrideNonUnitFunction.kt
+++ b/idea/testData/codeInsight/overrideImplement/overrideNonUnitFunction.kt
@@ -1,4 +1,4 @@
-trait A {
+interface A {
     fun foo(value : String) : Int = 0
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/overrideNonUnitFunction.kt.after b/idea/testData/codeInsight/overrideImplement/overrideNonUnitFunction.kt.after
index 1d5b6d79774..2d0f95fa907 100644
--- a/idea/testData/codeInsight/overrideImplement/overrideNonUnitFunction.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/overrideNonUnitFunction.kt.after
@@ -1,4 +1,4 @@
-trait A {
+interface A {
     fun foo(value : String) : Int = 0
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/overridePrimitiveProperty.kt b/idea/testData/codeInsight/overrideImplement/overridePrimitiveProperty.kt
index 20dabe4d3ed..df5767bb358 100644
--- a/idea/testData/codeInsight/overrideImplement/overridePrimitiveProperty.kt
+++ b/idea/testData/codeInsight/overrideImplement/overridePrimitiveProperty.kt
@@ -1,4 +1,4 @@
-trait T {
+interface T {
     val a1: Byte
     val a2: Short
     val a3: Int
diff --git a/idea/testData/codeInsight/overrideImplement/overridePrimitiveProperty.kt.after b/idea/testData/codeInsight/overrideImplement/overridePrimitiveProperty.kt.after
index 50be12ba22c..5960f4336ec 100644
--- a/idea/testData/codeInsight/overrideImplement/overridePrimitiveProperty.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/overridePrimitiveProperty.kt.after
@@ -1,4 +1,4 @@
-trait T {
+interface T {
     val a1: Byte
     val a2: Short
     val a3: Int
diff --git a/idea/testData/codeInsight/overrideImplement/overrideUnitFunction.kt b/idea/testData/codeInsight/overrideImplement/overrideUnitFunction.kt
index 60755b6601b..3e194ab46c7 100644
--- a/idea/testData/codeInsight/overrideImplement/overrideUnitFunction.kt
+++ b/idea/testData/codeInsight/overrideImplement/overrideUnitFunction.kt
@@ -1,4 +1,4 @@
-trait A {
+interface A {
     fun foo(value : String) : Unit = 0
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/overrideUnitFunction.kt.after b/idea/testData/codeInsight/overrideImplement/overrideUnitFunction.kt.after
index 70065100f1a..d9d39beb533 100644
--- a/idea/testData/codeInsight/overrideImplement/overrideUnitFunction.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/overrideUnitFunction.kt.after
@@ -1,4 +1,4 @@
-trait A {
+interface A {
     fun foo(value : String) : Unit = 0
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/propagationKJK/foo/Foo.kt b/idea/testData/codeInsight/overrideImplement/propagationKJK/foo/Foo.kt
index e0a420c153c..7bcfffa61fe 100644
--- a/idea/testData/codeInsight/overrideImplement/propagationKJK/foo/Foo.kt
+++ b/idea/testData/codeInsight/overrideImplement/propagationKJK/foo/Foo.kt
@@ -1,5 +1,5 @@
 package foo
 
-public trait Foo {
+public interface Foo {
     fun f(): Any
 }
diff --git a/idea/testData/codeInsight/overrideImplement/property.kt b/idea/testData/codeInsight/overrideImplement/property.kt
index 0f08af46b60..9f6087fb3bb 100644
--- a/idea/testData/codeInsight/overrideImplement/property.kt
+++ b/idea/testData/codeInsight/overrideImplement/property.kt
@@ -1,4 +1,4 @@
-trait T {
+interface T {
     val v : Int
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/property.kt.after b/idea/testData/codeInsight/overrideImplement/property.kt.after
index 82bc29b271b..46c15873f2e 100644
--- a/idea/testData/codeInsight/overrideImplement/property.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/property.kt.after
@@ -1,4 +1,4 @@
-trait T {
+interface T {
     val v : Int
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/respectCaretPosition.kt b/idea/testData/codeInsight/overrideImplement/respectCaretPosition.kt
index 8a8e9fe779a..7cea47dc0bd 100644
--- a/idea/testData/codeInsight/overrideImplement/respectCaretPosition.kt
+++ b/idea/testData/codeInsight/overrideImplement/respectCaretPosition.kt
@@ -1,4 +1,4 @@
-trait Test {
+interface Test {
     public open fun test()
     protected open val testProp : Int
 }
diff --git a/idea/testData/codeInsight/overrideImplement/respectCaretPosition.kt.after b/idea/testData/codeInsight/overrideImplement/respectCaretPosition.kt.after
index 2e87f3a5049..f1a81bf3cc1 100644
--- a/idea/testData/codeInsight/overrideImplement/respectCaretPosition.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/respectCaretPosition.kt.after
@@ -1,4 +1,4 @@
-trait Test {
+interface Test {
     public open fun test()
     protected open val testProp : Int
 }
diff --git a/idea/testData/codeInsight/overrideImplement/sameTypeName/foo/Array.kt b/idea/testData/codeInsight/overrideImplement/sameTypeName/foo/Array.kt
index 0c3cf4f534c..59cee65f288 100644
--- a/idea/testData/codeInsight/overrideImplement/sameTypeName/foo/Array.kt
+++ b/idea/testData/codeInsight/overrideImplement/sameTypeName/foo/Array.kt
@@ -4,6 +4,6 @@ package lib
 public class Array {
 }
 
-public trait ArrayFactory {
+public interface ArrayFactory {
     fun create() : Array
 }
\ No newline at end of file
diff --git a/idea/testData/codeInsight/overrideImplement/starProjections.kt b/idea/testData/codeInsight/overrideImplement/starProjections.kt
index 9adeaef343c..04b997347dc 100644
--- a/idea/testData/codeInsight/overrideImplement/starProjections.kt
+++ b/idea/testData/codeInsight/overrideImplement/starProjections.kt
@@ -1,6 +1,6 @@
 class C<T : C<T>>
 
-trait Base {
+interface Base {
     fun foo(c: C<*>)
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/starProjections.kt.after b/idea/testData/codeInsight/overrideImplement/starProjections.kt.after
index ba1f59792b7..9033070807b 100644
--- a/idea/testData/codeInsight/overrideImplement/starProjections.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/starProjections.kt.after
@@ -1,6 +1,6 @@
 class C<T : C<T>>
 
-trait Base {
+interface Base {
     fun foo(c: C<*>)
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/traitGenericImplement.kt b/idea/testData/codeInsight/overrideImplement/traitGenericImplement.kt
index b2387d42ad4..781ea521f50 100644
--- a/idea/testData/codeInsight/overrideImplement/traitGenericImplement.kt
+++ b/idea/testData/codeInsight/overrideImplement/traitGenericImplement.kt
@@ -1,4 +1,4 @@
-trait G<T> {
+interface G<T> {
     fun foo(t : T) : T
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/traitGenericImplement.kt.after b/idea/testData/codeInsight/overrideImplement/traitGenericImplement.kt.after
index 3111b802c11..f61791b5d75 100644
--- a/idea/testData/codeInsight/overrideImplement/traitGenericImplement.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/traitGenericImplement.kt.after
@@ -1,4 +1,4 @@
-trait G<T> {
+interface G<T> {
     fun foo(t : T) : T
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/traitNullableFunction.kt b/idea/testData/codeInsight/overrideImplement/traitNullableFunction.kt
index e1dcebe7663..a71c940a94b 100644
--- a/idea/testData/codeInsight/overrideImplement/traitNullableFunction.kt
+++ b/idea/testData/codeInsight/overrideImplement/traitNullableFunction.kt
@@ -1,4 +1,4 @@
-trait Some {
+interface Some {
     fun foo(some : Int?) : Int
 }
 
diff --git a/idea/testData/codeInsight/overrideImplement/traitNullableFunction.kt.after b/idea/testData/codeInsight/overrideImplement/traitNullableFunction.kt.after
index 2ef222e6f35..568c9e50dd0 100644
--- a/idea/testData/codeInsight/overrideImplement/traitNullableFunction.kt.after
+++ b/idea/testData/codeInsight/overrideImplement/traitNullableFunction.kt.after
@@ -1,4 +1,4 @@
-trait Some {
+interface Some {
     fun foo(some : Int?) : Int
 }
 
diff --git a/idea/testData/compilerMessages/k2jvm/visibilityError/src/test.kt b/idea/testData/compilerMessages/k2jvm/visibilityError/src/test.kt
index 78a4da5b9b7..169a6ae276f 100644
--- a/idea/testData/compilerMessages/k2jvm/visibilityError/src/test.kt
+++ b/idea/testData/compilerMessages/k2jvm/visibilityError/src/test.kt
@@ -1,4 +1,4 @@
-public trait TestTrait {
+public interface TestTrait {
     public fun f()
 }
 
diff --git a/idea/testData/copyPaste/imports/AlreadyImportedViaStar.kt b/idea/testData/copyPaste/imports/AlreadyImportedViaStar.kt
index ef05dbc04da..cff68a00a82 100644
--- a/idea/testData/copyPaste/imports/AlreadyImportedViaStar.kt
+++ b/idea/testData/copyPaste/imports/AlreadyImportedViaStar.kt
@@ -3,7 +3,7 @@ package a
 import a.E.ENTRY
 import a.Outer.*
 
-trait T
+interface T
 
 class A(i: Int) {}
 
@@ -34,7 +34,7 @@ class Outer {
     }
     object NestedObj {
     }
-    trait NestedTrait {
+    interface NestedTrait {
     }
     annotation class NestedAnnotation
 }
diff --git a/idea/testData/copyPaste/imports/ClassObject.kt b/idea/testData/copyPaste/imports/ClassObject.kt
index 5ddaa580eb4..9bd4c729e97 100644
--- a/idea/testData/copyPaste/imports/ClassObject.kt
+++ b/idea/testData/copyPaste/imports/ClassObject.kt
@@ -1,6 +1,6 @@
 package a
 
-trait T
+interface T
 
 class A {
     companion object: T {
diff --git a/idea/testData/copyPaste/imports/ClassObjectInner.kt b/idea/testData/copyPaste/imports/ClassObjectInner.kt
index 89f98639734..29811208d46 100644
--- a/idea/testData/copyPaste/imports/ClassObjectInner.kt
+++ b/idea/testData/copyPaste/imports/ClassObjectInner.kt
@@ -14,7 +14,7 @@ class Outer {
         }
         object NestedObj {
         }
-        trait NestedTrait {
+        interface NestedTrait {
         }
         annotation class NestedAnnotation
     }
diff --git a/idea/testData/copyPaste/imports/DelegatedProperty.kt b/idea/testData/copyPaste/imports/DelegatedProperty.kt
index b6514a872f9..c0afed6f5d4 100644
--- a/idea/testData/copyPaste/imports/DelegatedProperty.kt
+++ b/idea/testData/copyPaste/imports/DelegatedProperty.kt
@@ -1,7 +1,7 @@
 // NO_ERRORS_DUMP
 package a
 
-trait T
+interface T
 
 fun T.get(thisRef: B, desc: PropertyMetadata): Int {
     return 3
diff --git a/idea/testData/copyPaste/imports/ImportDependency.dependency.kt b/idea/testData/copyPaste/imports/ImportDependency.dependency.kt
index 58f4653dedb..a0018009b4d 100644
--- a/idea/testData/copyPaste/imports/ImportDependency.dependency.kt
+++ b/idea/testData/copyPaste/imports/ImportDependency.dependency.kt
@@ -1,6 +1,6 @@
 package d
 
-trait T
+interface T
 
 class A(i: Int) {}
 
@@ -31,7 +31,7 @@ class Outer {
     }
     object NestedObj {
     }
-    trait NestedTrait {
+    interface NestedTrait {
     }
     annotation class NestedAnnotation
 }
diff --git a/idea/testData/copyPaste/imports/ImportedElementCopied.expected.kt b/idea/testData/copyPaste/imports/ImportedElementCopied.expected.kt
index fa1bb63cb62..8863764d732 100644
--- a/idea/testData/copyPaste/imports/ImportedElementCopied.expected.kt
+++ b/idea/testData/copyPaste/imports/ImportedElementCopied.expected.kt
@@ -15,7 +15,7 @@ class Outer {
     }
     object NestedObj {
     }
-    trait NestedTrait {
+    interface NestedTrait {
     }
     annotation class NestedAnnotation
 }
diff --git a/idea/testData/copyPaste/imports/ImportedElementCopied.kt b/idea/testData/copyPaste/imports/ImportedElementCopied.kt
index c629bab0b23..4cb4a04dc71 100644
--- a/idea/testData/copyPaste/imports/ImportedElementCopied.kt
+++ b/idea/testData/copyPaste/imports/ImportedElementCopied.kt
@@ -16,7 +16,7 @@ import a.E.ENTRY
     }
     object NestedObj {
     }
-    trait NestedTrait {
+    interface NestedTrait {
     }
     annotation class NestedAnnotation
 }
diff --git a/idea/testData/copyPaste/imports/Inner.kt b/idea/testData/copyPaste/imports/Inner.kt
index 0558599edd8..b51d9ea6b8f 100644
--- a/idea/testData/copyPaste/imports/Inner.kt
+++ b/idea/testData/copyPaste/imports/Inner.kt
@@ -13,7 +13,7 @@ class Outer {
     }
     object NestedObj {
     }
-    trait NestedTrait {
+    interface NestedTrait {
     }
     annotation class NestedAnnotation
 }
diff --git a/idea/testData/copyPaste/imports/KotlinLibrary/Dependency.kt b/idea/testData/copyPaste/imports/KotlinLibrary/Dependency.kt
index 695460c1f34..888bbb3f059 100644
--- a/idea/testData/copyPaste/imports/KotlinLibrary/Dependency.kt
+++ b/idea/testData/copyPaste/imports/KotlinLibrary/Dependency.kt
@@ -1,6 +1,6 @@
 package d
 
-trait T
+interface T
 
 class A(i: Int) {}
 
@@ -32,7 +32,7 @@ class Outer {
     }
     object NestedObj {
     }
-    trait NestedTrait {
+    interface NestedTrait {
     }
     annotation class NestedAnnotation
 }
diff --git a/idea/testData/copyPaste/imports/NoImportForSamePackage.kt b/idea/testData/copyPaste/imports/NoImportForSamePackage.kt
index 2db5f8d6fc7..25d3c09b8b1 100644
--- a/idea/testData/copyPaste/imports/NoImportForSamePackage.kt
+++ b/idea/testData/copyPaste/imports/NoImportForSamePackage.kt
@@ -3,7 +3,7 @@ package a
 import a.E.ENTRY
 import a.Outer.*
 
-trait T
+interface T
 
 class A(i: Int) {}
 
@@ -34,7 +34,7 @@ class Outer {
     }
     object NestedObj {
     }
-    trait NestedTrait {
+    interface NestedTrait {
     }
     annotation class NestedAnnotation
 }
diff --git a/idea/testData/copyPaste/imports/Object.kt b/idea/testData/copyPaste/imports/Object.kt
index d19f74f47fe..789ba3ddd69 100644
--- a/idea/testData/copyPaste/imports/Object.kt
+++ b/idea/testData/copyPaste/imports/Object.kt
@@ -4,7 +4,7 @@ object B {
     fun f()
 }
 
-trait T
+interface T
 
 object A: T {
 }
diff --git a/idea/testData/copyPaste/imports/ReferencedElementAlsoCopied.expected.kt b/idea/testData/copyPaste/imports/ReferencedElementAlsoCopied.expected.kt
index 7ec846954d6..4cdac29413c 100644
--- a/idea/testData/copyPaste/imports/ReferencedElementAlsoCopied.expected.kt
+++ b/idea/testData/copyPaste/imports/ReferencedElementAlsoCopied.expected.kt
@@ -2,7 +2,7 @@
 // ERROR: Function 'ext' must have a body
 package to
 
-trait T
+interface T
 
 class A(i: Int) {}
 
diff --git a/idea/testData/copyPaste/imports/ReferencedElementAlsoCopied.kt b/idea/testData/copyPaste/imports/ReferencedElementAlsoCopied.kt
index 06d895dc4f3..0b4903a7270 100644
--- a/idea/testData/copyPaste/imports/ReferencedElementAlsoCopied.kt
+++ b/idea/testData/copyPaste/imports/ReferencedElementAlsoCopied.kt
@@ -1,6 +1,6 @@
 package a
 
-<selection>trait T
+<selection>interface T
 
 class A(i: Int) {}
 
diff --git a/idea/testData/copyPaste/imports/Trait.kt b/idea/testData/copyPaste/imports/Trait.kt
index 80d27f9d783..fcab8fe685f 100644
--- a/idea/testData/copyPaste/imports/Trait.kt
+++ b/idea/testData/copyPaste/imports/Trait.kt
@@ -1,5 +1,5 @@
 package a
 
-trait A
+interface A
 
 <selection>class C(): A {}</selection>
\ No newline at end of file
diff --git a/idea/testData/copyPaste/imports/TypeParameter.kt b/idea/testData/copyPaste/imports/TypeParameter.kt
index 189d4349e56..9610d532c18 100644
--- a/idea/testData/copyPaste/imports/TypeParameter.kt
+++ b/idea/testData/copyPaste/imports/TypeParameter.kt
@@ -2,6 +2,6 @@ package a
 
 class A {}
 
-trait T<H>
+interface T<H>
 
 <selection>fun f(): T<A></selection>
diff --git a/idea/testData/debugger/positionManager/classObject.kt b/idea/testData/debugger/positionManager/classObject.kt
index 12fa25440b8..ac20e62c6a3 100644
--- a/idea/testData/debugger/positionManager/classObject.kt
+++ b/idea/testData/debugger/positionManager/classObject.kt
@@ -36,7 +36,7 @@ class A {
     }
 }
 
-trait T {
+interface T {
     companion object {
         val prop = 1 // T\$Companion
     }
diff --git a/idea/testData/debugger/positionManager/trait.kt b/idea/testData/debugger/positionManager/trait.kt
index a8df4a5355c..523d57442ba 100644
--- a/idea/testData/debugger/positionManager/trait.kt
+++ b/idea/testData/debugger/positionManager/trait.kt
@@ -1,4 +1,4 @@
-trait A {
+interface A {
     fun foo() {
         ""   // A\$\$TImpl
     }
diff --git a/idea/testData/debugger/tinyApp/outs/evSkipAnonymousObject.out b/idea/testData/debugger/tinyApp/outs/evSkipAnonymousObject.out
index 9427a38c98d..9833ee21b85 100644
--- a/idea/testData/debugger/tinyApp/outs/evSkipAnonymousObject.out
+++ b/idea/testData/debugger/tinyApp/outs/evSkipAnonymousObject.out
@@ -21,7 +21,7 @@ fun main(args: Array<String>) {
     }
 }
 
-trait T {
+interface T {
     fun f() {}
 }
 
diff --git a/idea/testData/debugger/tinyApp/src/evaluate/singleBreakpoint/compilingEvaluator/ceObject.kt b/idea/testData/debugger/tinyApp/src/evaluate/singleBreakpoint/compilingEvaluator/ceObject.kt
index 9a298af3791..4bb883a8815 100644
--- a/idea/testData/debugger/tinyApp/src/evaluate/singleBreakpoint/compilingEvaluator/ceObject.kt
+++ b/idea/testData/debugger/tinyApp/src/evaluate/singleBreakpoint/compilingEvaluator/ceObject.kt
@@ -5,7 +5,7 @@ fun main(args: Array<String>) {
     args.size()
 }
 
-trait T {
+interface T {
     fun test() = 1
 }
 
diff --git a/idea/testData/debugger/tinyApp/src/evaluate/singleBreakpoint/extraVariables/evSkipAnonymousObject.kt b/idea/testData/debugger/tinyApp/src/evaluate/singleBreakpoint/extraVariables/evSkipAnonymousObject.kt
index c40960a231b..ab92ed3d50f 100644
--- a/idea/testData/debugger/tinyApp/src/evaluate/singleBreakpoint/extraVariables/evSkipAnonymousObject.kt
+++ b/idea/testData/debugger/tinyApp/src/evaluate/singleBreakpoint/extraVariables/evSkipAnonymousObject.kt
@@ -17,7 +17,7 @@ fun main(args: Array<String>) {
     }
 }
 
-trait T {
+interface T {
     fun f() {}
 }
 
diff --git a/idea/testData/debugger/tinyApp/src/evaluate/singleBreakpoint/extractThisInTrait.kt b/idea/testData/debugger/tinyApp/src/evaluate/singleBreakpoint/extractThisInTrait.kt
index ab302df9776..76959e025c3 100644
--- a/idea/testData/debugger/tinyApp/src/evaluate/singleBreakpoint/extractThisInTrait.kt
+++ b/idea/testData/debugger/tinyApp/src/evaluate/singleBreakpoint/extractThisInTrait.kt
@@ -4,7 +4,7 @@ fun main(args: Array<String>) {
     TImpl().foo()
 }
 
-trait T {
+interface T {
     fun foo() {
         //Breakpoint!
         val a = 1
diff --git a/idea/testData/decompiler/decompiledText/Enum/Dependency.kt b/idea/testData/decompiler/decompiledText/Enum/Dependency.kt
index 1a3c2a306f0..7320ba22720 100644
--- a/idea/testData/decompiler/decompiledText/Enum/Dependency.kt
+++ b/idea/testData/decompiler/decompiledText/Enum/Dependency.kt
@@ -1,6 +1,6 @@
 package dependency
 
-trait Tr {
+interface Tr {
     fun f() {
     }
 }
diff --git a/idea/testData/decompiler/decompiledText/SimpleClass/Dependency.kt b/idea/testData/decompiler/decompiledText/SimpleClass/Dependency.kt
index 56b902d82e9..21f48f6adcf 100644
--- a/idea/testData/decompiler/decompiledText/SimpleClass/Dependency.kt
+++ b/idea/testData/decompiler/decompiledText/SimpleClass/Dependency.kt
@@ -9,5 +9,5 @@ class A {
 open class D<T, G> {
 }
 
-trait Tr {
+interface Tr {
 }
diff --git a/idea/testData/decompiler/decompiledText/TestPackage/TestPackage.kt b/idea/testData/decompiler/decompiledText/TestPackage/TestPackage.kt
index c730cdee046..e841d262004 100644
--- a/idea/testData/decompiler/decompiledText/TestPackage/TestPackage.kt
+++ b/idea/testData/decompiler/decompiledText/TestPackage/TestPackage.kt
@@ -7,4 +7,4 @@ private var i = 2
 fun Int.plus(i: Int = 1) = this + i
 
 class ShouldNotBeVisible1
-trait ShouldNotBeVisible2
+interface ShouldNotBeVisible2
diff --git a/idea/testData/decompiler/internalClasses/InternalClasses.kt b/idea/testData/decompiler/internalClasses/InternalClasses.kt
index 0c904821719..aeae7c383ae 100644
--- a/idea/testData/decompiler/internalClasses/InternalClasses.kt
+++ b/idea/testData/decompiler/internalClasses/InternalClasses.kt
@@ -1,13 +1,13 @@
 package test
 
-trait T {
+interface T {
     fun foo() {
     }
 
     fun boo()
 }
 
-trait TT : T {
+interface TT : T {
 }
 
 fun f() {
@@ -23,7 +23,7 @@ fun f() {
     class MyLocalClass {
     }
 
-    trait MyLocalTrait {
+    interface MyLocalTrait {
     }
 
     val myAnonymousObject = object {
diff --git a/idea/testData/decompiler/navigation/library/main.kt b/idea/testData/decompiler/navigation/library/main.kt
index 913ba00a9cd..38b0f29eae8 100644
--- a/idea/testData/decompiler/navigation/library/main.kt
+++ b/idea/testData/decompiler/navigation/library/main.kt
@@ -1,6 +1,6 @@
 package testData.libraries
 
-public trait SimpleTrait {
+public interface SimpleTrait {
 }
 
 public class SimpleClass {
@@ -16,7 +16,7 @@ public class WithInnerAndObject {
     }
 
     class MyInner {
-        trait MyInnerInner {
+        interface MyInnerInner {
             fun innerInnerMethod()
         }
     }
diff --git a/idea/testData/decompiler/stubBuilder/Delegation/Delegation.kt b/idea/testData/decompiler/stubBuilder/Delegation/Delegation.kt
index e1aba835399..e89e93081f3 100644
--- a/idea/testData/decompiler/stubBuilder/Delegation/Delegation.kt
+++ b/idea/testData/decompiler/stubBuilder/Delegation/Delegation.kt
@@ -1,4 +1,4 @@
-trait T {
+interface T {
     fun f()
     val g: Int
 }
diff --git a/idea/testData/decompiler/stubBuilder/InheritingClasses/InheritingClasses.kt b/idea/testData/decompiler/stubBuilder/InheritingClasses/InheritingClasses.kt
index 131899cb4ab..ff708140bb3 100644
--- a/idea/testData/decompiler/stubBuilder/InheritingClasses/InheritingClasses.kt
+++ b/idea/testData/decompiler/stubBuilder/InheritingClasses/InheritingClasses.kt
@@ -15,21 +15,21 @@ class InheritingClasses {
         override val ap = 5
     }
 
-    trait C {
+    interface C {
         val c: Int
     }
 
-    trait D<T> : C {
+    interface D<T> : C {
         override val c: Int
     }
 
-    trait E
+    interface E
     class G : B(), C, D<Int>, E
 
 
     class InheritAny {
-        trait SomeTrait
-        trait SomeTrait2
+        interface SomeTrait
+        interface SomeTrait2
 
         class ImplicitAny
 
diff --git a/idea/testData/decompiler/stubBuilder/Objects/Objects.kt b/idea/testData/decompiler/stubBuilder/Objects/Objects.kt
index 2641be53fce..e394c177618 100644
--- a/idea/testData/decompiler/stubBuilder/Objects/Objects.kt
+++ b/idea/testData/decompiler/stubBuilder/Objects/Objects.kt
@@ -25,5 +25,5 @@ public object Objects {
 
 }
 
-trait A {
+interface A {
 }
\ No newline at end of file
diff --git a/idea/testData/decompiler/stubBuilder/TypeBoundsAndDelegationSpecifiers/TypeBoundsAndDelegationSpecifiers.kt b/idea/testData/decompiler/stubBuilder/TypeBoundsAndDelegationSpecifiers/TypeBoundsAndDelegationSpecifiers.kt
index 07611293f03..6dc5c88fc3f 100644
--- a/idea/testData/decompiler/stubBuilder/TypeBoundsAndDelegationSpecifiers/TypeBoundsAndDelegationSpecifiers.kt
+++ b/idea/testData/decompiler/stubBuilder/TypeBoundsAndDelegationSpecifiers/TypeBoundsAndDelegationSpecifiers.kt
@@ -1,6 +1,6 @@
 package test
 
 open class A
-trait T
+interface T
 
 class TypeBoundsAndDelegationSpecifiers<H : Any?, G : Any, C: T>() : A(), T where H : List<String>, G : CharSequence, C: Any?
\ No newline at end of file
diff --git a/idea/testData/diagnosticMessage/cannotInferVisibility.kt b/idea/testData/diagnosticMessage/cannotInferVisibility.kt
index 9c492cfa864..cbff2dd0641 100644
--- a/idea/testData/diagnosticMessage/cannotInferVisibility.kt
+++ b/idea/testData/diagnosticMessage/cannotInferVisibility.kt
@@ -1,12 +1,12 @@
 // !DIAGNOSTICS_NUMBER: 1
 // !DIAGNOSTICS: CANNOT_INFER_VISIBILITY
 
-trait T {
+interface T {
     internal val foo: String
 }
 
-trait U {
+interface U {
     protected val foo: String
 }
 
-trait V : T, U
+interface V : T, U
diff --git a/idea/testData/diagnosticMessage/differentNamesForSameParameter.kt b/idea/testData/diagnosticMessage/differentNamesForSameParameter.kt
index 2068868b42b..77494e75958 100644
--- a/idea/testData/diagnosticMessage/differentNamesForSameParameter.kt
+++ b/idea/testData/diagnosticMessage/differentNamesForSameParameter.kt
@@ -1,11 +1,11 @@
 // !DIAGNOSTICS_NUMBER: 1
 // !DIAGNOSTICS: DIFFERENT_NAMES_FOR_THE_SAME_PARAMETER_IN_SUPERTYPES
 
-trait A {
+interface A {
     fun foo(x: Int)
 }
 
-trait B {
+interface B {
     fun foo(y: Int) {}
 }
 
diff --git a/idea/testData/diagnosticMessage/multipleDefaultsFromSupertypes.kt b/idea/testData/diagnosticMessage/multipleDefaultsFromSupertypes.kt
index f2fee385486..ad62666451f 100644
--- a/idea/testData/diagnosticMessage/multipleDefaultsFromSupertypes.kt
+++ b/idea/testData/diagnosticMessage/multipleDefaultsFromSupertypes.kt
@@ -1,11 +1,11 @@
 // !DIAGNOSTICS_NUMBER: 1
 // !DIAGNOSTICS: MULTIPLE_DEFAULTS_INHERITED_FROM_SUPERTYPES_WHEN_NO_EXPLICIT_OVERRIDE
 
-trait C {
+interface C {
     fun foo(x: Int = 42)
 }
 
-trait D {
+interface D {
     fun foo(x: Int = 239) {}
 }
 
diff --git a/idea/testData/diagnosticMessage/typeMismatchWithNothing.kt b/idea/testData/diagnosticMessage/typeMismatchWithNothing.kt
index cd0eb14154f..2d15094f53b 100644
--- a/idea/testData/diagnosticMessage/typeMismatchWithNothing.kt
+++ b/idea/testData/diagnosticMessage/typeMismatchWithNothing.kt
@@ -3,7 +3,7 @@
 
 package b
 
-trait A<T>
+interface A<T>
 
 fun infer<T>(a: A<T>) : T {}
 
diff --git a/idea/testData/diagnosticMessage/upperBoundViolated.kt b/idea/testData/diagnosticMessage/upperBoundViolated.kt
index 1ac0c1beadd..911ff178dc6 100644
--- a/idea/testData/diagnosticMessage/upperBoundViolated.kt
+++ b/idea/testData/diagnosticMessage/upperBoundViolated.kt
@@ -18,7 +18,7 @@ fun test2(a: Any, s: MutableSet<String>) {
 }
 
 //--------------
-trait A
+interface A
 class B
 
 fun baz<T: R, R: B>(t: T, r: R) where T: A {
diff --git a/idea/testData/diagnosticMessage/wrongReturnTypeInImplementation.kt b/idea/testData/diagnosticMessage/wrongReturnTypeInImplementation.kt
index 6870ed12458..40dd0987d70 100644
--- a/idea/testData/diagnosticMessage/wrongReturnTypeInImplementation.kt
+++ b/idea/testData/diagnosticMessage/wrongReturnTypeInImplementation.kt
@@ -2,21 +2,21 @@
 // !DIAGNOSTICS: ABSTRACT_MEMBER_NOT_IMPLEMENTED
 // !MESSAGE_TYPE: TEXT
 
-trait T1
-trait T2 : T1
-trait T3 : T2
-trait T4 : T3
+interface T1
+interface T2 : T1
+interface T3 : T2
+interface T4 : T3
 
 
-trait A {
+interface A {
     fun f(): T1
 }
 
-trait B {
+interface B {
     fun f(): T2 = null!!
 }
 
-trait C {
+interface C {
     fun f(): T3
 }
 
diff --git a/idea/testData/editor/optimizeImports/ClassMemberImported.dependency.kt b/idea/testData/editor/optimizeImports/ClassMemberImported.dependency.kt
index c8ed1576230..3075855c30c 100644
--- a/idea/testData/editor/optimizeImports/ClassMemberImported.dependency.kt
+++ b/idea/testData/editor/optimizeImports/ClassMemberImported.dependency.kt
@@ -7,7 +7,7 @@ class A {
     val p: Int = 1
 }
 
-trait T {
+interface T {
     fun f() {
     }
 
diff --git a/idea/testData/editor/quickDoc/AtTypeParameter.kt b/idea/testData/editor/quickDoc/AtTypeParameter.kt
index ed345b8ddca..a3642f959d5 100644
--- a/idea/testData/editor/quickDoc/AtTypeParameter.kt
+++ b/idea/testData/editor/quickDoc/AtTypeParameter.kt
@@ -1,4 +1,4 @@
-trait Base
+interface Base
 
 class Some<<caret>T: Base>
 
diff --git a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedAnonymousObjects.1.kt b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedAnonymousObjects.1.kt
index 35dbdffe237..386692d974e 100644
--- a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedAnonymousObjects.1.kt
+++ b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedAnonymousObjects.1.kt
@@ -1,5 +1,5 @@
 fun foo() {
-    public trait T: A
+    public interface T: A
 
     val a = object: A() {}
 
diff --git a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedAnonymousObjects.results.txt b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedAnonymousObjects.results.txt
index 70b82fb30aa..2b9e026c1e5 100644
--- a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedAnonymousObjects.results.txt
+++ b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedAnonymousObjects.results.txt
@@ -1,3 +1,3 @@
-Unclassified usage (2: 18) public trait T: A
+Unclassified usage (2: 22) public interface T: A
 Unclassified usage (4: 13) val a = object: A() {}
 Unclassified usage (7: 17) val b = object: T {}
diff --git a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedClasses.1.kt b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedClasses.1.kt
index f2c78275033..4104284f814 100644
--- a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedClasses.1.kt
+++ b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedClasses.1.kt
@@ -1,6 +1,6 @@
 public open class X: A()
 
-public trait T: A
+public interface T: A
 
 public open class Y: X()
 
diff --git a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedClasses.results.txt b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedClasses.results.txt
index e2533a0dcec..2e3cceba574 100644
--- a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedClasses.results.txt
+++ b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedClasses.results.txt
@@ -1,4 +1,4 @@
 Unclassified usage (1: 19) public open class X: A()
-Unclassified usage (3: 14) public trait T: A
+Unclassified usage (3: 18) public interface T: A
 Unclassified usage (5: 19) public open class Y: X()
 Unclassified usage (7: 14) public class Z: Y(), T
\ No newline at end of file
diff --git a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedInnerClasses.1.kt b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedInnerClasses.1.kt
index 87d94664872..5fccc5b6f54 100644
--- a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedInnerClasses.1.kt
+++ b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedInnerClasses.1.kt
@@ -1,7 +1,7 @@
 public class Outer {
     public open class X: A()
 
-    public trait T: A
+    public interface T: A
 
     public class Inner {
         public open class Y: X()
diff --git a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedInnerClasses.results.txt b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedInnerClasses.results.txt
index e2b3a4004ec..80894b874eb 100644
--- a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedInnerClasses.results.txt
+++ b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedInnerClasses.results.txt
@@ -1,4 +1,4 @@
 Unclassified usage (2: 23) public open class X: A()
-Unclassified usage (4: 18) public trait T: A
+Unclassified usage (4: 22) public interface T: A
 Unclassified usage (7: 27) public open class Y: X()
 Unclassified usage (9: 22) public class Z: Y(), T
\ No newline at end of file
diff --git a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedInnerObjects.1.kt b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedInnerObjects.1.kt
index 74a3ce6c01f..2f82152baac 100644
--- a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedInnerObjects.1.kt
+++ b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedInnerObjects.1.kt
@@ -1,5 +1,5 @@
 class Outer {
-    public trait T: A
+    public interface T: A
 
     public object O1: A()
 
diff --git a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedInnerObjects.results.txt b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedInnerObjects.results.txt
index 72eb88703d0..d4f5c49bdab 100644
--- a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedInnerObjects.results.txt
+++ b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedInnerObjects.results.txt
@@ -1,3 +1,3 @@
-Unclassified usage (2: 18) public trait T: A
+Unclassified usage (2: 22) public interface T: A
 Unclassified usage (4: 19) public object O1: A()
 Unclassified usage (7: 23) public object O2: T
diff --git a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedLocalClasses.1.kt b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedLocalClasses.1.kt
index ec54897132a..cece5ceb989 100644
--- a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedLocalClasses.1.kt
+++ b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedLocalClasses.1.kt
@@ -1,7 +1,7 @@
 fun foo() {
     public open class X: A()
 
-    public trait T: A
+    public interface T: A
 
     fun bar() {
         public open class Y: X()
diff --git a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedLocalClasses.results.txt b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedLocalClasses.results.txt
index e2b3a4004ec..80894b874eb 100644
--- a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedLocalClasses.results.txt
+++ b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedLocalClasses.results.txt
@@ -1,4 +1,4 @@
 Unclassified usage (2: 23) public open class X: A()
-Unclassified usage (4: 18) public trait T: A
+Unclassified usage (4: 22) public interface T: A
 Unclassified usage (7: 27) public open class Y: X()
 Unclassified usage (9: 22) public class Z: Y(), T
\ No newline at end of file
diff --git a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedLocalObjects.1.kt b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedLocalObjects.1.kt
index 5fc78ea5233..17a5608024e 100644
--- a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedLocalObjects.1.kt
+++ b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedLocalObjects.1.kt
@@ -1,5 +1,5 @@
 fun foo() {
-    public trait T: A
+    public interface T: A
 
     public object O1: A()
 
diff --git a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedLocalObjects.results.txt b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedLocalObjects.results.txt
index 8164858751b..6de4df280eb 100644
--- a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedLocalObjects.results.txt
+++ b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedLocalObjects.results.txt
@@ -1,3 +1,3 @@
-Unclassified usage (2: 18) public trait T: A
+Unclassified usage (2: 22) public interface T: A
 Unclassified usage (4: 19) public object O1: A()
 Unclassified usage (7: 23) public object O2: T
\ No newline at end of file
diff --git a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedObjects.1.kt b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedObjects.1.kt
index 578ead6ed0c..b2d11e21dcb 100644
--- a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedObjects.1.kt
+++ b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedObjects.1.kt
@@ -1,4 +1,4 @@
-public trait T: A
+public interface T: A
 
 public object O1: A()
 
diff --git a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedObjects.results.txt b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedObjects.results.txt
index ab975e9c7a6..a78529186ce 100644
--- a/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedObjects.results.txt
+++ b/idea/testData/findUsages/java/findJavaClassUsages/JKClassDerivedObjects.results.txt
@@ -1,3 +1,3 @@
-Unclassified usage (1: 14) public trait T: A
+Unclassified usage (1: 18) public interface T: A
 Unclassified usage (3: 15) public object O1: A()
 Unclassified usage (5: 15) public object O2: T
diff --git a/idea/testData/findUsages/java/findJavaClassUsages/JKDerivedInterfaces.1.kt b/idea/testData/findUsages/java/findJavaClassUsages/JKDerivedInterfaces.1.kt
index ba62e0e2d65..13d8c7eb572 100644
--- a/idea/testData/findUsages/java/findJavaClassUsages/JKDerivedInterfaces.1.kt
+++ b/idea/testData/findUsages/java/findJavaClassUsages/JKDerivedInterfaces.1.kt
@@ -1,6 +1,6 @@
 public open class X: A
 
-public trait T: A
+public interface T: A
 
 public open class Y: X()
 
diff --git a/idea/testData/findUsages/java/findJavaClassUsages/JKDerivedInterfaces.results.txt b/idea/testData/findUsages/java/findJavaClassUsages/JKDerivedInterfaces.results.txt
index 1e3df9c4b34..3dc3b840f90 100644
--- a/idea/testData/findUsages/java/findJavaClassUsages/JKDerivedInterfaces.results.txt
+++ b/idea/testData/findUsages/java/findJavaClassUsages/JKDerivedInterfaces.results.txt
@@ -1 +1 @@
-Unclassified usage (3: 14) public trait T: A
+Unclassified usage (3: 18) public interface T: A
diff --git a/idea/testData/findUsages/java/findJavaClassUsages/JKInterfaceDerivedClasses.1.kt b/idea/testData/findUsages/java/findJavaClassUsages/JKInterfaceDerivedClasses.1.kt
index c1667fea80b..d5c5bca2cc9 100644
--- a/idea/testData/findUsages/java/findJavaClassUsages/JKInterfaceDerivedClasses.1.kt
+++ b/idea/testData/findUsages/java/findJavaClassUsages/JKInterfaceDerivedClasses.1.kt
@@ -1,6 +1,6 @@
 public open class X: A
 
-public trait T: A
+public interface T: A
 
 public open class Y: X()
 
diff --git a/idea/testData/findUsages/java/findJavaClassUsages/JKInterfaceDerivedInnerClasses.1.kt b/idea/testData/findUsages/java/findJavaClassUsages/JKInterfaceDerivedInnerClasses.1.kt
index 895e3c0e23f..7cd33542407 100644
--- a/idea/testData/findUsages/java/findJavaClassUsages/JKInterfaceDerivedInnerClasses.1.kt
+++ b/idea/testData/findUsages/java/findJavaClassUsages/JKInterfaceDerivedInnerClasses.1.kt
@@ -1,7 +1,7 @@
 class Outer {
     public open class X: A
 
-    public trait T: A
+    public interface T: A
 
     class Inner {
         public open class Y: X()
diff --git a/idea/testData/findUsages/java/findJavaClassUsages/JKInterfaceDerivedLocalClasses.1.kt b/idea/testData/findUsages/java/findJavaClassUsages/JKInterfaceDerivedLocalClasses.1.kt
index b907024a4a4..f65aee928e9 100644
--- a/idea/testData/findUsages/java/findJavaClassUsages/JKInterfaceDerivedLocalClasses.1.kt
+++ b/idea/testData/findUsages/java/findJavaClassUsages/JKInterfaceDerivedLocalClasses.1.kt
@@ -1,7 +1,7 @@
 fun foo() {
     open class X: A
 
-    trait T: A
+    interface T: A
 
     fun bar() {
         public open class Y: X()
diff --git a/idea/testData/findUsages/java/findJavaClassUsages/JKInterfaceDerivedLocalTraits.1.kt b/idea/testData/findUsages/java/findJavaClassUsages/JKInterfaceDerivedLocalTraits.1.kt
index f08f80d10c8..fd08ad4962f 100644
--- a/idea/testData/findUsages/java/findJavaClassUsages/JKInterfaceDerivedLocalTraits.1.kt
+++ b/idea/testData/findUsages/java/findJavaClassUsages/JKInterfaceDerivedLocalTraits.1.kt
@@ -1,10 +1,10 @@
 fun foo() {
     open class X: A
 
-    trait T: A
+    interface T: A
 
     fun bar() {
-        public trait Y: X
+        public interface Y: X
 
         public class Z: T
     }
diff --git a/idea/testData/findUsages/java/findJavaClassUsages/JKInterfaceDerivedLocalTraits.results.txt b/idea/testData/findUsages/java/findJavaClassUsages/JKInterfaceDerivedLocalTraits.results.txt
index 1789eae5c71..de9b8cac3b0 100644
--- a/idea/testData/findUsages/java/findJavaClassUsages/JKInterfaceDerivedLocalTraits.results.txt
+++ b/idea/testData/findUsages/java/findJavaClassUsages/JKInterfaceDerivedLocalTraits.results.txt
@@ -1,2 +1,2 @@
-Unclassified usage (4: 11) trait T: A
-Unclassified usage (7: 22) public trait Y: X
+Unclassified usage (4: 15) interface T: A
+Unclassified usage (7: 26) public interface Y: X
\ No newline at end of file
diff --git a/idea/testData/findUsages/kotlin/defaultObject/inContainingClass.0.kt b/idea/testData/findUsages/kotlin/defaultObject/inContainingClass.0.kt
index 01b3633b51b..377107f20f5 100644
--- a/idea/testData/findUsages/kotlin/defaultObject/inContainingClass.0.kt
+++ b/idea/testData/findUsages/kotlin/defaultObject/inContainingClass.0.kt
@@ -20,7 +20,7 @@ class A() {
     }
 }
 
-trait Foo
+interface Foo
 
 fun Foo.ext() {
 }
\ No newline at end of file
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/javaClassFunctionUsages1.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/javaClassFunctionUsages1.0.kt
index 958adb73294..5d7853e4497 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/javaClassFunctionUsages1.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/javaClassFunctionUsages1.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: functionUsages
-trait <caret>X {
+interface <caret>X {
     val a: String
         get() {
             return ""
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/javaClassFunctionUsages2.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/javaClassFunctionUsages2.0.kt
index 4029acdbc7c..0ff4e915370 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/javaClassFunctionUsages2.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/javaClassFunctionUsages2.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: functionUsages
-trait X {
+interface X {
     val a: String
         get() {
             return ""
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/javaClassPropertyUsages1.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/javaClassPropertyUsages1.0.kt
index a679467e9fe..3e7d8bba585 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/javaClassPropertyUsages1.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/javaClassPropertyUsages1.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: propertyUsages
-trait <caret>X {
+interface <caret>X {
     val a: String
         get() {
             return ""
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/javaClassPropertyUsages2.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/javaClassPropertyUsages2.0.kt
index 470c607af57..1d1e982d9b7 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/javaClassPropertyUsages2.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/javaClassPropertyUsages2.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: propertyUsages
-trait X {
+interface X {
     val a: String
         get() {
             return ""
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/javaDerivedClassUsages1.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/javaDerivedClassUsages1.0.kt
index d63c8301fd4..16ef0bbc6e5 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/javaDerivedClassUsages1.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/javaDerivedClassUsages1.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: derivedClasses
-trait X {
+interface X {
 
 }
 
@@ -12,6 +12,6 @@ open class C: Y {
 
 }
 
-trait Z: A {
+interface Z: A {
 
 }
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/javaDerivedClassUsages2.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/javaDerivedClassUsages2.0.kt
index 47aac1897e5..cf578df3dd3 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/javaDerivedClassUsages2.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/javaDerivedClassUsages2.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: derivedClasses
-trait <caret>X {
+interface <caret>X {
 
 }
 
@@ -12,6 +12,6 @@ open class C: Y {
 
 }
 
-trait Z: A {
+interface Z: A {
 
 }
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/javaDerivedInterfaceUsages1.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/javaDerivedInterfaceUsages1.0.kt
index 8cef471c8b5..55c3375450b 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/javaDerivedInterfaceUsages1.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/javaDerivedInterfaceUsages1.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: derivedInterfaces
-trait X {
+interface X {
 
 }
 
@@ -12,6 +12,6 @@ open class C: Y {
 
 }
 
-trait Z: A {
+interface Z: A {
 
 }
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/javaDerivedInterfaceUsages1.results.txt b/idea/testData/findUsages/kotlin/findClassUsages/javaDerivedInterfaceUsages1.results.txt
index 3657834e238..ff4aa1e0ee8 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/javaDerivedInterfaceUsages1.results.txt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/javaDerivedInterfaceUsages1.results.txt
@@ -1,2 +1,2 @@
-Unclassified usage (15: 7) trait Z: A {
+Unclassified usage (15: 11) interface Z: A {
 Unclassified usage (9: 11) interface U extends Z {
\ No newline at end of file
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/javaDerivedInterfaceUsages2.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/javaDerivedInterfaceUsages2.0.kt
index 9b664cf0959..d011ec25f37 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/javaDerivedInterfaceUsages2.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/javaDerivedInterfaceUsages2.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: derivedInterfaces
-trait <caret>X {
+interface <caret>X {
 
 }
 
@@ -12,6 +12,6 @@ open class C: Y {
 
 }
 
-trait Z: A {
+interface Z: A {
 
 }
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/javaDerivedInterfaceUsages2.results.txt b/idea/testData/findUsages/kotlin/findClassUsages/javaDerivedInterfaceUsages2.results.txt
index 8317542a628..f65dd90603c 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/javaDerivedInterfaceUsages2.results.txt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/javaDerivedInterfaceUsages2.results.txt
@@ -1,3 +1,3 @@
-Unclassified usage (15: 7) trait Z: A {
+Unclassified usage (15: 11) interface Z: A {
 Unclassified usage (5: 11) interface Y extends X {
 Unclassified usage (9: 11) interface U extends Z {
\ No newline at end of file
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedAnonymousObjects.1.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedAnonymousObjects.1.kt
index 4317e71dedb..73fe03c437f 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedAnonymousObjects.1.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedAnonymousObjects.1.kt
@@ -2,7 +2,7 @@
 // OPTIONS: derivedClasses
 
 fun foo() {
-    trait Z: A {
+    interface Z: A {
 
     }
 
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedClasses.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedClasses.0.kt
index f5dcac0ee45..3920973b60d 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedClasses.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedClasses.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: derivedClasses
-trait X {
+interface X {
 
 }
 
@@ -8,6 +8,6 @@ open class <caret>A: X {
 
 }
 
-trait Y: X {
+interface Y: X {
 
 }
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedClasses.1.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedClasses.1.kt
index 7f4355cfe09..fb35870d282 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedClasses.1.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedClasses.1.kt
@@ -8,10 +8,10 @@ open class C: Y {
 
 }
 
-trait Z: A {
+interface Z: A {
 
 }
 
-trait U: Z {
+interface U: Z {
 
 }
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedInnerClasses.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedInnerClasses.0.kt
index f5dcac0ee45..3920973b60d 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedInnerClasses.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedInnerClasses.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: derivedClasses
-trait X {
+interface X {
 
 }
 
@@ -8,6 +8,6 @@ open class <caret>A: X {
 
 }
 
-trait Y: X {
+interface Y: X {
 
 }
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedInnerClasses.1.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedInnerClasses.1.kt
index 80ac657377b..80b8974d41e 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedInnerClasses.1.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedInnerClasses.1.kt
@@ -10,7 +10,7 @@ class Outer {
     }
 
     class Inner {
-        trait Z: A {
+        interface Z: A {
 
         }
 
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedInnerObjects.1.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedInnerObjects.1.kt
index a920a90b3d2..8d0e2b209c1 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedInnerObjects.1.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedInnerObjects.1.kt
@@ -1,7 +1,7 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: derivedClasses
 class Outer {
-    trait Z: A {
+    interface Z: A {
 
     }
 
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedLocalClasses.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedLocalClasses.0.kt
index f5dcac0ee45..3920973b60d 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedLocalClasses.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedLocalClasses.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: derivedClasses
-trait X {
+interface X {
 
 }
 
@@ -8,6 +8,6 @@ open class <caret>A: X {
 
 }
 
-trait Y: X {
+interface Y: X {
 
 }
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedLocalClasses.1.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedLocalClasses.1.kt
index 6229bad761c..06c5fa971da 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedLocalClasses.1.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedLocalClasses.1.kt
@@ -11,11 +11,11 @@ fun foo() {
     }
 
     fun bar() {
-        trait Z: A {
+        interface Z: A {
 
         }
 
-        trait U: Z {
+        interface U: Z {
 
         }
     }
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedLocalObjects.1.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedLocalObjects.1.kt
index eb3a243887f..286bef41020 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedLocalObjects.1.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedLocalObjects.1.kt
@@ -2,7 +2,7 @@
 // OPTIONS: derivedClasses
 
 fun foo() {
-    trait Z: A {
+    interface Z: A {
 
     }
 
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedLocalTraits.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedLocalTraits.0.kt
index 74cbb2c1bec..d5a620572c7 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedLocalTraits.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedLocalTraits.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: derivedInterfaces
-trait X {
+interface X {
 
 }
 
@@ -8,6 +8,6 @@ open class <caret>A: X {
 
 }
 
-trait Y: X {
+interface Y: X {
 
 }
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedLocalTraits.1.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedLocalTraits.1.kt
index f816abdac1f..31cef5ad423 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedLocalTraits.1.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedLocalTraits.1.kt
@@ -11,11 +11,11 @@ fun foo() {
     }
 
     fun bar() {
-        trait Z: A {
+        interface Z: A {
 
         }
 
-        trait U: Z {
+        interface U: Z {
 
         }
     }
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedLocalTraits.results.txt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedLocalTraits.results.txt
index 50d233927d2..880c25297da 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedLocalTraits.results.txt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedLocalTraits.results.txt
@@ -1,2 +1,2 @@
-Unclassified usage (14: 15) trait Z: A {
-Unclassified usage (18: 15) trait U: Z {
+Unclassified usage (14: 19) interface Z: A {
+Unclassified usage (18: 19) interface U: Z {
\ No newline at end of file
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedObjects.1.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedObjects.1.kt
index f511d58d23f..b8196903dbd 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedObjects.1.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedObjects.1.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: derivedClasses
-trait Z: A {
+interface Z: A {
 
 }
 
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedTraits.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedTraits.0.kt
index 74cbb2c1bec..d5a620572c7 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedTraits.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedTraits.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: derivedInterfaces
-trait X {
+interface X {
 
 }
 
@@ -8,6 +8,6 @@ open class <caret>A: X {
 
 }
 
-trait Y: X {
+interface Y: X {
 
 }
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedTraits.1.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedTraits.1.kt
index 24778a14683..de17d05a4c4 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedTraits.1.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedTraits.1.kt
@@ -8,10 +8,10 @@ open class C: Y {
 
 }
 
-trait Z: A {
+interface Z: A {
 
 }
 
-trait U: Z {
+interface U: Z {
 
 }
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedTraits.results.txt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedTraits.results.txt
index ba47031e7b6..d580ff914b6 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedTraits.results.txt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassDerivedTraits.results.txt
@@ -1,2 +1,2 @@
-Unclassified usage (11: 7) trait Z: A {
-Unclassified usage (15: 7) trait U: Z {
\ No newline at end of file
+Unclassified usage (11: 11) interface Z: A {
+Unclassified usage (15: 11) interface U: Z {
\ No newline at end of file
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassFunctionUsages1.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassFunctionUsages1.0.kt
index 958adb73294..5d7853e4497 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassFunctionUsages1.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassFunctionUsages1.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: functionUsages
-trait <caret>X {
+interface <caret>X {
     val a: String
         get() {
             return ""
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassFunctionUsages2.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassFunctionUsages2.0.kt
index 4029acdbc7c..0ff4e915370 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassFunctionUsages2.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassFunctionUsages2.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: functionUsages
-trait X {
+interface X {
     val a: String
         get() {
             return ""
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassPropertyUsages1.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassPropertyUsages1.0.kt
index a679467e9fe..3e7d8bba585 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassPropertyUsages1.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassPropertyUsages1.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: propertyUsages
-trait <caret>X {
+interface <caret>X {
     val a: String
         get() {
             return ""
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassPropertyUsages2.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassPropertyUsages2.0.kt
index be1a36f0c92..589ee8fe753 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassPropertyUsages2.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinClassPropertyUsages2.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: propertyUsages
-trait X {
+interface X {
     val a: String
         get() {
             return ""
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinLocalClassDerivedAnonymousObjects.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinLocalClassDerivedAnonymousObjects.0.kt
index 75874762760..a4f6cffc80a 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinLocalClassDerivedAnonymousObjects.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinLocalClassDerivedAnonymousObjects.0.kt
@@ -5,7 +5,7 @@ fun foo() {
 
     val b = object: A() {}
 
-    trait T: A
+    interface T: A
 
     fun bar() {
         val c = object: A() {}
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinLocalClassDerivedLocalClasses.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinLocalClassDerivedLocalClasses.0.kt
index 7495c905ad7..1180de75594 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinLocalClassDerivedLocalClasses.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinLocalClassDerivedLocalClasses.0.kt
@@ -5,7 +5,7 @@ fun foo() {
 
     class B: A()
 
-    trait T: A
+    interface T: A
 
     fun bar() {
         class C: A()
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinLocalClassDerivedLocalObjects.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinLocalClassDerivedLocalObjects.0.kt
index a67f7cb548c..132b0d44622 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinLocalClassDerivedLocalObjects.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinLocalClassDerivedLocalObjects.0.kt
@@ -5,7 +5,7 @@ fun foo() {
 
     object B: A()
 
-    trait T: A
+    interface T: A
 
     fun bar() {
         object C: A()
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinLocalClassDerivedLocalTraits.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinLocalClassDerivedLocalTraits.0.kt
index 76ca752c64c..e3c8578657f 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinLocalClassDerivedLocalTraits.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinLocalClassDerivedLocalTraits.0.kt
@@ -3,10 +3,10 @@
 fun foo() {
     open class <caret>A
 
-    trait T: A
+    interface T: A
 
     fun bar() {
-        trait U: T
+        interface U: T
     }
 }
 
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinLocalClassDerivedLocalTraits.results.txt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinLocalClassDerivedLocalTraits.results.txt
index 833f3dde3ca..1937920df81 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinLocalClassDerivedLocalTraits.results.txt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinLocalClassDerivedLocalTraits.results.txt
@@ -1,2 +1,2 @@
-Unclassified usage (6: 11) trait T: A
-Unclassified usage (9: 15) trait U: T
+Unclassified usage (6: 15) interface T: A
+Unclassified usage (9: 19) interface U: T
\ No newline at end of file
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedAnonymousObjects.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedAnonymousObjects.0.kt
index 4adcff251f7..691ee8ca09b 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedAnonymousObjects.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedAnonymousObjects.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: derivedClasses
-trait <caret>X {
+interface <caret>X {
 
 }
 
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedClasses.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedClasses.0.kt
index 65608ebf054..a1bce719774 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedClasses.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedClasses.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: derivedClasses
-trait <caret>X {
+interface <caret>X {
 
 }
 
@@ -8,6 +8,6 @@ open class A: X {
 
 }
 
-trait Y: X {
+interface Y: X {
 
 }
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedClasses.1.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedClasses.1.kt
index 7f4355cfe09..fb35870d282 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedClasses.1.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedClasses.1.kt
@@ -8,10 +8,10 @@ open class C: Y {
 
 }
 
-trait Z: A {
+interface Z: A {
 
 }
 
-trait U: Z {
+interface U: Z {
 
 }
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedInnerClasses.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedInnerClasses.0.kt
index 65608ebf054..a1bce719774 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedInnerClasses.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedInnerClasses.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: derivedClasses
-trait <caret>X {
+interface <caret>X {
 
 }
 
@@ -8,6 +8,6 @@ open class A: X {
 
 }
 
-trait Y: X {
+interface Y: X {
 
 }
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedInnerClasses.1.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedInnerClasses.1.kt
index e796c98dbc5..b1e9f596491 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedInnerClasses.1.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedInnerClasses.1.kt
@@ -10,11 +10,11 @@ class Outer {
     }
 
     class Inner {
-        trait Z: A {
+        interface Z: A {
 
         }
 
-        trait U: Z {
+        interface U: Z {
 
         }
     }
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedInnerObjects.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedInnerObjects.0.kt
index 65608ebf054..a1bce719774 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedInnerObjects.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedInnerObjects.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: derivedClasses
-trait <caret>X {
+interface <caret>X {
 
 }
 
@@ -8,6 +8,6 @@ open class A: X {
 
 }
 
-trait Y: X {
+interface Y: X {
 
 }
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedLocalClasses.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedLocalClasses.0.kt
index 65608ebf054..a1bce719774 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedLocalClasses.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedLocalClasses.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: derivedClasses
-trait <caret>X {
+interface <caret>X {
 
 }
 
@@ -8,6 +8,6 @@ open class A: X {
 
 }
 
-trait Y: X {
+interface Y: X {
 
 }
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedLocalClasses.1.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedLocalClasses.1.kt
index 6229bad761c..06c5fa971da 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedLocalClasses.1.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedLocalClasses.1.kt
@@ -11,11 +11,11 @@ fun foo() {
     }
 
     fun bar() {
-        trait Z: A {
+        interface Z: A {
 
         }
 
-        trait U: Z {
+        interface U: Z {
 
         }
     }
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedLocalObjects.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedLocalObjects.0.kt
index 4adcff251f7..691ee8ca09b 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedLocalObjects.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedLocalObjects.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: derivedClasses
-trait <caret>X {
+interface <caret>X {
 
 }
 
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedLocalTraits.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedLocalTraits.0.kt
index e93929b5426..0f8bb641b28 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedLocalTraits.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedLocalTraits.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: derivedInterfaces
-trait <caret>X {
+interface <caret>X {
 
 }
 
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedLocalTraits.1.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedLocalTraits.1.kt
index ad61f018c53..825d436fb65 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedLocalTraits.1.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedLocalTraits.1.kt
@@ -7,11 +7,11 @@ fun foo() {
     }
 
     fun bar() {
-        trait Z: A {
+        interface Z: A {
 
         }
 
-        trait U: Z {
+        interface U: Z {
 
         }
     }
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedLocalTraits.results.txt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedLocalTraits.results.txt
index aa47bf4af81..f6afce4bd96 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedLocalTraits.results.txt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedLocalTraits.results.txt
@@ -1,2 +1,2 @@
-Unclassified usage (10: 15) trait Z: A {
-Unclassified usage (14: 15) trait U: Z {
+Unclassified usage (10: 19) interface Z: A {
+Unclassified usage (14: 19) interface U: Z {
\ No newline at end of file
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedObjects.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedObjects.0.kt
index 65608ebf054..a1bce719774 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedObjects.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedObjects.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: derivedClasses
-trait <caret>X {
+interface <caret>X {
 
 }
 
@@ -8,6 +8,6 @@ open class A: X {
 
 }
 
-trait Y: X {
+interface Y: X {
 
 }
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedTraits.0.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedTraits.0.kt
index 421730e1cf5..82cdcdbdef9 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedTraits.0.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedTraits.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetClass
 // OPTIONS: derivedInterfaces
-trait <caret>X {
+interface <caret>X {
 
 }
 
@@ -8,6 +8,6 @@ open class A: X {
 
 }
 
-trait Y: X {
+interface Y: X {
 
 }
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedTraits.1.kt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedTraits.1.kt
index 24778a14683..de17d05a4c4 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedTraits.1.kt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedTraits.1.kt
@@ -8,10 +8,10 @@ open class C: Y {
 
 }
 
-trait Z: A {
+interface Z: A {
 
 }
 
-trait U: Z {
+interface U: Z {
 
 }
diff --git a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedTraits.results.txt b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedTraits.results.txt
index 1952f112ab2..25bed06446b 100644
--- a/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedTraits.results.txt
+++ b/idea/testData/findUsages/kotlin/findClassUsages/kotlinTraitDerivedTraits.results.txt
@@ -1,3 +1,3 @@
-Unclassified usage (11: 7) trait Y: X {
-Unclassified usage (11: 7) trait Z: A {
-Unclassified usage (15: 7) trait U: Z {
\ No newline at end of file
+Unclassified usage (11: 11) interface Y: X {
+Unclassified usage (11: 11) interface Z: A {
+Unclassified usage (15: 11) interface U: Z {
\ No newline at end of file
diff --git a/idea/testData/findUsages/kotlin/findFunctionUsages/kotlinOverloadAndExtensionUsages.0.kt b/idea/testData/findUsages/kotlin/findFunctionUsages/kotlinOverloadAndExtensionUsages.0.kt
index 27aaa133e8d..74ce2fb0a99 100644
--- a/idea/testData/findUsages/kotlin/findFunctionUsages/kotlinOverloadAndExtensionUsages.0.kt
+++ b/idea/testData/findUsages/kotlin/findFunctionUsages/kotlinOverloadAndExtensionUsages.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetNamedFunction
 // OPTIONS: overloadUsages
-trait X<T> {
+interface X<T> {
 }
 
 fun <T> X<T>.foo(a: Number, b: Number) {
diff --git a/idea/testData/findUsages/kotlin/findFunctionUsages/kotlinOverloadAndExtensionUsages2.0.kt b/idea/testData/findUsages/kotlin/findFunctionUsages/kotlinOverloadAndExtensionUsages2.0.kt
index 84785359e5d..f3b91b71101 100644
--- a/idea/testData/findUsages/kotlin/findFunctionUsages/kotlinOverloadAndExtensionUsages2.0.kt
+++ b/idea/testData/findUsages/kotlin/findFunctionUsages/kotlinOverloadAndExtensionUsages2.0.kt
@@ -1,6 +1,6 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetNamedFunction
 // OPTIONS: overloadUsages
-trait X {
+interface X {
 
 }
 
diff --git a/idea/testData/findUsages/kotlin/findFunctionUsages/kotlinTraitImplThroughDelegate.0.kt b/idea/testData/findUsages/kotlin/findFunctionUsages/kotlinTraitImplThroughDelegate.0.kt
index 79ac40d91c0..2b08de2a0a6 100644
--- a/idea/testData/findUsages/kotlin/findFunctionUsages/kotlinTraitImplThroughDelegate.0.kt
+++ b/idea/testData/findUsages/kotlin/findFunctionUsages/kotlinTraitImplThroughDelegate.0.kt
@@ -2,7 +2,7 @@
 // OPTIONS: usages, skipImports
 package server
 
-trait TraitWithImpl {
+interface TraitWithImpl {
     fun <caret>foo() = 1
 }
 
diff --git a/idea/testData/findUsages/kotlin/findFunctionUsages/kotlinTraitNoImplThroughDelegate.0.kt b/idea/testData/findUsages/kotlin/findFunctionUsages/kotlinTraitNoImplThroughDelegate.0.kt
index e553c835df9..8451db06d0b 100644
--- a/idea/testData/findUsages/kotlin/findFunctionUsages/kotlinTraitNoImplThroughDelegate.0.kt
+++ b/idea/testData/findUsages/kotlin/findFunctionUsages/kotlinTraitNoImplThroughDelegate.0.kt
@@ -2,7 +2,7 @@
 // OPTIONS: usages, skipImports
 package server
 
-trait TraitNoImpl {
+interface TraitNoImpl {
     fun <caret>foo()
 }
 
diff --git a/idea/testData/findUsages/kotlin/findFunctionUsages/usagesOfBaseForFunction.0.kt b/idea/testData/findUsages/kotlin/findFunctionUsages/usagesOfBaseForFunction.0.kt
index 329863c1c32..07588e122d7 100644
--- a/idea/testData/findUsages/kotlin/findFunctionUsages/usagesOfBaseForFunction.0.kt
+++ b/idea/testData/findUsages/kotlin/findFunctionUsages/usagesOfBaseForFunction.0.kt
@@ -1,7 +1,7 @@
 // PSI_ELEMENT: org.jetbrains.kotlin.psi.JetNamedFunction
 // OPTIONS: usages, skipImports
 
-trait A {
+interface A {
     fun foo()
 }
 
diff --git a/idea/testData/findUsages/kotlin/findPropertyUsages/kotlinClassObjectPropertyUsage.0.kt b/idea/testData/findUsages/kotlin/findPropertyUsages/kotlinClassObjectPropertyUsage.0.kt
index 2284c647369..15a2aee3f37 100644
--- a/idea/testData/findUsages/kotlin/findPropertyUsages/kotlinClassObjectPropertyUsage.0.kt
+++ b/idea/testData/findUsages/kotlin/findPropertyUsages/kotlinClassObjectPropertyUsage.0.kt
@@ -2,7 +2,7 @@
 // OPTIONS: usages
 package server
 
-trait Some {
+interface Some {
     companion object {
         val <caret>XX = 1
     }
diff --git a/idea/testData/folding/checkCollapse/imports.kt b/idea/testData/folding/checkCollapse/imports.kt
index 6ea9d3cd13c..513f3d4ee9d 100644
--- a/idea/testData/folding/checkCollapse/imports.kt
+++ b/idea/testData/folding/checkCollapse/imports.kt
@@ -3,6 +3,6 @@ package some
 import <fold text='...' expand='~false~'>first
 import second</fold>
 
-trait A
+interface A
 
 // SET_TRUE: setCollapseImports
\ No newline at end of file
diff --git a/idea/testData/formatter/ClassLineBreak.after.inv.kt b/idea/testData/formatter/ClassLineBreak.after.inv.kt
index cd1b7e99349..0def4a6e462 100644
--- a/idea/testData/formatter/ClassLineBreak.after.inv.kt
+++ b/idea/testData/formatter/ClassLineBreak.after.inv.kt
@@ -8,10 +8,10 @@ class A {
     }
 }
 
-trait A {
+interface A {
 }
 
-trait A {
+interface A {
 }
 
 object A {
diff --git a/idea/testData/formatter/ClassLineBreak.after.kt b/idea/testData/formatter/ClassLineBreak.after.kt
index a3a57bf9f5f..5a779f865a2 100644
--- a/idea/testData/formatter/ClassLineBreak.after.kt
+++ b/idea/testData/formatter/ClassLineBreak.after.kt
@@ -12,11 +12,11 @@ class A
     }
 }
 
-trait A
+interface A
 {
 }
 
-trait A
+interface A
 {
 }
 
diff --git a/idea/testData/formatter/ClassLineBreak.kt b/idea/testData/formatter/ClassLineBreak.kt
index fc6877adaf6..592c89d14a1 100644
--- a/idea/testData/formatter/ClassLineBreak.kt
+++ b/idea/testData/formatter/ClassLineBreak.kt
@@ -10,10 +10,10 @@ class A
     }
 }
 
-trait A {
+interface A {
 }
 
-trait A
+interface A
 {
 }
 
diff --git a/idea/testData/formatter/DelegationList.after.inv.kt b/idea/testData/formatter/DelegationList.after.inv.kt
index 77d5b0e2206..dd2a3cfdb02 100644
--- a/idea/testData/formatter/DelegationList.after.inv.kt
+++ b/idea/testData/formatter/DelegationList.after.inv.kt
@@ -1,6 +1,6 @@
-trait A1
-trait A2
-trait A3
+interface A1
+interface A2
+interface A3
 
 open class B1
 
diff --git a/idea/testData/formatter/DelegationList.after.kt b/idea/testData/formatter/DelegationList.after.kt
index 9adf3e5cb81..5fcaf7e7d08 100644
--- a/idea/testData/formatter/DelegationList.after.kt
+++ b/idea/testData/formatter/DelegationList.after.kt
@@ -1,6 +1,6 @@
-trait A1
-trait A2
-trait A3
+interface A1
+interface A2
+interface A3
 
 open class B1
 
diff --git a/idea/testData/formatter/DelegationList.kt b/idea/testData/formatter/DelegationList.kt
index 7bd9fd0d8eb..5b8839eba3c 100644
--- a/idea/testData/formatter/DelegationList.kt
+++ b/idea/testData/formatter/DelegationList.kt
@@ -1,6 +1,6 @@
-trait A1
-trait A2
-trait A3
+interface A1
+interface A2
+interface A3
 
 open class B1
 
diff --git a/idea/testData/formatter/EmptyLineAfterObjectDeclaration.after.kt b/idea/testData/formatter/EmptyLineAfterObjectDeclaration.after.kt
index dd634b2729d..d84ec812139 100644
--- a/idea/testData/formatter/EmptyLineAfterObjectDeclaration.after.kt
+++ b/idea/testData/formatter/EmptyLineAfterObjectDeclaration.after.kt
@@ -24,7 +24,7 @@ class C1
 
 object O6
 
-trait T1
+interface T1
 
 // -----
 
@@ -62,7 +62,7 @@ class C2
 
 object O13 {}
 
-trait T2
+interface T2
 
 // -----
 
@@ -105,7 +105,7 @@ class C3
 object O20 {
 }
 
-trait T3
+interface T3
 
 // -----
 
diff --git a/idea/testData/formatter/EmptyLineAfterObjectDeclaration.kt b/idea/testData/formatter/EmptyLineAfterObjectDeclaration.kt
index 163e44eeba1..75334e02322 100644
--- a/idea/testData/formatter/EmptyLineAfterObjectDeclaration.kt
+++ b/idea/testData/formatter/EmptyLineAfterObjectDeclaration.kt
@@ -19,7 +19,7 @@ class C1
 // -----
 
 object O6
-trait T1
+interface T1
 
 // -----
 
@@ -51,7 +51,7 @@ class C2
 // -----
 
 object O13 {}
-trait T2
+interface T2
 
 // -----
 
@@ -88,7 +88,7 @@ class C3
 
 object O20 {
 }
-trait T3
+interface T3
 
 // -----
 
diff --git a/idea/testData/formatter/EmptyLineBetweeAbstractFunctions.after.kt b/idea/testData/formatter/EmptyLineBetweeAbstractFunctions.after.kt
index 6efafe6d761..170addc5e64 100644
--- a/idea/testData/formatter/EmptyLineBetweeAbstractFunctions.after.kt
+++ b/idea/testData/formatter/EmptyLineBetweeAbstractFunctions.after.kt
@@ -1,4 +1,4 @@
-trait Some {
+interface Some {
     fun f1()
     fun f2()
 }
diff --git a/idea/testData/formatter/EmptyLineBetweeAbstractFunctions.kt b/idea/testData/formatter/EmptyLineBetweeAbstractFunctions.kt
index 6efafe6d761..170addc5e64 100644
--- a/idea/testData/formatter/EmptyLineBetweeAbstractFunctions.kt
+++ b/idea/testData/formatter/EmptyLineBetweeAbstractFunctions.kt
@@ -1,4 +1,4 @@
-trait Some {
+interface Some {
     fun f1()
     fun f2()
 }
diff --git a/idea/testData/formatter/NewLineForRBrace.after.kt b/idea/testData/formatter/NewLineForRBrace.after.kt
index cc3441309fd..c2490184dd1 100644
--- a/idea/testData/formatter/NewLineForRBrace.after.kt
+++ b/idea/testData/formatter/NewLineForRBrace.after.kt
@@ -20,9 +20,9 @@ object O2 {
     }
 }
 
-trait T1 {}
+interface T1 {}
 
-trait T2 {
+interface T2 {
     val some = 1
 }
 
diff --git a/idea/testData/formatter/NewLineForRBrace.kt b/idea/testData/formatter/NewLineForRBrace.kt
index 757c1d00282..a646059d7f3 100644
--- a/idea/testData/formatter/NewLineForRBrace.kt
+++ b/idea/testData/formatter/NewLineForRBrace.kt
@@ -15,9 +15,9 @@ object O1 {}
 object O2 {
     fun test() {}}
 
-trait T1 {}
+interface T1 {}
 
-trait T2 {
+interface T2 {
     val some = 1}
 
 enum class E1 {
diff --git a/idea/testData/formatter/SpaceAroundExtendColonInObjects.after.inv.kt b/idea/testData/formatter/SpaceAroundExtendColonInObjects.after.inv.kt
index 024a7b0a44b..b5b9ce65ab0 100644
--- a/idea/testData/formatter/SpaceAroundExtendColonInObjects.after.inv.kt
+++ b/idea/testData/formatter/SpaceAroundExtendColonInObjects.after.inv.kt
@@ -1,4 +1,4 @@
-trait A
+interface A
 
 object Some1: A {
 
diff --git a/idea/testData/formatter/SpaceAroundExtendColonInObjects.after.kt b/idea/testData/formatter/SpaceAroundExtendColonInObjects.after.kt
index 7f6c81442c4..2232d93e6b5 100644
--- a/idea/testData/formatter/SpaceAroundExtendColonInObjects.after.kt
+++ b/idea/testData/formatter/SpaceAroundExtendColonInObjects.after.kt
@@ -1,4 +1,4 @@
-trait A
+interface A
 
 object Some1 :A {
 
diff --git a/idea/testData/formatter/SpaceAroundExtendColonInObjects.kt b/idea/testData/formatter/SpaceAroundExtendColonInObjects.kt
index e7796470f10..4930b907cde 100644
--- a/idea/testData/formatter/SpaceAroundExtendColonInObjects.kt
+++ b/idea/testData/formatter/SpaceAroundExtendColonInObjects.kt
@@ -1,4 +1,4 @@
-trait A
+interface A
 
 object Some1     :    A {
 
diff --git a/idea/testData/formatter/SpacesInQualifiedExpressions.after.kt b/idea/testData/formatter/SpacesInQualifiedExpressions.after.kt
index acab5f7bcb0..3363a87a71d 100644
--- a/idea/testData/formatter/SpacesInQualifiedExpressions.after.kt
+++ b/idea/testData/formatter/SpacesInQualifiedExpressions.after.kt
@@ -1,4 +1,4 @@
-trait Test {
+interface Test {
     fun foo(): Test
 }
 
diff --git a/idea/testData/formatter/SpacesInQualifiedExpressions.kt b/idea/testData/formatter/SpacesInQualifiedExpressions.kt
index c9783bc19da..665a0f94cc7 100644
--- a/idea/testData/formatter/SpacesInQualifiedExpressions.kt
+++ b/idea/testData/formatter/SpacesInQualifiedExpressions.kt
@@ -1,4 +1,4 @@
-trait Test {
+interface Test {
     fun foo(): Test
 }
 
diff --git a/idea/testData/hierarchy/class/sub/AllFromClass/main.kt b/idea/testData/hierarchy/class/sub/AllFromClass/main.kt
index 3be283ecfcd..1e8490f3ab3 100644
--- a/idea/testData/hierarchy/class/sub/AllFromClass/main.kt
+++ b/idea/testData/hierarchy/class/sub/AllFromClass/main.kt
@@ -2,11 +2,11 @@ open class <caret>A
 
 open class B: A()
 
-trait T: A
+interface T: A
 
 open class C: B()
 
-trait U: T
+interface U: T
 
 object O1: A()
 
diff --git a/idea/testData/hierarchy/class/sub/AllFromTrait/main.kt b/idea/testData/hierarchy/class/sub/AllFromTrait/main.kt
index 372b045336b..4786edb09d2 100644
--- a/idea/testData/hierarchy/class/sub/AllFromTrait/main.kt
+++ b/idea/testData/hierarchy/class/sub/AllFromTrait/main.kt
@@ -1,12 +1,12 @@
-trait <caret>A
+interface <caret>A
 
 open class B: A
 
-trait T: A
+interface T: A
 
 open class C: B()
 
-trait U: T
+interface U: T
 
 object O1: A
 
diff --git a/idea/testData/hierarchy/class/sub/ClassFromTrait/main.kt b/idea/testData/hierarchy/class/sub/ClassFromTrait/main.kt
index f2e5d9e2c93..bf6e8407f3e 100644
--- a/idea/testData/hierarchy/class/sub/ClassFromTrait/main.kt
+++ b/idea/testData/hierarchy/class/sub/ClassFromTrait/main.kt
@@ -1,4 +1,4 @@
-trait <caret>A
+interface <caret>A
 
 class B: A
 
diff --git a/idea/testData/hierarchy/class/sub/ObjectFromTrait/main.kt b/idea/testData/hierarchy/class/sub/ObjectFromTrait/main.kt
index bb701a7764c..36a57f3b1de 100644
--- a/idea/testData/hierarchy/class/sub/ObjectFromTrait/main.kt
+++ b/idea/testData/hierarchy/class/sub/ObjectFromTrait/main.kt
@@ -1,4 +1,4 @@
-trait <caret>A
+interface <caret>A
 
 object B: A
 
diff --git a/idea/testData/hierarchy/class/sub/TraitFromClass/main.kt b/idea/testData/hierarchy/class/sub/TraitFromClass/main.kt
index d65150647e8..ec57c5e3cdb 100644
--- a/idea/testData/hierarchy/class/sub/TraitFromClass/main.kt
+++ b/idea/testData/hierarchy/class/sub/TraitFromClass/main.kt
@@ -1,26 +1,26 @@
 open class <caret>A
 
-trait B: A()
+interface B: A()
 
-class MyClass(a: A = run { trait X: A(); object: A() {} }) {
-    inner trait G: A() {}
+class MyClass(a: A = run { interface X: A(); object: A() {} }) {
+    inner interface G: A() {}
 
     init {
-        trait C: A()
+        interface C: A()
     }
 
-    fun foo(a: A = run { trait X: A(); object: A() {} }) {
-        trait D: A()
+    fun foo(a: A = run { interface X: A(); object: A() {} }) {
+        interface D: A()
 
         val t = object {
-            inner trait F: A()
+            inner interface F: A()
         }
     }
 }
 
 val bar: Int
     get() {
-        trait E: A()
+        interface E: A()
 
         return 0
     }
\ No newline at end of file
diff --git a/idea/testData/hierarchy/class/sub/TraitFromTrait/main.kt b/idea/testData/hierarchy/class/sub/TraitFromTrait/main.kt
index e64271cf66b..7c1f2a3b532 100644
--- a/idea/testData/hierarchy/class/sub/TraitFromTrait/main.kt
+++ b/idea/testData/hierarchy/class/sub/TraitFromTrait/main.kt
@@ -1,26 +1,26 @@
-trait <caret>A
+interface <caret>A
 
-trait B: A
+interface B: A
 
-class MyClass(a: A = run { trait X: A; object: A {} }) {
-    inner trait G: A {}
+class MyClass(a: A = run { interface X: A; object: A {} }) {
+    inner interface G: A {}
 
     init {
-        trait C: A
+        interface C: A
     }
 
-    fun foo(a: A = run { trait X: A; object: A {} }) {
-        trait D: A
+    fun foo(a: A = run { interface X: A; object: A {} }) {
+        interface D: A
 
         val t = object {
-            inner trait F: A
+            inner interface F: A
         }
     }
 }
 
 val bar: Int
     get() {
-        trait E: A
+        interface E: A
 
         return 0
     }
\ No newline at end of file
diff --git a/idea/testData/hierarchy/class/super/TwoTraits/main.kt b/idea/testData/hierarchy/class/super/TwoTraits/main.kt
index 144226e98f5..0cce0148f80 100644
--- a/idea/testData/hierarchy/class/super/TwoTraits/main.kt
+++ b/idea/testData/hierarchy/class/super/TwoTraits/main.kt
@@ -1,4 +1,4 @@
 class MyClass<caret>: A, B
 
-trait A
-trait B
\ No newline at end of file
+interface A
+interface B
\ No newline at end of file
diff --git a/idea/testData/hierarchy/class/type/TwoChildren/main.kt b/idea/testData/hierarchy/class/type/TwoChildren/main.kt
index d3963e8d997..0daf10bed78 100644
--- a/idea/testData/hierarchy/class/type/TwoChildren/main.kt
+++ b/idea/testData/hierarchy/class/type/TwoChildren/main.kt
@@ -1,4 +1,4 @@
-trait MyClass<caret>
+interface MyClass<caret>
 
 class A: MyClass
 class B: MyClass
\ No newline at end of file
diff --git a/idea/testData/hierarchy/overrides/javaMethodInClass/main1.kt b/idea/testData/hierarchy/overrides/javaMethodInClass/main1.kt
index 2a2dc362ce8..97e7ca63515 100644
--- a/idea/testData/hierarchy/overrides/javaMethodInClass/main1.kt
+++ b/idea/testData/hierarchy/overrides/javaMethodInClass/main1.kt
@@ -1,4 +1,4 @@
-trait T: A {
+interface T: A {
     override fun foo() {
 
     }
diff --git a/idea/testData/hierarchy/overrides/javaMethodInInterface/main1.kt b/idea/testData/hierarchy/overrides/javaMethodInInterface/main1.kt
index f2d09991937..dd5bddeeafe 100644
--- a/idea/testData/hierarchy/overrides/javaMethodInInterface/main1.kt
+++ b/idea/testData/hierarchy/overrides/javaMethodInInterface/main1.kt
@@ -1,4 +1,4 @@
-trait T: A {
+interface T: A {
     override fun foo() {
 
     }
diff --git a/idea/testData/hierarchy/overrides/kotlinFunctionInClass/main0.kt b/idea/testData/hierarchy/overrides/kotlinFunctionInClass/main0.kt
index 034d0d51a31..194944c6ad8 100644
--- a/idea/testData/hierarchy/overrides/kotlinFunctionInClass/main0.kt
+++ b/idea/testData/hierarchy/overrides/kotlinFunctionInClass/main0.kt
@@ -10,7 +10,7 @@ open class X: T() {
     }
 }
 
-open trait Y: T() {
+open interface Y: T() {
     override fun foo() {
 
     }
diff --git a/idea/testData/hierarchy/overrides/kotlinFunctionInTrait/main0.kt b/idea/testData/hierarchy/overrides/kotlinFunctionInTrait/main0.kt
index 2dd4eb7d699..e11d90dbf0b 100644
--- a/idea/testData/hierarchy/overrides/kotlinFunctionInTrait/main0.kt
+++ b/idea/testData/hierarchy/overrides/kotlinFunctionInTrait/main0.kt
@@ -1,4 +1,4 @@
-trait T {
+interface T {
     fun <caret>foo()
 }
 
diff --git a/idea/testData/hierarchy/overrides/kotlinPropertyInClass/main0.kt b/idea/testData/hierarchy/overrides/kotlinPropertyInClass/main0.kt
index 7b6319fd274..9027d458c7a 100644
--- a/idea/testData/hierarchy/overrides/kotlinPropertyInClass/main0.kt
+++ b/idea/testData/hierarchy/overrides/kotlinPropertyInClass/main0.kt
@@ -8,7 +8,7 @@ open class X: T() {
         set(value: String) {}
 }
 
-trait Y: T {
+interface Y: T {
     override var foo: String
         get() = ""
         set(value: String) {}
diff --git a/idea/testData/hierarchy/overrides/kotlinPropertyInTrait/main0.kt b/idea/testData/hierarchy/overrides/kotlinPropertyInTrait/main0.kt
index f714f8e694a..94c07bfc82c 100644
--- a/idea/testData/hierarchy/overrides/kotlinPropertyInTrait/main0.kt
+++ b/idea/testData/hierarchy/overrides/kotlinPropertyInTrait/main0.kt
@@ -1,4 +1,4 @@
-trait T {
+interface T {
     open var <caret>foo: String
 }
 
@@ -8,7 +8,7 @@ open class X: T {
         set(value: String) {}
 }
 
-open trait Y: T {
+open interface Y: T {
     override var foo: String
         get() = ""
         set(value: String) {}
diff --git a/idea/testData/highlighter/TypesAndAnnotations.kt b/idea/testData/highlighter/TypesAndAnnotations.kt
index 75f627c25ac..77ece2f4208 100644
--- a/idea/testData/highlighter/TypesAndAnnotations.kt
+++ b/idea/testData/highlighter/TypesAndAnnotations.kt
@@ -1,4 +1,4 @@
-trait <info textAttributesKey="KOTLIN_TRAIT">TheTrait</info> {
+interface <info textAttributesKey="KOTLIN_TRAIT">TheTrait</info> {
 }
 
 class <info textAttributesKey="KOTLIN_CLASS">TheClass</info> : <info textAttributesKey="KOTLIN_TRAIT">TheTrait</info> {
diff --git a/idea/testData/highlighter/VariablesAsFunctions.kt b/idea/testData/highlighter/VariablesAsFunctions.kt
index 3f55a7efd31..8c153a6d901 100644
--- a/idea/testData/highlighter/VariablesAsFunctions.kt
+++ b/idea/testData/highlighter/VariablesAsFunctions.kt
@@ -1,4 +1,4 @@
-trait <info textAttributesKey="KOTLIN_TRAIT">FunctionLike</info> {
+interface <info textAttributesKey="KOTLIN_TRAIT">FunctionLike</info> {
     fun <info textAttributesKey="KOTLIN_FUNCTION_DECLARATION">invoke</info>() {
     }
 }
diff --git a/idea/testData/highlighter/deprecated/ClassObject.kt b/idea/testData/highlighter/deprecated/ClassObject.kt
index 8dcd94a9e76..a0d84f96e30 100644
--- a/idea/testData/highlighter/deprecated/ClassObject.kt
+++ b/idea/testData/highlighter/deprecated/ClassObject.kt
@@ -18,7 +18,7 @@ class MyClass(): MyTrait {
     }
 }
 
-trait MyTrait {
+interface MyTrait {
     deprecated("Use A instead") companion object {
         val test: String = ""
     }
diff --git a/idea/testData/highlighter/deprecated/Trait.kt b/idea/testData/highlighter/deprecated/Trait.kt
index 91ec7acad5c..bfb45d07178 100644
--- a/idea/testData/highlighter/deprecated/Trait.kt
+++ b/idea/testData/highlighter/deprecated/Trait.kt
@@ -1,4 +1,4 @@
-deprecated("Use A instead") trait MyTrait { }
+deprecated("Use A instead") interface MyTrait { }
 
 fun test() {
    val a: <warning descr="[DEPRECATED_SYMBOL_WITH_MESSAGE] 'MyTrait' is deprecated. Use A instead">MyTrait</warning>? = null
diff --git a/idea/testData/indentationOnNewline/InDelegationListAfterComma.after.inv.kt b/idea/testData/indentationOnNewline/InDelegationListAfterComma.after.inv.kt
index bae53c1620b..38667969a52 100644
--- a/idea/testData/indentationOnNewline/InDelegationListAfterComma.after.inv.kt
+++ b/idea/testData/indentationOnNewline/InDelegationListAfterComma.after.inv.kt
@@ -1,6 +1,6 @@
 // SET_TRUE: ALIGN_MULTILINE_EXTENDS_LIST
 
-trait A1
+interface A1
 
 class A {
     class Simpleclass() : A1,
diff --git a/idea/testData/indentationOnNewline/InDelegationListAfterComma.after.kt b/idea/testData/indentationOnNewline/InDelegationListAfterComma.after.kt
index e5bbca12506..a37ca143898 100644
--- a/idea/testData/indentationOnNewline/InDelegationListAfterComma.after.kt
+++ b/idea/testData/indentationOnNewline/InDelegationListAfterComma.after.kt
@@ -1,6 +1,6 @@
 // SET_TRUE: ALIGN_MULTILINE_EXTENDS_LIST
 
-trait A1
+interface A1
 
 class A {
     class Simpleclass() : A1,
diff --git a/idea/testData/indentationOnNewline/InDelegationListAfterComma.kt b/idea/testData/indentationOnNewline/InDelegationListAfterComma.kt
index 50b850c1e4b..48841427261 100644
--- a/idea/testData/indentationOnNewline/InDelegationListAfterComma.kt
+++ b/idea/testData/indentationOnNewline/InDelegationListAfterComma.kt
@@ -1,6 +1,6 @@
 // SET_TRUE: ALIGN_MULTILINE_EXTENDS_LIST
 
-trait A1
+interface A1
 
 class A {
     class Simpleclass() : A1, <caret>
diff --git a/idea/testData/indentationOnNewline/InDelegationListNotEmpty.after.inv.kt b/idea/testData/indentationOnNewline/InDelegationListNotEmpty.after.inv.kt
index 5ca4744f35b..9ec57d41928 100644
--- a/idea/testData/indentationOnNewline/InDelegationListNotEmpty.after.inv.kt
+++ b/idea/testData/indentationOnNewline/InDelegationListNotEmpty.after.inv.kt
@@ -1,6 +1,6 @@
 // SET_TRUE: ALIGN_MULTILINE_EXTENDS_LIST
 
-trait A1
+interface A1
 
 open class B1
 
diff --git a/idea/testData/indentationOnNewline/InDelegationListNotEmpty.after.kt b/idea/testData/indentationOnNewline/InDelegationListNotEmpty.after.kt
index 50494caefad..fa21aaed3ee 100644
--- a/idea/testData/indentationOnNewline/InDelegationListNotEmpty.after.kt
+++ b/idea/testData/indentationOnNewline/InDelegationListNotEmpty.after.kt
@@ -1,6 +1,6 @@
 // SET_TRUE: ALIGN_MULTILINE_EXTENDS_LIST
 
-trait A1
+interface A1
 
 open class B1
 
diff --git a/idea/testData/indentationOnNewline/InDelegationListNotEmpty.kt b/idea/testData/indentationOnNewline/InDelegationListNotEmpty.kt
index d209617cf3e..7025478c495 100644
--- a/idea/testData/indentationOnNewline/InDelegationListNotEmpty.kt
+++ b/idea/testData/indentationOnNewline/InDelegationListNotEmpty.kt
@@ -1,6 +1,6 @@
 // SET_TRUE: ALIGN_MULTILINE_EXTENDS_LIST
 
-trait A1
+interface A1
 
 open class B1
 
diff --git a/idea/testData/indentationOnNewline/InEnumInitializerListAfterColon.after.inv.kt b/idea/testData/indentationOnNewline/InEnumInitializerListAfterColon.after.inv.kt
index 8e1dacb1353..c96a5888b21 100644
--- a/idea/testData/indentationOnNewline/InEnumInitializerListAfterColon.after.inv.kt
+++ b/idea/testData/indentationOnNewline/InEnumInitializerListAfterColon.after.inv.kt
@@ -1,6 +1,6 @@
 // SET_TRUE: ALIGN_MULTILINE_EXTENDS_LIST
 
-trait A1
+interface A1
 
 enum class EnumTest {
     ENTRY:
diff --git a/idea/testData/indentationOnNewline/InEnumInitializerListAfterColon.after.kt b/idea/testData/indentationOnNewline/InEnumInitializerListAfterColon.after.kt
index 8e1dacb1353..c96a5888b21 100644
--- a/idea/testData/indentationOnNewline/InEnumInitializerListAfterColon.after.kt
+++ b/idea/testData/indentationOnNewline/InEnumInitializerListAfterColon.after.kt
@@ -1,6 +1,6 @@
 // SET_TRUE: ALIGN_MULTILINE_EXTENDS_LIST
 
-trait A1
+interface A1
 
 enum class EnumTest {
     ENTRY:
diff --git a/idea/testData/indentationOnNewline/InEnumInitializerListAfterColon.kt b/idea/testData/indentationOnNewline/InEnumInitializerListAfterColon.kt
index c29d21d6335..d7ca1e4ee5d 100644
--- a/idea/testData/indentationOnNewline/InEnumInitializerListAfterColon.kt
+++ b/idea/testData/indentationOnNewline/InEnumInitializerListAfterColon.kt
@@ -1,6 +1,6 @@
 // SET_TRUE: ALIGN_MULTILINE_EXTENDS_LIST
 
-trait A1
+interface A1
 
 enum class EnumTest {
     ENTRY: <caret>
diff --git a/idea/testData/indentationOnNewline/InEnumInitializerListAfterComma.after.inv.kt b/idea/testData/indentationOnNewline/InEnumInitializerListAfterComma.after.inv.kt
index eb53831c90f..cea8d3b0776 100644
--- a/idea/testData/indentationOnNewline/InEnumInitializerListAfterComma.after.inv.kt
+++ b/idea/testData/indentationOnNewline/InEnumInitializerListAfterComma.after.inv.kt
@@ -1,6 +1,6 @@
 // SET_TRUE: ALIGN_MULTILINE_EXTENDS_LIST
 
-trait A1
+interface A1
 
 enum class EnumTest {
     ENTRY: EnumTest(),
diff --git a/idea/testData/indentationOnNewline/InEnumInitializerListAfterComma.after.kt b/idea/testData/indentationOnNewline/InEnumInitializerListAfterComma.after.kt
index 905d8e3f133..173df3340fc 100644
--- a/idea/testData/indentationOnNewline/InEnumInitializerListAfterComma.after.kt
+++ b/idea/testData/indentationOnNewline/InEnumInitializerListAfterComma.after.kt
@@ -1,6 +1,6 @@
 // SET_TRUE: ALIGN_MULTILINE_EXTENDS_LIST
 
-trait A1
+interface A1
 
 enum class EnumTest {
     ENTRY: EnumTest(),
diff --git a/idea/testData/indentationOnNewline/InEnumInitializerListAfterComma.kt b/idea/testData/indentationOnNewline/InEnumInitializerListAfterComma.kt
index 657f7f824d0..31d5be06cff 100644
--- a/idea/testData/indentationOnNewline/InEnumInitializerListAfterComma.kt
+++ b/idea/testData/indentationOnNewline/InEnumInitializerListAfterComma.kt
@@ -1,6 +1,6 @@
 // SET_TRUE: ALIGN_MULTILINE_EXTENDS_LIST
 
-trait A1
+interface A1
 
 enum class EnumTest {
     ENTRY: EnumTest(), <caret>
diff --git a/idea/testData/indentationOnNewline/InEnumInitializerListNotEmpty.after.inv.kt b/idea/testData/indentationOnNewline/InEnumInitializerListNotEmpty.after.inv.kt
index cf5efcefb45..54c905e37a7 100644
--- a/idea/testData/indentationOnNewline/InEnumInitializerListNotEmpty.after.inv.kt
+++ b/idea/testData/indentationOnNewline/InEnumInitializerListNotEmpty.after.inv.kt
@@ -1,6 +1,6 @@
 // SET_TRUE: ALIGN_MULTILINE_EXTENDS_LIST
 
-trait A1
+interface A1
 
 enum class EnumTest {
     ENTRY: EnumTest(),
diff --git a/idea/testData/indentationOnNewline/InEnumInitializerListNotEmpty.after.kt b/idea/testData/indentationOnNewline/InEnumInitializerListNotEmpty.after.kt
index 8cffbdb9df6..4161f8535fb 100644
--- a/idea/testData/indentationOnNewline/InEnumInitializerListNotEmpty.after.kt
+++ b/idea/testData/indentationOnNewline/InEnumInitializerListNotEmpty.after.kt
@@ -1,6 +1,6 @@
 // SET_TRUE: ALIGN_MULTILINE_EXTENDS_LIST
 
-trait A1
+interface A1
 
 enum class EnumTest {
     ENTRY: EnumTest(),
diff --git a/idea/testData/indentationOnNewline/InEnumInitializerListNotEmpty.kt b/idea/testData/indentationOnNewline/InEnumInitializerListNotEmpty.kt
index d20fc3a8d04..33fd8fefbc9 100644
--- a/idea/testData/indentationOnNewline/InEnumInitializerListNotEmpty.kt
+++ b/idea/testData/indentationOnNewline/InEnumInitializerListNotEmpty.kt
@@ -1,6 +1,6 @@
 // SET_TRUE: ALIGN_MULTILINE_EXTENDS_LIST
 
-trait A1
+interface A1
 
 enum class EnumTest {
     ENTRY: EnumTest(), <caret>A1
diff --git a/idea/testData/inspections/unusedSymbol/parameter/paramPropertyOverride.kt b/idea/testData/inspections/unusedSymbol/parameter/paramPropertyOverride.kt
index bf3cc11e1da..e4bbca1d204 100644
--- a/idea/testData/inspections/unusedSymbol/parameter/paramPropertyOverride.kt
+++ b/idea/testData/inspections/unusedSymbol/parameter/paramPropertyOverride.kt
@@ -1,4 +1,4 @@
-trait Trait {
+interface Trait {
     val member: String
 }
 
diff --git a/idea/testData/inspections/unusedSymbol/property/classMemberOverride.kt b/idea/testData/inspections/unusedSymbol/property/classMemberOverride.kt
index 8d98c464f3e..789d370c29b 100644
--- a/idea/testData/inspections/unusedSymbol/property/classMemberOverride.kt
+++ b/idea/testData/inspections/unusedSymbol/property/classMemberOverride.kt
@@ -1,4 +1,4 @@
-trait Trait {
+interface Trait {
     val member: String
 }
 
diff --git a/idea/testData/intentions/convertFunctionToProperty/addExplicitAnonymousType.kt b/idea/testData/intentions/convertFunctionToProperty/addExplicitAnonymousType.kt
index 4178865268f..adb4ebfec5f 100644
--- a/idea/testData/intentions/convertFunctionToProperty/addExplicitAnonymousType.kt
+++ b/idea/testData/intentions/convertFunctionToProperty/addExplicitAnonymousType.kt
@@ -1,4 +1,4 @@
-trait T {
+interface T {
     fun bar()
 }
 
diff --git a/idea/testData/intentions/convertFunctionToProperty/addExplicitAnonymousType.kt.after b/idea/testData/intentions/convertFunctionToProperty/addExplicitAnonymousType.kt.after
index 88412592408..ef9d83f555c 100644
--- a/idea/testData/intentions/convertFunctionToProperty/addExplicitAnonymousType.kt.after
+++ b/idea/testData/intentions/convertFunctionToProperty/addExplicitAnonymousType.kt.after
@@ -1,4 +1,4 @@
-trait T {
+interface T {
     fun bar()
 }
 
diff --git a/idea/testData/intentions/convertFunctionToProperty/overrides.kt b/idea/testData/intentions/convertFunctionToProperty/overrides.kt
index 30c8fa8db5d..7ac83244514 100644
--- a/idea/testData/intentions/convertFunctionToProperty/overrides.kt
+++ b/idea/testData/intentions/convertFunctionToProperty/overrides.kt
@@ -1,6 +1,6 @@
 package test
 
-trait T {
+interface T {
     fun foo(): Boolean
 }
 
diff --git a/idea/testData/intentions/convertFunctionToProperty/overrides.kt.after b/idea/testData/intentions/convertFunctionToProperty/overrides.kt.after
index 5754ead2370..8097e6f7fe7 100644
--- a/idea/testData/intentions/convertFunctionToProperty/overrides.kt.after
+++ b/idea/testData/intentions/convertFunctionToProperty/overrides.kt.after
@@ -1,6 +1,6 @@
 package test
 
-trait T {
+interface T {
     val foo: Boolean
 }
 
diff --git a/idea/testData/intentions/convertPropertyToFunction/overrides.kt b/idea/testData/intentions/convertPropertyToFunction/overrides.kt
index 4e0692609dd..df1543f05ea 100644
--- a/idea/testData/intentions/convertPropertyToFunction/overrides.kt
+++ b/idea/testData/intentions/convertPropertyToFunction/overrides.kt
@@ -1,6 +1,6 @@
 package test
 
-trait T {
+interface T {
     val foo: Boolean
 }
 
diff --git a/idea/testData/intentions/convertPropertyToFunction/overrides.kt.after b/idea/testData/intentions/convertPropertyToFunction/overrides.kt.after
index 37d9d07824c..0a693bd44d8 100644
--- a/idea/testData/intentions/convertPropertyToFunction/overrides.kt.after
+++ b/idea/testData/intentions/convertPropertyToFunction/overrides.kt.after
@@ -1,6 +1,6 @@
 package test
 
-trait T {
+interface T {
     fun foo(): Boolean
 }
 
diff --git a/idea/testData/intentions/convertToExpressionBody/anonymousObjectExpression.kt b/idea/testData/intentions/convertToExpressionBody/anonymousObjectExpression.kt
index 063a2c8ad86..9bb2981e989 100644
--- a/idea/testData/intentions/convertToExpressionBody/anonymousObjectExpression.kt
+++ b/idea/testData/intentions/convertToExpressionBody/anonymousObjectExpression.kt
@@ -1,4 +1,4 @@
-trait I {
+interface I {
     fun foo(): String
 }
 
diff --git a/idea/testData/intentions/convertToExpressionBody/anonymousObjectExpression.kt.after b/idea/testData/intentions/convertToExpressionBody/anonymousObjectExpression.kt.after
index 4bbf62a4786..2d75ef40c5c 100644
--- a/idea/testData/intentions/convertToExpressionBody/anonymousObjectExpression.kt.after
+++ b/idea/testData/intentions/convertToExpressionBody/anonymousObjectExpression.kt.after
@@ -1,4 +1,4 @@
-trait I {
+interface I {
     fun foo(): String
 }
 
diff --git a/idea/testData/intentions/infixCallToOrdinary/functionLiteralArgument.kt b/idea/testData/intentions/infixCallToOrdinary/functionLiteralArgument.kt
index 5b67ae91742..57518537c71 100644
--- a/idea/testData/intentions/infixCallToOrdinary/functionLiteralArgument.kt
+++ b/idea/testData/intentions/infixCallToOrdinary/functionLiteralArgument.kt
@@ -1,4 +1,4 @@
-trait Foo {
+interface Foo {
     fun foo(f: (Int) -> Unit)
 }
 fun foo(x: Foo) {
diff --git a/idea/testData/intentions/infixCallToOrdinary/functionLiteralArgument.kt.after b/idea/testData/intentions/infixCallToOrdinary/functionLiteralArgument.kt.after
index 86a4b701ab8..6eefdcc0907 100644
--- a/idea/testData/intentions/infixCallToOrdinary/functionLiteralArgument.kt.after
+++ b/idea/testData/intentions/infixCallToOrdinary/functionLiteralArgument.kt.after
@@ -1,4 +1,4 @@
-trait Foo {
+interface Foo {
     fun foo(f: (Int) -> Unit)
 }
 fun foo(x: Foo) {
diff --git a/idea/testData/intentions/removeUnnecessaryParentheses/necessaryParentheses5.kt b/idea/testData/intentions/removeUnnecessaryParentheses/necessaryParentheses5.kt
index 777af8bdd7d..494b05895ca 100644
--- a/idea/testData/intentions/removeUnnecessaryParentheses/necessaryParentheses5.kt
+++ b/idea/testData/intentions/removeUnnecessaryParentheses/necessaryParentheses5.kt
@@ -1,5 +1,5 @@
 // IS_APPLICABLE: false
-trait Foo {
+interface Foo {
     fun get(x : Any) : Foo
     fun plus(x : Any) : Foo
 }
diff --git a/idea/testData/intentions/removeUnnecessaryParentheses/unnecessaryParentheses3.kt b/idea/testData/intentions/removeUnnecessaryParentheses/unnecessaryParentheses3.kt
index ad8965c1179..b96a1338482 100644
--- a/idea/testData/intentions/removeUnnecessaryParentheses/unnecessaryParentheses3.kt
+++ b/idea/testData/intentions/removeUnnecessaryParentheses/unnecessaryParentheses3.kt
@@ -1,4 +1,4 @@
-trait Foo {
+interface Foo {
     fun get(x : Any) : Foo
 }
 fun foo(x: Foo) {
diff --git a/idea/testData/intentions/removeUnnecessaryParentheses/unnecessaryParentheses3.kt.after b/idea/testData/intentions/removeUnnecessaryParentheses/unnecessaryParentheses3.kt.after
index 3830c0ed018..50b541447d3 100644
--- a/idea/testData/intentions/removeUnnecessaryParentheses/unnecessaryParentheses3.kt.after
+++ b/idea/testData/intentions/removeUnnecessaryParentheses/unnecessaryParentheses3.kt.after
@@ -1,4 +1,4 @@
-trait Foo {
+interface Foo {
     fun get(x : Any) : Foo
 }
 fun foo(x: Foo) {
diff --git a/idea/testData/intentions/removeUnnecessaryParentheses/unnecessaryParentheses4.kt b/idea/testData/intentions/removeUnnecessaryParentheses/unnecessaryParentheses4.kt
index 325def59ded..afd088c2ec4 100644
--- a/idea/testData/intentions/removeUnnecessaryParentheses/unnecessaryParentheses4.kt
+++ b/idea/testData/intentions/removeUnnecessaryParentheses/unnecessaryParentheses4.kt
@@ -1,4 +1,4 @@
-trait Foo {
+interface Foo {
     fun inc() : Foo
     fun not() : Foo
 }
diff --git a/idea/testData/intentions/removeUnnecessaryParentheses/unnecessaryParentheses4.kt.after b/idea/testData/intentions/removeUnnecessaryParentheses/unnecessaryParentheses4.kt.after
index e7c0b19209b..f4f0d4cc866 100644
--- a/idea/testData/intentions/removeUnnecessaryParentheses/unnecessaryParentheses4.kt.after
+++ b/idea/testData/intentions/removeUnnecessaryParentheses/unnecessaryParentheses4.kt.after
@@ -1,4 +1,4 @@
-trait Foo {
+interface Foo {
     fun inc() : Foo
     fun not() : Foo
 }
diff --git a/idea/testData/intentions/toInfixCall/functionLiteralArgument.kt b/idea/testData/intentions/toInfixCall/functionLiteralArgument.kt
index 7401cb46229..321daf2389c 100644
--- a/idea/testData/intentions/toInfixCall/functionLiteralArgument.kt
+++ b/idea/testData/intentions/toInfixCall/functionLiteralArgument.kt
@@ -2,6 +2,6 @@ fun foo(x: Foo) {
     x.<caret>foo { it * 2 }
 }
 
-trait Foo {
+interface Foo {
     fun foo(f: (Int) -> Int)
 }
diff --git a/idea/testData/intentions/toInfixCall/functionLiteralArgument.kt.after b/idea/testData/intentions/toInfixCall/functionLiteralArgument.kt.after
index 8870231e2a2..925a009a343 100644
--- a/idea/testData/intentions/toInfixCall/functionLiteralArgument.kt.after
+++ b/idea/testData/intentions/toInfixCall/functionLiteralArgument.kt.after
@@ -2,6 +2,6 @@ fun foo(x: Foo) {
     x foo { it * 2 }
 }
 
-trait Foo {
+interface Foo {
     fun foo(f: (Int) -> Int)
 }
diff --git a/idea/testData/intentions/toInfixCall/multipleArguments.kt b/idea/testData/intentions/toInfixCall/multipleArguments.kt
index de15862ecc2..97af0733658 100644
--- a/idea/testData/intentions/toInfixCall/multipleArguments.kt
+++ b/idea/testData/intentions/toInfixCall/multipleArguments.kt
@@ -1,5 +1,5 @@
 // IS_APPLICABLE: false
-trait Foo {
+interface Foo {
     fun foo(a: Int, b: Int)
 }
 
diff --git a/idea/testData/intentions/toInfixCall/namedArgument.kt b/idea/testData/intentions/toInfixCall/namedArgument.kt
index a4078442256..1d44d394302 100644
--- a/idea/testData/intentions/toInfixCall/namedArgument.kt
+++ b/idea/testData/intentions/toInfixCall/namedArgument.kt
@@ -3,6 +3,6 @@ fun foo(x: Foo) {
     x.<caret>foo(bar = x)
 }
 
-trait Foo {
+interface Foo {
     fun foo(baz: Int = 0, bar: Foo? = null)
 }
diff --git a/idea/testData/intentions/toInfixCall/simpleArgumentAndFunctionLiteralArgument.kt b/idea/testData/intentions/toInfixCall/simpleArgumentAndFunctionLiteralArgument.kt
index d9abb78bcfa..24a7e4d2600 100644
--- a/idea/testData/intentions/toInfixCall/simpleArgumentAndFunctionLiteralArgument.kt
+++ b/idea/testData/intentions/toInfixCall/simpleArgumentAndFunctionLiteralArgument.kt
@@ -3,6 +3,6 @@ fun foo(x: Foo) {
     x.<caret>foo(1) { it * 2 }
 }
 
-trait Foo {
+interface Foo {
     fun foo(a: Int, f: (Int) -> Int)
 }
diff --git a/idea/testData/javaFacade/classWithObjectLiteralInClassObjectField.kt b/idea/testData/javaFacade/classWithObjectLiteralInClassObjectField.kt
index 652327231e2..455149b1723 100644
--- a/idea/testData/javaFacade/classWithObjectLiteralInClassObjectField.kt
+++ b/idea/testData/javaFacade/classWithObjectLiteralInClassObjectField.kt
@@ -1,6 +1,6 @@
 package test
 
-trait A
+interface A
 
 class <caret>B {
     companion object {
diff --git a/idea/testData/javaFacade/classWithObjectLiteralInConstructorProperty.kt b/idea/testData/javaFacade/classWithObjectLiteralInConstructorProperty.kt
index 1ef6a42dade..7072f39e42e 100644
--- a/idea/testData/javaFacade/classWithObjectLiteralInConstructorProperty.kt
+++ b/idea/testData/javaFacade/classWithObjectLiteralInConstructorProperty.kt
@@ -1,5 +1,5 @@
 package test
 
-trait A
+interface A
 
 class <caret>B(val bar: A = object: A {}, val withError = object: A {}, notProperty = object: A {})
\ No newline at end of file
diff --git a/idea/testData/javaFacade/classWithObjectLiteralInField.kt b/idea/testData/javaFacade/classWithObjectLiteralInField.kt
index 9f965fd0843..7c6a64f3b5d 100644
--- a/idea/testData/javaFacade/classWithObjectLiteralInField.kt
+++ b/idea/testData/javaFacade/classWithObjectLiteralInField.kt
@@ -1,6 +1,6 @@
 package test
 
-trait A
+interface A
 
 public class <caret>B {
     private val bar = object : A {}
diff --git a/idea/testData/javaFacade/classWithObjectLiteralInFun.kt b/idea/testData/javaFacade/classWithObjectLiteralInFun.kt
index 7b6f00d0404..e09e1c8ee2f 100644
--- a/idea/testData/javaFacade/classWithObjectLiteralInFun.kt
+++ b/idea/testData/javaFacade/classWithObjectLiteralInFun.kt
@@ -1,6 +1,6 @@
 package test
 
-trait A
+interface A
 
 public class <caret>B {
     private fun bar() = object : A { }
diff --git a/idea/testData/javaFacade/localClassSubclass.kt b/idea/testData/javaFacade/localClassSubclass.kt
index f0730571ec7..3bb9fb002e5 100644
--- a/idea/testData/javaFacade/localClassSubclass.kt
+++ b/idea/testData/javaFacade/localClassSubclass.kt
@@ -1,6 +1,6 @@
 class A
 fun foo() {
-    trait Z: A {}
+    interface Z: A {}
     fun bar() {
         class <caret>O2: Z {}
     }
diff --git a/idea/testData/javaFacade/wrapFunWithImplInTrait.kt b/idea/testData/javaFacade/wrapFunWithImplInTrait.kt
index 0c35751bc7f..942756941ba 100644
--- a/idea/testData/javaFacade/wrapFunWithImplInTrait.kt
+++ b/idea/testData/javaFacade/wrapFunWithImplInTrait.kt
@@ -1,4 +1,4 @@
-trait Some {
+interface Some {
   fun <caret>some() {
   }
 }
\ No newline at end of file
diff --git a/idea/testData/javaFacade/wrapFunWithoutImplInTrait.kt b/idea/testData/javaFacade/wrapFunWithoutImplInTrait.kt
index 72bf27949e0..635dc3e17f8 100644
--- a/idea/testData/javaFacade/wrapFunWithoutImplInTrait.kt
+++ b/idea/testData/javaFacade/wrapFunWithoutImplInTrait.kt
@@ -1,3 +1,3 @@
-trait Some {
+interface Some {
   fun <caret>some()
 }
\ No newline at end of file
diff --git a/idea/testData/javaFacade/wrapVarPropertyWithAccessorsInTrait.kt b/idea/testData/javaFacade/wrapVarPropertyWithAccessorsInTrait.kt
index 9b324ad7dc7..b4285f512fb 100644
--- a/idea/testData/javaFacade/wrapVarPropertyWithAccessorsInTrait.kt
+++ b/idea/testData/javaFacade/wrapVarPropertyWithAccessorsInTrait.kt
@@ -1,4 +1,4 @@
-trait Hello {
+interface Hello {
     var <caret>some: String
         get() = "Hi"
         set(value) {}
diff --git a/idea/testData/kotlinAndJavaChecker/AssignKotlinClassToObjectInJava.kt b/idea/testData/kotlinAndJavaChecker/AssignKotlinClassToObjectInJava.kt
index 197c1d06979..160755275e8 100644
--- a/idea/testData/kotlinAndJavaChecker/AssignKotlinClassToObjectInJava.kt
+++ b/idea/testData/kotlinAndJavaChecker/AssignKotlinClassToObjectInJava.kt
@@ -1,2 +1,2 @@
 class KotlinClass
-trait KotlinTrait
+interface KotlinTrait
diff --git a/idea/testData/kotlinAndJavaChecker/ImplementedMethodsFromTraits.kt b/idea/testData/kotlinAndJavaChecker/ImplementedMethodsFromTraits.kt
index 3b10d43d742..a63822e9137 100644
--- a/idea/testData/kotlinAndJavaChecker/ImplementedMethodsFromTraits.kt
+++ b/idea/testData/kotlinAndJavaChecker/ImplementedMethodsFromTraits.kt
@@ -1,4 +1,4 @@
-public trait A {
+public interface A {
     public fun foo() {}
 }
 
diff --git a/idea/testData/kotlinAndJavaChecker/JvmOverloadsFunctions.kt b/idea/testData/kotlinAndJavaChecker/JvmOverloadsFunctions.kt
index 0c2ad9d36c5..9eada24682f 100644
--- a/idea/testData/kotlinAndJavaChecker/JvmOverloadsFunctions.kt
+++ b/idea/testData/kotlinAndJavaChecker/JvmOverloadsFunctions.kt
@@ -1,6 +1,6 @@
 package test.kotlin
 
-trait A
+interface A
 
 kotlin.jvm.overloads
 public fun foo<T : A>(k: Class<T>, a: A, b: Boolean = false, s: String="hello"): List<T> {
diff --git a/idea/testData/multiFileHighlighting/dependencies/enums.kt b/idea/testData/multiFileHighlighting/dependencies/enums.kt
index a49758fc378..e84d7d71590 100644
--- a/idea/testData/multiFileHighlighting/dependencies/enums.kt
+++ b/idea/testData/multiFileHighlighting/dependencies/enums.kt
@@ -1,6 +1,6 @@
 package enums
 
-trait Base {
+interface Base {
     fun f() {
     }
 }
diff --git a/idea/testData/multiFileHighlighting/dependencies/util.kt b/idea/testData/multiFileHighlighting/dependencies/util.kt
index bd6a258f167..1cbe0451c83 100644
--- a/idea/testData/multiFileHighlighting/dependencies/util.kt
+++ b/idea/testData/multiFileHighlighting/dependencies/util.kt
@@ -1,10 +1,10 @@
 public package util
 
-trait T {
+interface T {
     fun f()
 }
 
-trait T2 {
+interface T2 {
     fun g() {
     }
 }
diff --git a/idea/testData/navigation/gotoClass/inClassObject.kt b/idea/testData/navigation/gotoClass/inClassObject.kt
index ccde6fa34d5..f5cd2df42c8 100644
--- a/idea/testData/navigation/gotoClass/inClassObject.kt
+++ b/idea/testData/navigation/gotoClass/inClassObject.kt
@@ -4,9 +4,9 @@ class InClassObject {
     companion object {
         class ClassObjectClass {}
 
-        trait ClassObjectTrait {}
+        interface ClassObjectTrait {}
 
-        trait ClassObjectTraitWithImpl {
+        interface ClassObjectTraitWithImpl {
             fun foo() {}
         }
 
diff --git a/idea/testData/navigation/gotoClass/localDeclarations.kt b/idea/testData/navigation/gotoClass/localDeclarations.kt
index 8be79d4de0d..e066c91866d 100644
--- a/idea/testData/navigation/gotoClass/localDeclarations.kt
+++ b/idea/testData/navigation/gotoClass/localDeclarations.kt
@@ -1,9 +1,9 @@
 fun foo() {
     class LocalClass {}
 
-    trait LocalTrait {}
+    interface LocalTrait {}
 
-    trait LocalTraitWithImpl {
+    interface LocalTraitWithImpl {
         fun foo() {}
     }
 
diff --git a/idea/testData/navigation/gotoClass/noImplementationTrait.kt b/idea/testData/navigation/gotoClass/noImplementationTrait.kt
index 13ed9e7edf6..e1d70b2f78a 100644
--- a/idea/testData/navigation/gotoClass/noImplementationTrait.kt
+++ b/idea/testData/navigation/gotoClass/noImplementationTrait.kt
@@ -1,6 +1,6 @@
 package test
 
-trait NoImplementationTrait {
+interface NoImplementationTrait {
     fun foo(): Int
     fun some(): String
 }
diff --git a/idea/testData/navigation/gotoClass/traitWithFunImplement.kt b/idea/testData/navigation/gotoClass/traitWithFunImplement.kt
index 0635d144bd2..6fd391986d8 100644
--- a/idea/testData/navigation/gotoClass/traitWithFunImplement.kt
+++ b/idea/testData/navigation/gotoClass/traitWithFunImplement.kt
@@ -1,6 +1,6 @@
 package test
 
-trait TraitWithFunImplement {
+interface TraitWithFunImplement {
     fun foo(): Int {
         return 12;
     }
diff --git a/idea/testData/navigation/gotoSuper/ClassSimple.test b/idea/testData/navigation/gotoSuper/ClassSimple.test
index ce53dfcb7c5..24e992ae5ba 100644
--- a/idea/testData/navigation/gotoSuper/ClassSimple.test
+++ b/idea/testData/navigation/gotoSuper/ClassSimple.test
@@ -1,6 +1,6 @@
 // FILE: before.kt
-trait Some
+interface Some
 class <caret>SomeObject: Some
 // FILE: after.kt
-trait <caret>Some
+interface <caret>Some
 class SomeObject: Some
\ No newline at end of file
diff --git a/idea/testData/navigation/gotoSuper/DelegatedFun.test b/idea/testData/navigation/gotoSuper/DelegatedFun.test
index 34446d6ebd2..0344341e1b7 100644
--- a/idea/testData/navigation/gotoSuper/DelegatedFun.test
+++ b/idea/testData/navigation/gotoSuper/DelegatedFun.test
@@ -1,9 +1,9 @@
 // FILE: before.kt
-trait A {
+interface A {
   fun f() {}
 }
 
-trait B : A
+interface B : A
 
 open class C(b : B) : B by b, A {
 }
@@ -13,11 +13,11 @@ class D(b : B) : C(b) {
 }
 
 // FILE: after.kt
-trait A {
+interface A {
   fun <caret>f() {}
 }
 
-trait B : A
+interface B : A
 
 open class C(b : B) : B by b, A {
 }
diff --git a/idea/testData/navigation/gotoSuper/DelegatedProperty.test b/idea/testData/navigation/gotoSuper/DelegatedProperty.test
index 31b9ec75f24..33b9ba53eba 100644
--- a/idea/testData/navigation/gotoSuper/DelegatedProperty.test
+++ b/idea/testData/navigation/gotoSuper/DelegatedProperty.test
@@ -1,10 +1,10 @@
 // FILE: before.kt
-trait A {
+interface A {
     val f: Int
         get() = 3
 }
 
-trait B : A
+interface B : A
 
 open class C(b : B) : B by b, A {
 }
@@ -14,12 +14,12 @@ class D(b : B) : C(b) {
 }
 
 // FILE: after.kt
-trait A {
+interface A {
     val <caret>f: Int
         get() = 3
 }
 
-trait B : A
+interface B : A
 
 open class C(b : B) : B by b, A {
 }
diff --git a/idea/testData/navigation/gotoSuper/FakeOverrideFun.test b/idea/testData/navigation/gotoSuper/FakeOverrideFun.test
index 42d689e87d0..0afbe0a30bb 100644
--- a/idea/testData/navigation/gotoSuper/FakeOverrideFun.test
+++ b/idea/testData/navigation/gotoSuper/FakeOverrideFun.test
@@ -1,23 +1,23 @@
 // FILE: before.kt
-trait A {
+interface A {
   fun f() {}
 }
 
-trait B : A
+interface B : A
 
-trait C : B, A
+interface C : B, A
 
 class SomeClass() : C {
   override fun <caret>f() {}
 }
 // FILE: after.kt
-trait A {
+interface A {
   fun <caret>f() {}
 }
 
-trait B : A
+interface B : A
 
-trait C : B, A
+interface C : B, A
 
 class SomeClass() : C {
   override fun f() {}
diff --git a/idea/testData/navigation/gotoSuper/FakeOverrideFunWithMostRelevantImplementation.test b/idea/testData/navigation/gotoSuper/FakeOverrideFunWithMostRelevantImplementation.test
index 11a4b60625a..b4bf7184d88 100644
--- a/idea/testData/navigation/gotoSuper/FakeOverrideFunWithMostRelevantImplementation.test
+++ b/idea/testData/navigation/gotoSuper/FakeOverrideFunWithMostRelevantImplementation.test
@@ -1,27 +1,27 @@
 // FILE: before.kt
-trait A {
+interface A {
     fun f() {}
 }
 
-trait B : A {
+interface B : A {
     override fun f() {}
 }
 
-trait C : B, A
+interface C : B, A
 
 class SomeClass() : C {
     override fun <caret>f() {}
 }
 // FILE: after.kt
-trait A {
+interface A {
     fun f() {}
 }
 
-trait B : A {
+interface B : A {
     override fun <caret>f() {}
 }
 
-trait C : B, A
+interface C : B, A
 
 class SomeClass() : C {
     override fun f() {}
diff --git a/idea/testData/navigation/gotoSuper/FakeOverrideProperty.test b/idea/testData/navigation/gotoSuper/FakeOverrideProperty.test
index 8212da6fb02..657eaec8bb8 100644
--- a/idea/testData/navigation/gotoSuper/FakeOverrideProperty.test
+++ b/idea/testData/navigation/gotoSuper/FakeOverrideProperty.test
@@ -1,25 +1,25 @@
 // FILE: before.kt
-trait A {
+interface A {
     val f: Int
         get() = 2
 }
 
-trait B : A
+interface B : A
 
-trait C : B, A
+interface C : B, A
 
 class SomeClass() : C {
     override val <caret>f: Int = 4
 }
 // FILE: after.kt
-trait A {
+interface A {
     val <caret>f: Int
         get() = 2
 }
 
-trait B : A
+interface B : A
 
-trait C : B, A
+interface C : B, A
 
 class SomeClass() : C {
     override val f: Int = 4
diff --git a/idea/testData/navigation/gotoSuper/FunctionSimple.test b/idea/testData/navigation/gotoSuper/FunctionSimple.test
index d363f865f80..40fd7ddffaa 100644
--- a/idea/testData/navigation/gotoSuper/FunctionSimple.test
+++ b/idea/testData/navigation/gotoSuper/FunctionSimple.test
@@ -1,5 +1,5 @@
 // FILE: before.kt
-trait Some {
+interface Some {
   fun test()
 }
 class SomeObject: Some {
@@ -8,7 +8,7 @@ class SomeObject: Some {
   }
 }
 // FILE: after.kt
-trait Some {
+interface Some {
   fun <caret>test()
 }
 class SomeObject: Some {
diff --git a/idea/testData/navigation/gotoSuper/ObjectSimple.test b/idea/testData/navigation/gotoSuper/ObjectSimple.test
index b21ccc71077..bd2cac085d8 100644
--- a/idea/testData/navigation/gotoSuper/ObjectSimple.test
+++ b/idea/testData/navigation/gotoSuper/ObjectSimple.test
@@ -1,6 +1,6 @@
 // FILE: b.kt
-trait Some
+interface Some
 object <caret>SomeObject: Some
 // FILE: a.kt
-trait <caret>Some
+interface <caret>Some
 object SomeObject: Some
\ No newline at end of file
diff --git a/idea/testData/navigation/gotoSuper/PropertySimple.test b/idea/testData/navigation/gotoSuper/PropertySimple.test
index 0282d13c6d4..51127d26dcd 100644
--- a/idea/testData/navigation/gotoSuper/PropertySimple.test
+++ b/idea/testData/navigation/gotoSuper/PropertySimple.test
@@ -1,12 +1,12 @@
 // FILE: b.kt
-trait Some {
+interface Some {
     val test: Int
 }
 class SomeObject: Some {
     override val <caret>test: Int = 1
 }
 // FILE: a.kt
-trait Some {
+interface Some {
     val <caret>test: Int
 }
 class SomeObject: Some {
diff --git a/idea/testData/navigation/gotoSuper/TraitSimple.test b/idea/testData/navigation/gotoSuper/TraitSimple.test
index 65c9f2ce61d..c8889274312 100644
--- a/idea/testData/navigation/gotoSuper/TraitSimple.test
+++ b/idea/testData/navigation/gotoSuper/TraitSimple.test
@@ -1,6 +1,6 @@
 // FILE: a.kt
 open class First
-trait <caret>Second: First
+interface <caret>Second: First
 // FILE: b.kt
 open class <caret>First
-trait Second: First
\ No newline at end of file
+interface Second: First
\ No newline at end of file
diff --git a/idea/testData/navigation/gotoSymbol/properties.kt b/idea/testData/navigation/gotoSymbol/properties.kt
index eac3b2a38cb..7c8aa0f3844 100644
--- a/idea/testData/navigation/gotoSymbol/properties.kt
+++ b/idea/testData/navigation/gotoSymbol/properties.kt
@@ -4,7 +4,7 @@ fun some() {
   val testInFun = 12
 }
 
-trait SomeTrait {
+interface SomeTrait {
   val testInTrait
 }
 
diff --git a/idea/testData/navigation/implementations/TraitImplementorsWithDeclaration.kt b/idea/testData/navigation/implementations/TraitImplementorsWithDeclaration.kt
index cad7672e41a..6c8a6d17b0e 100644
--- a/idea/testData/navigation/implementations/TraitImplementorsWithDeclaration.kt
+++ b/idea/testData/navigation/implementations/TraitImplementorsWithDeclaration.kt
@@ -1,8 +1,8 @@
 package testing
 
-trait Test
+interface Test
 
-trait TestMore: <caret>Test
+interface TestMore: <caret>Test
 
 open class TestClass1: Test
 
diff --git a/idea/testData/navigation/implementations/multifile/ImplementJavaInterfaceInKotlin/ImplementJavaInterfaceInKotlin.kt b/idea/testData/navigation/implementations/multifile/ImplementJavaInterfaceInKotlin/ImplementJavaInterfaceInKotlin.kt
index f838bd56236..cc2654912ba 100644
--- a/idea/testData/navigation/implementations/multifile/ImplementJavaInterfaceInKotlin/ImplementJavaInterfaceInKotlin.kt
+++ b/idea/testData/navigation/implementations/multifile/ImplementJavaInterfaceInKotlin/ImplementJavaInterfaceInKotlin.kt
@@ -1,4 +1,4 @@
-trait KotlinTrait: <caret>JavaBase
+interface KotlinTrait: <caret>JavaBase
 
 class KotlinClass : JavaBase
 
diff --git a/idea/testData/navigation/implementations/multifile/ImplementKotlinTraitInJava/ImplementKotlinTraitInJava.kt b/idea/testData/navigation/implementations/multifile/ImplementKotlinTraitInJava/ImplementKotlinTraitInJava.kt
index 9bc94742d5e..4fd60f4e69c 100644
--- a/idea/testData/navigation/implementations/multifile/ImplementKotlinTraitInJava/ImplementKotlinTraitInJava.kt
+++ b/idea/testData/navigation/implementations/multifile/ImplementKotlinTraitInJava/ImplementKotlinTraitInJava.kt
@@ -1,8 +1,8 @@
 package testing.kt
 
-trait Base
+interface Base
 
-trait Derived: <caret>Base
+interface Derived: <caret>Base
 
 // REF: (testing.jj).JavaClass
 // REF: (testing.jj).JavaInterface
diff --git a/idea/testData/parameterInfo/functionParameterInfo/ExtensionOnClassObject.kt b/idea/testData/parameterInfo/functionParameterInfo/ExtensionOnClassObject.kt
index ba1950af3f4..14e69004c68 100644
--- a/idea/testData/parameterInfo/functionParameterInfo/ExtensionOnClassObject.kt
+++ b/idea/testData/parameterInfo/functionParameterInfo/ExtensionOnClassObject.kt
@@ -1,4 +1,4 @@
-trait A
+interface A
 
 fun A.foo(i: Int) = i
 
diff --git a/idea/testData/quickfix/abstract/redundantAbstract.kt b/idea/testData/quickfix/abstract/redundantAbstract.kt
index 4cf5dd59500..64c1228fc3c 100644
--- a/idea/testData/quickfix/abstract/redundantAbstract.kt
+++ b/idea/testData/quickfix/abstract/redundantAbstract.kt
@@ -1,4 +1,4 @@
 // "Remove redundant 'abstract' modifier" "true"
-trait A {
+interface A {
     <caret>abstract fun foo()
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/abstract/redundantAbstract.kt.after b/idea/testData/quickfix/abstract/redundantAbstract.kt.after
index 6fc13b24bc1..dc9e9ed81e0 100644
--- a/idea/testData/quickfix/abstract/redundantAbstract.kt.after
+++ b/idea/testData/quickfix/abstract/redundantAbstract.kt.after
@@ -1,4 +1,4 @@
 // "Remove redundant 'abstract' modifier" "true"
-trait A {
+interface A {
     <caret>fun foo()
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/anonymousObject.kt b/idea/testData/quickfix/anonymousObject.kt
index ba2400ae917..e7c3e210113 100644
--- a/idea/testData/quickfix/anonymousObject.kt
+++ b/idea/testData/quickfix/anonymousObject.kt
@@ -2,7 +2,7 @@
 // ACTION: Implement members
 // ACTION: Split property declaration
 // ERROR: <html>Object must be declared abstract or implement abstract member<br/><b>internal</b> <b>abstract</b> <b>fun</b> foo(): kotlin.Unit <i>defined in</i> T</html>
-trait T {
+interface T {
     fun foo()
 }
 
diff --git a/idea/testData/quickfix/autoImports/divOperator.after.kt b/idea/testData/quickfix/autoImports/divOperator.after.kt
index 2143938a0b4..6a19712decf 100644
--- a/idea/testData/quickfix/autoImports/divOperator.after.kt
+++ b/idea/testData/quickfix/autoImports/divOperator.after.kt
@@ -5,7 +5,7 @@ package h
 
 import util.div
 
-trait H
+interface H
 
 fun f(h: H) {
     h / 3
diff --git a/idea/testData/quickfix/autoImports/divOperator.before.Main.kt b/idea/testData/quickfix/autoImports/divOperator.before.Main.kt
index 4c1866501ef..30caf7ff708 100644
--- a/idea/testData/quickfix/autoImports/divOperator.before.Main.kt
+++ b/idea/testData/quickfix/autoImports/divOperator.before.Main.kt
@@ -3,7 +3,7 @@
 
 package h
 
-trait H
+interface H
 
 fun f(h: H) {
     h <caret>/ 3
diff --git a/idea/testData/quickfix/autoImports/falsePostfixOperator.before.Main.kt b/idea/testData/quickfix/autoImports/falsePostfixOperator.before.Main.kt
index 822b54894df..cdde5198289 100644
--- a/idea/testData/quickfix/autoImports/falsePostfixOperator.before.Main.kt
+++ b/idea/testData/quickfix/autoImports/falsePostfixOperator.before.Main.kt
@@ -8,7 +8,7 @@
 
 package h
 
-trait H
+interface H
 
 [suppress("UNUSED_CHANGED_VALUE")]
 fun f(h: H?) {
diff --git a/idea/testData/quickfix/autoImports/importTrait.before.data.Sample.kt b/idea/testData/quickfix/autoImports/importTrait.before.data.Sample.kt
index ca7f9f4bdcb..e23ed8c32c3 100644
--- a/idea/testData/quickfix/autoImports/importTrait.before.data.Sample.kt
+++ b/idea/testData/quickfix/autoImports/importTrait.before.data.Sample.kt
@@ -1,3 +1,3 @@
 package importTrait.data
 
-trait TestTrait
\ No newline at end of file
+interface TestTrait
\ No newline at end of file
diff --git a/idea/testData/quickfix/autoImports/infixCall.after.kt b/idea/testData/quickfix/autoImports/infixCall.after.kt
index 878c6d59211..b27ccfab924 100644
--- a/idea/testData/quickfix/autoImports/infixCall.after.kt
+++ b/idea/testData/quickfix/autoImports/infixCall.after.kt
@@ -5,7 +5,7 @@ package h
 
 import util.foo
 
-trait H
+interface H
 
 fun f(h: H) {
     h foo h
diff --git a/idea/testData/quickfix/autoImports/infixCall.before.Main.kt b/idea/testData/quickfix/autoImports/infixCall.before.Main.kt
index 10edb71f9f9..59d31c0e73e 100644
--- a/idea/testData/quickfix/autoImports/infixCall.before.Main.kt
+++ b/idea/testData/quickfix/autoImports/infixCall.before.Main.kt
@@ -3,7 +3,7 @@
 
 package h
 
-trait H
+interface H
 
 fun f(h: H) {
     h <caret>foo h
diff --git a/idea/testData/quickfix/autoImports/minusOperator.after.kt b/idea/testData/quickfix/autoImports/minusOperator.after.kt
index bd2cea4c843..1a6ff060fb6 100644
--- a/idea/testData/quickfix/autoImports/minusOperator.after.kt
+++ b/idea/testData/quickfix/autoImports/minusOperator.after.kt
@@ -5,7 +5,7 @@ package h
 
 import util.minus
 
-trait H
+interface H
 
 fun f(h: H?) {
     h - "other"
diff --git a/idea/testData/quickfix/autoImports/minusOperator.before.Main.kt b/idea/testData/quickfix/autoImports/minusOperator.before.Main.kt
index 4ab1546c5bc..da664475041 100644
--- a/idea/testData/quickfix/autoImports/minusOperator.before.Main.kt
+++ b/idea/testData/quickfix/autoImports/minusOperator.before.Main.kt
@@ -3,7 +3,7 @@
 
 package h
 
-trait H
+interface H
 
 fun f(h: H?) {
     h <caret>- "other"
diff --git a/idea/testData/quickfix/autoImports/plusOperator.after.kt b/idea/testData/quickfix/autoImports/plusOperator.after.kt
index e3fd38cdc85..6c98780c5ea 100644
--- a/idea/testData/quickfix/autoImports/plusOperator.after.kt
+++ b/idea/testData/quickfix/autoImports/plusOperator.after.kt
@@ -5,7 +5,7 @@ package h
 
 import util.plus
 
-trait H
+interface H
 
 fun f(h: H?) {
     h + "other"
diff --git a/idea/testData/quickfix/autoImports/plusOperator.before.Main.kt b/idea/testData/quickfix/autoImports/plusOperator.before.Main.kt
index 5d1e3378432..476a4d30fdb 100644
--- a/idea/testData/quickfix/autoImports/plusOperator.before.Main.kt
+++ b/idea/testData/quickfix/autoImports/plusOperator.before.Main.kt
@@ -3,7 +3,7 @@
 
 package h
 
-trait H
+interface H
 
 fun f(h: H?) {
     h <caret>+ "other"
diff --git a/idea/testData/quickfix/autoImports/postfixOperator.after.kt b/idea/testData/quickfix/autoImports/postfixOperator.after.kt
index 4cd807644ab..560bbd29450 100644
--- a/idea/testData/quickfix/autoImports/postfixOperator.after.kt
+++ b/idea/testData/quickfix/autoImports/postfixOperator.after.kt
@@ -5,7 +5,7 @@ package h
 
 import util.inc
 
-trait H
+interface H
 
 fun f(h: H?) {
     var h1 = h
diff --git a/idea/testData/quickfix/autoImports/postfixOperator.before.Main.kt b/idea/testData/quickfix/autoImports/postfixOperator.before.Main.kt
index 9e5696144a2..b0d3384014f 100644
--- a/idea/testData/quickfix/autoImports/postfixOperator.before.Main.kt
+++ b/idea/testData/quickfix/autoImports/postfixOperator.before.Main.kt
@@ -3,7 +3,7 @@
 
 package h
 
-trait H
+interface H
 
 fun f(h: H?) {
     var h1 = h
diff --git a/idea/testData/quickfix/autoImports/timesAssign.after.kt b/idea/testData/quickfix/autoImports/timesAssign.after.kt
index 065592f1a64..641c1dd713a 100644
--- a/idea/testData/quickfix/autoImports/timesAssign.after.kt
+++ b/idea/testData/quickfix/autoImports/timesAssign.after.kt
@@ -5,7 +5,7 @@ package h
 
 import util.timesAssign
 
-trait H
+interface H
 
 fun f(h: H) {
     h *= 3
diff --git a/idea/testData/quickfix/autoImports/timesAssign.before.Main.kt b/idea/testData/quickfix/autoImports/timesAssign.before.Main.kt
index e58dc0399ed..8cf5557ee21 100644
--- a/idea/testData/quickfix/autoImports/timesAssign.before.Main.kt
+++ b/idea/testData/quickfix/autoImports/timesAssign.before.Main.kt
@@ -3,7 +3,7 @@
 
 package h
 
-trait H
+interface H
 
 fun f(h: H) {
     h <caret>*= 3
diff --git a/idea/testData/quickfix/autoImports/unaryMinusOperator.after.kt b/idea/testData/quickfix/autoImports/unaryMinusOperator.after.kt
index 5d4fccc55fd..36ce590e8d0 100644
--- a/idea/testData/quickfix/autoImports/unaryMinusOperator.after.kt
+++ b/idea/testData/quickfix/autoImports/unaryMinusOperator.after.kt
@@ -5,7 +5,7 @@ package h
 
 import util.minus
 
-trait H
+interface H
 
 fun f(h: H?) {
     -h
diff --git a/idea/testData/quickfix/autoImports/unaryMinusOperator.before.Main.kt b/idea/testData/quickfix/autoImports/unaryMinusOperator.before.Main.kt
index f8ea7f7a7a2..b0b05cbb5c6 100644
--- a/idea/testData/quickfix/autoImports/unaryMinusOperator.before.Main.kt
+++ b/idea/testData/quickfix/autoImports/unaryMinusOperator.before.Main.kt
@@ -3,7 +3,7 @@
 
 package h
 
-trait H
+interface H
 
 fun f(h: H?) {
     <caret>-h
diff --git a/idea/testData/quickfix/autoImports/unaryPlusOperator.after.kt b/idea/testData/quickfix/autoImports/unaryPlusOperator.after.kt
index c58f2627f71..b030430ae17 100644
--- a/idea/testData/quickfix/autoImports/unaryPlusOperator.after.kt
+++ b/idea/testData/quickfix/autoImports/unaryPlusOperator.after.kt
@@ -5,7 +5,7 @@ package h
 
 import util.plus
 
-trait H
+interface H
 
 fun f(h: H?) {
     +h
diff --git a/idea/testData/quickfix/autoImports/unaryPlusOperator.before.Main.kt b/idea/testData/quickfix/autoImports/unaryPlusOperator.before.Main.kt
index 42ad2f4093d..111d52305d4 100644
--- a/idea/testData/quickfix/autoImports/unaryPlusOperator.before.Main.kt
+++ b/idea/testData/quickfix/autoImports/unaryPlusOperator.before.Main.kt
@@ -3,7 +3,7 @@
 
 package h
 
-trait H
+interface H
 
 fun f(h: H?) {
     <caret>+h
diff --git a/idea/testData/quickfix/changeSignature/addParameterToFakeOverride.kt b/idea/testData/quickfix/changeSignature/addParameterToFakeOverride.kt
index a04b2b514bf..ce178e18cc1 100644
--- a/idea/testData/quickfix/changeSignature/addParameterToFakeOverride.kt
+++ b/idea/testData/quickfix/changeSignature/addParameterToFakeOverride.kt
@@ -1,16 +1,16 @@
 // "Add parameter to function 'f'" "true"
-trait Z {
+interface Z {
     fun f()
 }
 
-trait ZZ {
+interface ZZ {
     fun f()
 }
 
-trait ZZZ: Z, ZZ {
+interface ZZZ: Z, ZZ {
 }
 
-trait ZZZZ : ZZZ {
+interface ZZZZ : ZZZ {
     override fun f()
 }
 
diff --git a/idea/testData/quickfix/changeSignature/addParameterToFakeOverride.kt.after b/idea/testData/quickfix/changeSignature/addParameterToFakeOverride.kt.after
index c677e8445a7..891f0eb8948 100644
--- a/idea/testData/quickfix/changeSignature/addParameterToFakeOverride.kt.after
+++ b/idea/testData/quickfix/changeSignature/addParameterToFakeOverride.kt.after
@@ -1,16 +1,16 @@
 // "Add parameter to function 'f'" "true"
-trait Z {
+interface Z {
     fun f(i: Int)
 }
 
-trait ZZ {
+interface ZZ {
     fun f(i: Int)
 }
 
-trait ZZZ: Z, ZZ {
+interface ZZZ: Z, ZZ {
 }
 
-trait ZZZZ : ZZZ {
+interface ZZZZ : ZZZ {
     override fun f(i: Int)
 }
 
diff --git a/idea/testData/quickfix/changeSignature/complexHierarchy.kt b/idea/testData/quickfix/changeSignature/complexHierarchy.kt
index 24d994f9799..321ee884d28 100644
--- a/idea/testData/quickfix/changeSignature/complexHierarchy.kt
+++ b/idea/testData/quickfix/changeSignature/complexHierarchy.kt
@@ -1,31 +1,31 @@
 // "Add parameter to function 'f'" "true"
-trait OA {
+interface OA {
     fun f(a: Int)
 }
 
-trait OB {
+interface OB {
     fun f(a: Int)
 }
 
-trait O : OA, OB {
+interface O : OA, OB {
     override fun f(a: Int)
 }
 
-trait OO : O {
+interface OO : O {
     override fun f(a: Int) {
     }
 }
 
-trait OOO : OO {
+interface OOO : OO {
     override fun f(a: Int) {}
 }
 
-trait OOOA : OOO {
+interface OOOA : OOO {
     override fun f(a: Int) {
     }
 }
 
-trait OOOB : OOO {
+interface OOOB : OOO {
     override fun f(a: Int) {
     }
 }
diff --git a/idea/testData/quickfix/changeSignature/complexHierarchy.kt.after b/idea/testData/quickfix/changeSignature/complexHierarchy.kt.after
index dcb4d1e310f..0ec0a828a64 100644
--- a/idea/testData/quickfix/changeSignature/complexHierarchy.kt.after
+++ b/idea/testData/quickfix/changeSignature/complexHierarchy.kt.after
@@ -1,31 +1,31 @@
 // "Add parameter to function 'f'" "true"
-trait OA {
+interface OA {
     fun f(a: Int, i: Int)
 }
 
-trait OB {
+interface OB {
     fun f(a: Int, i: Int)
 }
 
-trait O : OA, OB {
+interface O : OA, OB {
     override fun f(a: Int, i: Int)
 }
 
-trait OO : O {
+interface OO : O {
     override fun f(a: Int, i: Int) {
     }
 }
 
-trait OOO : OO {
+interface OOO : OO {
     override fun f(a: Int, i: Int) {}
 }
 
-trait OOOA : OOO {
+interface OOOA : OOO {
     override fun f(a: Int, i: Int) {
     }
 }
 
-trait OOOB : OOO {
+interface OOOB : OOO {
     override fun f(a: Int, i: Int) {
     }
 }
diff --git a/idea/testData/quickfix/changeSignature/complexHierarchyHead.kt b/idea/testData/quickfix/changeSignature/complexHierarchyHead.kt
index 48f5b9a4311..84976f1cd52 100644
--- a/idea/testData/quickfix/changeSignature/complexHierarchyHead.kt
+++ b/idea/testData/quickfix/changeSignature/complexHierarchyHead.kt
@@ -1,31 +1,31 @@
 // "Remove parameter 'a'" "true"
-trait OA {
+interface OA {
     fun f(a: Int)
 }
 
-trait OB {
+interface OB {
     fun f(a: Int)
 }
 
-trait O : OA, OB {
+interface O : OA, OB {
     override fun f(a: Int)
 }
 
-trait OO : O {
+interface OO : O {
     override fun f(a: Int) {
     }
 }
 
-trait OOO : OO {
+interface OOO : OO {
     override fun f(a: Int) {}
 }
 
-trait OOOA : OOO {
+interface OOOA : OOO {
     override fun f(a: Int) {
     }
 }
 
-trait OOOB : OOO {
+interface OOOB : OOO {
     override fun f(a: Int) {
     }
 }
diff --git a/idea/testData/quickfix/changeSignature/complexHierarchyHead.kt.after b/idea/testData/quickfix/changeSignature/complexHierarchyHead.kt.after
index df449ddbf11..47f96ccd121 100644
--- a/idea/testData/quickfix/changeSignature/complexHierarchyHead.kt.after
+++ b/idea/testData/quickfix/changeSignature/complexHierarchyHead.kt.after
@@ -1,31 +1,31 @@
 // "Remove parameter 'a'" "true"
-trait OA {
+interface OA {
     fun f()
 }
 
-trait OB {
+interface OB {
     fun f(a: Int)
 }
 
-trait O : OA, OB {
+interface O : OA, OB {
     override fun f()
 }
 
-trait OO : O {
+interface OO : O {
     override fun f() {
     }
 }
 
-trait OOO : OO {
+interface OOO : OO {
     override fun f() {}
 }
 
-trait OOOA : OOO {
+interface OOOA : OOO {
     override fun f() {
     }
 }
 
-trait OOOB : OOO {
+interface OOOB : OOO {
     override fun f() {
     }
 }
diff --git a/idea/testData/quickfix/changeSignature/complexHierarchyTail.kt b/idea/testData/quickfix/changeSignature/complexHierarchyTail.kt
index 5b242589c7b..edc9da7d797 100644
--- a/idea/testData/quickfix/changeSignature/complexHierarchyTail.kt
+++ b/idea/testData/quickfix/changeSignature/complexHierarchyTail.kt
@@ -1,31 +1,31 @@
 // "Add parameter to function 'f'" "true"
-trait OA {
+interface OA {
     fun f(a: Int)
 }
 
-trait OB {
+interface OB {
     fun f(a: Int)
 }
 
-trait O : OA, OB {
+interface O : OA, OB {
     override fun f(a: Int)
 }
 
-trait OO : O {
+interface OO : O {
     override fun f(a: Int) {
     }
 }
 
-trait OOO : OO {
+interface OOO : OO {
     override fun f(a: Int) {}
 }
 
-trait OOOA : OOO {
+interface OOOA : OOO {
     override fun f(a: Int) {
     }
 }
 
-trait OOOB : OOO {
+interface OOOB : OOO {
     override fun f(a: Int) {
     }
 }
diff --git a/idea/testData/quickfix/changeSignature/complexHierarchyTail.kt.after b/idea/testData/quickfix/changeSignature/complexHierarchyTail.kt.after
index 046fb3501ef..6e768cee396 100644
--- a/idea/testData/quickfix/changeSignature/complexHierarchyTail.kt.after
+++ b/idea/testData/quickfix/changeSignature/complexHierarchyTail.kt.after
@@ -1,31 +1,31 @@
 // "Add parameter to function 'f'" "true"
-trait OA {
+interface OA {
     fun f(a: Int, s: String)
 }
 
-trait OB {
+interface OB {
     fun f(a: Int, s: String)
 }
 
-trait O : OA, OB {
+interface O : OA, OB {
     override fun f(a: Int, s: String)
 }
 
-trait OO : O {
+interface OO : O {
     override fun f(a: Int, s: String) {
     }
 }
 
-trait OOO : OO {
+interface OOO : OO {
     override fun f(a: Int, s: String) {}
 }
 
-trait OOOA : OOO {
+interface OOOA : OOO {
     override fun f(a: Int, s: String) {
     }
 }
 
-trait OOOB : OOO {
+interface OOOB : OOO {
     override fun f(a: Int, s: String) {
     }
 }
diff --git a/idea/testData/quickfix/changeSignature/linearHierarchy.kt b/idea/testData/quickfix/changeSignature/linearHierarchy.kt
index 27f2c643e93..1e5dd0e25d5 100644
--- a/idea/testData/quickfix/changeSignature/linearHierarchy.kt
+++ b/idea/testData/quickfix/changeSignature/linearHierarchy.kt
@@ -1,14 +1,14 @@
 // "Add parameter to function 'f'" "true"
-trait O {
+interface O {
     fun f(a: Int)
 }
 
-trait OO : O {
+interface OO : O {
     override fun f(a: Int) {
     }
 }
 
-trait OOO : OO {
+interface OOO : OO {
     override fun f(a: Int) {}
 }
 
diff --git a/idea/testData/quickfix/changeSignature/linearHierarchy.kt.after b/idea/testData/quickfix/changeSignature/linearHierarchy.kt.after
index f7f4f8c093b..7fd95189c9e 100644
--- a/idea/testData/quickfix/changeSignature/linearHierarchy.kt.after
+++ b/idea/testData/quickfix/changeSignature/linearHierarchy.kt.after
@@ -1,14 +1,14 @@
 // "Add parameter to function 'f'" "true"
-trait O {
+interface O {
     fun f(a: Int, i: Int)
 }
 
-trait OO : O {
+interface OO : O {
     override fun f(a: Int, i: Int) {
     }
 }
 
-trait OOO : OO {
+interface OOO : OO {
     override fun f(a: Int, i: Int) {}
 }
 
diff --git a/idea/testData/quickfix/changeSignature/notEditable.kt b/idea/testData/quickfix/changeSignature/notEditable.kt
index b371f1c2599..e6ed21079d5 100644
--- a/idea/testData/quickfix/changeSignature/notEditable.kt
+++ b/idea/testData/quickfix/changeSignature/notEditable.kt
@@ -1,7 +1,7 @@
 // "class org.jetbrains.kotlin.idea.quickfix.RemoveFunctionParametersFix" "false"
 //ERROR: No value passed for parameter other
 
-trait StringComparable {
+interface StringComparable {
     public fun compareTo(other: String): Int = 0
 }
 
diff --git a/idea/testData/quickfix/changeSignature/removeParameterFromFakeOverride.kt b/idea/testData/quickfix/changeSignature/removeParameterFromFakeOverride.kt
index 234ffb36811..edff7da10e3 100644
--- a/idea/testData/quickfix/changeSignature/removeParameterFromFakeOverride.kt
+++ b/idea/testData/quickfix/changeSignature/removeParameterFromFakeOverride.kt
@@ -1,16 +1,16 @@
 // "Remove parameter 'i'" "true"
-trait Z {
+interface Z {
     fun f(i: Int)
 }
 
-trait ZZ {
+interface ZZ {
     fun f(i: Int)
 }
 
-trait ZZZ: Z, ZZ {
+interface ZZZ: Z, ZZ {
 }
 
-trait ZZZZ : ZZZ {
+interface ZZZZ : ZZZ {
     override fun f(i: Int)
 }
 
diff --git a/idea/testData/quickfix/changeSignature/removeParameterFromFakeOverride.kt.after b/idea/testData/quickfix/changeSignature/removeParameterFromFakeOverride.kt.after
index b19dad47615..2dda0668512 100644
--- a/idea/testData/quickfix/changeSignature/removeParameterFromFakeOverride.kt.after
+++ b/idea/testData/quickfix/changeSignature/removeParameterFromFakeOverride.kt.after
@@ -1,16 +1,16 @@
 // "Remove parameter 'i'" "true"
-trait Z {
+interface Z {
     fun f()
 }
 
-trait ZZ {
+interface ZZ {
     fun f()
 }
 
-trait ZZZ: Z, ZZ {
+interface ZZZ: Z, ZZ {
 }
 
-trait ZZZZ : ZZZ {
+interface ZZZZ : ZZZ {
     override fun f()
 }
 
diff --git a/idea/testData/quickfix/createFromUsage/createClass/callExpression/callWithSupertrait.kt b/idea/testData/quickfix/createFromUsage/createClass/callExpression/callWithSupertrait.kt
index af63b7b17a9..ee309ece98b 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/callExpression/callWithSupertrait.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/callExpression/callWithSupertrait.kt
@@ -1,5 +1,5 @@
 // "Create class 'Foo'" "true"
 
-trait A
+interface A
 
 fun test(): A = <caret>Foo(2, "2")
\ No newline at end of file
diff --git a/idea/testData/quickfix/createFromUsage/createClass/callExpression/callWithSupertrait.kt.after b/idea/testData/quickfix/createFromUsage/createClass/callExpression/callWithSupertrait.kt.after
index a05ce26dd9d..b451d99c043 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/callExpression/callWithSupertrait.kt.after
+++ b/idea/testData/quickfix/createFromUsage/createClass/callExpression/callWithSupertrait.kt.after
@@ -1,6 +1,6 @@
 // "Create class 'Foo'" "true"
 
-trait A
+interface A
 
 fun test(): A = Foo(2, "2")
 
diff --git a/idea/testData/quickfix/createFromUsage/createClass/callExpression/callWithSupertraitAndJavaReceiver.after.kt b/idea/testData/quickfix/createFromUsage/createClass/callExpression/callWithSupertraitAndJavaReceiver.after.kt
index 9aa72e47b88..0e72d0a6667 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/callExpression/callWithSupertraitAndJavaReceiver.after.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/callExpression/callWithSupertraitAndJavaReceiver.after.kt
@@ -1,6 +1,6 @@
 // "Create class 'Foo'" "true"
 // ERROR: Unresolved reference: Foo
 
-trait T
+interface T
 
 fun test(): T = J.Foo(2, "2")
\ No newline at end of file
diff --git a/idea/testData/quickfix/createFromUsage/createClass/callExpression/callWithSupertraitAndJavaReceiver.before.Main.kt b/idea/testData/quickfix/createFromUsage/createClass/callExpression/callWithSupertraitAndJavaReceiver.before.Main.kt
index 95078d17104..59aca23f788 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/callExpression/callWithSupertraitAndJavaReceiver.before.Main.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/callExpression/callWithSupertraitAndJavaReceiver.before.Main.kt
@@ -1,6 +1,6 @@
 // "Create class 'Foo'" "true"
 // ERROR: Unresolved reference: Foo
 
-trait T
+interface T
 
 fun test(): T = J.<caret>Foo(2, "2")
\ No newline at end of file
diff --git a/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/objectWithSupertrait.kt b/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/objectWithSupertrait.kt
index fc7906503eb..4a08f7987c0 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/objectWithSupertrait.kt
+++ b/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/objectWithSupertrait.kt
@@ -3,6 +3,6 @@ package p
 
 fun foo(): X = <caret>A
 
-trait X {
+interface X {
 
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/objectWithSupertrait.kt.after b/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/objectWithSupertrait.kt.after
index 544241d5126..3cdce366f29 100644
--- a/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/objectWithSupertrait.kt.after
+++ b/idea/testData/quickfix/createFromUsage/createClass/referenceExpression/objectWithSupertrait.kt.after
@@ -7,6 +7,6 @@ object A : X {
 
 }
 
-trait X {
+interface X {
 
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/createFromUsage/createFunction/call/extensionFunOnTrait.kt b/idea/testData/quickfix/createFromUsage/createFunction/call/extensionFunOnTrait.kt
index 1b151716133..a4255e896ee 100644
--- a/idea/testData/quickfix/createFromUsage/createFunction/call/extensionFunOnTrait.kt
+++ b/idea/testData/quickfix/createFromUsage/createFunction/call/extensionFunOnTrait.kt
@@ -1,6 +1,6 @@
 // "Create extension function 'foo'" "true"
 
-trait T
+interface T
 
 fun test(t: T) {
     val b: Boolean = t.<caret>foo("1", 2)
diff --git a/idea/testData/quickfix/createFromUsage/createFunction/call/extensionFunOnTrait.kt.after b/idea/testData/quickfix/createFromUsage/createFunction/call/extensionFunOnTrait.kt.after
index 4847a49e2c7..b92f694df3f 100644
--- a/idea/testData/quickfix/createFromUsage/createFunction/call/extensionFunOnTrait.kt.after
+++ b/idea/testData/quickfix/createFromUsage/createFunction/call/extensionFunOnTrait.kt.after
@@ -1,6 +1,6 @@
 // "Create extension function 'foo'" "true"
 
-trait T
+interface T
 
 fun test(t: T) {
     val b: Boolean = t.foo("1", 2)
diff --git a/idea/testData/quickfix/createFromUsage/createFunction/call/funOnTrait.kt b/idea/testData/quickfix/createFromUsage/createFunction/call/funOnTrait.kt
index 7982ddb2102..35759be190f 100644
--- a/idea/testData/quickfix/createFromUsage/createFunction/call/funOnTrait.kt
+++ b/idea/testData/quickfix/createFromUsage/createFunction/call/funOnTrait.kt
@@ -1,6 +1,6 @@
 // "Create function 'foo'" "true"
 
-trait T
+interface T
 
 fun test(t: T) {
     val b: Boolean = t.<caret>foo("1", 2)
diff --git a/idea/testData/quickfix/createFromUsage/createFunction/call/funOnTrait.kt.after b/idea/testData/quickfix/createFromUsage/createFunction/call/funOnTrait.kt.after
index 2d513870e32..68189988cee 100644
--- a/idea/testData/quickfix/createFromUsage/createFunction/call/funOnTrait.kt.after
+++ b/idea/testData/quickfix/createFromUsage/createFunction/call/funOnTrait.kt.after
@@ -1,6 +1,6 @@
 // "Create function 'foo'" "true"
 
-trait T {
+interface T {
     fun foo(s: String, i: Int): Boolean
 }
 
diff --git a/idea/testData/quickfix/createFromUsage/createSecondaryConstructor/callWithExpectedType.kt b/idea/testData/quickfix/createFromUsage/createSecondaryConstructor/callWithExpectedType.kt
index 5bab8f1fcd5..44d492ac87f 100644
--- a/idea/testData/quickfix/createFromUsage/createSecondaryConstructor/callWithExpectedType.kt
+++ b/idea/testData/quickfix/createFromUsage/createSecondaryConstructor/callWithExpectedType.kt
@@ -1,6 +1,6 @@
 // "Create secondary constructor" "true"
 
-trait T
+interface T
 
 class A: T
 
diff --git a/idea/testData/quickfix/createFromUsage/createSecondaryConstructor/callWithExpectedType.kt.after b/idea/testData/quickfix/createFromUsage/createSecondaryConstructor/callWithExpectedType.kt.after
index f1429ffb3e2..9a19aeffb59 100644
--- a/idea/testData/quickfix/createFromUsage/createSecondaryConstructor/callWithExpectedType.kt.after
+++ b/idea/testData/quickfix/createFromUsage/createSecondaryConstructor/callWithExpectedType.kt.after
@@ -1,6 +1,6 @@
 // "Create secondary constructor" "true"
 
-trait T
+interface T
 
 class A: T {
     constructor(i: Int) {
diff --git a/idea/testData/quickfix/createFromUsage/createSecondaryConstructor/delegatorToSuperCallNoClass.kt b/idea/testData/quickfix/createFromUsage/createSecondaryConstructor/delegatorToSuperCallNoClass.kt
index de9d2eab2f9..8af8675c455 100644
--- a/idea/testData/quickfix/createFromUsage/createSecondaryConstructor/delegatorToSuperCallNoClass.kt
+++ b/idea/testData/quickfix/createFromUsage/createSecondaryConstructor/delegatorToSuperCallNoClass.kt
@@ -1,7 +1,7 @@
 // "Create secondary constructor" "false"
 // ERROR: This class does not have a constructor
 
-trait T {
+interface T {
 
 }
 
diff --git a/idea/testData/quickfix/createFromUsage/createSecondaryConstructor/superCallNoClass.kt b/idea/testData/quickfix/createFromUsage/createSecondaryConstructor/superCallNoClass.kt
index 01af0abe100..86239476cdd 100644
--- a/idea/testData/quickfix/createFromUsage/createSecondaryConstructor/superCallNoClass.kt
+++ b/idea/testData/quickfix/createFromUsage/createSecondaryConstructor/superCallNoClass.kt
@@ -1,7 +1,7 @@
 // "Create secondary constructor" "false"
 // ERROR: Too many arguments for public constructor Any() defined in kotlin.Any
 
-trait T {
+interface T {
 
 }
 
diff --git a/idea/testData/quickfix/createFromUsage/createVariable/parameter/inAccessorInTrait.kt b/idea/testData/quickfix/createFromUsage/createVariable/parameter/inAccessorInTrait.kt
index 75f8334fee1..ef859cb03ee 100644
--- a/idea/testData/quickfix/createFromUsage/createVariable/parameter/inAccessorInTrait.kt
+++ b/idea/testData/quickfix/createFromUsage/createVariable/parameter/inAccessorInTrait.kt
@@ -4,7 +4,7 @@
 // ACTION: Create property 'foo'
 // ERROR: Unresolved reference: foo
 
-trait A {
+interface A {
     val test: Int get() {
         return <caret>foo
     }
diff --git a/idea/testData/quickfix/createFromUsage/createVariable/parameter/wrongReceiver.kt b/idea/testData/quickfix/createFromUsage/createVariable/parameter/wrongReceiver.kt
index 222e9dbbb8b..e7f433115c4 100644
--- a/idea/testData/quickfix/createFromUsage/createVariable/parameter/wrongReceiver.kt
+++ b/idea/testData/quickfix/createFromUsage/createVariable/parameter/wrongReceiver.kt
@@ -1,6 +1,6 @@
 // "Create parameter 'value'" "true"
 // DISABLE-ERRORS
-trait Tr {
+interface Tr {
     fun foo(value: String, b: String) = ""
     fun bar() = foo(<caret>value, b)
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/createFromUsage/createVariable/parameter/wrongReceiver.kt.after b/idea/testData/quickfix/createFromUsage/createVariable/parameter/wrongReceiver.kt.after
index 13778d25347..2f7679912c9 100644
--- a/idea/testData/quickfix/createFromUsage/createVariable/parameter/wrongReceiver.kt.after
+++ b/idea/testData/quickfix/createFromUsage/createVariable/parameter/wrongReceiver.kt.after
@@ -1,6 +1,6 @@
 // "Create parameter 'value'" "true"
 // DISABLE-ERRORS
-trait Tr {
+interface Tr {
     fun foo(value: String, b: String) = ""
     fun bar(value: String) = foo(value, b)
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/modifiers/addOpenToClassDeclaration/implementTraitFinalSupertype.kt b/idea/testData/quickfix/modifiers/addOpenToClassDeclaration/implementTraitFinalSupertype.kt
index f3f695af3a5..b1623460e9a 100644
--- a/idea/testData/quickfix/modifiers/addOpenToClassDeclaration/implementTraitFinalSupertype.kt
+++ b/idea/testData/quickfix/modifiers/addOpenToClassDeclaration/implementTraitFinalSupertype.kt
@@ -1,6 +1,6 @@
 // "Make A open" "true"
-trait X {}
-trait Y {}
+interface X {}
+interface Y {}
 
 class A {}
 class B : X, A<caret>(), Y {}
diff --git a/idea/testData/quickfix/modifiers/addOpenToClassDeclaration/implementTraitFinalSupertype.kt.after b/idea/testData/quickfix/modifiers/addOpenToClassDeclaration/implementTraitFinalSupertype.kt.after
index 43674ec3a1f..805ef93115f 100644
--- a/idea/testData/quickfix/modifiers/addOpenToClassDeclaration/implementTraitFinalSupertype.kt.after
+++ b/idea/testData/quickfix/modifiers/addOpenToClassDeclaration/implementTraitFinalSupertype.kt.after
@@ -1,6 +1,6 @@
 // "Make A open" "true"
-trait X {}
-trait Y {}
+interface X {}
+interface Y {}
 
 open class A {}
 class B : X, A<caret>(), Y {}
diff --git a/idea/testData/quickfix/modifiers/finalTrait.kt b/idea/testData/quickfix/modifiers/finalTrait.kt
index 61895997169..fe2afeb306d 100644
--- a/idea/testData/quickfix/modifiers/finalTrait.kt
+++ b/idea/testData/quickfix/modifiers/finalTrait.kt
@@ -1,2 +1,2 @@
 // "Remove 'final' modifier" "true"
-<caret>final trait A {}
\ No newline at end of file
+<caret>final interface A {}
\ No newline at end of file
diff --git a/idea/testData/quickfix/modifiers/finalTrait.kt.after b/idea/testData/quickfix/modifiers/finalTrait.kt.after
index d5b8bbf86c6..10b823842cc 100644
--- a/idea/testData/quickfix/modifiers/finalTrait.kt.after
+++ b/idea/testData/quickfix/modifiers/finalTrait.kt.after
@@ -1,2 +1,2 @@
 // "Remove 'final' modifier" "true"
-<caret>trait A {}
\ No newline at end of file
+<caret>interface A {}
\ No newline at end of file
diff --git a/idea/testData/quickfix/modifiers/illegalEnumAnnotation1.kt b/idea/testData/quickfix/modifiers/illegalEnumAnnotation1.kt
index 0abe3ab1ee9..d5cd36eb48f 100644
--- a/idea/testData/quickfix/modifiers/illegalEnumAnnotation1.kt
+++ b/idea/testData/quickfix/modifiers/illegalEnumAnnotation1.kt
@@ -1,3 +1,3 @@
 // "Remove 'enum' modifier" "true"
-<caret>enum trait A {
+<caret>enum interface A {
 }
diff --git a/idea/testData/quickfix/modifiers/illegalEnumAnnotation1.kt.after b/idea/testData/quickfix/modifiers/illegalEnumAnnotation1.kt.after
index 3ad26aeeb53..c5f63f389ae 100644
--- a/idea/testData/quickfix/modifiers/illegalEnumAnnotation1.kt.after
+++ b/idea/testData/quickfix/modifiers/illegalEnumAnnotation1.kt.after
@@ -1,3 +1,3 @@
 // "Remove 'enum' modifier" "true"
-<caret>trait A {
+<caret>interface A {
 }
diff --git a/idea/testData/quickfix/modifiers/removeInnerForClassInTrait.kt b/idea/testData/quickfix/modifiers/removeInnerForClassInTrait.kt
index 1f020514943..6eb5a15980d 100644
--- a/idea/testData/quickfix/modifiers/removeInnerForClassInTrait.kt
+++ b/idea/testData/quickfix/modifiers/removeInnerForClassInTrait.kt
@@ -1,4 +1,4 @@
 // "Remove 'inner' modifier" "true"
-trait A {
+interface A {
     inne<caret>r class B
 }
diff --git a/idea/testData/quickfix/modifiers/removeInnerForClassInTrait.kt.after b/idea/testData/quickfix/modifiers/removeInnerForClassInTrait.kt.after
index aab6a6c8405..c81d95a1aca 100644
--- a/idea/testData/quickfix/modifiers/removeInnerForClassInTrait.kt.after
+++ b/idea/testData/quickfix/modifiers/removeInnerForClassInTrait.kt.after
@@ -1,4 +1,4 @@
 // "Remove 'inner' modifier" "true"
-trait A {
+interface A {
     class B
 }
diff --git a/idea/testData/quickfix/modifiers/visibilityModiferParameter.kt b/idea/testData/quickfix/modifiers/visibilityModiferParameter.kt
index cf8682a0135..2f3016c17de 100644
--- a/idea/testData/quickfix/modifiers/visibilityModiferParameter.kt
+++ b/idea/testData/quickfix/modifiers/visibilityModiferParameter.kt
@@ -1,5 +1,5 @@
 // "Change visibility modifier" "true"
-trait ParseResult<out T> {
+interface ParseResult<out T> {
     public val success : Boolean
     public val value : T
 }
diff --git a/idea/testData/quickfix/modifiers/visibilityModiferParameter.kt.after b/idea/testData/quickfix/modifiers/visibilityModiferParameter.kt.after
index 7305e633640..4f2cf24af5c 100644
--- a/idea/testData/quickfix/modifiers/visibilityModiferParameter.kt.after
+++ b/idea/testData/quickfix/modifiers/visibilityModiferParameter.kt.after
@@ -1,5 +1,5 @@
 // "Change visibility modifier" "true"
-trait ParseResult<out T> {
+interface ParseResult<out T> {
     public val success : Boolean
     public val value : T
 }
diff --git a/idea/testData/quickfix/nullables/removeSupertypeNullable2.kt b/idea/testData/quickfix/nullables/removeSupertypeNullable2.kt
index 98eeb198fbb..afc76384fd6 100644
--- a/idea/testData/quickfix/nullables/removeSupertypeNullable2.kt
+++ b/idea/testData/quickfix/nullables/removeSupertypeNullable2.kt
@@ -1,3 +1,3 @@
 // "Remove '?'" "true"
-trait Foo {}
+interface Foo {}
 class Bar : Foo?<caret> {}
\ No newline at end of file
diff --git a/idea/testData/quickfix/nullables/removeSupertypeNullable2.kt.after b/idea/testData/quickfix/nullables/removeSupertypeNullable2.kt.after
index bc0baf2a8c7..958c54cf803 100644
--- a/idea/testData/quickfix/nullables/removeSupertypeNullable2.kt.after
+++ b/idea/testData/quickfix/nullables/removeSupertypeNullable2.kt.after
@@ -1,3 +1,3 @@
 // "Remove '?'" "true"
-trait Foo {}
+interface Foo {}
 class Bar : Foo<caret> {}
\ No newline at end of file
diff --git a/idea/testData/quickfix/override/nothingToOverride/addFunctionNoBody.kt b/idea/testData/quickfix/override/nothingToOverride/addFunctionNoBody.kt
index 705d1af6ec4..50648ae6a97 100644
--- a/idea/testData/quickfix/override/nothingToOverride/addFunctionNoBody.kt
+++ b/idea/testData/quickfix/override/nothingToOverride/addFunctionNoBody.kt
@@ -1,5 +1,5 @@
 // "Add 'open fun f()' to 'A'" "true"
-trait A
+interface A
 class B : A {
     <caret>override fun f() {}
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/override/nothingToOverride/addFunctionNoBody.kt.after b/idea/testData/quickfix/override/nothingToOverride/addFunctionNoBody.kt.after
index 177bcbf5637..dbc3bfa628a 100644
--- a/idea/testData/quickfix/override/nothingToOverride/addFunctionNoBody.kt.after
+++ b/idea/testData/quickfix/override/nothingToOverride/addFunctionNoBody.kt.after
@@ -1,5 +1,5 @@
 // "Add 'open fun f()' to 'A'" "true"
-trait A {
+interface A {
     open fun f()
 }
 
diff --git a/idea/testData/quickfix/override/nothingToOverride/addFunctionTrait.kt b/idea/testData/quickfix/override/nothingToOverride/addFunctionTrait.kt
index 3d2c4024c5b..0da59f6e865 100644
--- a/idea/testData/quickfix/override/nothingToOverride/addFunctionTrait.kt
+++ b/idea/testData/quickfix/override/nothingToOverride/addFunctionTrait.kt
@@ -1,5 +1,5 @@
 // "Add 'open fun f()' to 'A'" "true"
-trait A {
+interface A {
 }
 class B : A {
     <caret>override fun f() {}
diff --git a/idea/testData/quickfix/override/nothingToOverride/addFunctionTrait.kt.after b/idea/testData/quickfix/override/nothingToOverride/addFunctionTrait.kt.after
index 92dda9599a1..6ec12ff8e04 100644
--- a/idea/testData/quickfix/override/nothingToOverride/addFunctionTrait.kt.after
+++ b/idea/testData/quickfix/override/nothingToOverride/addFunctionTrait.kt.after
@@ -1,5 +1,5 @@
 // "Add 'open fun f()' to 'A'" "true"
-trait A {
+interface A {
     open fun f()
 }
 class B : A {
diff --git a/idea/testData/quickfix/override/nothingToOverride/addFunctionTwoTraits.kt b/idea/testData/quickfix/override/nothingToOverride/addFunctionTwoTraits.kt
index 48498de2050..0ad9d780232 100644
--- a/idea/testData/quickfix/override/nothingToOverride/addFunctionTwoTraits.kt
+++ b/idea/testData/quickfix/override/nothingToOverride/addFunctionTwoTraits.kt
@@ -1,6 +1,6 @@
 // "Add function to supertype..." "true"
-trait A {}
-trait B {}
+interface A {}
+interface B {}
 class C: A, B {
   <caret>override fun foo() {}
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/override/nothingToOverride/addFunctionTwoTraits.kt.after b/idea/testData/quickfix/override/nothingToOverride/addFunctionTwoTraits.kt.after
index 32dcc19553a..34f9addb525 100644
--- a/idea/testData/quickfix/override/nothingToOverride/addFunctionTwoTraits.kt.after
+++ b/idea/testData/quickfix/override/nothingToOverride/addFunctionTwoTraits.kt.after
@@ -1,8 +1,8 @@
 // "Add function to supertype..." "true"
-trait A {
+interface A {
     open fun foo()
 }
-trait B {}
+interface B {}
 class C: A, B {
   <caret>override fun foo() {}
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/override/nothingToOverride/addParameter.kt b/idea/testData/quickfix/override/nothingToOverride/addParameter.kt
index 2b000bfd26d..c36f93e77b0 100644
--- a/idea/testData/quickfix/override/nothingToOverride/addParameter.kt
+++ b/idea/testData/quickfix/override/nothingToOverride/addParameter.kt
@@ -1,5 +1,5 @@
 // "Change function signature to 'fun f(a: Int)'" "true"
-trait A {
+interface A {
     fun f(a: Int)
 }
 
diff --git a/idea/testData/quickfix/override/nothingToOverride/addParameter.kt.after b/idea/testData/quickfix/override/nothingToOverride/addParameter.kt.after
index 140e3dad9bb..d14b9efc9ed 100644
--- a/idea/testData/quickfix/override/nothingToOverride/addParameter.kt.after
+++ b/idea/testData/quickfix/override/nothingToOverride/addParameter.kt.after
@@ -1,5 +1,5 @@
 // "Change function signature to 'fun f(a: Int)'" "true"
-trait A {
+interface A {
     fun f(a: Int)
 }
 
diff --git a/idea/testData/quickfix/override/nothingToOverride/addParameterGenericClass.kt b/idea/testData/quickfix/override/nothingToOverride/addParameterGenericClass.kt
index 877ea9b002f..00adc592125 100644
--- a/idea/testData/quickfix/override/nothingToOverride/addParameterGenericClass.kt
+++ b/idea/testData/quickfix/override/nothingToOverride/addParameterGenericClass.kt
@@ -1,5 +1,5 @@
 // "Change function signature to 'fun f(a: Int, x: T)'" "true"
-trait A<R> {
+interface A<R> {
     fun f(a: Int, b: R)
 }
 
diff --git a/idea/testData/quickfix/override/nothingToOverride/addParameterGenericClass.kt.after b/idea/testData/quickfix/override/nothingToOverride/addParameterGenericClass.kt.after
index 4545caca6e6..73ab8394c46 100644
--- a/idea/testData/quickfix/override/nothingToOverride/addParameterGenericClass.kt.after
+++ b/idea/testData/quickfix/override/nothingToOverride/addParameterGenericClass.kt.after
@@ -1,5 +1,5 @@
 // "Change function signature to 'fun f(a: Int, x: T)'" "true"
-trait A<R> {
+interface A<R> {
     fun f(a: Int, b: R)
 }
 
diff --git a/idea/testData/quickfix/override/nothingToOverride/addParameterMultiple.kt b/idea/testData/quickfix/override/nothingToOverride/addParameterMultiple.kt
index eb51e002a8d..a2b3760a5e5 100644
--- a/idea/testData/quickfix/override/nothingToOverride/addParameterMultiple.kt
+++ b/idea/testData/quickfix/override/nothingToOverride/addParameterMultiple.kt
@@ -1,6 +1,6 @@
 // "Change function signature..." "true"
 // ERROR: <html>Class 'B' must be declared abstract or implement abstract member<br/><b>internal</b> <b>abstract</b> <b>fun</b> f(a: kotlin.String): kotlin.Unit <i>defined in</i> A</html>
-trait A {
+interface A {
     fun f(a: Int)
     fun f(a: String)
 }
diff --git a/idea/testData/quickfix/override/nothingToOverride/addParameterMultiple.kt.after b/idea/testData/quickfix/override/nothingToOverride/addParameterMultiple.kt.after
index dce551bfd69..aa6e26b3103 100644
--- a/idea/testData/quickfix/override/nothingToOverride/addParameterMultiple.kt.after
+++ b/idea/testData/quickfix/override/nothingToOverride/addParameterMultiple.kt.after
@@ -1,6 +1,6 @@
 // "Change function signature..." "true"
 // ERROR: <html>Class 'B' must be declared abstract or implement abstract member<br/><b>internal</b> <b>abstract</b> <b>fun</b> f(a: kotlin.String): kotlin.Unit <i>defined in</i> A</html>
-trait A {
+interface A {
     fun f(a: Int)
     fun f(a: String)
 }
diff --git a/idea/testData/quickfix/override/nothingToOverride/addParameterPreserveVisibility.kt b/idea/testData/quickfix/override/nothingToOverride/addParameterPreserveVisibility.kt
index 535e0fc57b5..453c6161f2e 100644
--- a/idea/testData/quickfix/override/nothingToOverride/addParameterPreserveVisibility.kt
+++ b/idea/testData/quickfix/override/nothingToOverride/addParameterPreserveVisibility.kt
@@ -1,5 +1,5 @@
 // "Change function signature to 'fun f(a: Int)'" "true"
-trait A {
+interface A {
     fun f(a: Int)
 }
 
diff --git a/idea/testData/quickfix/override/nothingToOverride/addParameterPreserveVisibility.kt.after b/idea/testData/quickfix/override/nothingToOverride/addParameterPreserveVisibility.kt.after
index 4526cfb63c4..58a5fc849e4 100644
--- a/idea/testData/quickfix/override/nothingToOverride/addParameterPreserveVisibility.kt.after
+++ b/idea/testData/quickfix/override/nothingToOverride/addParameterPreserveVisibility.kt.after
@@ -1,5 +1,5 @@
 // "Change function signature to 'fun f(a: Int)'" "true"
-trait A {
+interface A {
     fun f(a: Int)
 }
 
diff --git a/idea/testData/quickfix/override/nothingToOverride/addParameterTwoSupertraits.kt b/idea/testData/quickfix/override/nothingToOverride/addParameterTwoSupertraits.kt
index 0dec998ca03..15132d07187 100644
--- a/idea/testData/quickfix/override/nothingToOverride/addParameterTwoSupertraits.kt
+++ b/idea/testData/quickfix/override/nothingToOverride/addParameterTwoSupertraits.kt
@@ -1,9 +1,9 @@
 // "Change function signature to 'fun f(a: Int)'" "true"
-trait A {
+interface A {
     fun f(a: Int)
 }
 
-trait B : A {
+interface B : A {
 }
 
 class C : B {
diff --git a/idea/testData/quickfix/override/nothingToOverride/addParameterTwoSupertraits.kt.after b/idea/testData/quickfix/override/nothingToOverride/addParameterTwoSupertraits.kt.after
index 6519cdd6b28..c627a59b5ef 100644
--- a/idea/testData/quickfix/override/nothingToOverride/addParameterTwoSupertraits.kt.after
+++ b/idea/testData/quickfix/override/nothingToOverride/addParameterTwoSupertraits.kt.after
@@ -1,9 +1,9 @@
 // "Change function signature to 'fun f(a: Int)'" "true"
-trait A {
+interface A {
     fun f(a: Int)
 }
 
-trait B : A {
+interface B : A {
 }
 
 class C : B {
diff --git a/idea/testData/quickfix/override/nothingToOverride/changeParameterTypeInTrait.kt b/idea/testData/quickfix/override/nothingToOverride/changeParameterTypeInTrait.kt
index 939c58e2e18..422907eb808 100644
--- a/idea/testData/quickfix/override/nothingToOverride/changeParameterTypeInTrait.kt
+++ b/idea/testData/quickfix/override/nothingToOverride/changeParameterTypeInTrait.kt
@@ -1,8 +1,8 @@
 // "Change function signature to 'fun f(a: Int)'" "true"
-trait A {
+interface A {
     fun f(a: Int)
 }
 
-trait B : A {
+interface B : A {
     <caret>override fun f(a: String)
 }
diff --git a/idea/testData/quickfix/override/nothingToOverride/changeParameterTypeInTrait.kt.after b/idea/testData/quickfix/override/nothingToOverride/changeParameterTypeInTrait.kt.after
index f3ddffa3f11..77b79e536a1 100644
--- a/idea/testData/quickfix/override/nothingToOverride/changeParameterTypeInTrait.kt.after
+++ b/idea/testData/quickfix/override/nothingToOverride/changeParameterTypeInTrait.kt.after
@@ -1,8 +1,8 @@
 // "Change function signature to 'fun f(a: Int)'" "true"
-trait A {
+interface A {
     fun f(a: Int)
 }
 
-trait B : A {
+interface B : A {
     <caret>override fun f(a: Int)
 }
diff --git a/idea/testData/quickfix/override/nothingToOverride/changeParameterTypeSuperTrait.kt b/idea/testData/quickfix/override/nothingToOverride/changeParameterTypeSuperTrait.kt
index e862a9182e3..cd52a8c0243 100644
--- a/idea/testData/quickfix/override/nothingToOverride/changeParameterTypeSuperTrait.kt
+++ b/idea/testData/quickfix/override/nothingToOverride/changeParameterTypeSuperTrait.kt
@@ -1,5 +1,5 @@
 // "Change function signature to 'fun f(a: Int)'" "true"
-trait A {
+interface A {
     fun f(a: Int)
 }
 
diff --git a/idea/testData/quickfix/override/nothingToOverride/changeParameterTypeSuperTrait.kt.after b/idea/testData/quickfix/override/nothingToOverride/changeParameterTypeSuperTrait.kt.after
index 140e3dad9bb..d14b9efc9ed 100644
--- a/idea/testData/quickfix/override/nothingToOverride/changeParameterTypeSuperTrait.kt.after
+++ b/idea/testData/quickfix/override/nothingToOverride/changeParameterTypeSuperTrait.kt.after
@@ -1,5 +1,5 @@
 // "Change function signature to 'fun f(a: Int)'" "true"
-trait A {
+interface A {
     fun f(a: Int)
 }
 
diff --git a/idea/testData/quickfix/override/nothingToOverride/removeParameter.kt b/idea/testData/quickfix/override/nothingToOverride/removeParameter.kt
index ff09f07cb7b..ae1e0da44d5 100644
--- a/idea/testData/quickfix/override/nothingToOverride/removeParameter.kt
+++ b/idea/testData/quickfix/override/nothingToOverride/removeParameter.kt
@@ -1,5 +1,5 @@
 // "Change function signature to 'fun f()'" "true"
-trait A {
+interface A {
     fun f()
 }
 
diff --git a/idea/testData/quickfix/override/nothingToOverride/removeParameter.kt.after b/idea/testData/quickfix/override/nothingToOverride/removeParameter.kt.after
index 78bdd68d27f..5a9b06e0ab1 100644
--- a/idea/testData/quickfix/override/nothingToOverride/removeParameter.kt.after
+++ b/idea/testData/quickfix/override/nothingToOverride/removeParameter.kt.after
@@ -1,5 +1,5 @@
 // "Change function signature to 'fun f()'" "true"
-trait A {
+interface A {
     fun f()
 }
 
diff --git a/idea/testData/quickfix/override/nothingToOverride/removeParameterTwoTraits.kt b/idea/testData/quickfix/override/nothingToOverride/removeParameterTwoTraits.kt
index ed30fb7ec6d..0bdbe7fe12c 100644
--- a/idea/testData/quickfix/override/nothingToOverride/removeParameterTwoTraits.kt
+++ b/idea/testData/quickfix/override/nothingToOverride/removeParameterTwoTraits.kt
@@ -1,8 +1,8 @@
 // "Change function signature to 'fun f()'" "true"
-trait A {
+interface A {
     fun f()
 }
-trait B {
+interface B {
     fun f()
 }
 
diff --git a/idea/testData/quickfix/override/nothingToOverride/removeParameterTwoTraits.kt.after b/idea/testData/quickfix/override/nothingToOverride/removeParameterTwoTraits.kt.after
index 437b44dba53..dc755078dfa 100644
--- a/idea/testData/quickfix/override/nothingToOverride/removeParameterTwoTraits.kt.after
+++ b/idea/testData/quickfix/override/nothingToOverride/removeParameterTwoTraits.kt.after
@@ -1,8 +1,8 @@
 // "Change function signature to 'fun f()'" "true"
-trait A {
+interface A {
     fun f()
 }
-trait B {
+interface B {
     fun f()
 }
 
diff --git a/idea/testData/quickfix/override/nothingToOverride/swapParametersGenericClass.kt b/idea/testData/quickfix/override/nothingToOverride/swapParametersGenericClass.kt
index b27aa30931e..cd62fbb43d0 100644
--- a/idea/testData/quickfix/override/nothingToOverride/swapParametersGenericClass.kt
+++ b/idea/testData/quickfix/override/nothingToOverride/swapParametersGenericClass.kt
@@ -1,5 +1,5 @@
 // "Change function signature to 'fun f(y: S, x: List<Set<R>>)'" "true"
-trait A<P,Q> {
+interface A<P,Q> {
     fun f(a: Q, b: List<Set<P>>)
 }
 
diff --git a/idea/testData/quickfix/override/nothingToOverride/swapParametersGenericClass.kt.after b/idea/testData/quickfix/override/nothingToOverride/swapParametersGenericClass.kt.after
index 9564cbe6cdb..4ac0afe0123 100644
--- a/idea/testData/quickfix/override/nothingToOverride/swapParametersGenericClass.kt.after
+++ b/idea/testData/quickfix/override/nothingToOverride/swapParametersGenericClass.kt.after
@@ -1,5 +1,5 @@
 // "Change function signature to 'fun f(y: S, x: List<Set<R>>)'" "true"
-trait A<P,Q> {
+interface A<P,Q> {
     fun f(a: Q, b: List<Set<P>>)
 }
 
diff --git a/idea/testData/quickfix/override/overriddingMultipleFinalMethods.kt b/idea/testData/quickfix/override/overriddingMultipleFinalMethods.kt
index 1348a5ef6ba..9aaf95e59ca 100644
--- a/idea/testData/quickfix/override/overriddingMultipleFinalMethods.kt
+++ b/idea/testData/quickfix/override/overriddingMultipleFinalMethods.kt
@@ -3,15 +3,15 @@ open class A {
     fun foo() {}
 }
 
-trait X {
+interface X {
     final fun foo() {}
 }
 
-trait Y {
+interface Y {
     final fun foo() {}
 }
 
-trait Z {
+interface Z {
     fun foo() {}
 }
 
diff --git a/idea/testData/quickfix/override/overriddingMultipleFinalMethods.kt.after b/idea/testData/quickfix/override/overriddingMultipleFinalMethods.kt.after
index 40e7bf22aa4..c70f98a2c8f 100644
--- a/idea/testData/quickfix/override/overriddingMultipleFinalMethods.kt.after
+++ b/idea/testData/quickfix/override/overriddingMultipleFinalMethods.kt.after
@@ -3,15 +3,15 @@ open class A {
     open fun foo() {}
 }
 
-trait X {
+interface X {
     open fun foo() {}
 }
 
-trait Y {
+interface Y {
     open fun foo() {}
 }
 
-trait Z {
+interface Z {
     fun foo() {}
 }
 
diff --git a/idea/testData/quickfix/override/overridingDelegatedMethod.kt b/idea/testData/quickfix/override/overridingDelegatedMethod.kt
index 5aa675f6417..993b3e47594 100644
--- a/idea/testData/quickfix/override/overridingDelegatedMethod.kt
+++ b/idea/testData/quickfix/override/overridingDelegatedMethod.kt
@@ -1,9 +1,9 @@
 // "Make XX.foo open" "true"
-trait X {
+interface X {
     fun foo()
 }
 
-trait XX : X {
+interface XX : X {
     override final fun foo() {
 
     }
diff --git a/idea/testData/quickfix/override/overridingDelegatedMethod.kt.after b/idea/testData/quickfix/override/overridingDelegatedMethod.kt.after
index 947827648ec..f3cb4cb20db 100644
--- a/idea/testData/quickfix/override/overridingDelegatedMethod.kt.after
+++ b/idea/testData/quickfix/override/overridingDelegatedMethod.kt.after
@@ -1,9 +1,9 @@
 // "Make XX.foo open" "true"
-trait X {
+interface X {
     fun foo()
 }
 
-trait XX : X {
+interface XX : X {
     override open fun foo() {
 
     }
diff --git a/idea/testData/quickfix/override/overridingFakeOverride.kt b/idea/testData/quickfix/override/overridingFakeOverride.kt
index db622498481..87b23e8534e 100644
--- a/idea/testData/quickfix/override/overridingFakeOverride.kt
+++ b/idea/testData/quickfix/override/overridingFakeOverride.kt
@@ -1,15 +1,15 @@
 // "Make XX.foo open" "true"
-trait X {
+interface X {
     fun foo()
 }
 
-trait XX : X {
+interface XX : X {
     override final fun foo() {
 
     }
 }
 
-trait Y : X, XX {
+interface Y : X, XX {
 }
 
 class B() : Y {
diff --git a/idea/testData/quickfix/override/overridingFakeOverride.kt.after b/idea/testData/quickfix/override/overridingFakeOverride.kt.after
index 488beb30229..fe57956f6ce 100644
--- a/idea/testData/quickfix/override/overridingFakeOverride.kt.after
+++ b/idea/testData/quickfix/override/overridingFakeOverride.kt.after
@@ -1,15 +1,15 @@
 // "Make XX.foo open" "true"
-trait X {
+interface X {
     fun foo()
 }
 
-trait XX : X {
+interface XX : X {
     override open fun foo() {
 
     }
 }
 
-trait Y : X, XX {
+interface Y : X, XX {
 }
 
 class B() : Y {
diff --git a/idea/testData/quickfix/override/overridingWritableAndNotWritableFinalMembers.kt b/idea/testData/quickfix/override/overridingWritableAndNotWritableFinalMembers.kt
index 71015dc2319..462ce75c616 100644
--- a/idea/testData/quickfix/override/overridingWritableAndNotWritableFinalMembers.kt
+++ b/idea/testData/quickfix/override/overridingWritableAndNotWritableFinalMembers.kt
@@ -3,7 +3,7 @@
 // ERROR: Cannot access '<init>': it is 'private' in 'E'
 // ERROR: 'ordinal' in 'E' is final and cannot be overridden
 enum class E {}
-trait X {
+interface X {
     final fun ordinal() : Int = 42
 }
 
diff --git a/idea/testData/quickfix/override/parameterNameChangedAmbiguousRename.kt b/idea/testData/quickfix/override/parameterNameChangedAmbiguousRename.kt
index d6a132640fe..723a2d52980 100644
--- a/idea/testData/quickfix/override/parameterNameChangedAmbiguousRename.kt
+++ b/idea/testData/quickfix/override/parameterNameChangedAmbiguousRename.kt
@@ -4,7 +4,7 @@ abstract class A {
     abstract fun foo(arg : Int) : Int;
 }
 
-trait X {
+interface X {
     fun foo(agr: Int) : Int;
 }
 
diff --git a/idea/testData/quickfix/override/parameterNameChangedMultipleOverrideRenamePossible.kt b/idea/testData/quickfix/override/parameterNameChangedMultipleOverrideRenamePossible.kt
index 1c3e3445fb7..7dd8db03d05 100644
--- a/idea/testData/quickfix/override/parameterNameChangedMultipleOverrideRenamePossible.kt
+++ b/idea/testData/quickfix/override/parameterNameChangedMultipleOverrideRenamePossible.kt
@@ -3,7 +3,7 @@ abstract class A {
     abstract fun foo(arg : Int) : Int;
 }
 
-trait X {
+interface X {
     fun foo(arg : Int) : Int;
 }
 
diff --git a/idea/testData/quickfix/override/parameterNameChangedMultipleOverrideRenamePossible.kt.after b/idea/testData/quickfix/override/parameterNameChangedMultipleOverrideRenamePossible.kt.after
index 9fb01d44854..5c83e370021 100644
--- a/idea/testData/quickfix/override/parameterNameChangedMultipleOverrideRenamePossible.kt.after
+++ b/idea/testData/quickfix/override/parameterNameChangedMultipleOverrideRenamePossible.kt.after
@@ -3,7 +3,7 @@ abstract class A {
     abstract fun foo(arg : Int) : Int;
 }
 
-trait X {
+interface X {
     fun foo(arg : Int) : Int;
 }
 
diff --git a/idea/testData/quickfix/override/typeMismatchOnOverride/cantChangeMultipleOverriddenPropertiesTypes.kt b/idea/testData/quickfix/override/typeMismatchOnOverride/cantChangeMultipleOverriddenPropertiesTypes.kt
index fa5b3205a7f..d2a79b49e7e 100644
--- a/idea/testData/quickfix/override/typeMismatchOnOverride/cantChangeMultipleOverriddenPropertiesTypes.kt
+++ b/idea/testData/quickfix/override/typeMismatchOnOverride/cantChangeMultipleOverriddenPropertiesTypes.kt
@@ -3,14 +3,14 @@
 // ACTION: Disable inspection
 // ACTION: Edit inspection profile setting
 // ERROR: <html>Return type is '(kotlin.Int) &rarr; kotlin.Int', which is not a subtype of overridden<br/><b>internal</b> <b>abstract</b> <b>val</b> x: (kotlin.String) &rarr; kotlin.Int <i>defined in</i> A</html>
-trait A {
+interface A {
     val x: (String) -> Int
 }
 
-trait B {
+interface B {
     val x: (String) -> Any
 }
 
-trait C : A, B {
+interface C : A, B {
     override val x: (Int) -> Int<caret>
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/override/typeMismatchOnOverride/cantChangeOverriddenPropertyTypeToMatchOverridingProperty.kt b/idea/testData/quickfix/override/typeMismatchOnOverride/cantChangeOverriddenPropertyTypeToMatchOverridingProperty.kt
index 0f2ddea678b..41863bf92a4 100644
--- a/idea/testData/quickfix/override/typeMismatchOnOverride/cantChangeOverriddenPropertyTypeToMatchOverridingProperty.kt
+++ b/idea/testData/quickfix/override/typeMismatchOnOverride/cantChangeOverriddenPropertyTypeToMatchOverridingProperty.kt
@@ -1,13 +1,13 @@
 // "class org.jetbrains.kotlin.idea.quickfix.ChangeVariableTypeFix" "false"
 // ERROR: <html>Var-property type is 'kotlin.String', which is not a type of overridden<br/><b>internal</b> <b>abstract</b> <b>var</b> x: kotlin.Int <i>defined in</i> A</html>
-trait A {
+interface A {
     var x: Int
 }
 
-trait B {
+interface B {
     var x: Any
 }
 
-trait C : A, B {
+interface C : A, B {
     override var x: String<caret>
 }
diff --git a/idea/testData/quickfix/override/typeMismatchOnOverride/cantChangePropertyTypeToMatchOverridenProperties.kt b/idea/testData/quickfix/override/typeMismatchOnOverride/cantChangePropertyTypeToMatchOverridenProperties.kt
index 2cffc07e9db..16e43a10873 100644
--- a/idea/testData/quickfix/override/typeMismatchOnOverride/cantChangePropertyTypeToMatchOverridenProperties.kt
+++ b/idea/testData/quickfix/override/typeMismatchOnOverride/cantChangePropertyTypeToMatchOverridenProperties.kt
@@ -1,13 +1,13 @@
 // "class org.jetbrains.kotlin.idea.quickfix.ChangeVariableTypeFix" "false"
 // ERROR: <html>Var-property type is 'kotlin.Int', which is not a type of overridden<br/><b>internal</b> <b>abstract</b> <b>var</b> x: kotlin.String <i>defined in</i> A</html>
-trait A {
+interface A {
     var x: String
 }
 
-trait B {
+interface B {
     var x: Any
 }
 
-trait C : A, B {
+interface C : A, B {
     override var x: Int<caret>
 }
diff --git a/idea/testData/quickfix/override/typeMismatchOnOverride/cantChangeReturnTypeOfOverriddenFunction.kt b/idea/testData/quickfix/override/typeMismatchOnOverride/cantChangeReturnTypeOfOverriddenFunction.kt
index 46142460927..c29416af000 100644
--- a/idea/testData/quickfix/override/typeMismatchOnOverride/cantChangeReturnTypeOfOverriddenFunction.kt
+++ b/idea/testData/quickfix/override/typeMismatchOnOverride/cantChangeReturnTypeOfOverriddenFunction.kt
@@ -1,13 +1,13 @@
 // "class org.jetbrains.kotlin.idea.quickfix.ChangeFunctionReturnTypeFix" "false"
 // ERROR: <html>Return type is 'kotlin.Long', which is not a subtype of overridden<br/><b>internal</b> <b>abstract</b> <b>fun</b> foo(): kotlin.Int <i>defined in</i> A</html>
-trait A {
+interface A {
     fun foo(): Int
 }
 
-trait B {
+interface B {
     fun foo(): String
 }
 
-trait C : A, B {
+interface C : A, B {
     override fun foo(): Long
 }
diff --git a/idea/testData/quickfix/override/typeMismatchOnOverride/changeOverriddenPropertyType1.kt b/idea/testData/quickfix/override/typeMismatchOnOverride/changeOverriddenPropertyType1.kt
index 9216f429193..fb4a20a54ca 100644
--- a/idea/testData/quickfix/override/typeMismatchOnOverride/changeOverriddenPropertyType1.kt
+++ b/idea/testData/quickfix/override/typeMismatchOnOverride/changeOverriddenPropertyType1.kt
@@ -1,12 +1,12 @@
 // "Change 'B.x' type to '(Int) -> Int'" "true"
-trait A {
+interface A {
     val x: (Int) -> Int
 }
 
-trait B {
+interface B {
     val x: (String) -> Any
 }
 
-trait C : A, B {
+interface C : A, B {
     override val x: (Int) -> Int<caret>
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/override/typeMismatchOnOverride/changeOverriddenPropertyType1.kt.after b/idea/testData/quickfix/override/typeMismatchOnOverride/changeOverriddenPropertyType1.kt.after
index 6a3586ed492..70c2748925f 100644
--- a/idea/testData/quickfix/override/typeMismatchOnOverride/changeOverriddenPropertyType1.kt.after
+++ b/idea/testData/quickfix/override/typeMismatchOnOverride/changeOverriddenPropertyType1.kt.after
@@ -1,12 +1,12 @@
 // "Change 'B.x' type to '(Int) -> Int'" "true"
-trait A {
+interface A {
     val x: (Int) -> Int
 }
 
-trait B {
+interface B {
     val x: (Int) -> Int
 }
 
-trait C : A, B {
+interface C : A, B {
     override val x: (Int) -> Int<caret>
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/override/typeMismatchOnOverride/changeOverriddenPropertyType2.kt b/idea/testData/quickfix/override/typeMismatchOnOverride/changeOverriddenPropertyType2.kt
index df144be7ce6..70db8cf0cfa 100644
--- a/idea/testData/quickfix/override/typeMismatchOnOverride/changeOverriddenPropertyType2.kt
+++ b/idea/testData/quickfix/override/typeMismatchOnOverride/changeOverriddenPropertyType2.kt
@@ -1,12 +1,12 @@
 // "Change 'A.x' type to 'String'" "true"
-trait A {
+interface A {
     var x: Int
 }
 
-trait B {
+interface B {
     var x: String
 }
 
-trait C : A, B {
+interface C : A, B {
     override var x: String<caret>
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/override/typeMismatchOnOverride/changeOverriddenPropertyType2.kt.after b/idea/testData/quickfix/override/typeMismatchOnOverride/changeOverriddenPropertyType2.kt.after
index fd1e09a06ce..6a8e5af5742 100644
--- a/idea/testData/quickfix/override/typeMismatchOnOverride/changeOverriddenPropertyType2.kt.after
+++ b/idea/testData/quickfix/override/typeMismatchOnOverride/changeOverriddenPropertyType2.kt.after
@@ -1,12 +1,12 @@
 // "Change 'A.x' type to 'String'" "true"
-trait A {
+interface A {
     var x: String
 }
 
-trait B {
+interface B {
     var x: String
 }
 
-trait C : A, B {
+interface C : A, B {
     override var x: String<caret>
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/override/typeMismatchOnOverride/changeOverridingPropertyTypeToFunctionType.kt b/idea/testData/quickfix/override/typeMismatchOnOverride/changeOverridingPropertyTypeToFunctionType.kt
index 6a6b1155d01..62252d5d257 100644
--- a/idea/testData/quickfix/override/typeMismatchOnOverride/changeOverridingPropertyTypeToFunctionType.kt
+++ b/idea/testData/quickfix/override/typeMismatchOnOverride/changeOverridingPropertyTypeToFunctionType.kt
@@ -1,7 +1,7 @@
 // "Change 'B.x' type to '(String) -> Int'" "true"
-trait A {
+interface A {
     var x: (String) -> Int
 }
-trait B : A {
+interface B : A {
     override var x: (Int) -> String<caret>
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/override/typeMismatchOnOverride/changeOverridingPropertyTypeToFunctionType.kt.after b/idea/testData/quickfix/override/typeMismatchOnOverride/changeOverridingPropertyTypeToFunctionType.kt.after
index 8bd2d6f38b3..830c4d30037 100644
--- a/idea/testData/quickfix/override/typeMismatchOnOverride/changeOverridingPropertyTypeToFunctionType.kt.after
+++ b/idea/testData/quickfix/override/typeMismatchOnOverride/changeOverridingPropertyTypeToFunctionType.kt.after
@@ -1,7 +1,7 @@
 // "Change 'B.x' type to '(String) -> Int'" "true"
-trait A {
+interface A {
     var x: (String) -> Int
 }
-trait B : A {
+interface B : A {
     override var x: (String) -> Int
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/override/typeMismatchOnOverride/changeReturnTypeOfOverriddenFunction.kt b/idea/testData/quickfix/override/typeMismatchOnOverride/changeReturnTypeOfOverriddenFunction.kt
index a8ccbc2551c..8be6208a63b 100644
--- a/idea/testData/quickfix/override/typeMismatchOnOverride/changeReturnTypeOfOverriddenFunction.kt
+++ b/idea/testData/quickfix/override/typeMismatchOnOverride/changeReturnTypeOfOverriddenFunction.kt
@@ -1,12 +1,12 @@
 // "Change 'A.foo' function return type to 'Long'" "true"
-trait A {
+interface A {
     fun foo(): Int
 }
 
-trait B {
+interface B {
     fun foo(): Number
 }
 
-trait C : A, B {
+interface C : A, B {
     override fun foo(): Long<caret>
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/override/typeMismatchOnOverride/changeReturnTypeOfOverriddenFunction.kt.after b/idea/testData/quickfix/override/typeMismatchOnOverride/changeReturnTypeOfOverriddenFunction.kt.after
index 0efefb16139..b07877239c6 100644
--- a/idea/testData/quickfix/override/typeMismatchOnOverride/changeReturnTypeOfOverriddenFunction.kt.after
+++ b/idea/testData/quickfix/override/typeMismatchOnOverride/changeReturnTypeOfOverriddenFunction.kt.after
@@ -1,12 +1,12 @@
 // "Change 'A.foo' function return type to 'Long'" "true"
-trait A {
+interface A {
     fun foo(): Long
 }
 
-trait B {
+interface B {
     fun foo(): Number
 }
 
-trait C : A, B {
+interface C : A, B {
     override fun foo(): Long<caret>
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/override/typeMismatchOnOverride/objectInsideBody.kt b/idea/testData/quickfix/override/typeMismatchOnOverride/objectInsideBody.kt
index f78c7bb5494..91ed00c9b69 100644
--- a/idea/testData/quickfix/override/typeMismatchOnOverride/objectInsideBody.kt
+++ b/idea/testData/quickfix/override/typeMismatchOnOverride/objectInsideBody.kt
@@ -1,6 +1,6 @@
 // "Change 'prop' type to 'Int'" "true"
 // ERROR: Null can not be a value of a non-null type kotlin.Int
-trait Test<T> {
+interface Test<T> {
     val prop : T
 }
 
diff --git a/idea/testData/quickfix/override/typeMismatchOnOverride/objectInsideBody.kt.after b/idea/testData/quickfix/override/typeMismatchOnOverride/objectInsideBody.kt.after
index 5c9da2c79b1..b7010c03e4b 100644
--- a/idea/testData/quickfix/override/typeMismatchOnOverride/objectInsideBody.kt.after
+++ b/idea/testData/quickfix/override/typeMismatchOnOverride/objectInsideBody.kt.after
@@ -1,6 +1,6 @@
 // "Change 'prop' type to 'Int'" "true"
 // ERROR: Null can not be a value of a non-null type kotlin.Int
-trait Test<T> {
+interface Test<T> {
     val prop : T
 }
 
diff --git a/idea/testData/quickfix/override/typeMismatchOnOverride/propertyReturnTypeMismatchOnOverride.kt b/idea/testData/quickfix/override/typeMismatchOnOverride/propertyReturnTypeMismatchOnOverride.kt
index 4378d809f4a..c8de1597a99 100644
--- a/idea/testData/quickfix/override/typeMismatchOnOverride/propertyReturnTypeMismatchOnOverride.kt
+++ b/idea/testData/quickfix/override/typeMismatchOnOverride/propertyReturnTypeMismatchOnOverride.kt
@@ -1,5 +1,5 @@
 // "Change 'A.x' type to 'Int'" "true"
-trait X {
+interface X {
     val x: Int
 }
 
diff --git a/idea/testData/quickfix/override/typeMismatchOnOverride/propertyReturnTypeMismatchOnOverride.kt.after b/idea/testData/quickfix/override/typeMismatchOnOverride/propertyReturnTypeMismatchOnOverride.kt.after
index 0f79cd40f9d..3b1c2c60650 100644
--- a/idea/testData/quickfix/override/typeMismatchOnOverride/propertyReturnTypeMismatchOnOverride.kt.after
+++ b/idea/testData/quickfix/override/typeMismatchOnOverride/propertyReturnTypeMismatchOnOverride.kt.after
@@ -1,5 +1,5 @@
 // "Change 'A.x' type to 'Int'" "true"
-trait X {
+interface X {
     val x: Int
 }
 
diff --git a/idea/testData/quickfix/override/typeMismatchOnOverride/returnTypeMismatchOnMultipleOverride.kt b/idea/testData/quickfix/override/typeMismatchOnOverride/returnTypeMismatchOnMultipleOverride.kt
index e4661ed3213..c13510b4c33 100644
--- a/idea/testData/quickfix/override/typeMismatchOnOverride/returnTypeMismatchOnMultipleOverride.kt
+++ b/idea/testData/quickfix/override/typeMismatchOnOverride/returnTypeMismatchOnMultipleOverride.kt
@@ -6,7 +6,7 @@ abstract class A {
     abstract fun foo() : S;
 }
 
-trait X {
+interface X {
     fun foo() : T;
 }
 
diff --git a/idea/testData/quickfix/override/typeMismatchOnOverride/returnTypeMismatchOnMultipleOverride.kt.after b/idea/testData/quickfix/override/typeMismatchOnOverride/returnTypeMismatchOnMultipleOverride.kt.after
index 8ffbf3dc546..21b5fdebe33 100644
--- a/idea/testData/quickfix/override/typeMismatchOnOverride/returnTypeMismatchOnMultipleOverride.kt.after
+++ b/idea/testData/quickfix/override/typeMismatchOnOverride/returnTypeMismatchOnMultipleOverride.kt.after
@@ -6,7 +6,7 @@ abstract class A {
     abstract fun foo() : S;
 }
 
-trait X {
+interface X {
     fun foo() : T;
 }
 
diff --git a/idea/testData/quickfix/override/typeMismatchOnOverride/returnTypeMismatchOnMultipleOverrideAmbiguity.kt b/idea/testData/quickfix/override/typeMismatchOnOverride/returnTypeMismatchOnMultipleOverrideAmbiguity.kt
index 02cf56124dd..d19e800e02a 100644
--- a/idea/testData/quickfix/override/typeMismatchOnOverride/returnTypeMismatchOnMultipleOverrideAmbiguity.kt
+++ b/idea/testData/quickfix/override/typeMismatchOnOverride/returnTypeMismatchOnMultipleOverrideAmbiguity.kt
@@ -6,7 +6,7 @@ abstract class A {
     abstract fun foo() : Int;
 }
 
-trait X {
+interface X {
     fun foo() : Long;
 }
 
diff --git a/idea/testData/quickfix/supercalls/typeArgumentsRedundantInSuperQualifier.kt b/idea/testData/quickfix/supercalls/typeArgumentsRedundantInSuperQualifier.kt
index 38c54874ba1..fed170d2b6b 100644
--- a/idea/testData/quickfix/supercalls/typeArgumentsRedundantInSuperQualifier.kt
+++ b/idea/testData/quickfix/supercalls/typeArgumentsRedundantInSuperQualifier.kt
@@ -1,5 +1,5 @@
 // "Remove type arguments" "true"
-trait Foo<T, T> {
+interface Foo<T, T> {
     fun f() {}
 }
 
diff --git a/idea/testData/quickfix/supercalls/typeArgumentsRedundantInSuperQualifier.kt.after b/idea/testData/quickfix/supercalls/typeArgumentsRedundantInSuperQualifier.kt.after
index 917da27869a..d8b9089f890 100644
--- a/idea/testData/quickfix/supercalls/typeArgumentsRedundantInSuperQualifier.kt.after
+++ b/idea/testData/quickfix/supercalls/typeArgumentsRedundantInSuperQualifier.kt.after
@@ -1,5 +1,5 @@
 // "Remove type arguments" "true"
-trait Foo<T, T> {
+interface Foo<T, T> {
     fun f() {}
 }
 
diff --git a/idea/testData/quickfix/suppress/declarationKinds/trait.kt b/idea/testData/quickfix/suppress/declarationKinds/trait.kt
index ca9d69e2758..8bcccf149b3 100644
--- a/idea/testData/quickfix/suppress/declarationKinds/trait.kt
+++ b/idea/testData/quickfix/suppress/declarationKinds/trait.kt
@@ -1,5 +1,5 @@
 // "Suppress 'REDUNDANT_NULLABLE' for interface C" "true"
 
-trait C {
+interface C {
     var foo: String?<caret>?
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/suppress/declarationKinds/trait.kt.after b/idea/testData/quickfix/suppress/declarationKinds/trait.kt.after
index 382c8dad791..198674ab239 100644
--- a/idea/testData/quickfix/suppress/declarationKinds/trait.kt.after
+++ b/idea/testData/quickfix/suppress/declarationKinds/trait.kt.after
@@ -1,6 +1,6 @@
 // "Suppress 'REDUNDANT_NULLABLE' for interface C" "true"
 
 @suppress("REDUNDANT_NULLABLE")
-trait C {
+interface C {
     var foo: String?<caret>?
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/typeAddition/ambiguousFunctionReturnType.kt b/idea/testData/quickfix/typeAddition/ambiguousFunctionReturnType.kt
index ba122d2879f..dae839466cc 100644
--- a/idea/testData/quickfix/typeAddition/ambiguousFunctionReturnType.kt
+++ b/idea/testData/quickfix/typeAddition/ambiguousFunctionReturnType.kt
@@ -1,9 +1,9 @@
 // "Specify return type explicitly" "true"
 package a
 
-trait A {}
+interface A {}
 
-trait B {}
+interface B {}
 
 class C {
     fun <caret>property() = object : B, A {}
diff --git a/idea/testData/quickfix/typeAddition/ambiguousFunctionReturnType.kt.after b/idea/testData/quickfix/typeAddition/ambiguousFunctionReturnType.kt.after
index 924687324e9..b289caf729e 100644
--- a/idea/testData/quickfix/typeAddition/ambiguousFunctionReturnType.kt.after
+++ b/idea/testData/quickfix/typeAddition/ambiguousFunctionReturnType.kt.after
@@ -1,9 +1,9 @@
 // "Specify return type explicitly" "true"
 package a
 
-trait A {}
+interface A {}
 
-trait B {}
+interface B {}
 
 class C {
     fun property(): B<caret> = object : B, A {}
diff --git a/idea/testData/quickfix/typeAddition/ambiguousPropertyReturnType.kt b/idea/testData/quickfix/typeAddition/ambiguousPropertyReturnType.kt
index 63463fad0d6..d9ea37d7b76 100644
--- a/idea/testData/quickfix/typeAddition/ambiguousPropertyReturnType.kt
+++ b/idea/testData/quickfix/typeAddition/ambiguousPropertyReturnType.kt
@@ -1,9 +1,9 @@
 // "Specify type explicitly" "true"
 package a
 
-trait A {}
+interface A {}
 
-trait B {}
+interface B {}
 
 class C {
     val <caret>property = object : B, A {}
diff --git a/idea/testData/quickfix/typeAddition/ambiguousPropertyReturnType.kt.after b/idea/testData/quickfix/typeAddition/ambiguousPropertyReturnType.kt.after
index 304923b09b8..171581ad5b8 100644
--- a/idea/testData/quickfix/typeAddition/ambiguousPropertyReturnType.kt.after
+++ b/idea/testData/quickfix/typeAddition/ambiguousPropertyReturnType.kt.after
@@ -1,9 +1,9 @@
 // "Specify type explicitly" "true"
 package a
 
-trait A {}
+interface A {}
 
-trait B {}
+interface B {}
 
 class C {
     val property: B<caret> = object : B, A {}
diff --git a/idea/testData/quickfix/typeImports/hasThisImport.kt b/idea/testData/quickfix/typeImports/hasThisImport.kt
index e8bfff62534..b395e997cfc 100644
--- a/idea/testData/quickfix/typeImports/hasThisImport.kt
+++ b/idea/testData/quickfix/typeImports/hasThisImport.kt
@@ -5,7 +5,7 @@ import java.util.Collections
 import java.util.List
 
 class M {
-    trait A {
+    interface A {
         val l = <caret>Collections.emptyList<Int>()
     }
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/typeImports/hasThisImport.kt.after b/idea/testData/quickfix/typeImports/hasThisImport.kt.after
index 932c76eee3c..0f0ab1954df 100644
--- a/idea/testData/quickfix/typeImports/hasThisImport.kt.after
+++ b/idea/testData/quickfix/typeImports/hasThisImport.kt.after
@@ -5,7 +5,7 @@ import java.util.Collections
 import java.util.List
 
 class M {
-    trait A {
+    interface A {
         val l: kotlin.List<Int><caret>
     }
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/typeImports/noImportJavaLang.kt b/idea/testData/quickfix/typeImports/noImportJavaLang.kt
index f38d36e5450..b0a1456a3db 100644
--- a/idea/testData/quickfix/typeImports/noImportJavaLang.kt
+++ b/idea/testData/quickfix/typeImports/noImportJavaLang.kt
@@ -2,7 +2,7 @@
 package a
 
 class M {
-    trait A {
+    interface A {
         abstract val e = <caret>Exception("")
     }
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/typeImports/noImportJavaLang.kt.after b/idea/testData/quickfix/typeImports/noImportJavaLang.kt.after
index 29a15e76f12..6460b7b7bdc 100644
--- a/idea/testData/quickfix/typeImports/noImportJavaLang.kt.after
+++ b/idea/testData/quickfix/typeImports/noImportJavaLang.kt.after
@@ -2,7 +2,7 @@
 package a
 
 class M {
-    trait A {
+    interface A {
         abstract val e: Exception<caret>
     }
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/typeImports/noImportJetStandard.kt b/idea/testData/quickfix/typeImports/noImportJetStandard.kt
index 95e1c419fb4..9f4da61a9a4 100644
--- a/idea/testData/quickfix/typeImports/noImportJetStandard.kt
+++ b/idea/testData/quickfix/typeImports/noImportJetStandard.kt
@@ -2,7 +2,7 @@
 package a
 
 class M {
-    trait A {
+    interface A {
         abstract val i = <caret>10
     }
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/typeImports/noImportJetStandard.kt.after b/idea/testData/quickfix/typeImports/noImportJetStandard.kt.after
index 385835f6bed..ccb62c0fcbd 100644
--- a/idea/testData/quickfix/typeImports/noImportJetStandard.kt.after
+++ b/idea/testData/quickfix/typeImports/noImportJetStandard.kt.after
@@ -2,7 +2,7 @@
 package a
 
 class M {
-    trait A {
+    interface A {
         abstract val i: Int<caret>
     }
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/typeImports/toImport1.kt b/idea/testData/quickfix/typeImports/toImport1.kt
index 22c36963441..eef2956b4e8 100644
--- a/idea/testData/quickfix/typeImports/toImport1.kt
+++ b/idea/testData/quickfix/typeImports/toImport1.kt
@@ -4,7 +4,7 @@ package a
 import java.util.Collections
 
 class M {
-    trait A {
+    interface A {
         abstract val l = <caret>Collections.emptyList<Int>()
     }
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/typeImports/toImport1.kt.after b/idea/testData/quickfix/typeImports/toImport1.kt.after
index f3340895408..adc3e9018d8 100644
--- a/idea/testData/quickfix/typeImports/toImport1.kt.after
+++ b/idea/testData/quickfix/typeImports/toImport1.kt.after
@@ -4,7 +4,7 @@ package a
 import java.util.Collections
 
 class M {
-    trait A {
+    interface A {
         abstract val l: List<Int><caret>
     }
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/typeMismatch/anonymousObjectInCall.kt b/idea/testData/quickfix/typeMismatch/anonymousObjectInCall.kt
index 3d13d58fb98..ba8da8cadd9 100644
--- a/idea/testData/quickfix/typeMismatch/anonymousObjectInCall.kt
+++ b/idea/testData/quickfix/typeMismatch/anonymousObjectInCall.kt
@@ -1,5 +1,5 @@
 // "Change parameter 't' type of function 'foo' to 'T'" "true"
-trait T
+interface T
 
 fun Int.foo(t: Int) {
 
diff --git a/idea/testData/quickfix/typeMismatch/anonymousObjectInCall.kt.after b/idea/testData/quickfix/typeMismatch/anonymousObjectInCall.kt.after
index 761bf1a1717..e63110da02e 100644
--- a/idea/testData/quickfix/typeMismatch/anonymousObjectInCall.kt.after
+++ b/idea/testData/quickfix/typeMismatch/anonymousObjectInCall.kt.after
@@ -1,5 +1,5 @@
 // "Change parameter 't' type of function 'foo' to 'T'" "true"
-trait T
+interface T
 
 fun Int.foo(t: T) {
 
diff --git a/idea/testData/quickfix/typeMismatch/anonymousObjectInInfixCall.kt b/idea/testData/quickfix/typeMismatch/anonymousObjectInInfixCall.kt
index 7b777945146..36a7dc422b1 100644
--- a/idea/testData/quickfix/typeMismatch/anonymousObjectInInfixCall.kt
+++ b/idea/testData/quickfix/typeMismatch/anonymousObjectInInfixCall.kt
@@ -1,5 +1,5 @@
 // "Change parameter 't' type of function 'foo' to 'T'" "true"
-trait T
+interface T
 
 fun Int.foo(t: Int) = this
 
diff --git a/idea/testData/quickfix/typeMismatch/anonymousObjectInInfixCall.kt.after b/idea/testData/quickfix/typeMismatch/anonymousObjectInInfixCall.kt.after
index d9953fb9045..5f1e665ad0a 100644
--- a/idea/testData/quickfix/typeMismatch/anonymousObjectInInfixCall.kt.after
+++ b/idea/testData/quickfix/typeMismatch/anonymousObjectInInfixCall.kt.after
@@ -1,5 +1,5 @@
 // "Change parameter 't' type of function 'foo' to 'T'" "true"
-trait T
+interface T
 
 fun Int.foo(t: T) = this
 
diff --git a/idea/testData/quickfix/typeMismatch/anonymousObjectInInitializer.kt b/idea/testData/quickfix/typeMismatch/anonymousObjectInInitializer.kt
index a0f4413e808..f54fcd233ca 100644
--- a/idea/testData/quickfix/typeMismatch/anonymousObjectInInitializer.kt
+++ b/idea/testData/quickfix/typeMismatch/anonymousObjectInInitializer.kt
@@ -1,5 +1,5 @@
 // "Change 't' type to 'T'" "true"
-trait T
+interface T
 
 fun foo() {
     val t: Int = <caret>object: T{}
diff --git a/idea/testData/quickfix/typeMismatch/anonymousObjectInInitializer.kt.after b/idea/testData/quickfix/typeMismatch/anonymousObjectInInitializer.kt.after
index 465950f4304..db783117a4a 100644
--- a/idea/testData/quickfix/typeMismatch/anonymousObjectInInitializer.kt.after
+++ b/idea/testData/quickfix/typeMismatch/anonymousObjectInInitializer.kt.after
@@ -1,5 +1,5 @@
 // "Change 't' type to 'T'" "true"
-trait T
+interface T
 
 fun foo() {
     val t: T = object: T{}
diff --git a/idea/testData/quickfix/typeMismatch/anonymousObjectInReturn.kt b/idea/testData/quickfix/typeMismatch/anonymousObjectInReturn.kt
index 97518e26d96..16757ff6e38 100644
--- a/idea/testData/quickfix/typeMismatch/anonymousObjectInReturn.kt
+++ b/idea/testData/quickfix/typeMismatch/anonymousObjectInReturn.kt
@@ -1,5 +1,5 @@
 // "Change 'foo' function return type to 'T'" "true"
-trait T
+interface T
 
 fun foo() {
     return <caret>object: T{}
diff --git a/idea/testData/quickfix/typeMismatch/anonymousObjectInReturn.kt.after b/idea/testData/quickfix/typeMismatch/anonymousObjectInReturn.kt.after
index 439fb225691..eadfa2004d6 100644
--- a/idea/testData/quickfix/typeMismatch/anonymousObjectInReturn.kt.after
+++ b/idea/testData/quickfix/typeMismatch/anonymousObjectInReturn.kt.after
@@ -1,5 +1,5 @@
 // "Change 'foo' function return type to 'T'" "true"
-trait T
+interface T
 
 fun foo(): T {
     return object: T{}
diff --git a/idea/testData/quickfix/typeMismatch/casts/smartcastImpossible1.kt b/idea/testData/quickfix/typeMismatch/casts/smartcastImpossible1.kt
index 851403a695d..02e238fab02 100644
--- a/idea/testData/quickfix/typeMismatch/casts/smartcastImpossible1.kt
+++ b/idea/testData/quickfix/typeMismatch/casts/smartcastImpossible1.kt
@@ -1,6 +1,6 @@
 // "Cast expression 'a' to 'Foo'" "true"
 
-trait Foo {
+interface Foo {
     fun plus(x: Any) : Foo
 }
 
diff --git a/idea/testData/quickfix/typeMismatch/casts/smartcastImpossible1.kt.after b/idea/testData/quickfix/typeMismatch/casts/smartcastImpossible1.kt.after
index 9dba0503b32..366f5681c6c 100644
--- a/idea/testData/quickfix/typeMismatch/casts/smartcastImpossible1.kt.after
+++ b/idea/testData/quickfix/typeMismatch/casts/smartcastImpossible1.kt.after
@@ -1,6 +1,6 @@
 // "Cast expression 'a' to 'Foo'" "true"
 
-trait Foo {
+interface Foo {
     fun plus(x: Any) : Foo
 }
 
diff --git a/idea/testData/quickfix/typeMismatch/casts/smartcastImpossible2.kt b/idea/testData/quickfix/typeMismatch/casts/smartcastImpossible2.kt
index 3ac120e2310..2034e55a1e7 100644
--- a/idea/testData/quickfix/typeMismatch/casts/smartcastImpossible2.kt
+++ b/idea/testData/quickfix/typeMismatch/casts/smartcastImpossible2.kt
@@ -1,6 +1,6 @@
 // "Cast expression 'a' to 'Foo'" "true"
 
-trait Foo {
+interface Foo {
     fun not() : Foo
 }
 
diff --git a/idea/testData/quickfix/typeMismatch/casts/smartcastImpossible2.kt.after b/idea/testData/quickfix/typeMismatch/casts/smartcastImpossible2.kt.after
index bb09f214a35..2756f99ef68 100644
--- a/idea/testData/quickfix/typeMismatch/casts/smartcastImpossible2.kt.after
+++ b/idea/testData/quickfix/typeMismatch/casts/smartcastImpossible2.kt.after
@@ -1,6 +1,6 @@
 // "Cast expression 'a' to 'Foo'" "true"
 
-trait Foo {
+interface Foo {
     fun not() : Foo
 }
 
diff --git a/idea/testData/quickfix/typeMismatch/casts/smartcastImpossible3.kt b/idea/testData/quickfix/typeMismatch/casts/smartcastImpossible3.kt
index 6052755b029..a2b14f7bf57 100644
--- a/idea/testData/quickfix/typeMismatch/casts/smartcastImpossible3.kt
+++ b/idea/testData/quickfix/typeMismatch/casts/smartcastImpossible3.kt
@@ -1,6 +1,6 @@
 // "Cast expression 'x' to 'Foo<*>'" "true"
 
-trait Foo<T: Number> {
+interface Foo<T: Number> {
     fun bar()
 }
 
diff --git a/idea/testData/quickfix/typeMismatch/casts/smartcastImpossible3.kt.after b/idea/testData/quickfix/typeMismatch/casts/smartcastImpossible3.kt.after
index 3b08a6b2149..2ddebd2b1f7 100644
--- a/idea/testData/quickfix/typeMismatch/casts/smartcastImpossible3.kt.after
+++ b/idea/testData/quickfix/typeMismatch/casts/smartcastImpossible3.kt.after
@@ -1,6 +1,6 @@
 // "Cast expression 'x' to 'Foo<*>'" "true"
 
-trait Foo<T: Number> {
+interface Foo<T: Number> {
     fun bar()
 }
 
diff --git a/idea/testData/quickfix/typeMismatch/casts/typeMismatch3.kt b/idea/testData/quickfix/typeMismatch/casts/typeMismatch3.kt
index 46383dfd385..47c3bc48e66 100644
--- a/idea/testData/quickfix/typeMismatch/casts/typeMismatch3.kt
+++ b/idea/testData/quickfix/typeMismatch/casts/typeMismatch3.kt
@@ -1,8 +1,8 @@
 // "Cast expression 'a + a' to 'B'" "true"
-trait A {
+interface A {
     fun plus(x: Any): A
 }
-trait B : A
+interface B : A
 
 fun foo(a: A): B {
     return a + a<caret>
diff --git a/idea/testData/quickfix/typeMismatch/casts/typeMismatch3.kt.after b/idea/testData/quickfix/typeMismatch/casts/typeMismatch3.kt.after
index 4c0a55f7d31..491082178d1 100644
--- a/idea/testData/quickfix/typeMismatch/casts/typeMismatch3.kt.after
+++ b/idea/testData/quickfix/typeMismatch/casts/typeMismatch3.kt.after
@@ -1,8 +1,8 @@
 // "Cast expression 'a + a' to 'B'" "true"
-trait A {
+interface A {
     fun plus(x: Any): A
 }
-trait B : A
+interface B : A
 
 fun foo(a: A): B {
     return (a + a) as B<caret>
diff --git a/idea/testData/quickfix/typeMismatch/compareToTypeMismatch.kt b/idea/testData/quickfix/typeMismatch/compareToTypeMismatch.kt
index 1033e051114..b8028798e72 100644
--- a/idea/testData/quickfix/typeMismatch/compareToTypeMismatch.kt
+++ b/idea/testData/quickfix/typeMismatch/compareToTypeMismatch.kt
@@ -1,5 +1,5 @@
 // "Change 'A.compareTo' function return type to 'Int'" "true"
-trait A {
+interface A {
     fun compareTo(other: Any): String
 }
 fun foo(x: A) {
diff --git a/idea/testData/quickfix/typeMismatch/compareToTypeMismatch.kt.after b/idea/testData/quickfix/typeMismatch/compareToTypeMismatch.kt.after
index 218c5517070..2e6777b4499 100644
--- a/idea/testData/quickfix/typeMismatch/compareToTypeMismatch.kt.after
+++ b/idea/testData/quickfix/typeMismatch/compareToTypeMismatch.kt.after
@@ -1,5 +1,5 @@
 // "Change 'A.compareTo' function return type to 'Int'" "true"
-trait A {
+interface A {
     fun compareTo(other: Any): Int
 }
 fun foo(x: A) {
diff --git a/idea/testData/quickfix/typeMismatch/dontChangeOverriddenPropertyTypeToErrorType.kt b/idea/testData/quickfix/typeMismatch/dontChangeOverriddenPropertyTypeToErrorType.kt
index 5dbeb8ae299..4f4ebc0f521 100644
--- a/idea/testData/quickfix/typeMismatch/dontChangeOverriddenPropertyTypeToErrorType.kt
+++ b/idea/testData/quickfix/typeMismatch/dontChangeOverriddenPropertyTypeToErrorType.kt
@@ -4,9 +4,9 @@
 // ACTION: Edit inspection profile setting
 // ERROR: <html>Return type is '(kotlin.Int) &rarr; kotlin.Int', which is not a subtype of overridden<br/><b>internal</b> <b>abstract</b> <b>val</b> x: (kotlin.String) &rarr; [ERROR : Ay] <i>defined in</i> A</html>
 // ERROR: Unresolved reference: Ay
-trait A {
+interface A {
     val x: (String) -> Ay
 }
-trait B : A {
+interface B : A {
     override val x: (Int) -> Int<caret>
 }
\ No newline at end of file
diff --git a/idea/testData/quickfix/typeMismatch/expectedReturnTypeMismatch.kt b/idea/testData/quickfix/typeMismatch/expectedReturnTypeMismatch.kt
index c55df3630ea..2194b0bc545 100644
--- a/idea/testData/quickfix/typeMismatch/expectedReturnTypeMismatch.kt
+++ b/idea/testData/quickfix/typeMismatch/expectedReturnTypeMismatch.kt
@@ -1,6 +1,6 @@
 // "Change type from 'A' to 'B'" "true"
-trait A {}
-trait B : A {}
+interface A {}
+interface B : A {}
 
 fun foo(f: (B) -> B) {
     foo {
diff --git a/idea/testData/quickfix/typeMismatch/expectedReturnTypeMismatch.kt.after b/idea/testData/quickfix/typeMismatch/expectedReturnTypeMismatch.kt.after
index 05be595bbcb..a29b24e25ca 100644
--- a/idea/testData/quickfix/typeMismatch/expectedReturnTypeMismatch.kt.after
+++ b/idea/testData/quickfix/typeMismatch/expectedReturnTypeMismatch.kt.after
@@ -1,6 +1,6 @@
 // "Change type from 'A' to 'B'" "true"
-trait A {}
-trait B : A {}
+interface A {}
+interface B : A {}
 
 fun foo(f: (B) -> B) {
     foo {
diff --git a/idea/testData/quickfix/typeMismatch/fixOverloadedOperator/changeNotFunctionReturnType.kt b/idea/testData/quickfix/typeMismatch/fixOverloadedOperator/changeNotFunctionReturnType.kt
index 3fcbddff06c..28c05b878ba 100644
--- a/idea/testData/quickfix/typeMismatch/fixOverloadedOperator/changeNotFunctionReturnType.kt
+++ b/idea/testData/quickfix/typeMismatch/fixOverloadedOperator/changeNotFunctionReturnType.kt
@@ -1,5 +1,5 @@
 // "Change 'A.not' function return type to 'A'" "true"
-trait A {
+interface A {
     fun not(): String
     fun times(a: A): A
 }
diff --git a/idea/testData/quickfix/typeMismatch/fixOverloadedOperator/changeNotFunctionReturnType.kt.after b/idea/testData/quickfix/typeMismatch/fixOverloadedOperator/changeNotFunctionReturnType.kt.after
index 2e02e549264..ce0594d5c61 100644
--- a/idea/testData/quickfix/typeMismatch/fixOverloadedOperator/changeNotFunctionReturnType.kt.after
+++ b/idea/testData/quickfix/typeMismatch/fixOverloadedOperator/changeNotFunctionReturnType.kt.after
@@ -1,5 +1,5 @@
 // "Change 'A.not' function return type to 'A'" "true"
-trait A {
+interface A {
     fun not(): A
     fun times(a: A): A
 }
diff --git a/idea/testData/quickfix/typeMismatch/fixOverloadedOperator/changePlusFunctionReturnType.kt b/idea/testData/quickfix/typeMismatch/fixOverloadedOperator/changePlusFunctionReturnType.kt
index c83d83f0c41..e3915d9e301 100644
--- a/idea/testData/quickfix/typeMismatch/fixOverloadedOperator/changePlusFunctionReturnType.kt
+++ b/idea/testData/quickfix/typeMismatch/fixOverloadedOperator/changePlusFunctionReturnType.kt
@@ -1,5 +1,5 @@
 // "Change 'A.plus' function return type to '() -> Int'" "true"
-trait A {
+interface A {
     fun plus(a: A): String
 }
 
diff --git a/idea/testData/quickfix/typeMismatch/fixOverloadedOperator/changePlusFunctionReturnType.kt.after b/idea/testData/quickfix/typeMismatch/fixOverloadedOperator/changePlusFunctionReturnType.kt.after
index 5f841fe38b4..38a92aec5e0 100644
--- a/idea/testData/quickfix/typeMismatch/fixOverloadedOperator/changePlusFunctionReturnType.kt.after
+++ b/idea/testData/quickfix/typeMismatch/fixOverloadedOperator/changePlusFunctionReturnType.kt.after
@@ -1,5 +1,5 @@
 // "Change 'A.plus' function return type to '() -> Int'" "true"
-trait A {
+interface A {
     fun plus(a: A): () -> Int
 }
 
diff --git a/idea/testData/quickfix/typeMismatch/fixOverloadedOperator/changeTimesFunctionParameterType.kt b/idea/testData/quickfix/typeMismatch/fixOverloadedOperator/changeTimesFunctionParameterType.kt
index 837fc7af446..bc2f8b03cc2 100644
--- a/idea/testData/quickfix/typeMismatch/fixOverloadedOperator/changeTimesFunctionParameterType.kt
+++ b/idea/testData/quickfix/typeMismatch/fixOverloadedOperator/changeTimesFunctionParameterType.kt
@@ -1,5 +1,5 @@
 // "Change parameter 'a' type of function 'A.times' to 'String'" "true"
-trait A {
+interface A {
     fun times(a: A): A
 }
 
diff --git a/idea/testData/quickfix/typeMismatch/fixOverloadedOperator/changeTimesFunctionParameterType.kt.after b/idea/testData/quickfix/typeMismatch/fixOverloadedOperator/changeTimesFunctionParameterType.kt.after
index a0178c297d5..252bb1d98bd 100644
--- a/idea/testData/quickfix/typeMismatch/fixOverloadedOperator/changeTimesFunctionParameterType.kt.after
+++ b/idea/testData/quickfix/typeMismatch/fixOverloadedOperator/changeTimesFunctionParameterType.kt.after
@@ -1,5 +1,5 @@
 // "Change parameter 'a' type of function 'A.times' to 'String'" "true"
-trait A {
+interface A {
     fun times(a: String): A
 }
 
diff --git a/idea/testData/quickfix/typeMismatch/localClassInReturn1.kt b/idea/testData/quickfix/typeMismatch/localClassInReturn1.kt
index 1919274de64..020113b5f6f 100644
--- a/idea/testData/quickfix/typeMismatch/localClassInReturn1.kt
+++ b/idea/testData/quickfix/typeMismatch/localClassInReturn1.kt
@@ -1,6 +1,6 @@
 // "Change 'foo' function return type to 'U'" "true"
-trait T
-trait U
+interface T
+interface U
 
 fun foo() {
     open class A: T
diff --git a/idea/testData/quickfix/typeMismatch/localClassInReturn1.kt.after b/idea/testData/quickfix/typeMismatch/localClassInReturn1.kt.after
index 70acb9155e7..11edf6b5a20 100644
--- a/idea/testData/quickfix/typeMismatch/localClassInReturn1.kt.after
+++ b/idea/testData/quickfix/typeMismatch/localClassInReturn1.kt.after
@@ -1,6 +1,6 @@
 // "Change 'foo' function return type to 'U'" "true"
-trait T
-trait U
+interface T
+interface U
 
 fun foo(): U {
     open class A: T
diff --git a/idea/testData/quickfix/typeMismatch/localClassInReturn2.kt b/idea/testData/quickfix/typeMismatch/localClassInReturn2.kt
index b289985a493..16957285cc1 100644
--- a/idea/testData/quickfix/typeMismatch/localClassInReturn2.kt
+++ b/idea/testData/quickfix/typeMismatch/localClassInReturn2.kt
@@ -1,5 +1,5 @@
 // "Change 'foo' function return type to 'T'" "true"
-trait T
+interface T
 
 fun foo() {
     open class A: T
diff --git a/idea/testData/quickfix/typeMismatch/localClassInReturn2.kt.after b/idea/testData/quickfix/typeMismatch/localClassInReturn2.kt.after
index f7f98908194..24e9d12c771 100644
--- a/idea/testData/quickfix/typeMismatch/localClassInReturn2.kt.after
+++ b/idea/testData/quickfix/typeMismatch/localClassInReturn2.kt.after
@@ -1,5 +1,5 @@
 // "Change 'foo' function return type to 'T'" "true"
-trait T
+interface T
 
 fun foo(): T {
     open class A: T
diff --git a/idea/testData/quickfix/typeMismatch/parameterTypeMismatch/multiFakeOverride.kt b/idea/testData/quickfix/typeMismatch/parameterTypeMismatch/multiFakeOverride.kt
index 2766953deff..dc9ee242b1d 100644
--- a/idea/testData/quickfix/typeMismatch/parameterTypeMismatch/multiFakeOverride.kt
+++ b/idea/testData/quickfix/typeMismatch/parameterTypeMismatch/multiFakeOverride.kt
@@ -1,6 +1,6 @@
 // "class org.jetbrains.kotlin.idea.quickfix.ChangeParameterTypeFix" "false"
 // ERROR: <html>Type mismatch.<table><tr><td>Required:</td><td>kotlin.Int</td></tr><tr><td>Found:</td><td>kotlin.String</td></tr></table></html>
-trait A {
+interface A {
     fun f(i: Int): Boolean
 }
 
diff --git a/idea/testData/quickfix/typeMismatch/typeMismatchOnReturnedExpression/multiFakeOverride.kt b/idea/testData/quickfix/typeMismatch/typeMismatchOnReturnedExpression/multiFakeOverride.kt
index dbcb8365484..eaa1386e34e 100644
--- a/idea/testData/quickfix/typeMismatch/typeMismatchOnReturnedExpression/multiFakeOverride.kt
+++ b/idea/testData/quickfix/typeMismatch/typeMismatchOnReturnedExpression/multiFakeOverride.kt
@@ -4,7 +4,7 @@
 // ACTION: Disable 'Convert to Expression Body'
 // ACTION: Edit intention settings
 // ERROR: <html>Type mismatch.<table><tr><td>Required:</td><td>kotlin.Boolean</td></tr><tr><td>Found:</td><td>kotlin.Int</td></tr></table></html>
-trait A {
+interface A {
     fun f(): Int
 }
 
diff --git a/idea/testData/quickfix/typeMismatch/typeMismatchOnReturnedExpression/multiFakeOverrideForOperatorConvention.kt b/idea/testData/quickfix/typeMismatch/typeMismatchOnReturnedExpression/multiFakeOverrideForOperatorConvention.kt
index ae55376a13e..2d0e3cc50f4 100644
--- a/idea/testData/quickfix/typeMismatch/typeMismatchOnReturnedExpression/multiFakeOverrideForOperatorConvention.kt
+++ b/idea/testData/quickfix/typeMismatch/typeMismatchOnReturnedExpression/multiFakeOverrideForOperatorConvention.kt
@@ -7,7 +7,7 @@
 // ACTION: Edit intention settings
 // ACTION: Replace overloaded operator with function call
 // ERROR: <html>Type mismatch.<table><tr><td>Required:</td><td>kotlin.Int</td></tr><tr><td>Found:</td><td>kotlin.Boolean</td></tr></table></html>
-trait A {
+interface A {
     fun contains(i: Int): Boolean
 }
 
diff --git a/idea/testData/quickfix/typeProjection/projectionInImmediateArgumentToSupertype.kt b/idea/testData/quickfix/typeProjection/projectionInImmediateArgumentToSupertype.kt
index 7706db790ec..959f2db615d 100644
--- a/idea/testData/quickfix/typeProjection/projectionInImmediateArgumentToSupertype.kt
+++ b/idea/testData/quickfix/typeProjection/projectionInImmediateArgumentToSupertype.kt
@@ -1,4 +1,4 @@
 // "Remove 'in' modifier" "true"
-trait A<T> {}
+interface A<T> {}
 
 class B : A<<caret>in Int> {}
diff --git a/idea/testData/quickfix/typeProjection/projectionInImmediateArgumentToSupertype.kt.after b/idea/testData/quickfix/typeProjection/projectionInImmediateArgumentToSupertype.kt.after
index ab4e941bc3d..00142dc967f 100644
--- a/idea/testData/quickfix/typeProjection/projectionInImmediateArgumentToSupertype.kt.after
+++ b/idea/testData/quickfix/typeProjection/projectionInImmediateArgumentToSupertype.kt.after
@@ -1,4 +1,4 @@
 // "Remove 'in' modifier" "true"
-trait A<T> {}
+interface A<T> {}
 
 class B : A<Int> {}
diff --git a/idea/testData/refactoring/changeSignature/AddReceiverToGenericsWithOverridesAfter.kt b/idea/testData/refactoring/changeSignature/AddReceiverToGenericsWithOverridesAfter.kt
index 58c6f2a75c1..d7fe0a736a7 100644
--- a/idea/testData/refactoring/changeSignature/AddReceiverToGenericsWithOverridesAfter.kt
+++ b/idea/testData/refactoring/changeSignature/AddReceiverToGenericsWithOverridesAfter.kt
@@ -1,6 +1,6 @@
 class U<A>
 
-trait T<A> {
+interface T<A> {
     fun U<A>.foofoofoo<B>(b: B): Int
 }
 
diff --git a/idea/testData/refactoring/changeSignature/AddReceiverToGenericsWithOverridesBefore.kt b/idea/testData/refactoring/changeSignature/AddReceiverToGenericsWithOverridesBefore.kt
index 34bb8231cfb..600aec645fb 100644
--- a/idea/testData/refactoring/changeSignature/AddReceiverToGenericsWithOverridesBefore.kt
+++ b/idea/testData/refactoring/changeSignature/AddReceiverToGenericsWithOverridesBefore.kt
@@ -1,6 +1,6 @@
 class U<A>
 
-trait T<A> {
+interface T<A> {
     fun <caret>foofoofoo<B>(a: A, b: B): Int
 }
 
diff --git a/idea/testData/refactoring/changeSignature/FakeOverrideAfter.kt b/idea/testData/refactoring/changeSignature/FakeOverrideAfter.kt
index c280c658565..1d5139264b1 100644
--- a/idea/testData/refactoring/changeSignature/FakeOverrideAfter.kt
+++ b/idea/testData/refactoring/changeSignature/FakeOverrideAfter.kt
@@ -1,12 +1,12 @@
-trait A {
+interface A {
     fun f(i: Int) {}
 }
 
-trait B {
+interface B {
     fun f(i: Int) {}
 }
 
-trait C : A, B {
+interface C : A, B {
 
 }
 
diff --git a/idea/testData/refactoring/changeSignature/FakeOverrideBefore.kt b/idea/testData/refactoring/changeSignature/FakeOverrideBefore.kt
index be1c46463a8..fbd6c063c3c 100644
--- a/idea/testData/refactoring/changeSignature/FakeOverrideBefore.kt
+++ b/idea/testData/refactoring/changeSignature/FakeOverrideBefore.kt
@@ -1,12 +1,12 @@
-trait A {
+interface A {
     fun f() {}
 }
 
-trait B {
+interface B {
     fun f() {}
 }
 
-trait C : A, B {
+interface C : A, B {
 
 }
 
diff --git a/idea/testData/refactoring/changeSignature/GenericsWithOverridesAfter.kt b/idea/testData/refactoring/changeSignature/GenericsWithOverridesAfter.kt
index a171fdcae4e..fb3fb80ac38 100644
--- a/idea/testData/refactoring/changeSignature/GenericsWithOverridesAfter.kt
+++ b/idea/testData/refactoring/changeSignature/GenericsWithOverridesAfter.kt
@@ -1,6 +1,6 @@
 class U<A>
 
-trait T<A, B> {
+interface T<A, B> {
     fun foofoofoo<C>(a: List<C>, b: A?, c: U<B>): U<C>?
 }
 
diff --git a/idea/testData/refactoring/changeSignature/GenericsWithOverridesBefore.kt b/idea/testData/refactoring/changeSignature/GenericsWithOverridesBefore.kt
index 34c445933d6..a6adba21e93 100644
--- a/idea/testData/refactoring/changeSignature/GenericsWithOverridesBefore.kt
+++ b/idea/testData/refactoring/changeSignature/GenericsWithOverridesBefore.kt
@@ -1,6 +1,6 @@
 class U<A>
 
-trait T<A, B> {
+interface T<A, B> {
     fun <caret>foofoofoo<C>(a: A, b: B, c: C): Int
 }
 
diff --git a/idea/testData/refactoring/changeSignature/NoDefaultValuesInOverridesAfter.kt b/idea/testData/refactoring/changeSignature/NoDefaultValuesInOverridesAfter.kt
index 8cd2f78a6a6..5f6a6c2bda6 100644
--- a/idea/testData/refactoring/changeSignature/NoDefaultValuesInOverridesAfter.kt
+++ b/idea/testData/refactoring/changeSignature/NoDefaultValuesInOverridesAfter.kt
@@ -1,4 +1,4 @@
-trait T {
+interface T {
     fun foo(a: Int = 1,
             b: String = "2")
 }
diff --git a/idea/testData/refactoring/changeSignature/NoDefaultValuesInOverridesBefore.kt b/idea/testData/refactoring/changeSignature/NoDefaultValuesInOverridesBefore.kt
index 02033d30f9a..facaffaea6c 100644
--- a/idea/testData/refactoring/changeSignature/NoDefaultValuesInOverridesBefore.kt
+++ b/idea/testData/refactoring/changeSignature/NoDefaultValuesInOverridesBefore.kt
@@ -1,4 +1,4 @@
-trait T {
+interface T {
     fun <caret>foo(b: String = "2",
             a: Int = 1)
 }
diff --git a/idea/testData/refactoring/changeSignature/ParameterChangeInOverridesAfter.kt b/idea/testData/refactoring/changeSignature/ParameterChangeInOverridesAfter.kt
index 2c0d1b085a2..4eba690ced0 100644
--- a/idea/testData/refactoring/changeSignature/ParameterChangeInOverridesAfter.kt
+++ b/idea/testData/refactoring/changeSignature/ParameterChangeInOverridesAfter.kt
@@ -1,4 +1,4 @@
-trait Foo {
+interface Foo {
     fun bar(n: Int)
 }
 
diff --git a/idea/testData/refactoring/changeSignature/ParameterChangeInOverridesBefore.kt b/idea/testData/refactoring/changeSignature/ParameterChangeInOverridesBefore.kt
index 385b8d80d17..eab421e72fe 100644
--- a/idea/testData/refactoring/changeSignature/ParameterChangeInOverridesBefore.kt
+++ b/idea/testData/refactoring/changeSignature/ParameterChangeInOverridesBefore.kt
@@ -1,4 +1,4 @@
-trait Foo {
+interface Foo {
     fun <caret>bar(s: String)
 }
 
diff --git a/idea/testData/refactoring/changeSignature/PreferContainedInClassBefore.kt b/idea/testData/refactoring/changeSignature/PreferContainedInClassBefore.kt
index 91a361b51aa..946cbaaa83d 100644
--- a/idea/testData/refactoring/changeSignature/PreferContainedInClassBefore.kt
+++ b/idea/testData/refactoring/changeSignature/PreferContainedInClassBefore.kt
@@ -2,7 +2,7 @@ class A {
     fun f(param: Int)
 }
 
-trait B {
+interface B {
     fun f(p: Int)
 }
 
diff --git a/idea/testData/refactoring/extractFunction/basic/delegatingFunction.kt b/idea/testData/refactoring/extractFunction/basic/delegatingFunction.kt
index d2a65edeec4..02b002ee0a0 100644
--- a/idea/testData/refactoring/extractFunction/basic/delegatingFunction.kt
+++ b/idea/testData/refactoring/extractFunction/basic/delegatingFunction.kt
@@ -1,6 +1,6 @@
 // PARAM_DESCRIPTOR: val t: <no name provided> defined in foo
 // PARAM_TYPES: T
-trait T {
+interface T {
     fun test() {}
 }
 
diff --git a/idea/testData/refactoring/extractFunction/basic/delegatingFunction.kt.after b/idea/testData/refactoring/extractFunction/basic/delegatingFunction.kt.after
index b960e6c47e9..07b3caa0493 100644
--- a/idea/testData/refactoring/extractFunction/basic/delegatingFunction.kt.after
+++ b/idea/testData/refactoring/extractFunction/basic/delegatingFunction.kt.after
@@ -1,6 +1,6 @@
 // PARAM_DESCRIPTOR: val t: <no name provided> defined in foo
 // PARAM_TYPES: T
-trait T {
+interface T {
     fun test() {}
 }
 
diff --git a/idea/testData/refactoring/extractFunction/basic/fakeOverride.kt b/idea/testData/refactoring/extractFunction/basic/fakeOverride.kt
index 45d31e59355..53b4e9633ad 100644
--- a/idea/testData/refactoring/extractFunction/basic/fakeOverride.kt
+++ b/idea/testData/refactoring/extractFunction/basic/fakeOverride.kt
@@ -1,4 +1,4 @@
-trait T {
+interface T {
     fun test() {}
 }
 
diff --git a/idea/testData/refactoring/extractFunction/basic/fakeOverride.kt.after b/idea/testData/refactoring/extractFunction/basic/fakeOverride.kt.after
index 90e2ce1cedf..8587cfcbb4a 100644
--- a/idea/testData/refactoring/extractFunction/basic/fakeOverride.kt.after
+++ b/idea/testData/refactoring/extractFunction/basic/fakeOverride.kt.after
@@ -1,4 +1,4 @@
-trait T {
+interface T {
     fun test() {}
 }
 
diff --git a/idea/testData/refactoring/extractFunction/basic/traitFunction.kt b/idea/testData/refactoring/extractFunction/basic/traitFunction.kt
index ffb146c5aa6..d3ba092b4f7 100644
--- a/idea/testData/refactoring/extractFunction/basic/traitFunction.kt
+++ b/idea/testData/refactoring/extractFunction/basic/traitFunction.kt
@@ -1,4 +1,4 @@
-trait T{
+interface T{
     fun foo(): Int {
         return <selection>1</selection>
     }
diff --git a/idea/testData/refactoring/extractFunction/basic/traitFunction.kt.after b/idea/testData/refactoring/extractFunction/basic/traitFunction.kt.after
index 47587cb7b4f..7807b894d09 100644
--- a/idea/testData/refactoring/extractFunction/basic/traitFunction.kt.after
+++ b/idea/testData/refactoring/extractFunction/basic/traitFunction.kt.after
@@ -1,4 +1,4 @@
-trait T{
+interface T{
     fun foo(): Int {
         return i()
     }
diff --git a/idea/testData/refactoring/extractFunction/controlFlow/initializer/valueUsedInAnonymousObject.kt b/idea/testData/refactoring/extractFunction/controlFlow/initializer/valueUsedInAnonymousObject.kt
index b061ff68f50..5265387610a 100644
--- a/idea/testData/refactoring/extractFunction/controlFlow/initializer/valueUsedInAnonymousObject.kt
+++ b/idea/testData/refactoring/extractFunction/controlFlow/initializer/valueUsedInAnonymousObject.kt
@@ -6,6 +6,6 @@ fun main(args: Array<String>) {
     }
 }
 
-trait T {
+interface T {
     fun foo(n: Int): Int
 }
\ No newline at end of file
diff --git a/idea/testData/refactoring/extractFunction/controlFlow/initializer/valueUsedInAnonymousObject.kt.after b/idea/testData/refactoring/extractFunction/controlFlow/initializer/valueUsedInAnonymousObject.kt.after
index 5e9c1415762..9a697b264f9 100644
--- a/idea/testData/refactoring/extractFunction/controlFlow/initializer/valueUsedInAnonymousObject.kt.after
+++ b/idea/testData/refactoring/extractFunction/controlFlow/initializer/valueUsedInAnonymousObject.kt.after
@@ -11,6 +11,6 @@ private fun i(): Int {
     return a
 }
 
-trait T {
+interface T {
     fun foo(n: Int): Int
 }
\ No newline at end of file
diff --git a/idea/testData/refactoring/extractFunction/controlFlow/unextractable/anonymousObject.kt b/idea/testData/refactoring/extractFunction/controlFlow/unextractable/anonymousObject.kt
index 88bf5f6c903..8e25e0008e6 100644
--- a/idea/testData/refactoring/extractFunction/controlFlow/unextractable/anonymousObject.kt
+++ b/idea/testData/refactoring/extractFunction/controlFlow/unextractable/anonymousObject.kt
@@ -1,4 +1,4 @@
-trait Callable<T> {
+interface Callable<T> {
     fun call(): T
 }
 
diff --git a/idea/testData/refactoring/extractFunction/delegation/delegationByExpression.kt b/idea/testData/refactoring/extractFunction/delegation/delegationByExpression.kt
index 1734e9b3f2d..5376cb95f3c 100644
--- a/idea/testData/refactoring/extractFunction/delegation/delegationByExpression.kt
+++ b/idea/testData/refactoring/extractFunction/delegation/delegationByExpression.kt
@@ -2,7 +2,7 @@
 // PARAM_TYPES: kotlin.Int
 // PARAM_DESCRIPTOR: value-parameter val a: kotlin.Int defined in B.<init>
 // PARAM_DESCRIPTOR: value-parameter val b: kotlin.Int defined in B.<init>
-trait T
+interface T
 
 class A(a: Int, b: Int): T
 
diff --git a/idea/testData/refactoring/extractFunction/delegation/delegationByExpression.kt.after b/idea/testData/refactoring/extractFunction/delegation/delegationByExpression.kt.after
index 3a01bea0694..200d20644a0 100644
--- a/idea/testData/refactoring/extractFunction/delegation/delegationByExpression.kt.after
+++ b/idea/testData/refactoring/extractFunction/delegation/delegationByExpression.kt.after
@@ -2,7 +2,7 @@
 // PARAM_TYPES: kotlin.Int
 // PARAM_DESCRIPTOR: value-parameter val a: kotlin.Int defined in B.<init>
 // PARAM_DESCRIPTOR: value-parameter val b: kotlin.Int defined in B.<init>
-trait T
+interface T
 
 class A(a: Int, b: Int): T
 
diff --git a/idea/testData/refactoring/extractFunction/delegation/delegationByExpressionFull.kt b/idea/testData/refactoring/extractFunction/delegation/delegationByExpressionFull.kt
index 027c6e60ebf..b24cf8ee556 100644
--- a/idea/testData/refactoring/extractFunction/delegation/delegationByExpressionFull.kt
+++ b/idea/testData/refactoring/extractFunction/delegation/delegationByExpressionFull.kt
@@ -1,6 +1,6 @@
 // PARAM_TYPES: T
 // PARAM_DESCRIPTOR: value-parameter val t: T defined in B.<init>
-trait T
+interface T
 
 class A(a: Int, b: Int): T
 
diff --git a/idea/testData/refactoring/extractFunction/delegation/delegationByExpressionFull.kt.after b/idea/testData/refactoring/extractFunction/delegation/delegationByExpressionFull.kt.after
index b26ceb9cde4..c4047be9ddc 100644
--- a/idea/testData/refactoring/extractFunction/delegation/delegationByExpressionFull.kt.after
+++ b/idea/testData/refactoring/extractFunction/delegation/delegationByExpressionFull.kt.after
@@ -1,6 +1,6 @@
 // PARAM_TYPES: T
 // PARAM_DESCRIPTOR: value-parameter val t: T defined in B.<init>
-trait T
+interface T
 
 class A(a: Int, b: Int): T
 
diff --git a/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy1.kt b/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy1.kt
index ff2682a5d7f..13007831bde 100644
--- a/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy1.kt
+++ b/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy1.kt
@@ -1,6 +1,6 @@
 //PARAM_TYPES: C, AImpl, A
 //PARAM_DESCRIPTOR: value-parameter val c: C defined in foo
-trait A {
+interface A {
     fun doA()
 }
 
@@ -10,7 +10,7 @@ open class AImpl: A {
     }
 }
 
-trait B {
+interface B {
     fun doB()
 }
 
diff --git a/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy1.kt.after b/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy1.kt.after
index b9fb11952dc..3fe150079d4 100644
--- a/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy1.kt.after
+++ b/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy1.kt.after
@@ -1,6 +1,6 @@
 //PARAM_TYPES: C, AImpl, A
 //PARAM_DESCRIPTOR: value-parameter val c: C defined in foo
-trait A {
+interface A {
     fun doA()
 }
 
@@ -10,7 +10,7 @@ open class AImpl: A {
     }
 }
 
-trait B {
+interface B {
     fun doB()
 }
 
diff --git a/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy2.kt b/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy2.kt
index b1f131ac6cd..e6ec42e71e4 100644
--- a/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy2.kt
+++ b/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy2.kt
@@ -1,6 +1,6 @@
 //PARAM_TYPES: C, B
 //PARAM_DESCRIPTOR: value-parameter val c: C defined in foo
-trait A {
+interface A {
     fun doA()
 }
 
@@ -10,7 +10,7 @@ open class AImpl: A {
     }
 }
 
-trait B {
+interface B {
     fun doB()
 }
 
diff --git a/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy2.kt.after b/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy2.kt.after
index 965680aa0e9..64186d39038 100644
--- a/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy2.kt.after
+++ b/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy2.kt.after
@@ -1,6 +1,6 @@
 //PARAM_TYPES: C, B
 //PARAM_DESCRIPTOR: value-parameter val c: C defined in foo
-trait A {
+interface A {
     fun doA()
 }
 
@@ -10,7 +10,7 @@ open class AImpl: A {
     }
 }
 
-trait B {
+interface B {
     fun doB()
 }
 
diff --git a/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy3.kt b/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy3.kt
index a9b3756b8d5..f7c75d181cb 100644
--- a/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy3.kt
+++ b/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy3.kt
@@ -1,6 +1,6 @@
 //PARAM_TYPES: C
 //PARAM_DESCRIPTOR: value-parameter val c: C defined in foo
-trait A {
+interface A {
     fun doA()
 }
 
@@ -10,7 +10,7 @@ open class AImpl: A {
     }
 }
 
-trait B {
+interface B {
     fun doB()
 }
 
diff --git a/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy3.kt.after b/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy3.kt.after
index 1aa8b3d30dc..17def8e8674 100644
--- a/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy3.kt.after
+++ b/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy3.kt.after
@@ -1,6 +1,6 @@
 //PARAM_TYPES: C
 //PARAM_DESCRIPTOR: value-parameter val c: C defined in foo
-trait A {
+interface A {
     fun doA()
 }
 
@@ -10,7 +10,7 @@ open class AImpl: A {
     }
 }
 
-trait B {
+interface B {
     fun doB()
 }
 
diff --git a/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy4.kt b/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy4.kt
index 1a3cc6674fe..cedc81fb9a3 100644
--- a/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy4.kt
+++ b/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy4.kt
@@ -1,6 +1,6 @@
 //PARAM_TYPES: C
 //PARAM_DESCRIPTOR: value-parameter val c: C defined in foo
-trait A {
+interface A {
     fun doA()
 }
 
@@ -10,7 +10,7 @@ open class AImpl: A {
     }
 }
 
-trait B {
+interface B {
     fun doB()
 }
 
diff --git a/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy4.kt.after b/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy4.kt.after
index 4306a33fadb..94dc975c12f 100644
--- a/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy4.kt.after
+++ b/idea/testData/refactoring/extractFunction/parameters/candidateTypes/typeHierarchy4.kt.after
@@ -1,6 +1,6 @@
 //PARAM_TYPES: C
 //PARAM_DESCRIPTOR: value-parameter val c: C defined in foo
-trait A {
+interface A {
     fun doA()
 }
 
@@ -10,7 +10,7 @@ open class AImpl: A {
     }
 }
 
-trait B {
+interface B {
     fun doB()
 }
 
diff --git a/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/anonymousObject.kt b/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/anonymousObject.kt
index 5f51bf42fbb..7dc2f3e1463 100644
--- a/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/anonymousObject.kt
+++ b/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/anonymousObject.kt
@@ -1,4 +1,4 @@
-trait T
+interface T
 
 fun foo(): T {
     return <selection>object: T() {}</selection>
diff --git a/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/anonymousObject.kt.after b/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/anonymousObject.kt.after
index c188b4ca8dc..ed7ab918a86 100644
--- a/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/anonymousObject.kt.after
+++ b/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/anonymousObject.kt.after
@@ -1,4 +1,4 @@
-trait T
+interface T
 
 fun foo(): T {
     return t()
diff --git a/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/anonymousObjectWithCall.kt b/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/anonymousObjectWithCall.kt
index dec1f8a1436..c5498ae043d 100644
--- a/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/anonymousObjectWithCall.kt
+++ b/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/anonymousObjectWithCall.kt
@@ -1,4 +1,4 @@
-trait Callable<T> {
+interface Callable<T> {
     fun call(): T
 }
 
diff --git a/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclass.kt b/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclass.kt
index bf535a64bce..6b7261865e6 100644
--- a/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclass.kt
+++ b/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclass.kt
@@ -1,4 +1,4 @@
-trait T
+interface T
 
 fun foo(): T {
     class A: T
diff --git a/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclass.kt.after b/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclass.kt.after
index b92f1fd9896..16ed916fb6c 100644
--- a/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclass.kt.after
+++ b/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclass.kt.after
@@ -1,4 +1,4 @@
-trait T
+interface T
 
 fun foo(): T {
     class A: T
diff --git a/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclassParameter.kt b/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclassParameter.kt
index 776e61fc8b0..6b9b00c9f66 100644
--- a/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclassParameter.kt
+++ b/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclassParameter.kt
@@ -1,6 +1,6 @@
 // PARAM_DESCRIPTOR: val a: foo.A defined in foo.bar
 // PARAM_TYPES: T
-trait T
+interface T
 
 // SIBLING:
 fun foo(): T {
diff --git a/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclassParameter.kt.after b/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclassParameter.kt.after
index 39fd527e2a7..c161243ecaa 100644
--- a/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclassParameter.kt.after
+++ b/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclassParameter.kt.after
@@ -1,6 +1,6 @@
 // PARAM_DESCRIPTOR: val a: foo.A defined in foo.bar
 // PARAM_TYPES: T
-trait T
+interface T
 
 // SIBLING:
 fun foo(): T {
diff --git a/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclassParameterInLocalFun.kt b/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclassParameterInLocalFun.kt
index f85f38aa64e..46c301d28c2 100644
--- a/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclassParameterInLocalFun.kt
+++ b/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclassParameterInLocalFun.kt
@@ -1,6 +1,6 @@
 // PARAM_DESCRIPTOR: val a: foo.A defined in foo.bar
 // PARAM_TYPES: foo.A, T
-trait T
+interface T
 
 fun foo(): T {
     class A: T
diff --git a/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclassParameterInLocalFun.kt.after b/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclassParameterInLocalFun.kt.after
index e32b95330c7..2dc231e3d60 100644
--- a/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclassParameterInLocalFun.kt.after
+++ b/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclassParameterInLocalFun.kt.after
@@ -1,6 +1,6 @@
 // PARAM_DESCRIPTOR: val a: foo.A defined in foo.bar
 // PARAM_TYPES: foo.A, T
-trait T
+interface T
 
 fun foo(): T {
     class A: T
diff --git a/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclassParameterNoApproximation.kt b/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclassParameterNoApproximation.kt
index ebeeb79a7f2..b4a85150880 100644
--- a/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclassParameterNoApproximation.kt
+++ b/idea/testData/refactoring/extractFunction/parameters/nonDenotableTypes/localClassWithSuperclassParameterNoApproximation.kt
@@ -1,4 +1,4 @@
-trait T
+interface T
 
 // SIBLING:
 fun foo(): T {
diff --git a/idea/testData/refactoring/extractFunction/typeParameters/simpleTypeParameterWithConstraint.kt b/idea/testData/refactoring/extractFunction/typeParameters/simpleTypeParameterWithConstraint.kt
index b023ebb0909..feb5de1e85a 100644
--- a/idea/testData/refactoring/extractFunction/typeParameters/simpleTypeParameterWithConstraint.kt
+++ b/idea/testData/refactoring/extractFunction/typeParameters/simpleTypeParameterWithConstraint.kt
@@ -1,7 +1,7 @@
 // PARAM_TYPES: V
 // PARAM_DESCRIPTOR: value-parameter val v: V defined in foo
 open class Data(val x: Int)
-trait DataEx
+interface DataEx
 
 class Pair<A, B>(val a: A, val b: B)
 
diff --git a/idea/testData/refactoring/extractFunction/typeParameters/simpleTypeParameterWithConstraint.kt.after b/idea/testData/refactoring/extractFunction/typeParameters/simpleTypeParameterWithConstraint.kt.after
index 29e5f4e82a0..6c34363ad4b 100644
--- a/idea/testData/refactoring/extractFunction/typeParameters/simpleTypeParameterWithConstraint.kt.after
+++ b/idea/testData/refactoring/extractFunction/typeParameters/simpleTypeParameterWithConstraint.kt.after
@@ -1,7 +1,7 @@
 // PARAM_TYPES: V
 // PARAM_DESCRIPTOR: value-parameter val v: V defined in foo
 open class Data(val x: Int)
-trait DataEx
+interface DataEx
 
 class Pair<A, B>(val a: A, val b: B)
 
diff --git a/idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined1.kt b/idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined1.kt
index bae4f16ba97..f747d3b3dc8 100644
--- a/idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined1.kt
+++ b/idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined1.kt
@@ -5,8 +5,8 @@
 // PARAM_DESCRIPTOR: internal final inner class B<U : Data> where U : DataExEx defined in A
 // PARAM_DESCRIPTOR: value-parameter val v: V defined in A.B.foo
 open class Data(val x: Int)
-trait DataEx
-trait DataExEx
+interface DataEx
+interface DataExEx
 
 // SIBLING:
 class A<T: Data>(val t: T) where T: DataEx {
diff --git a/idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined1.kt.after b/idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined1.kt.after
index 8d2568d9047..97362da32c1 100644
--- a/idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined1.kt.after
+++ b/idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined1.kt.after
@@ -5,8 +5,8 @@
 // PARAM_DESCRIPTOR: internal final inner class B<U : Data> where U : DataExEx defined in A
 // PARAM_DESCRIPTOR: value-parameter val v: V defined in A.B.foo
 open class Data(val x: Int)
-trait DataEx
-trait DataExEx
+interface DataEx
+interface DataExEx
 
 // SIBLING:
 class A<T: Data>(val t: T) where T: DataEx {
diff --git a/idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined2.kt b/idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined2.kt
index c574a6052c5..dcfadd3eb0d 100644
--- a/idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined2.kt
+++ b/idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined2.kt
@@ -3,8 +3,8 @@
 // PARAM_DESCRIPTOR: internal final inner class B<U : Data> where U : DataExEx defined in A
 // PARAM_DESCRIPTOR: value-parameter val v: V defined in A.B.foo
 open class Data(val x: Int)
-trait DataEx
-trait DataExEx
+interface DataEx
+interface DataExEx
 
 class A<T: Data>(val t: T) where T: DataEx {
     // SIBLING:
diff --git a/idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined2.kt.after b/idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined2.kt.after
index 255e798c423..38448313464 100644
--- a/idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined2.kt.after
+++ b/idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined2.kt.after
@@ -3,8 +3,8 @@
 // PARAM_DESCRIPTOR: internal final inner class B<U : Data> where U : DataExEx defined in A
 // PARAM_DESCRIPTOR: value-parameter val v: V defined in A.B.foo
 open class Data(val x: Int)
-trait DataEx
-trait DataExEx
+interface DataEx
+interface DataExEx
 
 class A<T: Data>(val t: T) where T: DataEx {
     // SIBLING:
diff --git a/idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined3.kt b/idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined3.kt
index 166f611efee..cfd591774e0 100644
--- a/idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined3.kt
+++ b/idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined3.kt
@@ -1,8 +1,8 @@
 // PARAM_TYPES: V, Data
 // PARAM_DESCRIPTOR: value-parameter val v: V defined in A.B.foo
 open class Data(val x: Int)
-trait DataEx
-trait DataExEx
+interface DataEx
+interface DataExEx
 
 class A<T: Data>(val t: T) where T: DataEx {
     inner class B<U: Data>(val u: U) where U: DataExEx {
diff --git a/idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined3.kt.after b/idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined3.kt.after
index 1321103e3d0..58a34cf4dc6 100644
--- a/idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined3.kt.after
+++ b/idea/testData/refactoring/extractFunction/typeParameters/typeParametersAndConstraintsCombined3.kt.after
@@ -1,8 +1,8 @@
 // PARAM_TYPES: V, Data
 // PARAM_DESCRIPTOR: value-parameter val v: V defined in A.B.foo
 open class Data(val x: Int)
-trait DataEx
-trait DataExEx
+interface DataEx
+interface DataExEx
 
 class A<T: Data>(val t: T) where T: DataEx {
     inner class B<U: Data>(val u: U) where U: DataExEx {
diff --git a/idea/testData/refactoring/extractFunction/typeParameters/typeParametersCombinedAndThis.kt b/idea/testData/refactoring/extractFunction/typeParameters/typeParametersCombinedAndThis.kt
index 6ed8915366a..e9d6a2e4ddd 100644
--- a/idea/testData/refactoring/extractFunction/typeParameters/typeParametersCombinedAndThis.kt
+++ b/idea/testData/refactoring/extractFunction/typeParameters/typeParametersCombinedAndThis.kt
@@ -3,7 +3,7 @@
 // PARAM_DESCRIPTOR: internal final class A<T : Data> where T : DataEx defined in root package
 // PARAM_DESCRIPTOR: value-parameter val v: V defined in A.foo
 open class Data(val x: Int)
-trait DataEx
+interface DataEx
 
 // SIBLING:
 class A<T: Data>(val t: T) where T: DataEx {
diff --git a/idea/testData/refactoring/extractFunction/typeParameters/typeParametersCombinedAndThis.kt.after b/idea/testData/refactoring/extractFunction/typeParameters/typeParametersCombinedAndThis.kt.after
index 6cc1beee853..e53ae158a80 100644
--- a/idea/testData/refactoring/extractFunction/typeParameters/typeParametersCombinedAndThis.kt.after
+++ b/idea/testData/refactoring/extractFunction/typeParameters/typeParametersCombinedAndThis.kt.after
@@ -3,7 +3,7 @@
 // PARAM_DESCRIPTOR: internal final class A<T : Data> where T : DataEx defined in root package
 // PARAM_DESCRIPTOR: value-parameter val v: V defined in A.foo
 open class Data(val x: Int)
-trait DataEx
+interface DataEx
 
 // SIBLING:
 class A<T: Data>(val t: T) where T: DataEx {
diff --git a/idea/testData/refactoring/introduceParameter/functionWithApproximatedType.kt b/idea/testData/refactoring/introduceParameter/functionWithApproximatedType.kt
index 9daa9ac804f..a4ac8950557 100644
--- a/idea/testData/refactoring/introduceParameter/functionWithApproximatedType.kt
+++ b/idea/testData/refactoring/introduceParameter/functionWithApproximatedType.kt
@@ -1,4 +1,4 @@
-trait T
+interface T
 
 fun foo() {
     val a = <selection>object: T {}</selection>
diff --git a/idea/testData/refactoring/introduceParameter/functionWithApproximatedType.kt.after b/idea/testData/refactoring/introduceParameter/functionWithApproximatedType.kt.after
index a7bc568087d..3ee9e21375c 100644
--- a/idea/testData/refactoring/introduceParameter/functionWithApproximatedType.kt.after
+++ b/idea/testData/refactoring/introduceParameter/functionWithApproximatedType.kt.after
@@ -1,4 +1,4 @@
-trait T
+interface T
 
 fun foo(t: T = object : T {}) {
     val a = t
diff --git a/idea/testData/refactoring/introduceProperty/extractLazyToTrait.kt b/idea/testData/refactoring/introduceProperty/extractLazyToTrait.kt
index d9d3464f4ef..665172e2ccf 100644
--- a/idea/testData/refactoring/introduceProperty/extractLazyToTrait.kt
+++ b/idea/testData/refactoring/introduceProperty/extractLazyToTrait.kt
@@ -1,6 +1,6 @@
 // EXTRACTION_TARGET: lazy property
 
-trait T {
+interface T {
     fun foo(): Int = <selection>1</selection>
 }
 
diff --git a/idea/testData/refactoring/introduceProperty/extractWithGetterToTrait.kt b/idea/testData/refactoring/introduceProperty/extractWithGetterToTrait.kt
index 6cdb56977ec..ae74e6490a0 100644
--- a/idea/testData/refactoring/introduceProperty/extractWithGetterToTrait.kt
+++ b/idea/testData/refactoring/introduceProperty/extractWithGetterToTrait.kt
@@ -1,5 +1,5 @@
 // EXTRACTION_TARGET: property with getter
-trait T {
+interface T {
     fun foo(): Int {
         return <selection>1</selection>
     }
diff --git a/idea/testData/refactoring/introduceProperty/extractWithGetterToTrait.kt.after b/idea/testData/refactoring/introduceProperty/extractWithGetterToTrait.kt.after
index 8af70a973a6..7e2237af9d7 100644
--- a/idea/testData/refactoring/introduceProperty/extractWithGetterToTrait.kt.after
+++ b/idea/testData/refactoring/introduceProperty/extractWithGetterToTrait.kt.after
@@ -1,5 +1,5 @@
 // EXTRACTION_TARGET: property with getter
-trait T {
+interface T {
     val i: Int
         get() = 1
 
diff --git a/idea/testData/refactoring/introduceProperty/extractWithInitializerToTrait.kt b/idea/testData/refactoring/introduceProperty/extractWithInitializerToTrait.kt
index c8f9403011d..7c5bf9942bb 100644
--- a/idea/testData/refactoring/introduceProperty/extractWithInitializerToTrait.kt
+++ b/idea/testData/refactoring/introduceProperty/extractWithInitializerToTrait.kt
@@ -1,6 +1,6 @@
 // EXTRACTION_TARGET: property with initializer
 
-trait T {
+interface T {
     fun foo(): Int = <selection>1</selection>
 }
 
diff --git a/idea/testData/refactoring/introduceVariable/callUnderSmartCast.kt b/idea/testData/refactoring/introduceVariable/callUnderSmartCast.kt
index 6a823d232c2..fcd6ac13310 100644
--- a/idea/testData/refactoring/introduceVariable/callUnderSmartCast.kt
+++ b/idea/testData/refactoring/introduceVariable/callUnderSmartCast.kt
@@ -1,8 +1,8 @@
-trait T {
+interface T {
     fun foo(): Int
 }
 
-trait U: T
+interface U: T
 
 fun test(t: T): Int {
     return if (t is U)
diff --git a/idea/testData/refactoring/introduceVariable/callUnderSmartCast.kt.after b/idea/testData/refactoring/introduceVariable/callUnderSmartCast.kt.after
index 7cd75a4be79..321ceece163 100644
--- a/idea/testData/refactoring/introduceVariable/callUnderSmartCast.kt.after
+++ b/idea/testData/refactoring/introduceVariable/callUnderSmartCast.kt.after
@@ -1,8 +1,8 @@
-trait T {
+interface T {
     fun foo(): Int
 }
 
-trait U: T
+interface U: T
 
 fun test(t: T): Int {
     val i = t.foo()
diff --git a/idea/testData/refactoring/nameSuggester/AnonymousObjectWithSuper.kt b/idea/testData/refactoring/nameSuggester/AnonymousObjectWithSuper.kt
index cf14ec9ee4f..f20dab2bdc6 100644
--- a/idea/testData/refactoring/nameSuggester/AnonymousObjectWithSuper.kt
+++ b/idea/testData/refactoring/nameSuggester/AnonymousObjectWithSuper.kt
@@ -1,6 +1,6 @@
 // KT-4813
 
-trait A
+interface A
 
 fun foo() {
     <selection>object: A {}</selection>
diff --git a/idea/testData/refactoring/rename/renameKotlinBaseMethod/after/RenameKotlinBaseMethod.kt b/idea/testData/refactoring/rename/renameKotlinBaseMethod/after/RenameKotlinBaseMethod.kt
index 615eaeaf2bc..69eb2dfd097 100644
--- a/idea/testData/refactoring/rename/renameKotlinBaseMethod/after/RenameKotlinBaseMethod.kt
+++ b/idea/testData/refactoring/rename/renameKotlinBaseMethod/after/RenameKotlinBaseMethod.kt
@@ -1,6 +1,6 @@
 package testing.rename
 
-trait A {
+interface A {
     fun second() : Int
 }
 
diff --git a/idea/testData/refactoring/rename/renameKotlinBaseMethod/before/RenameKotlinBaseMethod.kt b/idea/testData/refactoring/rename/renameKotlinBaseMethod/before/RenameKotlinBaseMethod.kt
index 4f3bcd5ed52..4779f684e81 100644
--- a/idea/testData/refactoring/rename/renameKotlinBaseMethod/before/RenameKotlinBaseMethod.kt
+++ b/idea/testData/refactoring/rename/renameKotlinBaseMethod/before/RenameKotlinBaseMethod.kt
@@ -1,6 +1,6 @@
 package testing.rename
 
-trait A {
+interface A {
     fun first() : Int
 }
 
diff --git a/idea/testData/refactoring/rename/renameKotlinValProperty/after/RenameKotlinValProperty.kt b/idea/testData/refactoring/rename/renameKotlinValProperty/after/RenameKotlinValProperty.kt
index b1ffdefd379..2e4b9858fe0 100644
--- a/idea/testData/refactoring/rename/renameKotlinValProperty/after/RenameKotlinValProperty.kt
+++ b/idea/testData/refactoring/rename/renameKotlinValProperty/after/RenameKotlinValProperty.kt
@@ -1,6 +1,6 @@
 package testing.rename
 
-trait AP {
+interface AP {
     val second: Int // <--- Rename base here
 }
 
diff --git a/idea/testData/refactoring/rename/renameKotlinValProperty/before/RenameKotlinValProperty.kt b/idea/testData/refactoring/rename/renameKotlinValProperty/before/RenameKotlinValProperty.kt
index 47e90bf92ec..62f20396854 100644
--- a/idea/testData/refactoring/rename/renameKotlinValProperty/before/RenameKotlinValProperty.kt
+++ b/idea/testData/refactoring/rename/renameKotlinValProperty/before/RenameKotlinValProperty.kt
@@ -1,6 +1,6 @@
 package testing.rename
 
-trait AP {
+interface AP {
     val first: Int // <--- Rename base here
 }
 
diff --git a/idea/testData/refactoring/rename/renameKotlinVarProperty/after/RenameKotlinVarProperty.kt b/idea/testData/refactoring/rename/renameKotlinVarProperty/after/RenameKotlinVarProperty.kt
index ac273835aee..b178284c686 100644
--- a/idea/testData/refactoring/rename/renameKotlinVarProperty/after/RenameKotlinVarProperty.kt
+++ b/idea/testData/refactoring/rename/renameKotlinVarProperty/after/RenameKotlinVarProperty.kt
@@ -1,6 +1,6 @@
 package testing.rename
 
-trait AP {
+interface AP {
     var second: Int // <--- Rename base here, rename as Java getter and setter here
 }
 
diff --git a/idea/testData/refactoring/rename/renameKotlinVarProperty/before/RenameKotlinVarProperty.kt b/idea/testData/refactoring/rename/renameKotlinVarProperty/before/RenameKotlinVarProperty.kt
index 94a344dda52..012360e4e89 100644
--- a/idea/testData/refactoring/rename/renameKotlinVarProperty/before/RenameKotlinVarProperty.kt
+++ b/idea/testData/refactoring/rename/renameKotlinVarProperty/before/RenameKotlinVarProperty.kt
@@ -1,6 +1,6 @@
 package testing.rename
 
-trait AP {
+interface AP {
     var first: Int // <--- Rename base here, rename as Java getter and setter here
 }
 
diff --git a/idea/testData/resolve/referenceInJava/dependencies.kt b/idea/testData/resolve/referenceInJava/dependencies.kt
index 035fb64b0fc..19ec2ffcd8f 100644
--- a/idea/testData/resolve/referenceInJava/dependencies.kt
+++ b/idea/testData/resolve/referenceInJava/dependencies.kt
@@ -25,7 +25,7 @@ public object KotlinObject {
     fun f() = 1
 }
 
-public trait StaticFieldInClassObjectInTrait {
+public interface StaticFieldInClassObjectInTrait {
     companion object {
         public val XX: String = "xx"
     }
@@ -37,13 +37,13 @@ object PlatformStaticFun {
     }
 }
 
-trait TraitNoImpl {
+interface TraitNoImpl {
     fun foo()
 }
 
 public class TraitWithDelegatedNoImpl(f: TraitNoImpl): TraitNoImpl by f
 
-trait TraitWithImpl {
+interface TraitWithImpl {
     fun foo() = 1
 }
 
diff --git a/idea/testData/resolve/referenceInLib/inLibrarySource/test.kt b/idea/testData/resolve/referenceInLib/inLibrarySource/test.kt
index 4d84691c956..07ae657e92e 100644
--- a/idea/testData/resolve/referenceInLib/inLibrarySource/test.kt
+++ b/idea/testData/resolve/referenceInLib/inLibrarySource/test.kt
@@ -1,3 +1,3 @@
 package inlibrary.test
 
-trait Test
\ No newline at end of file
+interface Test
\ No newline at end of file
diff --git a/idea/testData/resolve/references/DefaultObjectAsReceiverForExtensionFunctionOnSuperType.kt b/idea/testData/resolve/references/DefaultObjectAsReceiverForExtensionFunctionOnSuperType.kt
index 4e15221c20b..aefbac44d3c 100644
--- a/idea/testData/resolve/references/DefaultObjectAsReceiverForExtensionFunctionOnSuperType.kt
+++ b/idea/testData/resolve/references/DefaultObjectAsReceiverForExtensionFunctionOnSuperType.kt
@@ -1,6 +1,6 @@
 package t
 
-trait Trait
+interface Trait
 
 open class A {
     companion object Companion : Trait {
diff --git a/idea/testData/resolve/references/DefaultObjectAsReceiverForMemberPropertyInSuperType.kt b/idea/testData/resolve/references/DefaultObjectAsReceiverForMemberPropertyInSuperType.kt
index a79f2052162..060eb3a9d31 100644
--- a/idea/testData/resolve/references/DefaultObjectAsReceiverForMemberPropertyInSuperType.kt
+++ b/idea/testData/resolve/references/DefaultObjectAsReceiverForMemberPropertyInSuperType.kt
@@ -1,6 +1,6 @@
 package t
 
-trait Trait {
+interface Trait {
     val some : Int get() = 1
 }
 
diff --git a/idea/testData/resolve/references/SeveralOverrides.kt b/idea/testData/resolve/references/SeveralOverrides.kt
index b3e9c9d15e5..5f05393ad8f 100644
--- a/idea/testData/resolve/references/SeveralOverrides.kt
+++ b/idea/testData/resolve/references/SeveralOverrides.kt
@@ -1,12 +1,12 @@
-trait A {
+interface A {
     fun foo()
 }
 
-trait B {
+interface B {
     fun foo()
 }
 
-trait C : A, B {
+interface C : A, B {
 
 }
 
diff --git a/idea/testData/resolve/references/delegatedPropertyAccessors/inSource/getMultipleDeclarations.kt b/idea/testData/resolve/references/delegatedPropertyAccessors/inSource/getMultipleDeclarations.kt
index 7987fc26172..11a6cbff382 100644
--- a/idea/testData/resolve/references/delegatedPropertyAccessors/inSource/getMultipleDeclarations.kt
+++ b/idea/testData/resolve/references/delegatedPropertyAccessors/inSource/getMultipleDeclarations.kt
@@ -1,14 +1,14 @@
 var x : Int <caret>by Baz()
 
-trait Foo {
+interface Foo {
   fun get(p1: Any?, p2: Any?): Int = 1
 }
 
-trait Bar {
+interface Bar {
   fun get(p1: Any?, p2: Any?): Int
 }
 
-trait Zoo {
+interface Zoo {
   fun set(p1: Any?, p2: Any?, p3: Any?)
 }
 
diff --git a/idea/testData/resolve/references/delegatedPropertyAccessors/inSource/getOneFakeOverride.kt b/idea/testData/resolve/references/delegatedPropertyAccessors/inSource/getOneFakeOverride.kt
index 8f8bf49f3bf..7e2391d83ea 100644
--- a/idea/testData/resolve/references/delegatedPropertyAccessors/inSource/getOneFakeOverride.kt
+++ b/idea/testData/resolve/references/delegatedPropertyAccessors/inSource/getOneFakeOverride.kt
@@ -1,6 +1,6 @@
 var x : Int <caret>by Baz()
 
-trait Foo {
+interface Foo {
   fun get(p1: Any?, p2: Any?): Int = 1
 }
 
diff --git a/idea/testData/resolve/references/forLoopIn/inSource/allExtensions.kt b/idea/testData/resolve/references/forLoopIn/inSource/allExtensions.kt
index cc9973302c4..929cd19723e 100644
--- a/idea/testData/resolve/references/forLoopIn/inSource/allExtensions.kt
+++ b/idea/testData/resolve/references/forLoopIn/inSource/allExtensions.kt
@@ -2,10 +2,10 @@ fun test(f: Foo) {
     for(i <caret>in f) {}
 }
 
-trait Foo
+interface Foo
 fun Foo.iterator(): Iterator
 
-trait Iterator
+interface Iterator
 
 fun Iterator.next(): Any
 fun Iterator.hasNext(): Boolean
diff --git a/idea/testData/resolve/references/forLoopIn/inSource/allMembers.kt b/idea/testData/resolve/references/forLoopIn/inSource/allMembers.kt
index d3baced2c90..2e4d5154b13 100644
--- a/idea/testData/resolve/references/forLoopIn/inSource/allMembers.kt
+++ b/idea/testData/resolve/references/forLoopIn/inSource/allMembers.kt
@@ -2,11 +2,11 @@ fun test(f: Foo) {
     for(i <caret>in f) {}
 }
 
-trait Foo {
+interface Foo {
   fun iterator(): Iterator
 }
 
-trait Iterator {
+interface Iterator {
   fun next(): Any
   fun hasNext(): Boolean
 }
diff --git a/idea/testData/resolve/references/forLoopIn/inSource/nextMissing.kt b/idea/testData/resolve/references/forLoopIn/inSource/nextMissing.kt
index 84c10aa24f5..f8ae644f675 100644
--- a/idea/testData/resolve/references/forLoopIn/inSource/nextMissing.kt
+++ b/idea/testData/resolve/references/forLoopIn/inSource/nextMissing.kt
@@ -2,11 +2,11 @@ fun test(f: Foo) {
     for(i <caret>in f) {}
 }
 
-trait Foo {
+interface Foo {
   fun iterator(): Iterator
 }
 
-trait Iterator {
+interface Iterator {
   fun hasNext(): Boolean
 }
 
diff --git a/idea/testData/safeDelete/deleteClass/kotlinClass/trait1.kt b/idea/testData/safeDelete/deleteClass/kotlinClass/trait1.kt
index db5643b508b..b04f22fa357 100644
--- a/idea/testData/safeDelete/deleteClass/kotlinClass/trait1.kt
+++ b/idea/testData/safeDelete/deleteClass/kotlinClass/trait1.kt
@@ -2,7 +2,7 @@ package test
 
 import test.A
 
-trait <caret>A {
+interface <caret>A {
 }
 
 class B {
diff --git a/idea/testData/safeDelete/deleteClass/kotlinClass/trait2.kt b/idea/testData/safeDelete/deleteClass/kotlinClass/trait2.kt
index 61c2c37148b..ff10996b830 100644
--- a/idea/testData/safeDelete/deleteClass/kotlinClass/trait2.kt
+++ b/idea/testData/safeDelete/deleteClass/kotlinClass/trait2.kt
@@ -2,7 +2,7 @@ package test
 
 import test.A
 
-trait <caret>A {
+interface <caret>A {
 
 }
 
diff --git a/idea/testData/safeDelete/deleteFunction/javaFunctionWithKotlin/mixedHierarchy1.kt b/idea/testData/safeDelete/deleteFunction/javaFunctionWithKotlin/mixedHierarchy1.kt
index 4bde1062335..03b93b25d3b 100644
--- a/idea/testData/safeDelete/deleteFunction/javaFunctionWithKotlin/mixedHierarchy1.kt
+++ b/idea/testData/safeDelete/deleteFunction/javaFunctionWithKotlin/mixedHierarchy1.kt
@@ -1,4 +1,4 @@
-trait B: A {
+interface B: A {
     public override fun foo() {
         throw UnsupportedOperationException()
     }
diff --git a/idea/testData/safeDelete/deleteFunction/javaFunctionWithKotlin/mixedHierarchy1.kt.after b/idea/testData/safeDelete/deleteFunction/javaFunctionWithKotlin/mixedHierarchy1.kt.after
index d1fffa7e4b8..ce98fd2cc43 100644
--- a/idea/testData/safeDelete/deleteFunction/javaFunctionWithKotlin/mixedHierarchy1.kt.after
+++ b/idea/testData/safeDelete/deleteFunction/javaFunctionWithKotlin/mixedHierarchy1.kt.after
@@ -1,4 +1,4 @@
-trait B: A {
+interface B: A {
 }
 
 class D: C() {
diff --git a/idea/testData/safeDelete/deleteFunction/javaFunctionWithKotlin/mixedHierarchy2.kt b/idea/testData/safeDelete/deleteFunction/javaFunctionWithKotlin/mixedHierarchy2.kt
index 4bde1062335..03b93b25d3b 100644
--- a/idea/testData/safeDelete/deleteFunction/javaFunctionWithKotlin/mixedHierarchy2.kt
+++ b/idea/testData/safeDelete/deleteFunction/javaFunctionWithKotlin/mixedHierarchy2.kt
@@ -1,4 +1,4 @@
-trait B: A {
+interface B: A {
     public override fun foo() {
         throw UnsupportedOperationException()
     }
diff --git a/idea/testData/safeDelete/deleteFunction/javaFunctionWithKotlin/mixedHierarchy2.kt.after b/idea/testData/safeDelete/deleteFunction/javaFunctionWithKotlin/mixedHierarchy2.kt.after
index d208f64b7a7..dedb9588a28 100644
--- a/idea/testData/safeDelete/deleteFunction/javaFunctionWithKotlin/mixedHierarchy2.kt.after
+++ b/idea/testData/safeDelete/deleteFunction/javaFunctionWithKotlin/mixedHierarchy2.kt.after
@@ -1,4 +1,4 @@
-trait B: A {
+interface B: A {
     public override fun foo() {
         throw UnsupportedOperationException()
     }
diff --git a/idea/testData/safeDelete/deleteFunction/kotlinFunction/implement1.kt b/idea/testData/safeDelete/deleteFunction/kotlinFunction/implement1.kt
index d682b537116..605f97ecbd8 100644
--- a/idea/testData/safeDelete/deleteFunction/kotlinFunction/implement1.kt
+++ b/idea/testData/safeDelete/deleteFunction/kotlinFunction/implement1.kt
@@ -1,4 +1,4 @@
-trait A {
+interface A {
     fun foo()
 }
 
diff --git a/idea/testData/safeDelete/deleteFunction/kotlinFunction/implement2.kt b/idea/testData/safeDelete/deleteFunction/kotlinFunction/implement2.kt
index d45ab2c6785..486655361f2 100644
--- a/idea/testData/safeDelete/deleteFunction/kotlinFunction/implement2.kt
+++ b/idea/testData/safeDelete/deleteFunction/kotlinFunction/implement2.kt
@@ -1,8 +1,8 @@
-trait A {
+interface A {
     fun foo()
 }
 
-trait Z {
+interface Z {
     fun foo()
 }
 
diff --git a/idea/testData/safeDelete/deleteFunction/kotlinFunction/overrideAndImplement1.kt b/idea/testData/safeDelete/deleteFunction/kotlinFunction/overrideAndImplement1.kt
index b11689d9a37..651df5222d7 100644
--- a/idea/testData/safeDelete/deleteFunction/kotlinFunction/overrideAndImplement1.kt
+++ b/idea/testData/safeDelete/deleteFunction/kotlinFunction/overrideAndImplement1.kt
@@ -4,7 +4,7 @@ open class A {
     }
 }
 
-trait Z {
+interface Z {
     fun foo()
 }
 
diff --git a/idea/testData/safeDelete/deleteFunction/kotlinFunction/overrideAndImplement2.kt b/idea/testData/safeDelete/deleteFunction/kotlinFunction/overrideAndImplement2.kt
index 053782794d8..feb0868d9e3 100644
--- a/idea/testData/safeDelete/deleteFunction/kotlinFunction/overrideAndImplement2.kt
+++ b/idea/testData/safeDelete/deleteFunction/kotlinFunction/overrideAndImplement2.kt
@@ -4,7 +4,7 @@ open class A {
     }
 }
 
-trait Z {
+interface Z {
     fun foo()
 }
 
diff --git a/idea/testData/safeDelete/deleteFunction/kotlinFunction/overrideAndImplement2.kt.after b/idea/testData/safeDelete/deleteFunction/kotlinFunction/overrideAndImplement2.kt.after
index 92575432fe6..2dbb7d7acee 100644
--- a/idea/testData/safeDelete/deleteFunction/kotlinFunction/overrideAndImplement2.kt.after
+++ b/idea/testData/safeDelete/deleteFunction/kotlinFunction/overrideAndImplement2.kt.after
@@ -1,7 +1,7 @@
 open class A {
 }
 
-trait Z {
+interface Z {
     fun foo()
 }
 
diff --git a/idea/testData/safeDelete/deleteFunction/kotlinFunction/overrideAndImplement3.kt b/idea/testData/safeDelete/deleteFunction/kotlinFunction/overrideAndImplement3.kt
index dc21d3ae47d..65be0b58ad5 100644
--- a/idea/testData/safeDelete/deleteFunction/kotlinFunction/overrideAndImplement3.kt
+++ b/idea/testData/safeDelete/deleteFunction/kotlinFunction/overrideAndImplement3.kt
@@ -4,7 +4,7 @@ open class A {
     }
 }
 
-trait Z {
+interface Z {
     fun <caret>foo()
 }
 
diff --git a/idea/testData/safeDelete/deleteFunction/kotlinFunction/overrideAndImplement3.kt.after b/idea/testData/safeDelete/deleteFunction/kotlinFunction/overrideAndImplement3.kt.after
index 3e95abc9cc9..bcabeae65cf 100644
--- a/idea/testData/safeDelete/deleteFunction/kotlinFunction/overrideAndImplement3.kt.after
+++ b/idea/testData/safeDelete/deleteFunction/kotlinFunction/overrideAndImplement3.kt.after
@@ -4,7 +4,7 @@ open class A {
     }
 }
 
-trait Z {
+interface Z {
 }
 
 class B: A(), Z {
diff --git a/idea/testData/safeDelete/deleteFunction/kotlinFunctionWithJava/implement2.kt b/idea/testData/safeDelete/deleteFunction/kotlinFunctionWithJava/implement2.kt
index f3a5a12bc65..205e3d2a76f 100644
--- a/idea/testData/safeDelete/deleteFunction/kotlinFunctionWithJava/implement2.kt
+++ b/idea/testData/safeDelete/deleteFunction/kotlinFunctionWithJava/implement2.kt
@@ -1,3 +1,3 @@
-trait A {
+interface A {
     fun <caret>foo()
 }
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteFunction/kotlinFunctionWithJava/implement2.kt.after b/idea/testData/safeDelete/deleteFunction/kotlinFunctionWithJava/implement2.kt.after
index 670cabdb241..e8750af5264 100644
--- a/idea/testData/safeDelete/deleteFunction/kotlinFunctionWithJava/implement2.kt.after
+++ b/idea/testData/safeDelete/deleteFunction/kotlinFunctionWithJava/implement2.kt.after
@@ -1,2 +1,2 @@
-trait A {
+interface A {
 }
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteFunction/kotlinFunctionWithJava/implement4.kt b/idea/testData/safeDelete/deleteFunction/kotlinFunctionWithJava/implement4.kt
index 3470b144414..7acecaaf9dc 100644
--- a/idea/testData/safeDelete/deleteFunction/kotlinFunctionWithJava/implement4.kt
+++ b/idea/testData/safeDelete/deleteFunction/kotlinFunctionWithJava/implement4.kt
@@ -1,7 +1,7 @@
-trait A {
+interface A {
     fun <caret>foo()
 }
 
-trait Z {
+interface Z {
     fun foo()
 }
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteFunction/kotlinFunctionWithJava/implement4.kt.after b/idea/testData/safeDelete/deleteFunction/kotlinFunctionWithJava/implement4.kt.after
index 4b0d260090e..dbd234d1d15 100644
--- a/idea/testData/safeDelete/deleteFunction/kotlinFunctionWithJava/implement4.kt.after
+++ b/idea/testData/safeDelete/deleteFunction/kotlinFunctionWithJava/implement4.kt.after
@@ -1,6 +1,6 @@
-trait A {
+interface A {
 }
 
-trait Z {
+interface Z {
     fun foo()
 }
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteFunction/kotlinFunctionWithJava/overrideAndImplement2.kt b/idea/testData/safeDelete/deleteFunction/kotlinFunctionWithJava/overrideAndImplement2.kt
index 46b50ab2ac9..ce63823558f 100644
--- a/idea/testData/safeDelete/deleteFunction/kotlinFunctionWithJava/overrideAndImplement2.kt
+++ b/idea/testData/safeDelete/deleteFunction/kotlinFunctionWithJava/overrideAndImplement2.kt
@@ -4,6 +4,6 @@ class A {
     }
 }
 
-trait Z {
+interface Z {
     fun foo()
 }
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteFunction/kotlinFunctionWithJava/overrideAndImplement2.kt.after b/idea/testData/safeDelete/deleteFunction/kotlinFunctionWithJava/overrideAndImplement2.kt.after
index ce7ab3cebd7..e4d532e21be 100644
--- a/idea/testData/safeDelete/deleteFunction/kotlinFunctionWithJava/overrideAndImplement2.kt.after
+++ b/idea/testData/safeDelete/deleteFunction/kotlinFunctionWithJava/overrideAndImplement2.kt.after
@@ -1,6 +1,6 @@
 class A {
 }
 
-trait Z {
+interface Z {
     fun foo()
 }
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteObject/kotlinObject/anonymousObject.kt b/idea/testData/safeDelete/deleteObject/kotlinObject/anonymousObject.kt
index 35918ecd1f5..6e087f952e5 100644
--- a/idea/testData/safeDelete/deleteObject/kotlinObject/anonymousObject.kt
+++ b/idea/testData/safeDelete/deleteObject/kotlinObject/anonymousObject.kt
@@ -1,4 +1,4 @@
-trait A
+interface A
 
 fun foo(): A {
     return <caret>object: A {
diff --git a/idea/testData/safeDelete/deleteObject/kotlinObject/anonymousObject.kt.after b/idea/testData/safeDelete/deleteObject/kotlinObject/anonymousObject.kt.after
index 9005f2d3de1..031371b4203 100644
--- a/idea/testData/safeDelete/deleteObject/kotlinObject/anonymousObject.kt.after
+++ b/idea/testData/safeDelete/deleteObject/kotlinObject/anonymousObject.kt.after
@@ -1,4 +1,4 @@
-trait A
+interface A
 
 fun foo(): A {
     return object: A {
diff --git a/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava1.kt b/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava1.kt
index 9e9f79c0f44..108cfd5636f 100644
--- a/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava1.kt
+++ b/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava1.kt
@@ -1,4 +1,4 @@
-trait B {
+interface B {
     public val foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava1.kt.after b/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava1.kt.after
index 9e9f79c0f44..108cfd5636f 100644
--- a/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava1.kt.after
+++ b/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava1.kt.after
@@ -1,4 +1,4 @@
-trait B {
+interface B {
     public val foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava2.kt b/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava2.kt
index 9e9f79c0f44..108cfd5636f 100644
--- a/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava2.kt
+++ b/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava2.kt
@@ -1,4 +1,4 @@
-trait B {
+interface B {
     public val foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava3.kt b/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava3.kt
index c11f4b99a0d..772e0982c62 100644
--- a/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava3.kt
+++ b/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava3.kt
@@ -1,4 +1,4 @@
-trait B {
+interface B {
     public var foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava3.kt.after b/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava3.kt.after
index c11f4b99a0d..772e0982c62 100644
--- a/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava3.kt.after
+++ b/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava3.kt.after
@@ -1,4 +1,4 @@
-trait B {
+interface B {
     public var foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava4.kt b/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava4.kt
index c11f4b99a0d..772e0982c62 100644
--- a/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava4.kt
+++ b/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava4.kt
@@ -1,4 +1,4 @@
-trait B {
+interface B {
     public var foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava5.kt b/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava5.kt
index c11f4b99a0d..772e0982c62 100644
--- a/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava5.kt
+++ b/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava5.kt
@@ -1,4 +1,4 @@
-trait B {
+interface B {
     public var foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava5.kt.after b/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava5.kt.after
index c11f4b99a0d..772e0982c62 100644
--- a/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava5.kt.after
+++ b/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava5.kt.after
@@ -1,4 +1,4 @@
-trait B {
+interface B {
     public var foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava6.kt b/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava6.kt
index c11f4b99a0d..772e0982c62 100644
--- a/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava6.kt
+++ b/idea/testData/safeDelete/deleteProperty/javaPropertyWithKotlin/middleJava6.kt
@@ -1,4 +1,4 @@
-trait B {
+interface B {
     public var foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement1.kt b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement1.kt
index 4eadc88fc83..d9870ed97ee 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement1.kt
+++ b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement1.kt
@@ -1,4 +1,4 @@
-trait A {
+interface A {
     val foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement2.kt b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement2.kt
index 397629c1b41..4eb93e22018 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement2.kt
+++ b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement2.kt
@@ -1,8 +1,8 @@
-trait A {
+interface A {
     val foo: String
 }
 
-trait Z {
+interface Z {
     val foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement3.kt b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement3.kt
index cc1513a24ac..4f31bfcff97 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement3.kt
+++ b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement3.kt
@@ -1,4 +1,4 @@
-trait A {
+interface A {
     var foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement4.kt b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement4.kt
index 44eba662d4b..827450c1d9d 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement4.kt
+++ b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement4.kt
@@ -1,8 +1,8 @@
-trait A {
+interface A {
     var foo: String
 }
 
-trait Z {
+interface Z {
     var foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement5.kt b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement5.kt
index 073ea92153b..d26c30a3285 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement5.kt
+++ b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement5.kt
@@ -1,4 +1,4 @@
-trait A {
+interface A {
     val <caret>foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement5.kt.after b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement5.kt.after
index 0871f59a81d..9c29de08c68 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement5.kt.after
+++ b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement5.kt.after
@@ -1,4 +1,4 @@
-trait A {
+interface A {
 }
 
 class B: A {
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement6.kt b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement6.kt
index f6e0d3090dc..b475bf44518 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement6.kt
+++ b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement6.kt
@@ -1,4 +1,4 @@
-trait A {
+interface A {
     var <caret>foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement6.kt.after b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement6.kt.after
index 0871f59a81d..9c29de08c68 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement6.kt.after
+++ b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement6.kt.after
@@ -1,4 +1,4 @@
-trait A {
+interface A {
 }
 
 class B: A {
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement7.kt b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement7.kt
index 5741c8a06a1..c842856da56 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement7.kt
+++ b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement7.kt
@@ -1,8 +1,8 @@
-trait A {
+interface A {
     val <caret>foo: String
 }
 
-trait Z {
+interface Z {
     val foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement7.kt.after b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement7.kt.after
index f64cb49eb15..bfbd6cdc134 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement7.kt.after
+++ b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement7.kt.after
@@ -1,7 +1,7 @@
-trait A {
+interface A {
 }
 
-trait Z {
+interface Z {
     val foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement8.kt b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement8.kt
index 2a4da6a8b3e..6352a397e17 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement8.kt
+++ b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement8.kt
@@ -1,8 +1,8 @@
-trait A {
+interface A {
     var <caret>foo: String
 }
 
-trait Z {
+interface Z {
     var foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement8.kt.after b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement8.kt.after
index 809e3d99802..7b0cd3bb11d 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement8.kt.after
+++ b/idea/testData/safeDelete/deleteProperty/kotlinProperty/implement8.kt.after
@@ -1,7 +1,7 @@
-trait A {
+interface A {
 }
 
-trait Z {
+interface Z {
     var foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement1.kt b/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement1.kt
index b5375ac18c3..495ccafa78c 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement1.kt
+++ b/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement1.kt
@@ -5,7 +5,7 @@ open class A {
         }
 }
 
-trait Z {
+interface Z {
     val foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement2.kt b/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement2.kt
index 6d50398b5e5..db7e41ed8d5 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement2.kt
+++ b/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement2.kt
@@ -5,7 +5,7 @@ open class A {
         }
 }
 
-trait Z {
+interface Z {
     val foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement2.kt.after b/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement2.kt.after
index 318931f9611..75ee862b11d 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement2.kt.after
+++ b/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement2.kt.after
@@ -1,7 +1,7 @@
 open class A {
 }
 
-trait Z {
+interface Z {
     val foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement3.kt b/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement3.kt
index db2514aed28..62d85188470 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement3.kt
+++ b/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement3.kt
@@ -8,7 +8,7 @@ open class A {
         }
 }
 
-trait Z {
+interface Z {
     var foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement4.kt b/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement4.kt
index dfe81b89bdf..d1073bbd7da 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement4.kt
+++ b/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement4.kt
@@ -8,7 +8,7 @@ open class A {
         }
 }
 
-trait Z {
+interface Z {
     var foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement4.kt.after b/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement4.kt.after
index d1b327a1ecd..c732f55c5b4 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement4.kt.after
+++ b/idea/testData/safeDelete/deleteProperty/kotlinProperty/overrideAndImplement4.kt.after
@@ -1,7 +1,7 @@
 open class A {
 }
 
-trait Z {
+interface Z {
     var foo: String
 }
 
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement1.kt b/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement1.kt
index 26e7a8e3b69..b28bde4f7c6 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement1.kt
+++ b/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement1.kt
@@ -1,7 +1,7 @@
-trait A {
+interface A {
     val <caret>foo: String
 }
 
-trait Z {
+interface Z {
     val foo: String
 }
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement1.kt.after b/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement1.kt.after
index 94649ec3262..c30f6222e7e 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement1.kt.after
+++ b/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement1.kt.after
@@ -1,6 +1,6 @@
-trait A {
+interface A {
 }
 
-trait Z {
+interface Z {
     val foo: String
 }
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement2.kt b/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement2.kt
index cde120d0433..46f4d2eb624 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement2.kt
+++ b/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement2.kt
@@ -1,3 +1,3 @@
-trait A {
+interface A {
     val <caret>foo: String
 }
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement2.kt.after b/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement2.kt.after
index 670cabdb241..e8750af5264 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement2.kt.after
+++ b/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement2.kt.after
@@ -1,2 +1,2 @@
-trait A {
+interface A {
 }
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement3.kt b/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement3.kt
index 5600171ddb9..35eaa85fb72 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement3.kt
+++ b/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement3.kt
@@ -1,7 +1,7 @@
-trait A {
+interface A {
     var <caret>foo: String
 }
 
-trait Z {
+interface Z {
     var foo: String
 }
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement3.kt.after b/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement3.kt.after
index 09c2215819e..4d8b4501058 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement3.kt.after
+++ b/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement3.kt.after
@@ -1,6 +1,6 @@
-trait A {
+interface A {
 }
 
-trait Z {
+interface Z {
     var foo: String
 }
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement4.kt b/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement4.kt
index d3dc5269244..877e0622072 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement4.kt
+++ b/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement4.kt
@@ -1,3 +1,3 @@
-trait A {
+interface A {
     var <caret>foo: String
 }
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement4.kt.after b/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement4.kt.after
index 670cabdb241..e8750af5264 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement4.kt.after
+++ b/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/implement4.kt.after
@@ -1,2 +1,2 @@
-trait A {
+interface A {
 }
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/overrideAndImplement1.kt b/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/overrideAndImplement1.kt
index af324af6f89..455da005cea 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/overrideAndImplement1.kt
+++ b/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/overrideAndImplement1.kt
@@ -2,6 +2,6 @@ open class A {
     public open val <caret>foo: String = ""
 }
 
-trait Z {
+interface Z {
     public val foo: String
 }
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/overrideAndImplement1.kt.after b/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/overrideAndImplement1.kt.after
index b113d6fca1c..8ba757faea2 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/overrideAndImplement1.kt.after
+++ b/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/overrideAndImplement1.kt.after
@@ -1,6 +1,6 @@
 open class A {
 }
 
-trait Z {
+interface Z {
     public val foo: String
 }
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/overrideAndImplement2.kt b/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/overrideAndImplement2.kt
index b7c42f595d3..52f3d6ce80e 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/overrideAndImplement2.kt
+++ b/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/overrideAndImplement2.kt
@@ -2,6 +2,6 @@ open class A {
     public open var <caret>foo: String = ""
 }
 
-trait Z {
+interface Z {
     public var foo: String
 }
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/overrideAndImplement2.kt.after b/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/overrideAndImplement2.kt.after
index 8a49833453f..7140a72bc7b 100644
--- a/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/overrideAndImplement2.kt.after
+++ b/idea/testData/safeDelete/deleteProperty/kotlinPropertyWithJava/overrideAndImplement2.kt.after
@@ -1,6 +1,6 @@
 open class A {
 }
 
-trait Z {
+interface Z {
     public var foo: String
 }
\ No newline at end of file
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages1.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages1.kt
index 5e88adeccfb..1862adada1e 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages1.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages1.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(<caret>a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages1.kt.after b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages1.kt.after
index c64de4d25bf..308c35fe8ba 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages1.kt.after
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages1.kt.after
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages2.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages2.kt
index 8a6ea9cb59f..78543f32985 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages2.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages2.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages2.kt.after b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages2.kt.after
index c64de4d25bf..308c35fe8ba 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages2.kt.after
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages2.kt.after
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages3.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages3.kt
index f746ce99bb7..4c2deefb999 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages3.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages3.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages3.kt.after b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages3.kt.after
index c64de4d25bf..308c35fe8ba 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages3.kt.after
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages3.kt.after
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages4.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages4.kt
index 5916d06f5a2..41cedb5fdbc 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages4.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages4.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages4.kt.after b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages4.kt.after
index c64de4d25bf..308c35fe8ba 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages4.kt.after
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages4.kt.after
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages5.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages5.kt
index ea5179d3b18..0a6931092dc 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages5.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages5.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages5.kt.after b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages5.kt.after
index c64de4d25bf..308c35fe8ba 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages5.kt.after
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithSafeUsages5.kt.after
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages1.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages1.kt
index 62cb424a473..e89a6bc2a60 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages1.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages1.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(<caret>a: Int, b: Int) {
         println(a)
     }
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages2.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages2.kt
index cfa0d433f9c..fd88855388c 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages2.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages2.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages3.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages3.kt
index 49b8f5316d4..2ce054d312b 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages3.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages3.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages4.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages4.kt
index c044d5e4be6..35bad567d17 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages4.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages4.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages5.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages5.kt
index d74c754a634..7494de3f9a7 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages5.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages5.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages6.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages6.kt
index c39d67c27b5..8b5437a13fe 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages6.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages6.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(a: Int, b: Int) {
         println(a)
     }
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages7.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages7.kt
index eb103648295..0621fe724d6 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages7.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages7.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages8.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages8.kt
index 460454a40b7..f130804bb3f 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages8.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameter/hierarchyWithUnsafeUsages8.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages1.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages1.kt
index 9cbcb20bcca..3183ec574b5 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages1.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages1.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(<caret>a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages1.kt.after b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages1.kt.after
index e93267cb7bf..51cb20a6fb1 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages1.kt.after
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages1.kt.after
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages2.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages2.kt
index 22d113a72d4..e850035c01d 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages2.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages2.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages2.kt.after b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages2.kt.after
index e93267cb7bf..51cb20a6fb1 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages2.kt.after
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages2.kt.after
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages3.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages3.kt
index 6a87fd84d1d..90e9ac7f8bf 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages3.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages3.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages3.kt.after b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages3.kt.after
index e93267cb7bf..51cb20a6fb1 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages3.kt.after
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages3.kt.after
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages4.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages4.kt
index 35426fea66d..7185b780555 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages4.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages4.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages4.kt.after b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages4.kt.after
index e93267cb7bf..51cb20a6fb1 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages4.kt.after
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages4.kt.after
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages5.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages5.kt
index 9210500ac90..821f68a781f 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages5.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages5.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages5.kt.after b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages5.kt.after
index e93267cb7bf..51cb20a6fb1 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages5.kt.after
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithSafeUsages5.kt.after
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithUnsafeUsages1.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithUnsafeUsages1.kt
index c6e1ea2a8e5..dcdeea1125d 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithUnsafeUsages1.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithUnsafeUsages1.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(<caret>a: Int, b: Int) {
         println(a)
     }
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithUnsafeUsages2.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithUnsafeUsages2.kt
index d667451af44..143debfb3d6 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithUnsafeUsages2.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithUnsafeUsages2.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithUnsafeUsages3.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithUnsafeUsages3.kt
index 9d9cb9186ce..4f0f5324bd9 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithUnsafeUsages3.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithUnsafeUsages3.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithUnsafeUsages4.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithUnsafeUsages4.kt
index 7fd34f1033c..6f5fcdc54ef 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithUnsafeUsages4.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithUnsafeUsages4.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithUnsafeUsages5.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithUnsafeUsages5.kt
index 031e52a7eb6..28e0ce53068 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithUnsafeUsages5.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/hierarchyWithUnsafeUsages5.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchy1.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchy1.kt
index 031e83ea45d..a01ad105bbb 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchy1.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchy1.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(<caret>a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchy1.kt.after b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchy1.kt.after
index dab76e81407..32798d85389 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchy1.kt.after
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchy1.kt.after
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchy2.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchy2.kt
index 2f77474192d..3736ab02836 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchy2.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchy2.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchy2.kt.after b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchy2.kt.after
index dab76e81407..32798d85389 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchy2.kt.after
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchy2.kt.after
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchy3.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchy3.kt
index 7eb4f3b1495..9c160c2ba37 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchy3.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchy3.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchy3.kt.after b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchy3.kt.after
index dab76e81407..32798d85389 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchy3.kt.after
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchy3.kt.after
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchyWithUnsafeUsages1.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchyWithUnsafeUsages1.kt
index 031e83ea45d..a01ad105bbb 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchyWithUnsafeUsages1.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchyWithUnsafeUsages1.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(<caret>a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchyWithUnsafeUsages2.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchyWithUnsafeUsages2.kt
index 2c98a5a1966..392d0a4ed5e 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchyWithUnsafeUsages2.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchyWithUnsafeUsages2.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(a: Int, b: Int)
 }
 
diff --git a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchyWithUnsafeUsages3.kt b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchyWithUnsafeUsages3.kt
index 7eb4f3b1495..9c160c2ba37 100644
--- a/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchyWithUnsafeUsages3.kt
+++ b/idea/testData/safeDelete/deleteValueParameter/kotlinValueParameterWithJava/mixedHierarchyWithUnsafeUsages3.kt
@@ -1,4 +1,4 @@
-trait Z {
+interface Z {
     open fun foo(a: Int, b: Int)
 }
 
diff --git a/idea/testData/shortenRefs/noShortening.kt b/idea/testData/shortenRefs/noShortening.kt
index 89b75813155..e03ae5c033e 100644
--- a/idea/testData/shortenRefs/noShortening.kt
+++ b/idea/testData/shortenRefs/noShortening.kt
@@ -1,4 +1,4 @@
-trait T : Iterable<String>
+interface T : Iterable<String>
 
 abstract class C : T {
     fun foo(c: C) {
diff --git a/idea/testData/shortenRefs/noShortening.kt.after b/idea/testData/shortenRefs/noShortening.kt.after
index bd5285f3b1c..cca7081e55a 100644
--- a/idea/testData/shortenRefs/noShortening.kt.after
+++ b/idea/testData/shortenRefs/noShortening.kt.after
@@ -1,4 +1,4 @@
-trait T : Iterable<String>
+interface T : Iterable<String>
 
 abstract class C : T {
     fun foo(c: C) {
diff --git a/idea/testData/structureView/fileStructure/CheckLocationForKotlin.Data.kt b/idea/testData/structureView/fileStructure/CheckLocationForKotlin.Data.kt
index 8c9b1042241..5863771b3a6 100644
--- a/idea/testData/structureView/fileStructure/CheckLocationForKotlin.Data.kt
+++ b/idea/testData/structureView/fileStructure/CheckLocationForKotlin.Data.kt
@@ -1,4 +1,4 @@
-trait First {
+interface First {
     fun foo123()
     fun foo12_()
     fun foo1_3()
diff --git a/idea/testData/structureView/fileStructure/DoNotShowParentsInLocationJava.Data.kt b/idea/testData/structureView/fileStructure/DoNotShowParentsInLocationJava.Data.kt
index 7f5b5d49cad..48de19719ef 100644
--- a/idea/testData/structureView/fileStructure/DoNotShowParentsInLocationJava.Data.kt
+++ b/idea/testData/structureView/fileStructure/DoNotShowParentsInLocationJava.Data.kt
@@ -1,5 +1,5 @@
-trait First
+interface First
 
-trait Second : First {
+interface Second : First {
     fun foo()
 }
\ No newline at end of file
diff --git a/idea/testData/structureView/fileStructure/DoNotShowParentsInLocationJava.kt b/idea/testData/structureView/fileStructure/DoNotShowParentsInLocationJava.kt
index 75a843444ee..8ad176bf8ea 100644
--- a/idea/testData/structureView/fileStructure/DoNotShowParentsInLocationJava.kt
+++ b/idea/testData/structureView/fileStructure/DoNotShowParentsInLocationJava.kt
@@ -1,3 +1,3 @@
-trait Third: Second
+interface Third: Second
 
 // WITH_INHERITED
\ No newline at end of file
diff --git a/idea/testData/structureView/fileStructure/InheritedDelegationMethods.Data.kt b/idea/testData/structureView/fileStructure/InheritedDelegationMethods.Data.kt
index 375d9192cd1..e4726da3cae 100644
--- a/idea/testData/structureView/fileStructure/InheritedDelegationMethods.Data.kt
+++ b/idea/testData/structureView/fileStructure/InheritedDelegationMethods.Data.kt
@@ -1,4 +1,4 @@
-trait Some {
+interface Some {
     fun first()
     fun second()
 }
diff --git a/idea/testData/structureView/fileStructure/InheritedLocalKotlin.kt b/idea/testData/structureView/fileStructure/InheritedLocalKotlin.kt
index bcc4716af7b..401529a3a7e 100644
--- a/idea/testData/structureView/fileStructure/InheritedLocalKotlin.kt
+++ b/idea/testData/structureView/fileStructure/InheritedLocalKotlin.kt
@@ -1,4 +1,4 @@
-trait TA {
+interface TA {
     fun some()
     val a: Int
 }
diff --git a/idea/testData/structureView/fileStructure/InheritedMembersWithSubstitutedTypes.Data.kt b/idea/testData/structureView/fileStructure/InheritedMembersWithSubstitutedTypes.Data.kt
index 8b6a1428f40..53e4e92b97f 100644
--- a/idea/testData/structureView/fileStructure/InheritedMembersWithSubstitutedTypes.Data.kt
+++ b/idea/testData/structureView/fileStructure/InheritedMembersWithSubstitutedTypes.Data.kt
@@ -1,7 +1,7 @@
-trait First<T> {
+interface First<T> {
     fun foo(a: T)
 }
 
-trait Second<U> : First<Int> {
+interface Second<U> : First<Int> {
     val a: U
 }
\ No newline at end of file
diff --git a/idea/testData/structureView/fileStructure/InheritedMembersWithSubstitutedTypes.kt b/idea/testData/structureView/fileStructure/InheritedMembersWithSubstitutedTypes.kt
index 2162d6de334..4f56362050c 100644
--- a/idea/testData/structureView/fileStructure/InheritedMembersWithSubstitutedTypes.kt
+++ b/idea/testData/structureView/fileStructure/InheritedMembersWithSubstitutedTypes.kt
@@ -1,4 +1,4 @@
-trait Third: Second<String>
+interface Third: Second<String>
 
 // Original type names are shown in members, behaviour is same to Java.
 
diff --git a/idea/testData/structureView/fileStructure/Render.kt b/idea/testData/structureView/fileStructure/Render.kt
index 1a12ee9d3ed..f64ecf25167 100644
--- a/idea/testData/structureView/fileStructure/Render.kt
+++ b/idea/testData/structureView/fileStructure/Render.kt
@@ -42,8 +42,8 @@ enum class Enum1 {
     SECOND
 }
 
-trait Trait
-trait Trait1: Trait
+interface Trait
+interface Trait1: Trait
 
 class TestWithWhere<T> where T: Any?
 fun <T> testWithWhere() where T: String {}
diff --git a/idea/testData/structureView/fileStructure/SeveralClasses.kt b/idea/testData/structureView/fileStructure/SeveralClasses.kt
index 0ec856f6826..97e4808d285 100644
--- a/idea/testData/structureView/fileStructure/SeveralClasses.kt
+++ b/idea/testData/structureView/fileStructure/SeveralClasses.kt
@@ -1,4 +1,4 @@
-trait A
+interface A
 open class B
 class Some: B(), A
 class Other: A
\ No newline at end of file
diff --git a/idea/testData/stubs/AnonymousObject.kt b/idea/testData/stubs/AnonymousObject.kt
index c2984e24a31..a52488326fb 100644
--- a/idea/testData/stubs/AnonymousObject.kt
+++ b/idea/testData/stubs/AnonymousObject.kt
@@ -1,3 +1,3 @@
 class A
-trait T
+interface T
 val obj = object : A(), T
\ No newline at end of file
diff --git a/idea/testData/stubs/LocalClass.kt b/idea/testData/stubs/LocalClass.kt
index 9f03c5411fc..9fada487e67 100644
--- a/idea/testData/stubs/LocalClass.kt
+++ b/idea/testData/stubs/LocalClass.kt
@@ -1,5 +1,5 @@
 class A
-trait T
+interface T
 fun foo() {
     class Test : A(), T
 }
\ No newline at end of file
diff --git a/idea/testData/stubs/LocalClassInLocalFunction.kt b/idea/testData/stubs/LocalClassInLocalFunction.kt
index ccccbd6c6e7..a0f8876c657 100644
--- a/idea/testData/stubs/LocalClassInLocalFunction.kt
+++ b/idea/testData/stubs/LocalClassInLocalFunction.kt
@@ -1,5 +1,5 @@
 class A
-trait T
+interface T
 fun foo() {
     fun bar() {
         class Test : A(), T
diff --git a/idea/testData/stubs/LocalNamedObject.kt b/idea/testData/stubs/LocalNamedObject.kt
index 1c517b16917..ab6d3d0e1dd 100644
--- a/idea/testData/stubs/LocalNamedObject.kt
+++ b/idea/testData/stubs/LocalNamedObject.kt
@@ -1,5 +1,5 @@
 class A
-trait T
+interface T
 fun foo() {
     object O: A(), T
 }
\ No newline at end of file
diff --git a/idea/testData/stubs/NamedObject.kt b/idea/testData/stubs/NamedObject.kt
index 0f328838ce5..9e04ba7960a 100644
--- a/idea/testData/stubs/NamedObject.kt
+++ b/idea/testData/stubs/NamedObject.kt
@@ -1,4 +1,4 @@
 class A
-trait T
+interface T
 object Test: A(), T {
 }
\ No newline at end of file
diff --git a/idea/testData/templates/interface.exp.kt b/idea/testData/templates/interface.exp.kt
index 9363c7e4379..c562b59ce9c 100644
--- a/idea/testData/templates/interface.exp.kt
+++ b/idea/testData/templates/interface.exp.kt
@@ -1,3 +1,3 @@
-trait SomeTrait {
+interface SomeTrait {
     <caret>
 }
\ No newline at end of file
diff --git a/idea/testData/unifier/equivalence/declarations/classesAndObjects/commonSuperclasses.kt b/idea/testData/unifier/equivalence/declarations/classesAndObjects/commonSuperclasses.kt
index 47a20c446bf..f3e3b37f671 100644
--- a/idea/testData/unifier/equivalence/declarations/classesAndObjects/commonSuperclasses.kt
+++ b/idea/testData/unifier/equivalence/declarations/classesAndObjects/commonSuperclasses.kt
@@ -1,6 +1,6 @@
 fun foo() {
     open class Z(p: Int)
-    trait T;
+    interface T;
 
     {
         <selection>class A: Z(1), T</selection>
diff --git a/idea/testData/unifier/equivalence/declarations/classesAndObjects/delegation.kt b/idea/testData/unifier/equivalence/declarations/classesAndObjects/delegation.kt
index ae23234a6b1..1e73816c717 100644
--- a/idea/testData/unifier/equivalence/declarations/classesAndObjects/delegation.kt
+++ b/idea/testData/unifier/equivalence/declarations/classesAndObjects/delegation.kt
@@ -1,6 +1,6 @@
 // DISABLE-ERRORS
 fun foo() {
-    trait T
+    interface T
     open class Z(p: Int): T;
 
     {
diff --git a/idea/testData/unifier/equivalence/declarations/classesAndObjects/matchedSuperclasses.kt b/idea/testData/unifier/equivalence/declarations/classesAndObjects/matchedSuperclasses.kt
index 4bb0b2997cc..8843d86b9d6 100644
--- a/idea/testData/unifier/equivalence/declarations/classesAndObjects/matchedSuperclasses.kt
+++ b/idea/testData/unifier/equivalence/declarations/classesAndObjects/matchedSuperclasses.kt
@@ -1,25 +1,25 @@
 fun foo() {
     <selection>{
         open class Z<T>(p: T)
-        trait T
+        interface T
         class A: Z<Int>(1), T
     }</selection>
 
     {
         open class Z<A>(r: A)
-        trait T
+        interface T
         class B: Z<Int>(1), T
     }
 
     {
         open class T<A>(r: A)
-        trait Z
+        interface Z
         class C: T<Int>(1), Z
     }
 
     {
         open class Z<T>(q: T)
-        trait T
+        interface T
         class D: Z<Int>(2), T
     }
 
@@ -30,13 +30,13 @@ fun foo() {
 
     {
         open class Z<A>(r: A)
-        trait T
+        interface T
         class F: Z<String>("1"), T
     }
 
     {
         open class Z(r: Int)
-        trait T
+        interface T
         class B: Z(1), T
     }
 }
\ No newline at end of file
diff --git a/idea/testData/unifier/equivalence/declarations/classesAndObjects/matchedSuperclasses.kt.match b/idea/testData/unifier/equivalence/declarations/classesAndObjects/matchedSuperclasses.kt.match
index 501c419d4ed..62933251f1b 100644
--- a/idea/testData/unifier/equivalence/declarations/classesAndObjects/matchedSuperclasses.kt.match
+++ b/idea/testData/unifier/equivalence/declarations/classesAndObjects/matchedSuperclasses.kt.match
@@ -1,17 +1,17 @@
 {
         open class Z<T>(p: T)
-        trait T
+        interface T
         class A: Z<Int>(1), T
     }
 
 {
         open class Z<A>(r: A)
-        trait T
+        interface T
         class B: Z<Int>(1), T
     }
 
 {
         open class T<A>(r: A)
-        trait Z
+        interface Z
         class C: T<Int>(1), Z
     }
\ No newline at end of file
diff --git a/idea/testData/unifier/equivalence/declarations/classesAndObjects/members.kt b/idea/testData/unifier/equivalence/declarations/classesAndObjects/members.kt
index 6f031f4193d..5f455a87d79 100644
--- a/idea/testData/unifier/equivalence/declarations/classesAndObjects/members.kt
+++ b/idea/testData/unifier/equivalence/declarations/classesAndObjects/members.kt
@@ -10,7 +10,7 @@ fun foo() {
 
         class X
         inner class Y
-        trait T
+        interface T
         object O
 
         val p = 1
@@ -54,7 +54,7 @@ fun foo() {
 
         fun a(p: kotlin.Int): kotlin.Int = b(p) + 1
 
-        trait T
+        interface T
     }
 
     class C {
@@ -67,7 +67,7 @@ fun foo() {
 
         class X
         inner class Y
-        trait T
+        interface T
         object O
 
         val p = 1
@@ -93,7 +93,7 @@ fun foo() {
 
         class X
         inner class Y
-        trait T
+        interface T
         object O
 
         val q = p + 1
@@ -119,7 +119,7 @@ fun foo() {
 
         class XX
         inner class Y
-        trait T
+        interface T
         object O
 
         val p = 1
diff --git a/idea/testData/unifier/equivalence/declarations/classesAndObjects/members.kt.match b/idea/testData/unifier/equivalence/declarations/classesAndObjects/members.kt.match
index abfa701c98f..ac4ff8bf10a 100644
--- a/idea/testData/unifier/equivalence/declarations/classesAndObjects/members.kt.match
+++ b/idea/testData/unifier/equivalence/declarations/classesAndObjects/members.kt.match
@@ -8,7 +8,7 @@ class A {
 
         class X
         inner class Y
-        trait T
+        interface T
         object O
 
         val p = 1
@@ -52,5 +52,5 @@ class B {
 
         fun a(p: kotlin.Int): kotlin.Int = b(p) + 1
 
-        trait T
+        interface T
     }
\ No newline at end of file
diff --git a/idea/testData/unifier/equivalence/declarations/classesAndObjects/superTypeOrder.kt b/idea/testData/unifier/equivalence/declarations/classesAndObjects/superTypeOrder.kt
index bb7896ef51b..5ba8733e1b7 100644
--- a/idea/testData/unifier/equivalence/declarations/classesAndObjects/superTypeOrder.kt
+++ b/idea/testData/unifier/equivalence/declarations/classesAndObjects/superTypeOrder.kt
@@ -1,7 +1,7 @@
 fun foo() {
     open class Z(p: Int)
-    trait T
-    trait U;
+    interface T
+    interface U;
 
     {
         <selection>class A: Z(1), T, U</selection>
diff --git a/idea/testData/unifier/equivalence/declarations/typeParameters/boundsAndConstraints.kt b/idea/testData/unifier/equivalence/declarations/typeParameters/boundsAndConstraints.kt
index ea9822a363e..738fcc08a50 100644
--- a/idea/testData/unifier/equivalence/declarations/typeParameters/boundsAndConstraints.kt
+++ b/idea/testData/unifier/equivalence/declarations/typeParameters/boundsAndConstraints.kt
@@ -1,5 +1,5 @@
 fun foo() {
-    trait T
+    interface T
 
     <selection>fun bar1<A, B, C>(a: A, b: B, c: C): A where B: A, C: B, C: T = c</selection>
 
diff --git a/idea/testData/unifier/equivalence/expressions/calls/callUnderSmartCast.kt b/idea/testData/unifier/equivalence/expressions/calls/callUnderSmartCast.kt
index 6a823d232c2..fcd6ac13310 100644
--- a/idea/testData/unifier/equivalence/expressions/calls/callUnderSmartCast.kt
+++ b/idea/testData/unifier/equivalence/expressions/calls/callUnderSmartCast.kt
@@ -1,8 +1,8 @@
-trait T {
+interface T {
     fun foo(): Int
 }
 
-trait U: T
+interface U: T
 
 fun test(t: T): Int {
     return if (t is U)
diff --git a/idea/testData/unifier/equivalence/expressions/super/multipleSuperTypes.kt b/idea/testData/unifier/equivalence/expressions/super/multipleSuperTypes.kt
index ae8e66e4b37..72a76088eab 100644
--- a/idea/testData/unifier/equivalence/expressions/super/multipleSuperTypes.kt
+++ b/idea/testData/unifier/equivalence/expressions/super/multipleSuperTypes.kt
@@ -1,4 +1,4 @@
-trait T {
+interface T {
     fun foo() {
 
     }
diff --git a/idea/testData/unifier/equivalence/expressions/this/anonymousObjects.kt b/idea/testData/unifier/equivalence/expressions/this/anonymousObjects.kt
index 65a75abfa72..bf86dd05ab0 100644
--- a/idea/testData/unifier/equivalence/expressions/this/anonymousObjects.kt
+++ b/idea/testData/unifier/equivalence/expressions/this/anonymousObjects.kt
@@ -1,4 +1,4 @@
-trait Foo {
+interface Foo {
     fun foo()
 }