Prohibit suspend function type in supertype list

#KT-15391 Fixed

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Errors.java

@@ -237,6 +237,7 @@ public interface Errors {
     DiagnosticFactory2<KtDeclaration, CallableMemberDescriptor, List<CallableMemberDescriptor>> DELEGATED_MEMBER_HIDES_SUPERTYPE_OVERRIDE = DiagnosticFactory2.create(ERROR);
     DiagnosticFactory0<KtTypeReference> SUPERTYPE_NOT_A_CLASS_OR_INTERFACE = DiagnosticFactory0.create(ERROR);
     DiagnosticFactory0<KtTypeReference> SUPERTYPE_IS_EXTENSION_FUNCTION_TYPE = DiagnosticFactory0.create(ERROR);
+    DiagnosticFactory0<KtTypeReference> SUPERTYPE_IS_SUSPEND_FUNCTION_TYPE = DiagnosticFactory0.create(ERROR);
 
     DiagnosticFactory0<PsiElement> NO_GENERICS_IN_SUPERTYPE_SPECIFIER = DiagnosticFactory0.create(ERROR);
 

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java

@@ -544,6 +544,7 @@ public class DefaultErrorMessages {
         MAP.put(MANY_CLASSES_IN_SUPERTYPE_LIST, "Only one class may appear in a supertype list");
         MAP.put(SUPERTYPE_NOT_A_CLASS_OR_INTERFACE, "Only classes and interfaces may serve as supertypes");
         MAP.put(SUPERTYPE_IS_EXTENSION_FUNCTION_TYPE, "Extension function type is not allowed as supertypes");
+        MAP.put(SUPERTYPE_IS_SUSPEND_FUNCTION_TYPE, "Suspend function type is not allowed as supertypes");
         MAP.put(SUPERTYPE_INITIALIZED_IN_INTERFACE, "Interfaces cannot initialize supertypes");
         MAP.put(CLASS_IN_SUPERTYPE_FOR_ENUM, "Enum class cannot inherit from classes");
         MAP.put(CONSTRUCTOR_IN_INTERFACE, "An interface may not have a constructor");

compiler/frontend/src/org/jetbrains/kotlin/resolve/BodyResolver.java

@@ -471,6 +471,9 @@ public class BodyResolver {
                 if (FunctionTypesKt.isExtensionFunctionType(supertype)) {
                     trace.report(SUPERTYPE_IS_EXTENSION_FUNCTION_TYPE.on(typeReference));
                 }
+                else if (FunctionTypesKt.isSuspendFunctionType(supertype)) {
+                    trace.report(SUPERTYPE_IS_SUSPEND_FUNCTION_TYPE.on(typeReference));
+                }
 
                 if (classDescriptor.getKind() != ClassKind.INTERFACE) {
                     if (supertypeOwner.getKind() == ClassKind.ENUM_CLASS) {

compiler/testData/diagnostics/tests/coroutines/suspendFunctionType/modifierApplicability.kt

@@ -16,3 +16,11 @@ typealias Test9 = suspend (() -> Unit) -> Unit
 typealias Test10 = suspend (suspend () -> Unit) -> Unit
 typealias Test11 = suspend () -> (suspend () -> Unit)
 typealias Test12 = suspend (suspend (() -> Unit)) -> Unit
+
+interface Supertype1 : <!SUPERTYPE_IS_SUSPEND_FUNCTION_TYPE!>suspend () -> Unit<!> {
+
+}
+
+interface Supertype2 : <!SUPERTYPE_IS_SUSPEND_FUNCTION_TYPE!>suspend String.() -> Unit<!> {
+
+}

compiler/testData/diagnostics/tests/coroutines/suspendFunctionType/modifierApplicability.txt

@@ -6,6 +6,20 @@ public interface SAM {
     public abstract fun run(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
+
+public interface Supertype1 : suspend () -> kotlin.Unit {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public abstract suspend override /*1*/ /*fake_override*/ fun invoke(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface Supertype2 : suspend kotlin.String.() -> kotlin.Unit {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public abstract suspend override /*1*/ /*fake_override*/ fun invoke(/*0*/ p1: kotlin.String): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
 public typealias Action = () -> kotlin.Unit
 public typealias Test1 = suspend () -> kotlin.Unit
 public typealias Test10 = suspend (suspend () -> kotlin.Unit) -> kotlin.Unit