Refactor FunctionHandle::isInterfaceDeclaration

- Give it more clear name mayBeUsedAsSuperImplementation
  because defining if it can be used as super-implementation
  this is what it used for
- The meaning is negated, so it's needed to negate its usages and impls
- Also, reuse it in findSuperImplementationForStubDelegation

compiler/backend-common/src/org/jetbrains/kotlin/backend/common/bridges/bridges.kt

@@ -27,7 +27,7 @@ interface FunctionHandle {
     * class ones (see [findConcreteSuperDeclaration] method in bridges.kt).
     * Note that interface methods with body compiled to jvm 8 target are assumed to be non-abstract in bridges method calculation
     * (more details in [DescriptorBasedFunctionHandle.isBodyOwner] comment).*/
-    val isInterfaceDeclaration: Boolean
+    val mayBeUsedAsSuperImplementation: Boolean
 
     fun getOverridden(): Iterable<FunctionHandle>
 }
@@ -114,7 +114,7 @@ fun <Function : FunctionHandle> findConcreteSuperDeclaration(function: Function)
     }
     result.removeAll(toRemove)
 
-    val concreteRelevantDeclarations = result.filter { !it.isAbstract && !it.isInterfaceDeclaration }
+    val concreteRelevantDeclarations = result.filter { !it.isAbstract && it.mayBeUsedAsSuperImplementation }
     if (concreteRelevantDeclarations.size != 1) {
         error("Concrete fake override $function should have exactly one concrete super-declaration: $concreteRelevantDeclarations")
     }

compiler/backend-common/src/org/jetbrains/kotlin/backend/common/bridges/impl.kt

@@ -72,8 +72,8 @@ class DescriptorBasedFunctionHandle(
     override val isAbstract: Boolean =
         descriptor.modality == Modality.ABSTRACT || !areDeclarationAndDefinitionSame(descriptor)
 
-    override val isInterfaceDeclaration: Boolean
+    override val mayBeUsedAsSuperImplementation: Boolean =
-        get() = DescriptorUtils.isInterface(descriptor.containingDeclaration)
+        !DescriptorUtils.isInterface(descriptor.containingDeclaration)
 
     override fun getOverridden() = overridden
 

compiler/backend/src/org/jetbrains/kotlin/codegen/builtinSpecialBridges.kt

@@ -153,19 +153,19 @@ private fun <Signature> findSuperImplementationForStubDelegation(
     areDeclarationAndDefinitionSame: (CallableMemberDescriptor) -> Boolean,
     signatureByDescriptor: (FunctionDescriptor) -> Signature
 ): FunctionDescriptor? {
-    val implementation = findConcreteSuperDeclaration(DescriptorBasedFunctionHandle(function, areDeclarationAndDefinitionSame)).descriptor
+    val implementation = findConcreteSuperDeclaration(DescriptorBasedFunctionHandle(function, areDeclarationAndDefinitionSame))
 
     // Implementation from interface will be generated by common mechanism
-    if (DescriptorUtils.isInterface(implementation.containingDeclaration)) return null
+    if (!implementation.mayBeUsedAsSuperImplementation) return null
 
     // Implementation in super-class already has proper signature
-    if (signatureByDescriptor(function) == signatureByDescriptor(implementation)) return null
+    if (signatureByDescriptor(function) == signatureByDescriptor(implementation.descriptor)) return null
 
     assert(function.modality == Modality.OPEN) {
         "Should generate stubs only for non-abstract built-ins, but ${function.name} is ${function.modality}"
     }
 
-    return implementation
+    return implementation.descriptor
 }
 
 private fun findAllReachableDeclarations(

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/BridgesConstruction.kt

@@ -171,8 +171,8 @@ data class IrBasedFunctionHandle(val function: IrSimpleFunction) : FunctionHandl
     override val isAbstract: Boolean =
         function.modality == Modality.ABSTRACT
 
-    override val isInterfaceDeclaration =
+    override val mayBeUsedAsSuperImplementation =
-        function.parentAsClass.isInterface
+        !function.parentAsClass.isInterface
 
     override fun getOverridden() =
         function.overriddenSymbols.map { IrBasedFunctionHandle(it.owner) }

compiler/tests/org/jetbrains/kotlin/codegen/BridgeTest.kt

@@ -28,7 +28,7 @@ class BridgeTest : TestCase() {
     private class Fun(val text: String) : FunctionHandle {
         override val isDeclaration: Boolean get() = text[1] == 'D'
         override val isAbstract: Boolean get() = text[0] == '-'
-        override val isInterfaceDeclaration: Boolean get() = false
+        override val mayBeUsedAsSuperImplementation: Boolean get() = true
         val signature: Char get() = text[2]
 
         val overriddenFunctions: MutableList<Fun> = arrayListOf()