JVM IR: Generate interface delegations for specialized interface defaults

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/InheritedDefaultMethodsOnClassesLowering.kt

@@ -50,10 +50,10 @@ private class InheritedDefaultMethodsOnClassesLowering(val context: JvmBackendCo
     }
 
     override fun lower(declaration: IrClass) {
-        super.visitClass(declaration)
+        if (!declaration.isJvmInterface)
-        if (declaration.isJvmInterface) return
+            generateInterfaceMethods(declaration)
 
-        generateInterfaceMethods(declaration)
+        super.visitClass(declaration)
     }
 
     private fun generateInterfaceMethods(irClass: IrClass) {
@@ -80,13 +80,14 @@ private class InheritedDefaultMethodsOnClassesLowering(val context: JvmBackendCo
         if (origin != IrDeclarationOrigin.FAKE_OVERRIDE) return null
         parent.let { if (it is IrClass && it.isJvmInterface) return null }
 
+        val implementation = resolveFakeOverride() ?: return null
+
         // Only generate interface delegation for functions immediately inherited from an interface.
         // (Otherwise, delegation will be present in the parent class)
-        if (overriddenSymbols.any { !it.owner.parentAsClass.isInterface && it.owner.modality != Modality.ABSTRACT }) {
+        if (overriddenSymbols.any { !it.owner.parentAsClass.isInterface && it.owner.modality != Modality.ABSTRACT && it.owner.resolveFakeOverride() == implementation }) {
             return null
         }
 
-        val implementation = resolveFakeOverride() ?: return null
         if (!implementation.hasInterfaceParent()
             || Visibilities.isPrivate(implementation.visibility)
             || implementation.isDefinitelyNotDefaultImplsMethod()

compiler/testData/codegen/box/bridges/propertyDiamondFakeOverride.kt

@@ -0,0 +1,16 @@
+// IGNORE_BACKEND_FIR: JVM_IR
+
+interface A {
+    val result: Any get() = "Fail"
+}
+
+interface B : A {
+    override val result: String get() = "OK"
+}
+
+abstract class AImpl : A
+
+class BImpl : AImpl(), B
+
+fun box(): String =
+    (BImpl() as A).result.toString()

compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java

@@ -1537,6 +1537,11 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             runTest("compiler/testData/codegen/box/bridges/propertyDiamond.kt");
         }
 
+        @TestMetadata("propertyDiamondFakeOverride.kt")
+        public void testPropertyDiamondFakeOverride() throws Exception {
+            runTest("compiler/testData/codegen/box/bridges/propertyDiamondFakeOverride.kt");
+        }
+
         @TestMetadata("propertyInConstructor.kt")
         public void testPropertyInConstructor() throws Exception {
             runTest("compiler/testData/codegen/box/bridges/propertyInConstructor.kt");

compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java

@@ -1537,6 +1537,11 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
             runTest("compiler/testData/codegen/box/bridges/propertyDiamond.kt");
         }
 
+        @TestMetadata("propertyDiamondFakeOverride.kt")
+        public void testPropertyDiamondFakeOverride() throws Exception {
+            runTest("compiler/testData/codegen/box/bridges/propertyDiamondFakeOverride.kt");
+        }
+
         @TestMetadata("propertyInConstructor.kt")
         public void testPropertyInConstructor() throws Exception {
             runTest("compiler/testData/codegen/box/bridges/propertyInConstructor.kt");

compiler/tests/org/jetbrains/kotlin/codegen/ir/FirBlackBoxCodegenTestGenerated.java

@@ -1517,6 +1517,11 @@ public class FirBlackBoxCodegenTestGenerated extends AbstractFirBlackBoxCodegenT
             runTest("compiler/testData/codegen/box/bridges/propertyDiamond.kt");
         }
 
+        @TestMetadata("propertyDiamondFakeOverride.kt")
+        public void testPropertyDiamondFakeOverride() throws Exception {
+            runTest("compiler/testData/codegen/box/bridges/propertyDiamondFakeOverride.kt");
+        }
+
         @TestMetadata("propertyInConstructor.kt")
         public void testPropertyInConstructor() throws Exception {
             runTest("compiler/testData/codegen/box/bridges/propertyInConstructor.kt");

compiler/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java

@@ -1517,6 +1517,11 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
             runTest("compiler/testData/codegen/box/bridges/propertyDiamond.kt");
         }
 
+        @TestMetadata("propertyDiamondFakeOverride.kt")
+        public void testPropertyDiamondFakeOverride() throws Exception {
+            runTest("compiler/testData/codegen/box/bridges/propertyDiamondFakeOverride.kt");
+        }
+
         @TestMetadata("propertyInConstructor.kt")
         public void testPropertyInConstructor() throws Exception {
             runTest("compiler/testData/codegen/box/bridges/propertyInConstructor.kt");

js/js.tests/test/org/jetbrains/kotlin/js/test/ir/semantics/IrJsCodegenBoxTestGenerated.java

@@ -1152,6 +1152,11 @@ public class IrJsCodegenBoxTestGenerated extends AbstractIrJsCodegenBoxTest {
             runTest("compiler/testData/codegen/box/bridges/propertyDiamond.kt");
         }
 
+        @TestMetadata("propertyDiamondFakeOverride.kt")
+        public void testPropertyDiamondFakeOverride() throws Exception {
+            runTest("compiler/testData/codegen/box/bridges/propertyDiamondFakeOverride.kt");
+        }
+
         @TestMetadata("propertyInConstructor.kt")
         public void testPropertyInConstructor() throws Exception {
             runTest("compiler/testData/codegen/box/bridges/propertyInConstructor.kt");

js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/JsCodegenBoxTestGenerated.java

@@ -1152,6 +1152,11 @@ public class JsCodegenBoxTestGenerated extends AbstractJsCodegenBoxTest {
             runTest("compiler/testData/codegen/box/bridges/propertyDiamond.kt");
         }
 
+        @TestMetadata("propertyDiamondFakeOverride.kt")
+        public void testPropertyDiamondFakeOverride() throws Exception {
+            runTest("compiler/testData/codegen/box/bridges/propertyDiamondFakeOverride.kt");
+        }
+
         @TestMetadata("propertyInConstructor.kt")
         public void testPropertyInConstructor() throws Exception {
             runTest("compiler/testData/codegen/box/bridges/propertyInConstructor.kt");