Fix reflection for local delegated properties inside interface

#KT-19690

compiler/backend/src/org/jetbrains/kotlin/codegen/serialization/JvmSerializerExtension.java

@@ -35,6 +35,7 @@ import org.jetbrains.kotlin.name.ClassId;
 import org.jetbrains.kotlin.name.FqName;
 import org.jetbrains.kotlin.protobuf.GeneratedMessageLite;
 import org.jetbrains.kotlin.resolve.BindingContext;
+import org.jetbrains.kotlin.resolve.DescriptorUtils;
 import org.jetbrains.kotlin.serialization.*;
 import org.jetbrains.kotlin.serialization.jvm.ClassMapperLite;
 import org.jetbrains.kotlin.serialization.jvm.JvmProtoBuf;
@@ -85,7 +86,9 @@ public class JvmSerializerExtension extends SerializerExtension {
             proto.setExtension(JvmProtoBuf.classModuleName, stringTable.getStringIndex(moduleName));
         }
 
-        writeLocalProperties(proto, typeMapper.mapClass(descriptor), JvmProtoBuf.classLocalVariable);
+        Type containerAsmType =
+                DescriptorUtils.isInterface(descriptor) ? typeMapper.mapDefaultImpls(descriptor) : typeMapper.mapClass(descriptor);
+        writeLocalProperties(proto, containerAsmType, JvmProtoBuf.classLocalVariable);
     }
 
     @Override

compiler/testData/codegen/box/reflection/properties/localDelegated/defaultImpls.kt

@@ -0,0 +1,23 @@
+// TARGET_BACKEND: JVM
+// WITH_REFLECT
+
+import kotlin.reflect.KProperty
+import kotlin.test.assertEquals
+
+object Delegate {
+    operator fun getValue(z: Any?, p: KProperty<*>): String? {
+        assertEquals("val x: kotlin.String?", p.toString())
+        return "OK"
+    }
+}
+
+interface Foo {
+    fun bar(): String {
+        val x by Delegate
+        return x!!
+    }
+}
+
+object O : Foo
+
+fun box(): String = O.bar()

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

@@ -16281,6 +16281,12 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
                     KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/codegen/box/reflection/properties/localDelegated"), Pattern.compile("^(.+)\\.kt$"), TargetBackend.JVM, true);
                 }
 
+                @TestMetadata("defaultImpls.kt")
+                public void testDefaultImpls() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/reflection/properties/localDelegated/defaultImpls.kt");
+                    doTest(fileName);
+                }
+
                 @TestMetadata("inlineFun.kt")
                 public void testInlineFun() throws Exception {
                     String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/reflection/properties/localDelegated/inlineFun.kt");

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

@@ -16281,6 +16281,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
                     KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/codegen/box/reflection/properties/localDelegated"), Pattern.compile("^(.+)\\.kt$"), TargetBackend.JVM, true);
                 }
 
+                @TestMetadata("defaultImpls.kt")
+                public void testDefaultImpls() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/reflection/properties/localDelegated/defaultImpls.kt");
+                    doTest(fileName);
+                }
+
                 @TestMetadata("inlineFun.kt")
                 public void testInlineFun() throws Exception {
                     String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/reflection/properties/localDelegated/inlineFun.kt");

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

@@ -16281,6 +16281,12 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
                     KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/codegen/box/reflection/properties/localDelegated"), Pattern.compile("^(.+)\\.kt$"), TargetBackend.JVM, true);
                 }
 
+                @TestMetadata("defaultImpls.kt")
+                public void testDefaultImpls() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/reflection/properties/localDelegated/defaultImpls.kt");
+                    doTest(fileName);
+                }
+
                 @TestMetadata("inlineFun.kt")
                 public void testInlineFun() throws Exception {
                     String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/reflection/properties/localDelegated/inlineFun.kt");

core/reflection.jvm/src/kotlin/reflect/jvm/internal/KClassImpl.kt

@@ -199,6 +199,15 @@ internal class KClassImpl<T : Any>(override val jClass: Class<T>) : KDeclaration
             staticScope.getContributedFunctions(name, NoLookupLocation.FROM_REFLECTION)
 
     override fun getLocalProperty(index: Int): PropertyDescriptor? {
+        // TODO: also check that this is a synthetic class (Metadata.k == 3)
+        if (jClass.simpleName == JvmAbi.DEFAULT_IMPLS_CLASS_NAME) {
+            jClass.declaringClass?.let { interfaceClass ->
+                if (interfaceClass.isInterface) {
+                    return (interfaceClass.kotlin as KClassImpl<*>).getLocalProperty(index)
+                }
+            }
+        }
+
         return (descriptor as? DeserializedClassDescriptor)?.let { descriptor ->
             val proto = descriptor.classProto.getExtension(JvmProtoBuf.classLocalVariable, index)
             val nameResolver = descriptor.c.nameResolver