Prevent generation of delegations to interfaces private methods

#KT-13381 Fixed
 #KT-13996 Fixed

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

@@ -106,7 +106,9 @@ object CodegenUtil {
             if (declaration !is CallableMemberDescriptor) continue
 
             val traitMember = findInterfaceImplementation(declaration)
-            if (traitMember == null || Visibilities.isPrivate(traitMember.visibility)) continue
+            if (traitMember == null ||
+                    Visibilities.isPrivate(traitMember.visibility) ||
+                    traitMember.visibility == Visibilities.INVISIBLE_FAKE) continue
 
             assert(traitMember.modality !== Modality.ABSTRACT) { "Cannot delegate to abstract trait method: $declaration" }
 

compiler/testData/codegen/box/regressions/kt13381.kt

@@ -0,0 +1,12 @@
+interface A {
+    // There must be no delegation methods for 'log' and 'bar' in C as they are private
+    private val log: String get() = "O"
+    private fun bar() = "K"
+
+    fun foo() = log + bar()
+}
+
+interface B : A
+class C : B
+
+fun box() = C().foo()

compiler/testData/codegen/bytecodeListing/noDelegationsToPrivateInterfaceMembers.kt

@@ -0,0 +1,10 @@
+interface A {
+    // There must be no delegation methods for 'log' and 'bar' in C as they are private
+    private val log: String get() = "O"
+    private fun bar() = "K"
+
+    fun foo() = log + bar()
+}
+
+interface B : A
+class C : B

compiler/testData/codegen/bytecodeListing/noDelegationsToPrivateInterfaceMembers.txt

@@ -0,0 +1,30 @@
+@kotlin.Metadata
+public final class A$DefaultImpls {
+    inner class A$DefaultImpls
+    private static method bar(p0: A): java.lang.String
+    public static @org.jetbrains.annotations.NotNull method foo(p0: A): java.lang.String
+    private static method getLog(p0: A): java.lang.String
+}
+
+@kotlin.Metadata
+public interface A {
+    inner class A$DefaultImpls
+    public abstract @org.jetbrains.annotations.NotNull method foo(): java.lang.String
+}
+
+@kotlin.Metadata
+public final class B$DefaultImpls {
+    inner class B$DefaultImpls
+    public static @org.jetbrains.annotations.NotNull method foo(p0: B): java.lang.String
+}
+
+@kotlin.Metadata
+public interface B {
+    inner class B$DefaultImpls
+}
+
+@kotlin.Metadata
+public final class C {
+    public method <init>(): void
+    public @org.jetbrains.annotations.NotNull method foo(): java.lang.String
+}

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

@@ -13666,6 +13666,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             doTest(fileName);
         }
 
+        @TestMetadata("kt13381.kt")
+        public void testKt13381() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/regressions/kt13381.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("kt1406.kt")
         public void testKt1406() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/regressions/kt1406.kt");

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

@@ -77,6 +77,12 @@ public class BytecodeListingTestGenerated extends AbstractBytecodeListingTest {
         doTest(fileName);
     }
 
+    @TestMetadata("noDelegationsToPrivateInterfaceMembers.kt")
+    public void testNoDelegationsToPrivateInterfaceMembers() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/bytecodeListing/noDelegationsToPrivateInterfaceMembers.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("samAdapterAndInlinedOne.kt")
     public void testSamAdapterAndInlinedOne() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/bytecodeListing/samAdapterAndInlinedOne.kt");