K2: repeat K1 behavior around multiple inheritance by delegation

#KT-56720 Fixed

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirNotImplementedOverrideChecker.kt

@@ -21,6 +21,7 @@ import org.jetbrains.kotlin.diagnostics.reportOn
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED
 import org.jetbrains.kotlin.fir.containingClassLookupTag
 import org.jetbrains.kotlin.fir.declarations.FirClass
+import org.jetbrains.kotlin.fir.declarations.FirDeclarationOrigin
 import org.jetbrains.kotlin.fir.declarations.FirRegularClass
 import org.jetbrains.kotlin.fir.declarations.utils.*
 import org.jetbrains.kotlin.fir.delegatedWrapperData
@@ -71,7 +72,12 @@ object FirNotImplementedOverrideChecker : FirClassChecker() {
                 val delegatedTo = delegatedWrapperData.wrapped.unwrapFakeOverrides().symbol
 
                 if (symbol.multipleDelegatesWithTheSameSignature == true) {
-                    manyImplementationsDelegationSymbols.add(symbol)
+                    if (directOverriddenMembersWithBaseScope.isNotEmpty() &&
+                        // We should report here if either 2+ members or single member with non-enhancement origin
+                        directOverriddenMembersWithBaseScope.singleOrNull()?.member?.origin != FirDeclarationOrigin.Enhancement
+                    ) {
+                        manyImplementationsDelegationSymbols.add(symbol)
+                    }
                 }
 
                 val firstFinal = filteredOverriddenMembers.firstOrNull { it.isFinal }

compiler/fir/fir2ir/tests-gen/org/jetbrains/kotlin/test/runners/codegen/FirLightTreeBlackBoxCodegenTestGenerated.java

@@ -18445,6 +18445,18 @@ public class FirLightTreeBlackBoxCodegenTestGenerated extends AbstractFirLightTr
             runTest("compiler/testData/codegen/box/fir/LookupTags.kt");
         }
 
+        @Test
+        @TestMetadata("manyImplFromOneJavaInterfaceWithDelegation.kt")
+        public void testManyImplFromOneJavaInterfaceWithDelegation() throws Exception {
+            runTest("compiler/testData/codegen/box/fir/manyImplFromOneJavaInterfaceWithDelegation.kt");
+        }
+
+        @Test
+        @TestMetadata("manyImplFromOneJavaInterfaceWithDelegation2.kt")
+        public void testManyImplFromOneJavaInterfaceWithDelegation2() throws Exception {
+            runTest("compiler/testData/codegen/box/fir/manyImplFromOneJavaInterfaceWithDelegation2.kt");
+        }
+
         @Test
         @TestMetadata("NameHighlighter.kt")
         public void testNameHighlighter() throws Exception {

compiler/fir/fir2ir/tests-gen/org/jetbrains/kotlin/test/runners/codegen/FirPsiBlackBoxCodegenTestGenerated.java

@@ -18445,6 +18445,18 @@ public class FirPsiBlackBoxCodegenTestGenerated extends AbstractFirPsiBlackBoxCo
             runTest("compiler/testData/codegen/box/fir/LookupTags.kt");
         }
 
+        @Test
+        @TestMetadata("manyImplFromOneJavaInterfaceWithDelegation.kt")
+        public void testManyImplFromOneJavaInterfaceWithDelegation() throws Exception {
+            runTest("compiler/testData/codegen/box/fir/manyImplFromOneJavaInterfaceWithDelegation.kt");
+        }
+
+        @Test
+        @TestMetadata("manyImplFromOneJavaInterfaceWithDelegation2.kt")
+        public void testManyImplFromOneJavaInterfaceWithDelegation2() throws Exception {
+            runTest("compiler/testData/codegen/box/fir/manyImplFromOneJavaInterfaceWithDelegation2.kt");
+        }
+
         @Test
         @TestMetadata("NameHighlighter.kt")
         public void testNameHighlighter() throws Exception {

compiler/testData/codegen/box/fir/manyImplFromOneJavaInterfaceWithDelegation.kt

@@ -0,0 +1,29 @@
+// TARGET_BACKEND: JVM_IR
+// JVM_TARGET: 1.8
+// FILE: A.java
+
+public interface A {
+    default String foo() {
+        return "OK";
+    }
+}
+
+// FILE: B.java
+
+public interface B extends A {}
+
+// FILE: C.java
+
+public interface C extends A {}
+
+// FILE: test.kt
+
+class Adapter : B, C
+
+class D(val adapter: Adapter) : B by adapter, C by adapter
+
+fun box(): String {
+    val adapter = Adapter()
+    val d = D(adapter)
+    return d.foo()
+}

compiler/testData/codegen/box/fir/manyImplFromOneJavaInterfaceWithDelegation2.kt

@@ -0,0 +1,30 @@
+// TARGET_BACKEND: JVM_IR
+// JVM_TARGET: 1.8
+// FILE: A.java
+
+public interface A {
+    default String foo() {
+        return "OK";
+    }
+}
+
+// FILE: B.java
+
+public interface B extends A {}
+
+// FILE: C.java
+
+public interface C extends A {}
+
+// FILE: test.kt
+
+class Adapter : B, C
+
+class D(val b: B, val c: C) : B by b, C by c
+
+fun box(): String {
+    val b = Adapter()
+    val c = Adapter()
+    val d = D(b, c)
+    return d.foo()
+}

compiler/testData/diagnostics/tests/override/manyImplFromOneJavaInterfaceWithDelegation.fir.kt

@@ -1,19 +0,0 @@
-// FILE: A.java
-
-public interface A {
-    default void foo() {}
-}
-
-// FILE: B.java
-
-public interface B extends A
-
-// FILE: C.java
-
-public interface C extends A
-
-// FILE: test.kt
-
-class Adapter : B, C
-
-<!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class D<!>(val adapter: Adapter) : B by adapter, C by adapter

compiler/testData/diagnostics/tests/override/manyImplFromOneJavaInterfaceWithDelegation.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // FILE: A.java
 
 public interface A {
@@ -6,14 +7,22 @@ public interface A {
 
 // FILE: B.java
 
-public interface B extends A
+public interface B extends A {}
 
 // FILE: C.java
 
-public interface C extends A
+public interface C extends A {}
+
+// FILE: CK.kt
+
+interface CK : A
 
 // FILE: test.kt
 
 class Adapter : B, C
 
 class D(val adapter: Adapter) : B by adapter, C by adapter
+class E(val b: B, val c: C) : B by b, C by c
+
+class AdapterK : B, CK
+class F(val adapter: AdapterK) : B by adapter, CK by adapter

compiler/testData/diagnostics/tests/override/manyImplFromOneKotlinInterfaceWithDelegation.kt

@@ -5,6 +5,10 @@ interface A {
     fun foo() {}
 }
 
+// FILE: BJ.java
+
+public interface BJ extends A {}
+
 // FILE: B.kt
 
 interface B : A
@@ -18,3 +22,7 @@ interface C : A
 class Adapter : B, C
 
 <!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class D<!>(val adapter: Adapter) : B by adapter, C by adapter
+
+class AdapterJ : BJ, C
+
+<!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class DJ<!>(val adapter: AdapterJ) : BJ by adapter, C by adapter

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/codegen/IrBlackBoxCodegenTestGenerated.java

@@ -18445,6 +18445,18 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
             runTest("compiler/testData/codegen/box/fir/LookupTags.kt");
         }
 
+        @Test
+        @TestMetadata("manyImplFromOneJavaInterfaceWithDelegation.kt")
+        public void testManyImplFromOneJavaInterfaceWithDelegation() throws Exception {
+            runTest("compiler/testData/codegen/box/fir/manyImplFromOneJavaInterfaceWithDelegation.kt");
+        }
+
+        @Test
+        @TestMetadata("manyImplFromOneJavaInterfaceWithDelegation2.kt")
+        public void testManyImplFromOneJavaInterfaceWithDelegation2() throws Exception {
+            runTest("compiler/testData/codegen/box/fir/manyImplFromOneJavaInterfaceWithDelegation2.kt");
+        }
+
         @Test
         @TestMetadata("NameHighlighter.kt")
         public void testNameHighlighter() throws Exception {

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/codegen/IrBlackBoxCodegenWithIrInlinerTestGenerated.java

@@ -18451,6 +18451,12 @@ public class IrBlackBoxCodegenWithIrInlinerTestGenerated extends AbstractIrBlack
             runTest("compiler/testData/codegen/box/fir/manyImplFromOneJavaInterfaceWithDelegation.kt");
         }
 
+        @Test
+        @TestMetadata("manyImplFromOneJavaInterfaceWithDelegation2.kt")
+        public void testManyImplFromOneJavaInterfaceWithDelegation2() throws Exception {
+            runTest("compiler/testData/codegen/box/fir/manyImplFromOneJavaInterfaceWithDelegation2.kt");
+        }
+
         @Test
         @TestMetadata("NameHighlighter.kt")
         public void testNameHighlighter() throws Exception {