Kapt+JVM_IR: generate delegated members correctly

Generate a declaration for each delegated member without body. If we
don't generate delegated declarations, subclasses will have incorrect IR
with unbound symbols in fake overrides.

 #KT-58027 Fixed

compiler/frontend/src/org/jetbrains/kotlin/resolve/DelegationResolver.kt

@@ -151,7 +151,11 @@ class DelegationResolver<T : CallableMemberDescriptor> private constructor(
         //   descriptor = Foo
         //   toInterface = Bar
         //   delegateExpressionType = typeof(baz)
-        // return Map<member of Foo, corresponding member of typeOf(baz)>
+        //
+        // This method returns a map where keys are members of Foo, and values are members of typeof(baz).
+        //
+        // In case delegation is to an error type, which is useful for KAPT stub generation mode, typeof(baz) has no members, so we return
+        // a map from each element to it (so keys = values in the returned map).
         fun getDelegates(
             descriptor: ClassDescriptor,
             toInterface: ClassDescriptor,
@@ -175,8 +179,11 @@ class DelegationResolver<T : CallableMemberDescriptor> private constructor(
                     val actualDelegates = DescriptorUtils.getAllOverriddenDescriptors(delegatingMember)
                         .filter { it.containingDeclaration == toInterface }
                         .map { overriddenDescriptor ->
+                            if (scopeType.isError) {
+                                overriddenDescriptor
+                            } else {
                                 val name = overriddenDescriptor.name
-                            // this is the actual member of delegateExpressionType that we are delegating to
+                                // This is the actual member of delegateExpressionType that we are delegating to.
                                 (scope.getContributedFunctions(name, NoLookupLocation.WHEN_CHECK_OVERRIDES) +
                                         scope.getContributedVariables(name, NoLookupLocation.WHEN_CHECK_OVERRIDES))
                                     .firstOrNull {
@@ -188,6 +195,7 @@ class DelegationResolver<T : CallableMemberDescriptor> private constructor(
                                         )
                                     }
                             }
+                        }
 
                     actualDelegates.firstOrNull()
                 }

compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/generators/ClassGenerator.kt

@@ -324,8 +324,10 @@ internal class ClassGenerator(
             // TODO could possibly refer to scoped type parameters for property accessors
             irFunction.returnType = delegatedDescriptor.returnType!!.toIrType()
 
+            if (context.configuration.generateBodies) {
                 irFunction.body = generateDelegateFunctionBody(irDelegate, delegatedDescriptor, delegateToDescriptor, irFunction)
             }
+        }
 
     private fun generateDelegateFunctionBody(
         irDelegate: IrField,

plugins/kapt3/kapt3-compiler/testData/converter/delegationAndCompanionObject.ir.txt

@@ -0,0 +1,39 @@
+@kotlin.Metadata()
+@kotlin.Suppress(names = {"UNRESOLVED_REFERENCE"})
+public abstract interface A {
+    @org.jetbrains.annotations.NotNull()
+    public static final A.Companion Companion = null;
+
+    public abstract void inject(@org.jetbrains.annotations.NotNull()
+    A.B b);
+
+    @org.jetbrains.annotations.NotNull()
+    public abstract java.lang.String getX();
+
+    @kotlin.Metadata()
+    public static abstract class B implements A {
+
+        public B() {
+            super();
+        }
+
+        @java.lang.Override()
+        @org.jetbrains.annotations.NotNull()
+        public java.lang.String getX() {
+            return null;
+        }
+
+        @java.lang.Override()
+        public void inject(@org.jetbrains.annotations.NotNull()
+        A.B b) {
+        }
+    }
+
+    @kotlin.Metadata()
+    public static final class Companion extends A.B {
+
+        private Companion() {
+            super();
+        }
+    }
+}

plugins/kapt3/kapt3-compiler/testData/converter/delegationAndCompanionObject.kt

@@ -0,0 +1,11 @@
+// CORRECT_ERROR_TYPES
+
+@Suppress("UNRESOLVED_REFERENCE")
+interface A {
+    fun inject(b: B)
+    val x: String
+
+    companion object : B()
+
+    abstract class B : A by Unresolved
+}

plugins/kapt3/kapt3-compiler/testData/converter/delegationAndCompanionObject.txt

@@ -0,0 +1,39 @@
+@kotlin.Metadata()
+@kotlin.Suppress(names = {"UNRESOLVED_REFERENCE"})
+public abstract interface A {
+    @org.jetbrains.annotations.NotNull()
+    public static final A.Companion Companion = null;
+
+    public abstract void inject(@org.jetbrains.annotations.NotNull()
+    A.B b);
+
+    @org.jetbrains.annotations.NotNull()
+    public abstract java.lang.String getX();
+
+    @kotlin.Metadata()
+    public static abstract class B implements A {
+
+        @java.lang.Override()
+        public void inject(@org.jetbrains.annotations.NotNull()
+        A.B b) {
+        }
+
+        @java.lang.Override()
+        @org.jetbrains.annotations.NotNull()
+        public java.lang.String getX() {
+            return null;
+        }
+
+        public B() {
+            super();
+        }
+    }
+
+    @kotlin.Metadata()
+    public static final class Companion extends A.B {
+
+        private Companion() {
+            super();
+        }
+    }
+}

plugins/kapt3/kapt3-compiler/tests-gen/org/jetbrains/kotlin/kapt3/test/runners/ClassFileToSourceStubConverterTestGenerated.java

@@ -157,6 +157,12 @@ public class ClassFileToSourceStubConverterTestGenerated extends AbstractClassFi
         runTest("plugins/kapt3/kapt3-compiler/testData/converter/delegatedProperties.kt");
     }
 
+    @Test
+    @TestMetadata("delegationAndCompanionObject.kt")
+    public void testDelegationAndCompanionObject() throws Exception {
+        runTest("plugins/kapt3/kapt3-compiler/testData/converter/delegationAndCompanionObject.kt");
+    }
+
     @Test
     @TestMetadata("deprecated.kt")
     public void testDeprecated() throws Exception {

plugins/kapt3/kapt3-compiler/tests-gen/org/jetbrains/kotlin/kapt3/test/runners/IrClassFileToSourceStubConverterTestGenerated.java

@@ -157,6 +157,12 @@ public class IrClassFileToSourceStubConverterTestGenerated extends AbstractIrCla
         runTest("plugins/kapt3/kapt3-compiler/testData/converter/delegatedProperties.kt");
     }
 
+    @Test
+    @TestMetadata("delegationAndCompanionObject.kt")
+    public void testDelegationAndCompanionObject() throws Exception {
+        runTest("plugins/kapt3/kapt3-compiler/testData/converter/delegationAndCompanionObject.kt");
+    }
+
     @Test
     @TestMetadata("deprecated.kt")
     public void testDeprecated() throws Exception {