FE 1.0: add deprecation ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED_WARNING

#KT-45508 Fixed

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsTestGenerated.java

@@ -16840,6 +16840,12 @@ public class FirOldFrontendDiagnosticsTestGenerated extends AbstractFirDiagnosti
                 runTest("compiler/testData/diagnostics/tests/java8Overrides/abstractBaseClassMemberNotImplemented.kt");
             }
 
+            @Test
+            @TestMetadata("abstractBaseClassMemberNotImplemented_15.kt")
+            public void testAbstractBaseClassMemberNotImplemented_15() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/java8Overrides/abstractBaseClassMemberNotImplemented_15.kt");
+            }
+
             @Test
             @TestMetadata("abstractVsAbstract.kt")
             public void testAbstractVsAbstract() throws Exception {
@@ -16869,6 +16875,12 @@ public class FirOldFrontendDiagnosticsTestGenerated extends AbstractFirDiagnosti
                 runTest("compiler/testData/diagnostics/tests/java8Overrides/implementingMethodOfAny.kt");
             }
 
+            @Test
+            @TestMetadata("kt45508.kt")
+            public void testKt45508() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/java8Overrides/kt45508.kt");
+            }
+
             @Test
             @TestMetadata("notAMethodOfAny.kt")
             public void testNotAMethodOfAny() throws Exception {

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsWithLightTreeTestGenerated.java

@@ -16840,6 +16840,12 @@ public class FirOldFrontendDiagnosticsWithLightTreeTestGenerated extends Abstrac
                 runTest("compiler/testData/diagnostics/tests/java8Overrides/abstractBaseClassMemberNotImplemented.kt");
             }
 
+            @Test
+            @TestMetadata("abstractBaseClassMemberNotImplemented_15.kt")
+            public void testAbstractBaseClassMemberNotImplemented_15() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/java8Overrides/abstractBaseClassMemberNotImplemented_15.kt");
+            }
+
             @Test
             @TestMetadata("abstractVsAbstract.kt")
             public void testAbstractVsAbstract() throws Exception {
@@ -16869,6 +16875,12 @@ public class FirOldFrontendDiagnosticsWithLightTreeTestGenerated extends Abstrac
                 runTest("compiler/testData/diagnostics/tests/java8Overrides/implementingMethodOfAny.kt");
             }
 
+            @Test
+            @TestMetadata("kt45508.kt")
+            public void testKt45508() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/java8Overrides/kt45508.kt");
+            }
+
             @Test
             @TestMetadata("notAMethodOfAny.kt")
             public void testNotAMethodOfAny() throws Exception {

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Errors.java

@@ -543,10 +543,14 @@ public interface Errors {
             DiagnosticFactory2.create(ERROR, DECLARATION_NAME);
     DiagnosticFactory2<KtClassOrObject, KtClassOrObject, CallableMemberDescriptor> ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED =
             DiagnosticFactory2.create(ERROR, DECLARATION_NAME);
+    DiagnosticFactory2<KtClassOrObject, KtClassOrObject, CallableMemberDescriptor> ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED_WARNING =
+            DiagnosticFactory2.create(WARNING, DECLARATION_NAME);
     DiagnosticFactory2<KtClassOrObject, KtClassOrObject, CallableMemberDescriptor> MANY_IMPL_MEMBER_NOT_IMPLEMENTED =
             DiagnosticFactory2.create(ERROR, DECLARATION_NAME);
     DiagnosticFactory2<KtClassOrObject, KtClassOrObject, CallableMemberDescriptor> MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED =
             DiagnosticFactory2.create(ERROR, DECLARATION_NAME);
+    DiagnosticFactory2<KtClassOrObject, KtClassOrObject, CallableMemberDescriptor> MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED_WARNING =
+            DiagnosticFactory2.create(WARNING, DECLARATION_NAME);
     DiagnosticFactory2<KtClassOrObject, ClassDescriptor, Collection<CallableMemberDescriptor>> INVISIBLE_ABSTRACT_MEMBER_FROM_SUPER =
             DiagnosticFactory2.create(ERROR, DECLARATION_NAME);
     DiagnosticFactory2<KtClassOrObject, ClassDescriptor, Collection<CallableMemberDescriptor>> INVISIBLE_ABSTRACT_MEMBER_FROM_SUPER_WARNING =

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java

@@ -853,11 +853,15 @@ public class DefaultErrorMessages {
                 FQ_NAMES_IN_TYPES);
         MAP.put(ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED, "{0} is not abstract and does not implement abstract base class member {1}",
                 RENDER_CLASS_OR_OBJECT, FQ_NAMES_IN_TYPES);
+        MAP.put(ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED_WARNING, "Deprecated: {0} is not abstract and does not implement abstract base class member {1}",
+                RENDER_CLASS_OR_OBJECT, FQ_NAMES_IN_TYPES);
 
         MAP.put(MANY_IMPL_MEMBER_NOT_IMPLEMENTED, "{0} must override {1} because it inherits many implementations of it",
                 RENDER_CLASS_OR_OBJECT, FQ_NAMES_IN_TYPES);
         MAP.put(MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED, "{0} must override {1} because it inherits multiple interface methods of it",
                 RENDER_CLASS_OR_OBJECT, FQ_NAMES_IN_TYPES);
+        MAP.put(MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED_WARNING, "Deprecated: {0} must override {1} because it inherits multiple interface methods of it",
+                RENDER_CLASS_OR_OBJECT, FQ_NAMES_IN_TYPES);
         MAP.put(INVISIBLE_ABSTRACT_MEMBER_FROM_SUPER, "{0} inherits invisible abstract members: {1}", NAME, commaSeparated(FQ_NAMES_IN_TYPES));
         MAP.put(INVISIBLE_ABSTRACT_MEMBER_FROM_SUPER_WARNING, "{0} inherits invisible abstract members: {1}", NAME, commaSeparated(FQ_NAMES_IN_TYPES));
 

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

@@ -23,6 +23,7 @@ import com.intellij.util.SmartList
 import com.intellij.util.containers.ContainerUtil
 import com.intellij.util.containers.SmartHashSet
 import org.jetbrains.kotlin.config.LanguageFeature
+import org.jetbrains.kotlin.config.LanguageFeature.AbstractClassMemberNotImplementedWithIntermediateAbstractClass
 import org.jetbrains.kotlin.config.LanguageVersionSettings
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.descriptors.CallableMemberDescriptor.Kind.DELEGATION
@@ -38,10 +39,7 @@ import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.resolve.DescriptorUtils.classCanHaveAbstractFakeOverride
 import org.jetbrains.kotlin.resolve.OverridingUtil.OverrideCompatibilityInfo.Result.OVERRIDABLE
 import org.jetbrains.kotlin.resolve.calls.callResolverUtil.isOrOverridesSynthesized
-import org.jetbrains.kotlin.resolve.descriptorUtil.getKotlinTypeRefiner
-import org.jetbrains.kotlin.resolve.descriptorUtil.module
 import org.jetbrains.kotlin.types.*
-import org.jetbrains.kotlin.types.checker.KotlinTypeChecker
 import org.jetbrains.kotlin.types.checker.KotlinTypeRefiner
 import org.jetbrains.kotlin.types.checker.NewKotlinTypeCheckerImpl
 import org.jetbrains.kotlin.types.refinement.TypeRefinement
@@ -128,20 +126,50 @@ class OverrideResolver(
         }
     }
 
-    private inner class CollectErrorInformationForInheritedMembersStrategy(
-        private val klass: KtClassOrObject,
-        private val classDescriptor: ClassDescriptor
+    private inner class CollectWarningInformationForInheritedMembersStrategy(
+        klass: KtClassOrObject,
+        classDescriptor: ClassDescriptor
+    ) : CollectErrorInformationForInheritedMembersStrategy(klass, classDescriptor) {
+        constructor(delegateStrategy: CollectErrorInformationForInheritedMembersStrategy) :
+                this(delegateStrategy.klass, delegateStrategy.classDescriptor)
+
+        override fun doReportErrors() {
+            val canHaveAbstractMembers = classCanHaveAbstractFakeOverride(classDescriptor)
+            if (abstractInBaseClassNoImpl.isNotEmpty() && !canHaveAbstractMembers) {
+                if (languageVersionSettings.supportsFeature(AbstractClassMemberNotImplementedWithIntermediateAbstractClass)) {
+                    trace.report(ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED.on(klass, klass, abstractInBaseClassNoImpl.first()))
+                } else {
+                    trace.report(ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED_WARNING.on(klass, klass, abstractInBaseClassNoImpl.first()))
+                }
+            }
+            if (conflictingInterfaceMembers.isNotEmpty()) {
+                val interfaceMember = conflictingInterfaceMembers.first()
+                if (languageVersionSettings.supportsFeature(AbstractClassMemberNotImplementedWithIntermediateAbstractClass)) {
+                    trace.report(MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED.on(klass, klass, interfaceMember))
+                } else {
+                    trace.report(MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED_WARNING.on(klass, klass, interfaceMember))
+                }
+            }
+        }
+    }
+
+    private open inner class CollectErrorInformationForInheritedMembersStrategy(
+        val klass: KtClassOrObject,
+        val classDescriptor: ClassDescriptor
     ) : CheckInheritedSignaturesReportStrategy, CheckOverrideReportStrategy {
 
         private val abstractNoImpl = linkedSetOf<CallableMemberDescriptor>()
-        private val abstractInBaseClassNoImpl = linkedSetOf<CallableMemberDescriptor>()
+        protected val abstractInBaseClassNoImpl = linkedSetOf<CallableMemberDescriptor>()
         private val abstractInvisibleSuper = linkedSetOf<CallableMemberDescriptor>()
         private val multipleImplementations = linkedSetOf<CallableMemberDescriptor>()
-        private val conflictingInterfaceMembers = linkedSetOf<CallableMemberDescriptor>()
+        protected val conflictingInterfaceMembers = linkedSetOf<CallableMemberDescriptor>()
         private val conflictingReturnTypes = linkedSetOf<CallableMemberDescriptor>()
 
         private val onceErrorsReported = SmartHashSet<DiagnosticFactoryWithPsiElement<*, *>>()
 
+        fun toDeprecationStrategy() =
+            CollectWarningInformationForInheritedMembersStrategy(this)
+
         override fun abstractMemberNotImplemented(descriptor: CallableMemberDescriptor) {
             abstractNoImpl.add(descriptor)
         }
@@ -233,7 +261,7 @@ class OverrideResolver(
             }
         }
 
-        internal fun doReportErrors() {
+        open fun doReportErrors() {
             val canHaveAbstractMembers = classCanHaveAbstractFakeOverride(classDescriptor)
             if (abstractInBaseClassNoImpl.isNotEmpty() && !canHaveAbstractMembers) {
                 trace.report(ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED.on(klass, klass, abstractInBaseClassNoImpl.first()))
@@ -251,10 +279,10 @@ class OverrideResolver(
 
             conflictingInterfaceMembers.removeAll(conflictingReturnTypes)
             multipleImplementations.removeAll(conflictingReturnTypes)
-            if (!conflictingInterfaceMembers.isEmpty()) {
-                trace.report(MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED.on(klass, klass, conflictingInterfaceMembers.iterator().next()))
-            } else if (!multipleImplementations.isEmpty()) {
-                trace.report(MANY_IMPL_MEMBER_NOT_IMPLEMENTED.on(klass, klass, multipleImplementations.iterator().next()))
+            if (conflictingInterfaceMembers.isNotEmpty()) {
+                trace.report(MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED.on(klass, klass, conflictingInterfaceMembers.first()))
+            } else if (multipleImplementations.isNotEmpty()) {
+                trace.report(MANY_IMPL_MEMBER_NOT_IMPLEMENTED.on(klass, klass, multipleImplementations.first()))
             }
         }
     }
@@ -342,7 +370,7 @@ class OverrideResolver(
                 }
             })
         } else if (!overriddenDescriptors.isEmpty() && !overridesBackwardCompatibilityHelper.overrideCanBeOmitted(declared)) {
-            val overridden = overriddenDescriptors.iterator().next()
+            val overridden = overriddenDescriptors.first()
             trace.report(VIRTUAL_MEMBER_HIDDEN.on(member, declared, overridden, overridden.containingDeclaration))
         }
     }
@@ -576,19 +604,11 @@ class OverrideResolver(
             }
         }
 
-        private fun checkInheritedAndDelegatedSignatures(
-            descriptor: CallableMemberDescriptor,
-            reportingStrategy: CheckInheritedSignaturesReportStrategy,
-            overrideReportStrategyForDelegates: CheckOverrideReportStrategy?,
-            kotlinTypeRefiner: KotlinTypeRefiner
-        ) {
-            val kind = descriptor.kind
-            if (kind != FAKE_OVERRIDE && kind != DELEGATION) return
-
-            val directOverridden = descriptor.overriddenDescriptors
+        private fun CallableMemberDescriptor.computeRelevantDirectlyOverridden(): Set<CallableMemberDescriptor> {
+            val directOverridden = overriddenDescriptors
 
             // directOverridden may be empty if user tries to delegate implementation of abstract class instead of interface
-            if (directOverridden.isEmpty()) return
+            if (directOverridden.isEmpty()) return emptySet()
 
             // collects map from the directly overridden descriptor to the set of declarations:
             // -- if directly overridden is not fake, the set consists of one element: this directly overridden
@@ -600,8 +620,20 @@ class OverrideResolver(
                 Sets.newLinkedHashSet(allOverriddenDeclarations)
             )
 
-            val relevantDirectlyOverridden =
-                getRelevantDirectlyOverridden(overriddenDeclarationsByDirectParent, allFilteredOverriddenDeclarations)
+            return getRelevantDirectlyOverridden(overriddenDeclarationsByDirectParent, allFilteredOverriddenDeclarations)
+        }
+
+        private fun checkInheritedAndDelegatedSignatures(
+            descriptor: CallableMemberDescriptor,
+            reportingStrategy: CheckInheritedSignaturesReportStrategy,
+            overrideReportStrategyForDelegates: CheckOverrideReportStrategy?,
+            kotlinTypeRefiner: KotlinTypeRefiner
+        ) {
+            val kind = descriptor.kind
+            if (kind != FAKE_OVERRIDE && kind != DELEGATION) return
+
+            val relevantDirectlyOverridden = descriptor.computeRelevantDirectlyOverridden()
+            if (relevantDirectlyOverridden.isEmpty()) return
 
             if (descriptor.visibility === DescriptorVisibilities.INVISIBLE_FAKE) {
                 checkInvisibleFakeOverride(descriptor, relevantDirectlyOverridden, reportingStrategy)
@@ -622,9 +654,7 @@ class OverrideResolver(
                 .filter { !isOrOverridesSynthesized(it) }
                 .partition { it.modality != Modality.ABSTRACT }
 
-            val numImplementations = concreteOverridden.size
-
-            when (numImplementations) {
+            when (concreteOverridden.size) {
                 0 ->
                     if (kind != DELEGATION) {
                         abstractOverridden.forEach {
@@ -664,7 +694,9 @@ class OverrideResolver(
 
         private fun checkMissingOverridesByJava8Restrictions(
             relevantDirectlyOverridden: Set<CallableMemberDescriptor>,
-            reportingStrategy: CheckInheritedSignaturesReportStrategy
+            reportingStrategy: CheckInheritedSignaturesReportStrategy,
+            onlyBaseClassMembers: Boolean = false,
+            overriddenInterfaceMembers: MutableList<CallableMemberDescriptor> = SmartList()
         ) {
             // Java 8:
             // -- class should implement an abstract member of a super-class,
@@ -675,31 +707,53 @@ class OverrideResolver(
             var overridesClassMember = false
             var overridesNonAbstractInterfaceMember = false
             var overridesAbstractInBaseClass: CallableMemberDescriptor? = null
-            val overriddenInterfaceMembers = SmartList<CallableMemberDescriptor>()
+            var fakeOverrideInBaseClass: CallableMemberDescriptor? = null
             for (overridden in relevantDirectlyOverridden) {
-                val containingDeclaration = overridden.containingDeclaration
-                if (containingDeclaration is ClassDescriptor) {
-                    if (containingDeclaration.kind == ClassKind.CLASS) {
-                        overridesClassMember = true
-                        if (overridden.modality === Modality.ABSTRACT) {
-                            overridesAbstractInBaseClass = overridden
-                        }
-                    } else if (containingDeclaration.kind == ClassKind.INTERFACE) {
-                        overriddenInterfaceMembers.add(overridden)
-                        if (overridden.modality !== Modality.ABSTRACT) {
-                            overridesNonAbstractInterfaceMember = true
-                        }
+                val containingDeclaration = overridden.containingDeclaration as? ClassDescriptor ?: continue
+                if (containingDeclaration.kind == ClassKind.CLASS) {
+                    if (overridden.kind == FAKE_OVERRIDE && !containingDeclaration.isExpect) {
+                        // Fake override in a class in fact can mean an interface member
+                        // We will process it at the end
+                        // Note: with expect containing class, the situation is unclear, so we miss this case
+                        // See extendExpectedClassWithAbstractMember.kt (BaseA, BaseAImpl, DerivedA1)
+                        fakeOverrideInBaseClass = overridden
+                    }
+                    overridesClassMember = true
+                    if (overridden.modality === Modality.ABSTRACT) {
+                        overridesAbstractInBaseClass = overridden
+                    }
+                } else if (containingDeclaration.kind == ClassKind.INTERFACE) {
+                    overriddenInterfaceMembers.add(overridden)
+                    if (overridden.modality !== Modality.ABSTRACT) {
+                        overridesNonAbstractInterfaceMember = true
                     }
                 }
             }
 
             if (overridesAbstractInBaseClass != null) {
                 reportingStrategy.abstractBaseClassMemberNotImplemented(overridesAbstractInBaseClass)
-            }
-            if (!overridesClassMember && overridesNonAbstractInterfaceMember && overriddenInterfaceMembers.size > 1) {
+            } else if (!onlyBaseClassMembers && !overridesClassMember &&
+                overridesNonAbstractInterfaceMember && overriddenInterfaceMembers.size > 1
+            ) {
                 for (member in overriddenInterfaceMembers) {
                     reportingStrategy.conflictingInterfaceMemberNotImplemented(member)
                 }
+            } else if (fakeOverrideInBaseClass != null) {
+                val newReportingStrategy = if (reportingStrategy is CollectErrorInformationForInheritedMembersStrategy) {
+                    reportingStrategy.toDeprecationStrategy()
+                } else reportingStrategy
+                checkMissingOverridesByJava8Restrictions(
+                    fakeOverrideInBaseClass.computeRelevantDirectlyOverridden(),
+                    reportingStrategy = newReportingStrategy,
+                    // Note: we don't report MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED_WARNING
+                    // in case all interface members are derived from fakeOverrideInClass
+                    // (in this case we already have warning or error on its container)
+                    onlyBaseClassMembers = overriddenInterfaceMembers.isEmpty(),
+                    overriddenInterfaceMembers
+                )
+                if (newReportingStrategy is CollectWarningInformationForInheritedMembersStrategy) {
+                    newReportingStrategy.doReportErrors()
+                }
             }
         }
 

compiler/testData/diagnostics/tests/java8Overrides/abstractBaseClassMemberNotImplemented.fir.kt

@@ -1,3 +1,5 @@
+// !LANGUAGE: +AbstractClassMemberNotImplementedWithIntermediateAbstractClass
+
 abstract class ALeft {
     abstract fun foo()
 }
@@ -6,4 +8,34 @@ interface IRight {
     fun foo() {}
 }
 
-class CDerived : ALeft(), IRight
+class CDerived : ALeft(), IRight
+
+abstract class CAbstract : ALeft(), IRight
+
+class CDerivedFromAbstract : CAbstract()
+
+interface ILeft {
+    fun foo()
+}
+
+abstract class AILeft : ILeft
+
+// Should be ERROR
+class AILeftImpl : AILeft(), IRight
+
+// Should be ERROR
+class RightLeft : ILeft, IRight
+
+interface IBase {
+    fun foo()
+}
+
+interface IBaseEx : IBase {
+    override fun foo() {}
+}
+
+abstract class AIBase : IBase
+
+abstract class AIIntermediate : AIBase(), IBaseEx
+
+class Impl : AIIntermediate()

compiler/testData/diagnostics/tests/java8Overrides/abstractBaseClassMemberNotImplemented.kt

@@ -1,3 +1,5 @@
+// !LANGUAGE: +AbstractClassMemberNotImplementedWithIntermediateAbstractClass
+
 abstract class ALeft {
     abstract fun foo()
 }
@@ -6,4 +8,34 @@ interface IRight {
     fun foo() {}
 }
 
-<!ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED!>class CDerived<!> : ALeft(), IRight
+<!ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED!>class CDerived<!> : ALeft(), IRight
+
+abstract class CAbstract : ALeft(), IRight
+
+<!ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED!>class CDerivedFromAbstract<!> : CAbstract()
+
+interface ILeft {
+    fun foo()
+}
+
+abstract class AILeft : ILeft
+
+// Should be ERROR
+<!ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED!>class AILeftImpl<!> : AILeft(), IRight
+
+// Should be ERROR
+<!MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED!>class RightLeft<!> : ILeft, IRight
+
+interface IBase {
+    fun foo()
+}
+
+interface IBaseEx : IBase {
+    override fun foo() {}
+}
+
+abstract class AIBase : IBase
+
+abstract class AIIntermediate : AIBase(), IBaseEx
+
+class Impl : AIIntermediate()

compiler/testData/diagnostics/tests/java8Overrides/abstractBaseClassMemberNotImplemented.txt

@@ -1,5 +1,37 @@
 package
 
+public abstract class AIBase : IBase {
+    public constructor AIBase()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract override /*1*/ /*fake_override*/ fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public abstract class AIIntermediate : AIBase, IBaseEx {
+    public constructor AIIntermediate()
+    public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*2*/ /*fake_override*/ fun foo(): kotlin.Unit
+    public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public abstract class AILeft : ILeft {
+    public constructor AILeft()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract override /*1*/ /*fake_override*/ fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class AILeftImpl : AILeft, IRight {
+    public constructor AILeftImpl()
+    public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*2*/ /*fake_override*/ fun foo(): kotlin.Unit
+    public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
 public abstract class ALeft {
     public constructor ALeft()
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
@@ -8,6 +40,14 @@ public abstract class ALeft {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
+public abstract class CAbstract : ALeft, IRight {
+    public constructor CAbstract()
+    public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*2*/ /*fake_override*/ fun foo(): kotlin.Unit
+    public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
 public final class CDerived : ALeft, IRight {
     public constructor CDerived()
     public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
@@ -16,9 +56,55 @@ public final class CDerived : ALeft, IRight {
     public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
+public final class CDerivedFromAbstract : CAbstract {
+    public constructor CDerivedFromAbstract()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface IBase {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface IBaseEx : IBase {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface ILeft {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
 public interface IRight {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open fun foo(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
+
+public final class Impl : AIIntermediate {
+    public constructor Impl()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class RightLeft : ILeft, IRight {
+    public constructor RightLeft()
+    public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*2*/ /*fake_override*/ fun foo(): kotlin.Unit
+    public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
+}
+

compiler/testData/diagnostics/tests/java8Overrides/abstractBaseClassMemberNotImplemented_15.fir.kt

@@ -0,0 +1,41 @@
+// !LANGUAGE: -AbstractClassMemberNotImplementedWithIntermediateAbstractClass
+
+abstract class ALeft {
+    abstract fun foo()
+}
+
+interface IRight {
+    fun foo() {}
+}
+
+class CDerived : ALeft(), IRight
+
+abstract class CAbstract : ALeft(), IRight
+
+class CDerivedFromAbstract : CAbstract()
+
+interface ILeft {
+    fun foo()
+}
+
+abstract class AILeft : ILeft
+
+// Should be ERROR
+class AILeftImpl : AILeft(), IRight
+
+// Should be ERROR
+class RightLeft : ILeft, IRight
+
+interface IBase {
+    fun foo()
+}
+
+interface IBaseEx : IBase {
+    override fun foo() {}
+}
+
+abstract class AIBase : IBase
+
+abstract class AIIntermediate : AIBase(), IBaseEx
+
+class Impl : AIIntermediate()

compiler/testData/diagnostics/tests/java8Overrides/abstractBaseClassMemberNotImplemented_15.kt

@@ -0,0 +1,41 @@
+// !LANGUAGE: -AbstractClassMemberNotImplementedWithIntermediateAbstractClass
+
+abstract class ALeft {
+    abstract fun foo()
+}
+
+interface IRight {
+    fun foo() {}
+}
+
+<!ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED!>class CDerived<!> : ALeft(), IRight
+
+abstract class CAbstract : ALeft(), IRight
+
+<!ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED_WARNING!>class CDerivedFromAbstract<!> : CAbstract()
+
+interface ILeft {
+    fun foo()
+}
+
+abstract class AILeft : ILeft
+
+// Should be ERROR
+<!ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED!>class AILeftImpl<!> : AILeft(), IRight
+
+// Should be ERROR
+<!MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED!>class RightLeft<!> : ILeft, IRight
+
+interface IBase {
+    fun foo()
+}
+
+interface IBaseEx : IBase {
+    override fun foo() {}
+}
+
+abstract class AIBase : IBase
+
+abstract class AIIntermediate : AIBase(), IBaseEx
+
+class Impl : AIIntermediate()

compiler/testData/diagnostics/tests/java8Overrides/abstractBaseClassMemberNotImplemented_15.txt

@@ -0,0 +1,110 @@
+package
+
+public abstract class AIBase : IBase {
+    public constructor AIBase()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract override /*1*/ /*fake_override*/ fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public abstract class AIIntermediate : AIBase, IBaseEx {
+    public constructor AIIntermediate()
+    public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*2*/ /*fake_override*/ fun foo(): kotlin.Unit
+    public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public abstract class AILeft : ILeft {
+    public constructor AILeft()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract override /*1*/ /*fake_override*/ fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class AILeftImpl : AILeft, IRight {
+    public constructor AILeftImpl()
+    public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*2*/ /*fake_override*/ fun foo(): kotlin.Unit
+    public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public abstract class ALeft {
+    public constructor ALeft()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public abstract class CAbstract : ALeft, IRight {
+    public constructor CAbstract()
+    public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*2*/ /*fake_override*/ fun foo(): kotlin.Unit
+    public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class CDerived : ALeft, IRight {
+    public constructor CDerived()
+    public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*2*/ /*fake_override*/ fun foo(): kotlin.Unit
+    public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class CDerivedFromAbstract : CAbstract {
+    public constructor CDerivedFromAbstract()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface IBase {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface IBaseEx : IBase {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface ILeft {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface IRight {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class Impl : AIIntermediate {
+    public constructor Impl()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class RightLeft : ILeft, IRight {
+    public constructor RightLeft()
+    public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*2*/ /*fake_override*/ fun foo(): kotlin.Unit
+    public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
+}
+

compiler/testData/diagnostics/tests/java8Overrides/kt45508.fir.kt

@@ -0,0 +1,29 @@
+interface A {
+    fun foo(): Any
+}
+
+interface B {
+    fun foo(): String = "A"
+}
+
+open class D: B
+
+open class C: D(), A
+
+// ------------
+
+class Test: Impl(), CProvider
+
+open class CC
+
+class DD: CC()
+
+interface CProvider {
+    fun getC(): CC
+}
+
+interface DProvider {
+    fun getC(): DD = DD()
+}
+
+open class Impl: DProvider

compiler/testData/diagnostics/tests/java8Overrides/kt45508.kt

@@ -0,0 +1,29 @@
+interface A {
+    fun foo(): Any
+}
+
+interface B {
+    fun foo(): String = "A"
+}
+
+open class D: B
+
+open <!MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED_WARNING!>class C<!>: D(), A
+
+// ------------
+
+<!MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED_WARNING!>class Test<!>: Impl(), CProvider
+
+open class CC
+
+class DD: CC()
+
+interface CProvider {
+    fun getC(): CC
+}
+
+interface DProvider {
+    fun getC(): DD = DD()
+}
+
+open class Impl: DProvider

compiler/testData/diagnostics/tests/java8Overrides/kt45508.txt

@@ -0,0 +1,75 @@
+package
+
+public interface A {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract fun foo(): kotlin.Any
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface B {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open fun foo(): kotlin.String
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public open class C : D, A {
+    public constructor C()
+    public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*2*/ /*fake_override*/ fun foo(): kotlin.String
+    public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public open class CC {
+    public constructor CC()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface CProvider {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract fun getC(): CC
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public open class D : B {
+    public constructor D()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun foo(): kotlin.String
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class DD : CC {
+    public constructor DD()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface DProvider {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open fun getC(): DD
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public open class Impl : DProvider {
+    public constructor Impl()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun getC(): DD
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class Test : Impl, CProvider {
+    public constructor Test()
+    public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*2*/ /*fake_override*/ fun getC(): DD
+    public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
+}

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

@@ -16846,6 +16846,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                 runTest("compiler/testData/diagnostics/tests/java8Overrides/abstractBaseClassMemberNotImplemented.kt");
             }
 
+            @Test
+            @TestMetadata("abstractBaseClassMemberNotImplemented_15.kt")
+            public void testAbstractBaseClassMemberNotImplemented_15() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/java8Overrides/abstractBaseClassMemberNotImplemented_15.kt");
+            }
+
             @Test
             @TestMetadata("abstractVsAbstract.kt")
             public void testAbstractVsAbstract() throws Exception {
@@ -16875,6 +16881,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                 runTest("compiler/testData/diagnostics/tests/java8Overrides/implementingMethodOfAny.kt");
             }
 
+            @Test
+            @TestMetadata("kt45508.kt")
+            public void testKt45508() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/java8Overrides/kt45508.kt");
+            }
+
             @Test
             @TestMetadata("notAMethodOfAny.kt")
             public void testNotAMethodOfAny() throws Exception {

compiler/util/src/org/jetbrains/kotlin/config/LanguageVersionSettings.kt

@@ -204,6 +204,7 @@ enum class LanguageFeature(
 
     DefinitelyNotNullTypeParameters(KOTLIN_1_6),
     ProhibitUsingNullableTypeParameterAgainstNotNullAnnotated(KOTLIN_1_6, kind = BUG_FIX),
+    AbstractClassMemberNotImplementedWithIntermediateAbstractClass(KOTLIN_1_6, kind = BUG_FIX),
 
     SuspendFunctionAsSupertype(KOTLIN_1_6),
 

idea/src/org/jetbrains/kotlin/idea/quickfix/QuickFixRegistrar.kt

@@ -77,6 +77,7 @@ class QuickFixRegistrar : QuickFixContributor {
         MUST_BE_INITIALIZED_OR_BE_ABSTRACT.registerFactory(addAbstractModifierFactory)
         ABSTRACT_MEMBER_NOT_IMPLEMENTED.registerFactory(addAbstractModifierFactory)
         ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED.registerFactory(addAbstractModifierFactory)
+        ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED_WARNING.registerFactory(addAbstractModifierFactory)
 
         MUST_BE_INITIALIZED_OR_BE_ABSTRACT.registerFactory(InitializePropertyQuickFixFactory)
         MUST_BE_INITIALIZED.registerFactory(InitializePropertyQuickFixFactory)
@@ -213,7 +214,9 @@ class QuickFixRegistrar : QuickFixContributor {
         val implementMembersAsParametersHandler = ImplementAsConstructorParameter()
         ABSTRACT_MEMBER_NOT_IMPLEMENTED.registerActions(implementMembersHandler, implementMembersAsParametersHandler)
         ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED.registerActions(implementMembersHandler, implementMembersAsParametersHandler)
+        ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED_WARNING.registerActions(implementMembersHandler, implementMembersAsParametersHandler)
         MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED.registerActions(implementMembersHandler, implementMembersAsParametersHandler)
+        MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED_WARNING.registerActions(implementMembersHandler, implementMembersAsParametersHandler)
         MANY_IMPL_MEMBER_NOT_IMPLEMENTED.registerActions(implementMembersHandler)
 
         VAL_WITH_SETTER.registerFactory(ChangeVariableMutabilityFix.VAL_WITH_SETTER_FACTORY)