[FE] Prohibit implementing java sealed classes

compiler/frontend.java/src/org/jetbrains/kotlin/resolve/jvm/checkers/ClassInheritsJavaSealedClassChecker.kt

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.resolve.jvm.checkers
+
+import org.jetbrains.kotlin.descriptors.ClassDescriptor
+import org.jetbrains.kotlin.descriptors.DeclarationDescriptor
+import org.jetbrains.kotlin.diagnostics.Errors
+import org.jetbrains.kotlin.load.java.lazy.descriptors.LazyJavaClassDescriptor
+import org.jetbrains.kotlin.psi.KtClassOrObject
+import org.jetbrains.kotlin.psi.KtDeclaration
+import org.jetbrains.kotlin.resolve.bindingContextUtil.getAbbreviatedTypeOrType
+import org.jetbrains.kotlin.resolve.checkers.DeclarationChecker
+import org.jetbrains.kotlin.resolve.checkers.DeclarationCheckerContext
+
+object ClassInheritsJavaSealedClassChecker : DeclarationChecker {
+    override fun check(declaration: KtDeclaration, descriptor: DeclarationDescriptor, context: DeclarationCheckerContext) {
+        if (descriptor !is ClassDescriptor || declaration !is KtClassOrObject) return
+        for (superTypeListEntry in declaration.superTypeListEntries) {
+            val typeReference = superTypeListEntry.typeReference ?: continue
+            val superType = typeReference.getAbbreviatedTypeOrType(context.trace.bindingContext)?.unwrap() ?: continue
+            val superClass = superType.constructor.declarationDescriptor as? LazyJavaClassDescriptor ?: continue
+            if (superClass.jClass.isSealed) {
+                context.trace.report(Errors.CLASS_INHERITS_JAVA_SEALED_CLASS.on(typeReference))
+            }
+        }
+    }
+}

compiler/frontend.java/src/org/jetbrains/kotlin/resolve/jvm/platform/JvmPlatformConfigurator.kt

@@ -41,7 +41,8 @@ object JvmPlatformConfigurator : PlatformConfiguratorBase(
         JvmMultifileClassStateChecker,
         SynchronizedOnInlineMethodChecker,
         DefaultCheckerInTailrec,
-        FunctionDelegateMemberNameClashChecker
+        FunctionDelegateMemberNameClashChecker,
+        ClassInheritsJavaSealedClassChecker
     ),
 
     additionalCallCheckers = listOf(

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

@@ -427,6 +427,7 @@ public interface Errors {
     DiagnosticFactory0<KtTypeReference> SEALED_SUPERTYPE = DiagnosticFactory0.create(ERROR);
     DiagnosticFactory0<KtTypeReference> SEALED_SUPERTYPE_IN_LOCAL_CLASS = DiagnosticFactory0.create(ERROR);
     DiagnosticFactory2<KtTypeReference, FqName, FqName> SEALED_INHERITOR_IN_DIFFERENT_PACKAGE = DiagnosticFactory2.create(ERROR);
+    DiagnosticFactory0<KtTypeReference> CLASS_INHERITS_JAVA_SEALED_CLASS = DiagnosticFactory0.create(ERROR);
 
     // Companion objects
 

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

@@ -634,6 +634,7 @@ public class DefaultErrorMessages {
         MAP.put(SEALED_SUPERTYPE, "This type is sealed, so it can be inherited by only its own nested classes or objects");
         MAP.put(SEALED_SUPERTYPE_IN_LOCAL_CLASS, "Local class cannot extend a sealed class");
         MAP.put(SEALED_INHERITOR_IN_DIFFERENT_PACKAGE, "Inheritor of sealed class or interface declared in package {1} but it must be in package {2} where base class is declared", TO_STRING, TO_STRING);
+        MAP.put(CLASS_INHERITS_JAVA_SEALED_CLASS, "Inheritance of java sealed classes is prohibited");
         MAP.put(SINGLETON_IN_SUPERTYPE, "Cannot inherit from a singleton");
         MAP.put(CLASS_CANNOT_BE_EXTENDED_DIRECTLY, "Class {0} cannot be extended directly", NAME);
 

compiler/testData/diagnostics/testsWithJava15/sealedClasses/kotlinInheritsJavaClass.kt

@@ -0,0 +1,11 @@
+// ISSUE: KT-41215
+
+// FILE: Base.java
+public sealed class Base permits A, B {}
+
+// FILE: A.java
+public final class A extends Base {}
+
+// FILE: B.kt
+
+class B : <!CLASS_INHERITS_JAVA_SEALED_CLASS!>Base<!>()

compiler/testData/diagnostics/testsWithJava15/sealedClasses/kotlinInheritsJavaClass.txt

@@ -0,0 +1,22 @@
+package
+
+public final class A : Base {
+    public constructor A()
+    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 final class B : Base {
+    public constructor B()
+    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 sealed class Base {
+    public constructor Base()
+    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
+}

compiler/testData/diagnostics/testsWithJava15/sealedClasses/kotlinInheritsJavaInterface.kt

@@ -0,0 +1,11 @@
+// ISSUE: KT-41215
+
+// FILE: Base.java
+public sealed interface Base permits A, B {}
+
+// FILE: A.java
+public final class A extends Base {}
+
+// FILE: B.kt
+
+class B : <!CLASS_INHERITS_JAVA_SEALED_CLASS!>Base<!>

compiler/testData/diagnostics/testsWithJava15/sealedClasses/kotlinInheritsJavaInterface.txt

@@ -0,0 +1,21 @@
+package
+
+public final class A : Base {
+    public constructor A()
+    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 final class B : Base {
+    public constructor B()
+    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 sealed interface Base {
+    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
+}