[FE] Prohibit inheritance of sealed classes in different module

KT-20423

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> SEALED_INHERITOR_IN_DIFFERENT_MODULE = DiagnosticFactory0.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(SEALED_INHERITOR_IN_DIFFERENT_MODULE, "Inheritance of sealed classes or interfaces from different module is prohibited");
         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/frontend/src/org/jetbrains/kotlin/resolve/PlatformConfiguratorBase.kt

@@ -42,6 +42,7 @@ private val DEFAULT_DECLARATION_CHECKERS = listOf(
     ContractDescriptionBlockChecker,
     PrivateInlineFunctionsReturningAnonymousObjectsChecker,
     SealedInheritorInSamePackageChecker,
+    SealedInheritorInSameModuleChecker,
     SealedInterfaceAllowedChecker,
 )
 

compiler/frontend/src/org/jetbrains/kotlin/resolve/checkers/SealedInheritorInSameModuleChecker.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.checkers
+
+import org.jetbrains.kotlin.descriptors.ClassDescriptor
+import org.jetbrains.kotlin.descriptors.DeclarationDescriptor
+import org.jetbrains.kotlin.descriptors.isSealed
+import org.jetbrains.kotlin.diagnostics.Errors
+import org.jetbrains.kotlin.psi.KtClassOrObject
+import org.jetbrains.kotlin.psi.KtDeclaration
+import org.jetbrains.kotlin.resolve.bindingContextUtil.getAbbreviatedTypeOrType
+import org.jetbrains.kotlin.resolve.descriptorUtil.module
+
+object SealedInheritorInSameModuleChecker : DeclarationChecker {
+    override fun check(declaration: KtDeclaration, descriptor: DeclarationDescriptor, context: DeclarationCheckerContext) {
+        if (descriptor !is ClassDescriptor || declaration !is KtClassOrObject) return
+        val currentModule = descriptor.module
+        for (superTypeListEntry in declaration.superTypeListEntries) {
+            val typeReference = superTypeListEntry.typeReference ?: continue
+            val superType = typeReference.getAbbreviatedTypeOrType(context.trace.bindingContext)?.unwrap() ?: continue
+            val superClass = superType.constructor.declarationDescriptor ?: continue
+            if (superClass.isSealed() && superClass.module != currentModule) {
+                context.trace.report(Errors.SEALED_INHERITOR_IN_DIFFERENT_MODULE.on(typeReference))
+            }
+        }
+    }
+}