'sealed' is now not 'final' by default + related code changes #KT-10266 Fixed

compiler/frontend/src/org/jetbrains/kotlin/cfg/WhenChecker.java

@@ -25,7 +25,6 @@ import org.jetbrains.kotlin.descriptors.ClassKind;
 import org.jetbrains.kotlin.descriptors.DeclarationDescriptor;
 import org.jetbrains.kotlin.descriptors.Modality;
 import org.jetbrains.kotlin.diagnostics.Errors;
-import org.jetbrains.kotlin.lexer.KtToken;
 import org.jetbrains.kotlin.lexer.KtTokens;
 import org.jetbrains.kotlin.psi.*;
 import org.jetbrains.kotlin.resolve.BindingContext;
@@ -60,7 +59,7 @@ public final class WhenChecker {
         if (type == null) return null;
         ClassDescriptor classDescriptor = TypeUtils.getClassDescriptor(type);
         if (classDescriptor == null) return null;
-        if (classDescriptor.getKind() != ClassKind.ENUM_CLASS || classDescriptor.getModality().isOverridable()) return null;
+        if (classDescriptor.getKind() != ClassKind.ENUM_CLASS) return null;
 
         return classDescriptor;
     }

compiler/frontend/src/org/jetbrains/kotlin/resolve/BodyResolver.java

@@ -488,8 +488,8 @@ public class BodyResolver {
                     trace.report(SINGLETON_IN_SUPERTYPE.on(typeReference));
                 }
             }
-            else if (constructor.isFinal() && !allowedFinalSupertypes.contains(constructor)) {
+            else if (!allowedFinalSupertypes.contains(constructor)) {
-                if (classDescriptor.getModality() == Modality.SEALED) {
+                if (classDescriptor != null && classDescriptor.getModality() == Modality.SEALED) {
                     DeclarationDescriptor containingDescriptor = supertypeOwner.getContainingDeclaration();
                     while (containingDescriptor != null && containingDescriptor != classDescriptor) {
                         containingDescriptor = containingDescriptor.getContainingDeclaration();
@@ -501,7 +501,7 @@ public class BodyResolver {
                         trace.report(SEALED_SUPERTYPE_IN_LOCAL_CLASS.on(typeReference));
                     }
                 }
-                else {
+                else if (constructor.isFinal()) {
                     trace.report(FINAL_SUPERTYPE.on(typeReference));
                 }
             }

compiler/frontend/src/org/jetbrains/kotlin/resolve/DescriptorResolver.java

@@ -614,10 +614,6 @@ public class DescriptorResolver {
     ) {
         if (DeclarationsCheckerKt.checkNotEnumEntry(upperBound, trace)) return;
         if (!TypeUtils.canHaveSubtypes(KotlinTypeChecker.DEFAULT, upperBoundType)) {
-            ClassifierDescriptor descriptor = upperBoundType.getConstructor().getDeclarationDescriptor();
-            if (descriptor instanceof ClassDescriptor) {
-                if (((ClassDescriptor) descriptor).getModality() == Modality.SEALED) return;
-            }
             trace.report(FINAL_UPPER_BOUND.on(upperBound, upperBoundType));
         }
         if (DynamicTypesKt.isDynamic(upperBoundType)) {

compiler/frontend/src/org/jetbrains/kotlin/types/expressions/PatternMatchingTypingVisitor.java

@@ -345,7 +345,7 @@ public class PatternMatchingTypingVisitor extends ExpressionTypingVisitor {
     /*
      * (a: SubjectType) is Type
      */
-    private void checkTypeCompatibility(
+    private static void checkTypeCompatibility(
             @NotNull ExpressionTypingContext context,
             @Nullable KotlinType type,
             @NotNull KotlinType subjectType,

compiler/testData/diagnostics/tests/sealed/NonExhaustiveWhenWithAdditionalCase.kt

@@ -15,7 +15,7 @@ sealed class Sealed(val x: Int) {
 fun foo(s: Sealed): Int {
     return <!NO_ELSE_IN_WHEN!>when<!>(s) {
         is Sealed.First -> 1
-        !is <!INCOMPATIBLE_TYPES!>Sealed.ITuple<!> -> 0
+        !is Sealed.ITuple -> 0
         // else required
     }
 }

compiler/testData/diagnostics/tests/sealed/WithInterface.kt

@@ -0,0 +1,10 @@
+interface Parent
+interface Child : Parent
+
+sealed class Page : Parent {
+  object One : Page(), Child
+  object Two : Page(), Child
+}
+
+// Ok: page is a Parent so it can be easily a Child
+fun test(page: Page): Boolean = page is Child

compiler/testData/diagnostics/tests/sealed/WithInterface.txt

@@ -0,0 +1,36 @@
+package
+
+public fun test(/*0*/ page: Page): kotlin.Boolean
+
+public interface Child : Parent {
+    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 Page : Parent {
+    private constructor Page()
+    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 object One : Page, Child {
+        private constructor One()
+        public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    public object Two : Page, Child {
+        private constructor Two()
+        public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+}
+
+public interface Parent {
+    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/tests/smartCasts/openInSealed.kt

@@ -0,0 +1,8 @@
+sealed class My(open val x: Int?) {
+    init {
+        if (x != null) {
+            // Should be error: property is open
+            <!SMARTCAST_IMPOSSIBLE!>x<!>.hashCode()
+        }
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/openInSealed.txt

@@ -0,0 +1,9 @@
+package
+
+public sealed class My {
+    private constructor My(/*0*/ x: kotlin.Int?)
+    public open val x: kotlin.Int?
+    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/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java

@@ -14300,6 +14300,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/sealed/WhenOnEmptySealed.kt");
                 doTest(fileName);
             }
+
+            @TestMetadata("WithInterface.kt")
+            public void testWithInterface() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/sealed/WithInterface.kt");
+                doTest(fileName);
+            }
         }
 
         @TestMetadata("compiler/testData/diagnostics/tests/secondaryConstructors")
@@ -15132,6 +15138,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("openInSealed.kt")
+            public void testOpenInSealed() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/smartCasts/openInSealed.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("ownerDeclaresBothModifies.kt")
             public void testOwnerDeclaresBothModifies() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/smartCasts/ownerDeclaresBothModifies.kt");

core/descriptors/src/org/jetbrains/kotlin/descriptors/Modality.kt

@@ -16,10 +16,12 @@
 
 package org.jetbrains.kotlin.descriptors
 
-enum class Modality private constructor(@get:JvmName("isOverridable") val isOverridable: Boolean) {
+// For sealed classes, isOverridable is false but isOverridableByMembers is true
+enum class Modality private constructor(val isOverridable: Boolean) {
     // THE ORDER OF ENTRIES MATTERS HERE
     FINAL(false),
-    SEALED(false),
+    // NB: class can be sealed but not function or property
+    SEALED(true),
     OPEN(true),
     ABSTRACT(true);