Data classes cannot have class supertypes, a new test, relevant test fixes

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

@@ -173,6 +173,7 @@ public interface Errors {
 
 
     DiagnosticFactory0<JetTypeReference> FINAL_SUPERTYPE = DiagnosticFactory0.create(ERROR);
+    DiagnosticFactory0<JetTypeReference> DATA_CLASS_CANNOT_HAVE_CLASS_SUPERTYPES = DiagnosticFactory0.create(WARNING);
     DiagnosticFactory0<JetTypeReference> SINGLETON_IN_SUPERTYPE = DiagnosticFactory0.create(ERROR);
     DiagnosticFactory0<JetNullableType> NULLABLE_SUPERTYPE = DiagnosticFactory0.create(ERROR, NULLABLE_TYPE);
     DiagnosticFactory0<JetTypeReference> DYNAMIC_SUPERTYPE = DiagnosticFactory0.create(ERROR);

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

@@ -415,6 +415,7 @@ public class DefaultErrorMessages {
         MAP.put(TRAIT_WITH_SUPERCLASS, "An interface cannot inherit from a class");
         MAP.put(SUPERTYPE_APPEARS_TWICE, "A supertype appears twice");
         MAP.put(FINAL_SUPERTYPE, "This type is final, so it cannot be inherited from");
+        MAP.put(DATA_CLASS_CANNOT_HAVE_CLASS_SUPERTYPES, "Data class inheritance from other classes is deprecated");
         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(SINGLETON_IN_SUPERTYPE, "Cannot inherit from a singleton");

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

@@ -440,6 +440,10 @@ public class BodyResolver {
                         trace.report(TRAIT_WITH_SUPERCLASS.on(typeReference));
                         addSupertype = false;
                     }
+                    else if (jetClass.hasModifier(JetTokens.DATA_KEYWORD)) {
+                        trace.report(DATA_CLASS_CANNOT_HAVE_CLASS_SUPERTYPES.on(typeReference));
+                        addSupertype = false;
+                    }
 
                     if (classAppeared) {
                         trace.report(MANY_CLASSES_IN_SUPERTYPE_LIST.on(typeReference));

compiler/testData/diagnostics/tests/dataClasses/dataInheritance.kt

@@ -0,0 +1,11 @@
+interface Allowed
+
+open class NotAllowed
+
+abstract data class Base(val x: Int)
+
+class Derived: Base(42)
+
+<!DATA_CLASS_OVERRIDE_CONFLICT!>data<!> class Nasty(x: Int, val y: Int): <!DATA_CLASS_CANNOT_HAVE_CLASS_SUPERTYPES!>Base<!>(x)
+
+data class Complex(val y: Int): Allowed, <!DATA_CLASS_CANNOT_HAVE_CLASS_SUPERTYPES!>NotAllowed<!>()

compiler/testData/diagnostics/tests/dataClasses/dataInheritance.txt

@@ -0,0 +1,56 @@
+package
+
+public interface Allowed {
+    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
+}
+
+@kotlin.data() public abstract class Base {
+    public constructor Base(/*0*/ x: kotlin.Int)
+    public final val x: kotlin.Int
+    public final /*synthesized*/ fun component1(): kotlin.Int
+    public final /*synthesized*/ fun copy(/*0*/ x: kotlin.Int = ...): 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
+}
+
+@kotlin.data() public final class Complex : Allowed, NotAllowed {
+    public constructor Complex(/*0*/ y: kotlin.Int)
+    public final val y: kotlin.Int
+    public final /*synthesized*/ fun component1(): kotlin.Int
+    public final /*synthesized*/ fun copy(/*0*/ y: kotlin.Int = ...): Complex
+    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 final class Derived : Base {
+    public constructor Derived()
+    public final override /*1*/ /*fake_override*/ val x: kotlin.Int
+    public final override /*1*/ /*fake_override*/ fun component1(): kotlin.Int
+    public final override /*1*/ /*fake_override*/ fun copy(/*0*/ x: kotlin.Int = ...): 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
+}
+
+@kotlin.data() public final class Nasty : Base {
+    public constructor Nasty(/*0*/ x: kotlin.Int, /*1*/ y: kotlin.Int)
+    public final override /*1*/ /*fake_override*/ val x: kotlin.Int
+    public final val y: kotlin.Int
+    public final override /*1*/ /*synthesized*/ fun component1(): kotlin.Int
+    public final override /*1*/ /*fake_override*/ fun copy(/*0*/ x: kotlin.Int = ...): Base
+    public final /*synthesized*/ fun copy(/*0*/ x: kotlin.Int, /*1*/ y: kotlin.Int = ...): Nasty
+    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 open class NotAllowed {
+    public constructor NotAllowed()
+    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/JetDiagnosticsTestGenerated.java

@@ -3330,6 +3330,12 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("dataInheritance.kt")
+            public void testDataInheritance() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/dataClasses/dataInheritance.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("emptyConstructor.kt")
             public void testEmptyConstructor() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/dataClasses/emptyConstructor.kt");