Allow data classes to inherit from other classes

#KT-10330 Fixed

compiler/frontend/src/org/jetbrains/kotlin/config/LanguageFeatureSettings.kt

@@ -25,7 +25,8 @@ enum class LanguageFeature(val sinceVersion: LanguageVersion) {
     LocalDelegatedProperties(KOTLIN_1_1),
     TopLevelSealedInheritance(KOTLIN_1_1),
     Coroutines(KOTLIN_1_1),
-    AdditionalBuiltInsMembers(KOTLIN_1_1)
+    AdditionalBuiltInsMembers(KOTLIN_1_1),
+    DataClassInheritance(KOTLIN_1_1),
     ;
 
     companion object {

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

@@ -26,6 +26,7 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.kotlin.builtins.FunctionTypesKt;
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns;
+import org.jetbrains.kotlin.config.LanguageFeature;
 import org.jetbrains.kotlin.config.LanguageFeatureSettings;
 import org.jetbrains.kotlin.descriptors.*;
 import org.jetbrains.kotlin.descriptors.impl.SyntheticFieldDescriptor;
@@ -475,7 +476,8 @@ public class BodyResolver {
                         trace.report(INTERFACE_WITH_SUPERCLASS.on(typeReference));
                         addSupertype = false;
                     }
-                    else if (ktClassOrObject.hasModifier(KtTokens.DATA_KEYWORD)) {
+                    else if (ktClassOrObject.hasModifier(KtTokens.DATA_KEYWORD) &&
+                             !languageFeatureSettings.supportsFeature(LanguageFeature.DataClassInheritance)) {
                         trace.report(DATA_CLASS_CANNOT_HAVE_CLASS_SUPERTYPES.on(typeReference));
                         addSupertype = false;
                     }

compiler/testData/codegen/box/dataClasses/nonTrivialFinalMemberInSuperClass.kt

@@ -1,6 +1,3 @@
-// TODO: remove the suppression once data classes can have supertypes
-@file:Suppress("DATA_CLASS_CANNOT_HAVE_CLASS_SUPERTYPES")
-
 abstract class Base {
     final override fun toString() = "OK"
     final override fun hashCode() = 42

compiler/testData/codegen/box/dataClasses/nonTrivialMemberInSuperClass.kt

@@ -1,6 +1,4 @@
 // See KT-6206 Always generate hashCode() and equals() for data classes even if base classes have non-trivial analogs
-// TODO: remove the suppression once data classes can have supertypes
-@file:Suppress("DATA_CLASS_CANNOT_HAVE_CLASS_SUPERTYPES")
 
 abstract class Base {
     override fun toString() = "Fail"

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

@@ -1,11 +1,13 @@
-interface Allowed
+interface SuperInterface
 
-open class NotAllowed
+open class SuperClass
 
 <!INCOMPATIBLE_MODIFIERS!>abstract<!> <!INCOMPATIBLE_MODIFIERS!>data<!> class Base(val x: Int)
 
 class Derived: Base(42)
 
-<!DATA_CLASS_OVERRIDE_CONFLICT!>data<!> class Nasty(val z: Int, val y: Int): <!DATA_CLASS_CANNOT_HAVE_CLASS_SUPERTYPES!>Base<!>(z)
+<!DATA_CLASS_OVERRIDE_CONFLICT!>data<!> class Nasty(val z: Int, val y: Int): Base(z)
 
-data class Complex(val y: Int): Allowed, <!DATA_CLASS_CANNOT_HAVE_CLASS_SUPERTYPES!>NotAllowed<!>()
+data class Complex(val y: Int): SuperInterface, SuperClass()
+
+<!DATA_CLASS_OVERRIDE_CONFLICT!>data<!> class SubData(val sss: String) : <!FINAL_SUPERTYPE!>Complex<!>(42)

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

@@ -1,11 +1,5 @@
 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
-}
-
 public abstract data class Base {
     public constructor Base(/*0*/ x: kotlin.Int)
     public final val x: kotlin.Int
@@ -16,7 +10,7 @@ public abstract data class Base {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-public final data class Complex : Allowed, NotAllowed {
+public final data class Complex : SuperInterface, SuperClass {
     public constructor Complex(/*0*/ y: kotlin.Int)
     public final val y: kotlin.Int
     public final operator /*synthesized*/ fun component1(): kotlin.Int
@@ -50,8 +44,26 @@ public final data class Nasty : Base {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
-public open class NotAllowed {
+public final data class SubData : Complex {
-    public constructor NotAllowed()
+    public constructor SubData(/*0*/ sss: kotlin.String)
+    public final val sss: kotlin.String
+    public final override /*1*/ /*fake_override*/ val y: kotlin.Int
+    public final override /*1*/ /*synthesized*/ fun component1(): kotlin.String
+    public final override /*1*/ /*fake_override*/ fun copy(/*0*/ y: kotlin.Int = ...): Complex
+    public final /*synthesized*/ fun copy(/*0*/ sss: kotlin.String = ...): SubData
+    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 SuperClass {
+    public constructor SuperClass()
+    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 SuperInterface {
     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/sourceCompatibility/noDataClassInheritance.kt

@@ -0,0 +1,13 @@
+// !LANGUAGE: -DataClassInheritance
+
+interface Allowed
+
+open class NotAllowed
+
+<!INCOMPATIBLE_MODIFIERS!>abstract<!> <!INCOMPATIBLE_MODIFIERS!>data<!> class Base(val x: Int)
+
+class Derived: Base(42)
+
+<!DATA_CLASS_OVERRIDE_CONFLICT!>data<!> class Nasty(val z: Int, val y: Int): <!DATA_CLASS_CANNOT_HAVE_CLASS_SUPERTYPES!>Base<!>(z)
+
+data class Complex(val y: Int): Allowed, <!DATA_CLASS_CANNOT_HAVE_CLASS_SUPERTYPES!>NotAllowed<!>()

compiler/testData/diagnostics/tests/sourceCompatibility/noDataClassInheritance.txt

@@ -0,0 +1,58 @@
+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
+}
+
+public abstract data class Base {
+    public constructor Base(/*0*/ x: kotlin.Int)
+    public final val x: kotlin.Int
+    public final operator /*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
+}
+
+public final data class Complex : Allowed, NotAllowed {
+    public constructor Complex(/*0*/ y: kotlin.Int)
+    public final val y: kotlin.Int
+    public final operator /*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
+}
+
+public final data class Nasty : Base {
+    public constructor Nasty(/*0*/ z: kotlin.Int, /*1*/ y: kotlin.Int)
+    public final override /*1*/ /*fake_override*/ val x: kotlin.Int
+    public final val y: kotlin.Int
+    public final val z: kotlin.Int
+    public final override /*1*/ /*synthesized*/ fun component1(): kotlin.Int
+    public final operator /*synthesized*/ fun component2(): kotlin.Int
+    public final override /*1*/ /*fake_override*/ fun copy(/*0*/ x: kotlin.Int = ...): Base
+    public final /*synthesized*/ fun copy(/*0*/ z: 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/DiagnosticsTestGenerated.java

@@ -18597,6 +18597,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/diagnostics/tests/sourceCompatibility"), Pattern.compile("^(.+)\\.kt$"), true);
             }
 
+            @TestMetadata("noDataClassInheritance.kt")
+            public void testNoDataClassInheritance() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/sourceCompatibility/noDataClassInheritance.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("noLocalDelegatedProperty.kt")
             public void testNoLocalDelegatedProperty() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/sourceCompatibility/noLocalDelegatedProperty.kt");