[cfe] Emit error for mixing in class outside of its library except mixin classes.

It is an error to mix in a class declaration that does not have the 'mixin' modifier, outside of its library for class declarations in a library version lower than sealed class' release version.

Change-Id: I318bb243705748eae60482b6c3513669f1cbb90c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/275440
Reviewed-by: Johnni Winther <[email protected]>

Author: kallentu

pkg/front_end/lib/src/fasta/source/source_loader.dart

@@ -2072,23 +2072,35 @@ severity: $severity
               noLength);
         }
       } else if (supertype is ClassBuilder &&
-          cls.libraryBuilder.libraryFeatures.sealedClass.isEnabled) {
-        // Check for implicit class mixins.
-        TypeBuilder? mixedInType = cls.mixedInTypeBuilder;
-        if (cls.isMixinApplication &&
-            mixedInType != null &&
-            mixedInType.declaration == supertype &&
-            !supertype.isMixinDeclaration) {
-          cls.addProblem(
-              templateCantUseClassAsMixin
-                  .withArguments(supertype.fullNameForErrors),
-              cls.charOffset,
-              noLength);
+          supertype.libraryBuilder.origin != cls.libraryBuilder.origin) {
+        if (supertype.libraryBuilder.library.languageVersion >=
+                ExperimentalFlag.classModifiers.experimentEnabledVersion &&
+            // TODO (kallentu): Only enable with classes that have the
+            // 'classModifiers' experiment enabled right now, otherwise the
+            // change breaks core libraries. Remove when class modifiers are
+            // done.
+            cls.libraryBuilder.libraryFeatures.classModifiers.isEnabled) {
+          // Check for implicit class mixins.
+          // Only classes declared with a 'mixin' modifier are allowed to be
+          // mixed in outside of its library.
+          TypeBuilder? mixedInType = cls.mixedInTypeBuilder;
+          bool isSuperTypeImplicitMixin = mixedInType != null &&
+              mixedInType.declaration == supertype &&
+              !supertype.isMixinDeclaration;
+          if (cls.isMixinApplication &&
+              isSuperTypeImplicitMixin &&
+              !supertype.isMixinClass) {
+            cls.addProblem(
+                templateCantUseClassAsMixin
+                    .withArguments(supertype.fullNameForErrors),
+                cls.charOffset,
+                noLength);
+          }
         }
 
         // Report error for subtyping outside of sealed supertype's library.
-        if (supertype.isSealed &&
-            supertype.libraryBuilder.origin != cls.libraryBuilder.origin) {
+        if (cls.libraryBuilder.libraryFeatures.sealedClass.isEnabled &&
+            supertype.isSealed) {
           // If the class is a mixin declaration with an `on` clause which is
           // the supertype we are evaluating right now, we want to avoid
           // reporting an error.

pkg/front_end/messages.status

@@ -65,6 +65,7 @@ CantInferPackagesFromPackageUri/example: Fail
 CantInferTypeDueToCircularity/example: Fail
 CantReadFile/part_wrapped_script: Fail # Importing file in the (now) part.
 CantUseClassAsMixin/analyzerCode: Fail
+CantUseClassAsMixin/part_wrapped_script: Fail # Uses imports
 CantUseControlFlowOrSpreadAsConstant/example: Fail
 CantUseDeferredPrefixAsConstant/part_wrapped_script: Fail # Importing file in the (now) part.
 CantUsePrefixAsExpression/part_wrapped_script: Fail # Importing file in the (now) part.

pkg/front_end/messages.yaml

@@ -6021,10 +6021,13 @@ SealedMixinSubtypeOutsideOfLibrary:
 
 CantUseClassAsMixin:
   problemMessage: "Class '#name' can't be used as a mixin."
-  experiments: sealed-class
-  script: |
-    class A {}
-    class B with A {}
+  experiments: class-modifiers
+  script:
+    main.dart:
+      import 'lib.dart';
+      class B with A {}
+    lib.dart:
+      class A {}
 
 UnspecifiedGetterNameInObjectPattern:
   problemMessage: "The getter name is not specified explicitly, and the pattern is not a variable. Try specifying the getter name explicitly, or using a variable pattern."
@@ -6033,4 +6036,3 @@ UnspecifiedGetterNameInObjectPattern:
   script: |
     abstract class A { int get foo;}
     test(dynamic x) { if (x case A(: 0)) {} }
-

pkg/front_end/parser_testcases/mixin_class/mixin_class.dart renamed to pkg/front_end/parser_testcases/class_modifiers/mixin/mixin_class.dart

@@ -8,3 +8,13 @@ abstract mixin class B {}
 
 mixin M {}
 mixin class C = Object with M;
+
+class AWith with A {}
+
+class BWith with B {}
+
+class CWith with C {}
+
+class MultipleWithMixin with A, M {}
+
+class MultipleWithAnotherClass with A, B {}

pkg/front_end/parser_testcases/mixin_class/mixin_class.dart.expect renamed to pkg/front_end/parser_testcases/class_modifiers/mixin/mixin_class.dart.expect

@@ -19,3 +19,63 @@ mixin class C = core::Object with self::M /*hasConstConstructor*/  {
     : super core::Object::•()
     ;
 }
+abstract class _AWith&Object&A = core::Object with self::A /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_AWith&Object&A
+    : super core::Object::•()
+    ;
+}
+class AWith extends self::_AWith&Object&A {
+  synthetic constructor •() → self::AWith
+    : super self::_AWith&Object&A::•()
+    ;
+}
+abstract class _BWith&Object&B = core::Object with self::B /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_BWith&Object&B
+    : super core::Object::•()
+    ;
+}
+class BWith extends self::_BWith&Object&B {
+  synthetic constructor •() → self::BWith
+    : super self::_BWith&Object&B::•()
+    ;
+}
+abstract class _CWith&Object&C = core::Object with self::C /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_CWith&Object&C
+    : super core::Object::•()
+    ;
+}
+class CWith extends self::_CWith&Object&C {
+  synthetic constructor •() → self::CWith
+    : super self::_CWith&Object&C::•()
+    ;
+}
+abstract class _MultipleWithMixin&Object&A = core::Object with self::A /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_MultipleWithMixin&Object&A
+    : super core::Object::•()
+    ;
+}
+abstract class _MultipleWithMixin&Object&A&M = self::_MultipleWithMixin&Object&A with self::M /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_MultipleWithMixin&Object&A&M
+    : super self::_MultipleWithMixin&Object&A::•()
+    ;
+}
+class MultipleWithMixin extends self::_MultipleWithMixin&Object&A&M {
+  synthetic constructor •() → self::MultipleWithMixin
+    : super self::_MultipleWithMixin&Object&A&M::•()
+    ;
+}
+abstract class _MultipleWithAnotherClass&Object&A = core::Object with self::A /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_MultipleWithAnotherClass&Object&A
+    : super core::Object::•()
+    ;
+}
+abstract class _MultipleWithAnotherClass&Object&A&B = self::_MultipleWithAnotherClass&Object&A with self::B /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_MultipleWithAnotherClass&Object&A&B
+    : super self::_MultipleWithAnotherClass&Object&A::•()
+    ;
+}
+class MultipleWithAnotherClass extends self::_MultipleWithAnotherClass&Object&A&B {
+  synthetic constructor •() → self::MultipleWithAnotherClass
+    : super self::_MultipleWithAnotherClass&Object&A&B::•()
+    ;
+}

pkg/front_end/parser_testcases/mixin_class/mixin_class.dart.intertwined.expect renamed to pkg/front_end/parser_testcases/class_modifiers/mixin/mixin_class.dart.intertwined.expect

@@ -19,3 +19,63 @@ mixin class C extends core::Object implements self::M /*isEliminatedMixin,hasCon
     : super core::Object::•()
     ;
 }
+abstract class _AWith&Object&A extends core::Object implements self::A /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_AWith&Object&A
+    : super core::Object::•()
+    ;
+}
+class AWith extends self::_AWith&Object&A {
+  synthetic constructor •() → self::AWith
+    : super self::_AWith&Object&A::•()
+    ;
+}
+abstract class _BWith&Object&B extends core::Object implements self::B /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_BWith&Object&B
+    : super core::Object::•()
+    ;
+}
+class BWith extends self::_BWith&Object&B {
+  synthetic constructor •() → self::BWith
+    : super self::_BWith&Object&B::•()
+    ;
+}
+abstract class _CWith&Object&C extends core::Object implements self::C /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_CWith&Object&C
+    : super core::Object::•()
+    ;
+}
+class CWith extends self::_CWith&Object&C {
+  synthetic constructor •() → self::CWith
+    : super self::_CWith&Object&C::•()
+    ;
+}
+abstract class _MultipleWithMixin&Object&A extends core::Object implements self::A /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_MultipleWithMixin&Object&A
+    : super core::Object::•()
+    ;
+}
+abstract class _MultipleWithMixin&Object&A&M extends self::_MultipleWithMixin&Object&A implements self::M /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_MultipleWithMixin&Object&A&M
+    : super self::_MultipleWithMixin&Object&A::•()
+    ;
+}
+class MultipleWithMixin extends self::_MultipleWithMixin&Object&A&M {
+  synthetic constructor •() → self::MultipleWithMixin
+    : super self::_MultipleWithMixin&Object&A&M::•()
+    ;
+}
+abstract class _MultipleWithAnotherClass&Object&A extends core::Object implements self::A /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_MultipleWithAnotherClass&Object&A
+    : super core::Object::•()
+    ;
+}
+abstract class _MultipleWithAnotherClass&Object&A&B extends self::_MultipleWithAnotherClass&Object&A implements self::B /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_MultipleWithAnotherClass&Object&A&B
+    : super self::_MultipleWithAnotherClass&Object&A::•()
+    ;
+}
+class MultipleWithAnotherClass extends self::_MultipleWithAnotherClass&Object&A&B {
+  synthetic constructor •() → self::MultipleWithAnotherClass
+    : super self::_MultipleWithAnotherClass&Object&A&B::•()
+    ;
+}

pkg/front_end/parser_testcases/mixin_class/mixin_class.dart.parser.expect renamed to pkg/front_end/parser_testcases/class_modifiers/mixin/mixin_class.dart.parser.expect

@@ -4,3 +4,8 @@ abstract mixin class B {}
 mixin M {}
 mixin
 class C = Object with M;
+class AWith with A {}
+class BWith with B {}
+class CWith with C {}
+class MultipleWithMixin with A, M {}
+class MultipleWithAnotherClass with A, B {}

pkg/front_end/parser_testcases/mixin_class/mixin_class.dart.scanner.expect renamed to pkg/front_end/parser_testcases/class_modifiers/mixin/mixin_class.dart.scanner.expect

@@ -19,3 +19,63 @@ mixin class C = core::Object with self::M /*hasConstConstructor*/  {
     : super core::Object::•()
     ;
 }
+abstract class _AWith&Object&A = core::Object with self::A /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_AWith&Object&A
+    : super core::Object::•()
+    ;
+}
+class AWith extends self::_AWith&Object&A {
+  synthetic constructor •() → self::AWith
+    : super self::_AWith&Object&A::•()
+    ;
+}
+abstract class _BWith&Object&B = core::Object with self::B /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_BWith&Object&B
+    : super core::Object::•()
+    ;
+}
+class BWith extends self::_BWith&Object&B {
+  synthetic constructor •() → self::BWith
+    : super self::_BWith&Object&B::•()
+    ;
+}
+abstract class _CWith&Object&C = core::Object with self::C /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_CWith&Object&C
+    : super core::Object::•()
+    ;
+}
+class CWith extends self::_CWith&Object&C {
+  synthetic constructor •() → self::CWith
+    : super self::_CWith&Object&C::•()
+    ;
+}
+abstract class _MultipleWithMixin&Object&A = core::Object with self::A /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_MultipleWithMixin&Object&A
+    : super core::Object::•()
+    ;
+}
+abstract class _MultipleWithMixin&Object&A&M = self::_MultipleWithMixin&Object&A with self::M /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_MultipleWithMixin&Object&A&M
+    : super self::_MultipleWithMixin&Object&A::•()
+    ;
+}
+class MultipleWithMixin extends self::_MultipleWithMixin&Object&A&M {
+  synthetic constructor •() → self::MultipleWithMixin
+    : super self::_MultipleWithMixin&Object&A&M::•()
+    ;
+}
+abstract class _MultipleWithAnotherClass&Object&A = core::Object with self::A /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_MultipleWithAnotherClass&Object&A
+    : super core::Object::•()
+    ;
+}
+abstract class _MultipleWithAnotherClass&Object&A&B = self::_MultipleWithAnotherClass&Object&A with self::B /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_MultipleWithAnotherClass&Object&A&B
+    : super self::_MultipleWithAnotherClass&Object&A::•()
+    ;
+}
+class MultipleWithAnotherClass extends self::_MultipleWithAnotherClass&Object&A&B {
+  synthetic constructor •() → self::MultipleWithAnotherClass
+    : super self::_MultipleWithAnotherClass&Object&A&B::•()
+    ;
+}

pkg/front_end/testcases/class_modifiers/mixin/mixin_class_declaration.dart

@@ -19,3 +19,63 @@ mixin class C = core::Object with self::M /*hasConstConstructor*/  {
     : super core::Object::•()
     ;
 }
+abstract class _AWith&Object&A = core::Object with self::A /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_AWith&Object&A
+    : super core::Object::•()
+    ;
+}
+class AWith extends self::_AWith&Object&A {
+  synthetic constructor •() → self::AWith
+    : super self::_AWith&Object&A::•()
+    ;
+}
+abstract class _BWith&Object&B = core::Object with self::B /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_BWith&Object&B
+    : super core::Object::•()
+    ;
+}
+class BWith extends self::_BWith&Object&B {
+  synthetic constructor •() → self::BWith
+    : super self::_BWith&Object&B::•()
+    ;
+}
+abstract class _CWith&Object&C = core::Object with self::C /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_CWith&Object&C
+    : super core::Object::•()
+    ;
+}
+class CWith extends self::_CWith&Object&C {
+  synthetic constructor •() → self::CWith
+    : super self::_CWith&Object&C::•()
+    ;
+}
+abstract class _MultipleWithMixin&Object&A = core::Object with self::A /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_MultipleWithMixin&Object&A
+    : super core::Object::•()
+    ;
+}
+abstract class _MultipleWithMixin&Object&A&M = self::_MultipleWithMixin&Object&A with self::M /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_MultipleWithMixin&Object&A&M
+    : super self::_MultipleWithMixin&Object&A::•()
+    ;
+}
+class MultipleWithMixin extends self::_MultipleWithMixin&Object&A&M {
+  synthetic constructor •() → self::MultipleWithMixin
+    : super self::_MultipleWithMixin&Object&A&M::•()
+    ;
+}
+abstract class _MultipleWithAnotherClass&Object&A = core::Object with self::A /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_MultipleWithAnotherClass&Object&A
+    : super core::Object::•()
+    ;
+}
+abstract class _MultipleWithAnotherClass&Object&A&B = self::_MultipleWithAnotherClass&Object&A with self::B /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_MultipleWithAnotherClass&Object&A&B
+    : super self::_MultipleWithAnotherClass&Object&A::•()
+    ;
+}
+class MultipleWithAnotherClass extends self::_MultipleWithAnotherClass&Object&A&B {
+  synthetic constructor •() → self::MultipleWithAnotherClass
+    : super self::_MultipleWithAnotherClass&Object&A&B::•()
+    ;
+}