[cfe] Add class modifiers to AST and dill files.

TEST=pkg/front_end/testcases/class_modifiers/...

Change-Id: I8befd64c359eb33a6acf003525b0c8cc6096df3d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/279331
Reviewed-by: Alexander Markov <alexmarkov@google.com>
Commit-Queue: Kallen Tu <kallentu@google.com>
Reviewed-by: Johnni Winther <johnniwinther@google.com>

pkg/front_end/lib/src/fasta/builder/class_builder.dart

@@ -93,6 +93,13 @@ abstract class ClassBuilder implements DeclarationBuilder, ClassMemberAccess {
 
   bool get isSealed;
 
+  bool get isBase;
+
+  bool get isInterface;
+
+  @override
+  bool get isFinal;
+
   bool get isAugmentation;
 
   bool get declaresConstConstructor;

pkg/front_end/lib/src/fasta/dill/dill_class_builder.dart

@@ -66,6 +66,15 @@ class DillClassBuilder extends ClassBuilderImpl {
   @override
   bool get isSealed => cls.isSealed;
 
+  @override
+  bool get isBase => cls.isBase;
+
+  @override
+  bool get isInterface => cls.isInterface;
+
+  @override
+  bool get isFinal => cls.isFinal;
+
   @override
   bool get isAugmentation => false;
 

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

@@ -1297,12 +1297,8 @@ class OutlineBuilder extends StackListenerImpl {
     TypeBuilder? supertype = nullIfParserRecovery(pop()) as TypeBuilder?;
     Token? mixinToken = pop(NullValues.Token) as Token?;
     Token? augmentToken = pop(NullValues.Token) as Token?;
-    // TODO(kallentu): AST work for class modifiers.
-    // ignore: unused_local_variable
     Token? finalToken = pop(NullValues.Token) as Token?;
-    // ignore: unused_local_variable
     Token? interfaceToken = pop(NullValues.Token) as Token?;
-    // ignore: unused_local_variable
     Token? baseToken = pop(NullValues.Token) as Token?;
     Token? sealedToken = pop(NullValues.Token) as Token?;
     // TODO(johnniwinther): Create builder for inline.
@@ -1403,6 +1399,9 @@ class OutlineBuilder extends StackListenerImpl {
             supertypeOffset,
             isMacro: macroToken != null,
             isSealed: sealedToken != null,
+            isBase: baseToken != null,
+            isInterface: interfaceToken != null,
+            isFinal: finalToken != null,
             isAugmentation: augmentToken != null,
             isMixinClass: mixinToken != null);
       }
@@ -1441,12 +1440,8 @@ class OutlineBuilder extends StackListenerImpl {
         nullIfParserRecovery(pop()) as List<TypeBuilder>?;
     List<TypeVariableBuilder>? typeVariables =
         pop(NullValues.TypeVariables) as List<TypeVariableBuilder>?;
-    // TODO(kallentu): Add AST support for mixin modifiers
-    // ignore: unused_local_variable
     Token? finalToken = pop(NullValues.Token) as Token?;
-    // ignore: unused_local_variable
     Token? interfaceToken = pop(NullValues.Token) as Token?;
-    // ignore: unused_local_variable
     Token? baseToken = pop(NullValues.Token) as Token?;
     Token? sealedToken = pop(NullValues.Token) as Token?;
     Token? augmentToken = pop(NullValues.Token) as Token?;
@@ -1505,6 +1500,9 @@ class OutlineBuilder extends StackListenerImpl {
           endToken.charOffset,
           -1,
           isSealed: sealedToken != null,
+          isBase: baseToken != null,
+          isInterface: interfaceToken != null,
+          isFinal: finalToken != null,
           isAugmentation: augmentToken != null);
     }
     libraryBuilder.setCurrentClassName(null);
@@ -2293,12 +2291,8 @@ class OutlineBuilder extends StackListenerImpl {
     Object? supertype = pop();
     Token? mixinToken = pop(NullValues.Token) as Token?;
     Token? augmentToken = pop(NullValues.Token) as Token?;
-    // TODO(kallentu): AST work for class modifiers.
-    // ignore: unused_local_variable
     Token? finalToken = pop(NullValues.Token) as Token?;
-    // ignore: unused_local_variable
     Token? interfaceToken = pop(NullValues.Token) as Token?;
-    // ignore: unused_local_variable
     Token? baseToken = pop(NullValues.Token) as Token?;
     Token? sealedToken = pop(NullValues.Token) as Token?;
     // TODO(johnniwinther): Report error on 'inline' here; it can't be used on
@@ -2381,6 +2375,9 @@ class OutlineBuilder extends StackListenerImpl {
           charEndOffset,
           isMacro: macroToken != null,
           isSealed: sealedToken != null,
+          isBase: baseToken != null,
+          isInterface: interfaceToken != null,
+          isFinal: finalToken != null,
           isAugmentation: augmentToken != null,
           isMixinClass: mixinToken != null);
     }

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

@@ -110,6 +110,15 @@ class SourceClassBuilder extends ClassBuilderImpl
   @override
   final bool isSealed;
 
+  @override
+  final bool isBase;
+
+  @override
+  final bool isInterface;
+
+  @override
+  final bool isFinal;
+
   @override
   final bool isAugmentation;
 
@@ -158,6 +167,9 @@ class SourceClassBuilder extends ClassBuilderImpl
       this.isMixinDeclaration = false,
       this.isMacro = false,
       this.isSealed = false,
+      this.isBase = false,
+      this.isInterface = false,
+      this.isFinal = false,
       this.isAugmentation = false,
       this.isMixinClass = false})
       : actualCls = initializeClass(cls, typeVariables, name, parent,
@@ -278,6 +290,9 @@ class SourceClassBuilder extends ClassBuilderImpl
     cls.isMacro = isMacro;
     cls.isMixinClass = isMixinClass;
     cls.isSealed = isSealed;
+    cls.isBase = isBase;
+    cls.isInterface = isInterface;
+    cls.isFinal = isFinal;
     if (interfaceBuilders != null) {
       for (int i = 0; i < interfaceBuilders!.length; ++i) {
         interfaceBuilders![i] = _checkSupertype(interfaceBuilders![i]);

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

@@ -1795,6 +1795,9 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
       int supertypeOffset,
       {required bool isMacro,
       required bool isSealed,
+      required bool isBase,
+      required bool isInterface,
+      required bool isFinal,
       required bool isAugmentation,
       required bool isMixinClass}) {
     _addClass(
@@ -1812,6 +1815,9 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
         supertypeOffset,
         isMacro: isMacro,
         isSealed: isSealed,
+        isBase: isBase,
+        isInterface: isInterface,
+        isFinal: isFinal,
         isAugmentation: isAugmentation,
         isMixinClass: isMixinClass);
   }
@@ -1828,6 +1834,9 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
       int endOffset,
       int supertypeOffset,
       {required bool isSealed,
+      required bool isBase,
+      required bool isInterface,
+      required bool isFinal,
       required bool isAugmentation}) {
     TypeBuilder? supertype;
     MixinApplicationBuilder? mixinApplication;
@@ -1855,6 +1864,9 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
         supertypeOffset,
         isMacro: false,
         isSealed: isSealed,
+        isBase: isBase,
+        isInterface: isInterface,
+        isFinal: isFinal,
         isAugmentation: isAugmentation,
         isMixinClass: false);
   }
@@ -1874,6 +1886,9 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
       int supertypeOffset,
       {required bool isMacro,
       required bool isSealed,
+      required bool isBase,
+      required bool isInterface,
+      required bool isFinal,
       required bool isAugmentation,
       required bool isMixinClass}) {
     // Nested declaration began in `OutlineBuilder.beginClassDeclaration`.
@@ -1914,6 +1929,9 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
             typeVariables: typeVariables,
             isMacro: false,
             isSealed: false,
+            isBase: false,
+            isInterface: false,
+            isFinal: false,
             // TODO(johnniwinther): How can we support class with mixins?
             isAugmentation: false,
             isMixinClass: false),
@@ -1932,6 +1950,9 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
         isMixinDeclaration: isMixinDeclaration,
         isMacro: isMacro,
         isSealed: isSealed,
+        isBase: isBase,
+        isInterface: isInterface,
+        isFinal: isFinal,
         isAugmentation: isAugmentation,
         isMixinClass: isMixinClass);
 
@@ -2286,6 +2307,9 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
       List<TypeBuilder>? interfaces,
       required bool isMacro,
       required bool isSealed,
+      required bool isBase,
+      required bool isInterface,
+      required bool isFinal,
       required bool isAugmentation,
       required bool isMixinClass}) {
     if (name == null) {
@@ -2523,6 +2547,9 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
             mixedInTypeBuilder: isMixinDeclaration ? null : mixin,
             isMacro: isNamedMixinApplication && isMacro,
             isSealed: isNamedMixinApplication && isSealed,
+            isBase: isNamedMixinApplication && isBase,
+            isInterface: isNamedMixinApplication && isInterface,
+            isFinal: isNamedMixinApplication && isFinal,
             isAugmentation: isNamedMixinApplication && isAugmentation,
             isMixinClass: isNamedMixinApplication && isMixinClass);
         // TODO(ahe, kmillikin): Should always be true?
@@ -2584,6 +2611,9 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
       int charEndOffset,
       {required bool isMacro,
       required bool isSealed,
+      required bool isBase,
+      required bool isInterface,
+      required bool isFinal,
       required bool isAugmentation,
       required bool isMixinClass}) {
     // Nested declaration began in `OutlineBuilder.beginNamedMixinApplication`.
@@ -2598,6 +2628,9 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
         interfaces: interfaces,
         isMacro: isMacro,
         isSealed: isSealed,
+        isBase: isBase,
+        isInterface: isInterface,
+        isFinal: isFinal,
         isAugmentation: isAugmentation,
         isMixinClass: isMixinClass)!;
     checkTypeVariables(typeVariables, supertype.declaration);
@@ -3100,6 +3133,9 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
             typeVariables: typeVariables,
             isMacro: false,
             isSealed: false,
+            isBase: false,
+            isInterface: false,
+            isFinal: false,
             isAugmentation: false,
             isMixinClass: false),
         interfaceBuilders,

pkg/front_end/testcases/class_modifiers/base/base_class_declaration.dart.strong.expect

@@ -2,19 +2,19 @@ library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+base class A extends core::Object {
   synthetic constructor •() → self::A
     : super core::Object::•()
     ;
 }
-abstract class B extends core::Object {
+abstract base class B extends core::Object {
   synthetic constructor •() → self::B
     : super core::Object::•()
     ;
 }
-abstract class M extends core::Object /*isMixinDeclaration*/  {
+abstract base class M extends core::Object /*isMixinDeclaration*/  {
 }
-class C = core::Object with self::M /*hasConstConstructor*/  {
+base class C = core::Object with self::M /*hasConstConstructor*/  {
   const synthetic constructor •() → self::C
     : super core::Object::•()
     ;

pkg/front_end/testcases/class_modifiers/base/base_class_declaration.dart.strong.transformed.expect

@@ -2,19 +2,19 @@ library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+base class A extends core::Object {
   synthetic constructor •() → self::A
     : super core::Object::•()
     ;
 }
-abstract class B extends core::Object {
+abstract base class B extends core::Object {
   synthetic constructor •() → self::B
     : super core::Object::•()
     ;
 }
-abstract class M extends core::Object /*isMixinDeclaration*/  {
+abstract base class M extends core::Object /*isMixinDeclaration*/  {
 }
-class C extends core::Object implements self::M /*isEliminatedMixin,hasConstConstructor*/  {
+base class C extends core::Object implements self::M /*isEliminatedMixin,hasConstConstructor*/  {
   const synthetic constructor •() → self::C
     : super core::Object::•()
     ;

pkg/front_end/testcases/class_modifiers/base/base_class_declaration.dart.weak.expect

@@ -2,19 +2,19 @@ library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+base class A extends core::Object {
   synthetic constructor •() → self::A
     : super core::Object::•()
     ;
 }
-abstract class B extends core::Object {
+abstract base class B extends core::Object {
   synthetic constructor •() → self::B
     : super core::Object::•()
     ;
 }
-abstract class M extends core::Object /*isMixinDeclaration*/  {
+abstract base class M extends core::Object /*isMixinDeclaration*/  {
 }
-class C = core::Object with self::M /*hasConstConstructor*/  {
+base class C = core::Object with self::M /*hasConstConstructor*/  {
   const synthetic constructor •() → self::C
     : super core::Object::•()
     ;

pkg/front_end/testcases/class_modifiers/base/base_class_declaration.dart.weak.modular.expect

@@ -2,19 +2,19 @@ library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+base class A extends core::Object {
   synthetic constructor •() → self::A
     : super core::Object::•()
     ;
 }
-abstract class B extends core::Object {
+abstract base class B extends core::Object {
   synthetic constructor •() → self::B
     : super core::Object::•()
     ;
 }
-abstract class M extends core::Object /*isMixinDeclaration*/  {
+abstract base class M extends core::Object /*isMixinDeclaration*/  {
 }
-class C = core::Object with self::M /*hasConstConstructor*/  {
+base class C = core::Object with self::M /*hasConstConstructor*/  {
   const synthetic constructor •() → self::C
     : super core::Object::•()
     ;

pkg/front_end/testcases/class_modifiers/base/base_class_declaration.dart.weak.outline.expect

@@ -2,17 +2,17 @@ library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+base class A extends core::Object {
   synthetic constructor •() → self::A
     ;
 }
-abstract class B extends core::Object {
+abstract base class B extends core::Object {
   synthetic constructor •() → self::B
     ;
 }
-abstract class M extends core::Object /*isMixinDeclaration*/  {
+abstract base class M extends core::Object /*isMixinDeclaration*/  {
 }
-class C = core::Object with self::M /*hasConstConstructor*/  {
+base class C = core::Object with self::M /*hasConstConstructor*/  {
   const synthetic constructor •() → self::C
     : super core::Object::•()
     ;

pkg/front_end/testcases/class_modifiers/base/base_class_declaration.dart.weak.transformed.expect

@@ -2,19 +2,19 @@ library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+base class A extends core::Object {
   synthetic constructor •() → self::A
     : super core::Object::•()
     ;
 }
-abstract class B extends core::Object {
+abstract base class B extends core::Object {
   synthetic constructor •() → self::B
     : super core::Object::•()
     ;
 }
-abstract class M extends core::Object /*isMixinDeclaration*/  {
+abstract base class M extends core::Object /*isMixinDeclaration*/  {
 }
-class C extends core::Object implements self::M /*isEliminatedMixin,hasConstConstructor*/  {
+base class C extends core::Object implements self::M /*isEliminatedMixin,hasConstConstructor*/  {
   const synthetic constructor •() → self::C
     : super core::Object::•()
     ;

pkg/front_end/testcases/class_modifiers/final/final_class_declaration.dart.strong.expect

@@ -2,19 +2,19 @@ library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+final class A extends core::Object {
   synthetic constructor •() → self::A
     : super core::Object::•()
     ;
 }
-abstract class B extends core::Object {
+abstract final class B extends core::Object {
   synthetic constructor •() → self::B
     : super core::Object::•()
     ;
 }
-abstract class M extends core::Object /*isMixinDeclaration*/  {
+abstract final class M extends core::Object /*isMixinDeclaration*/  {
 }
-class C = core::Object with self::M /*hasConstConstructor*/  {
+final class C = core::Object with self::M /*hasConstConstructor*/  {
   const synthetic constructor •() → self::C
     : super core::Object::•()
     ;

pkg/front_end/testcases/class_modifiers/final/final_class_declaration.dart.strong.transformed.expect

@@ -2,19 +2,19 @@ library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+final class A extends core::Object {
   synthetic constructor •() → self::A
     : super core::Object::•()
     ;
 }
-abstract class B extends core::Object {
+abstract final class B extends core::Object {
   synthetic constructor •() → self::B
     : super core::Object::•()
     ;
 }
-abstract class M extends core::Object /*isMixinDeclaration*/  {
+abstract final class M extends core::Object /*isMixinDeclaration*/  {
 }
-class C extends core::Object implements self::M /*isEliminatedMixin,hasConstConstructor*/  {
+final class C extends core::Object implements self::M /*isEliminatedMixin,hasConstConstructor*/  {
   const synthetic constructor •() → self::C
     : super core::Object::•()
     ;

pkg/front_end/testcases/class_modifiers/final/final_class_declaration.dart.weak.expect

@@ -2,19 +2,19 @@ library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+final class A extends core::Object {
   synthetic constructor •() → self::A
     : super core::Object::•()
     ;
 }
-abstract class B extends core::Object {
+abstract final class B extends core::Object {
   synthetic constructor •() → self::B
     : super core::Object::•()
     ;
 }
-abstract class M extends core::Object /*isMixinDeclaration*/  {
+abstract final class M extends core::Object /*isMixinDeclaration*/  {
 }
-class C = core::Object with self::M /*hasConstConstructor*/  {
+final class C = core::Object with self::M /*hasConstConstructor*/  {
   const synthetic constructor •() → self::C
     : super core::Object::•()
     ;

pkg/front_end/testcases/class_modifiers/final/final_class_declaration.dart.weak.modular.expect

@@ -2,19 +2,19 @@ library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+final class A extends core::Object {
   synthetic constructor •() → self::A
     : super core::Object::•()
     ;
 }
-abstract class B extends core::Object {
+abstract final class B extends core::Object {
   synthetic constructor •() → self::B
     : super core::Object::•()
     ;
 }
-abstract class M extends core::Object /*isMixinDeclaration*/  {
+abstract final class M extends core::Object /*isMixinDeclaration*/  {
 }
-class C = core::Object with self::M /*hasConstConstructor*/  {
+final class C = core::Object with self::M /*hasConstConstructor*/  {
   const synthetic constructor •() → self::C
     : super core::Object::•()
     ;

pkg/front_end/testcases/class_modifiers/final/final_class_declaration.dart.weak.outline.expect

@@ -2,17 +2,17 @@ library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+final class A extends core::Object {
   synthetic constructor •() → self::A
     ;
 }
-abstract class B extends core::Object {
+abstract final class B extends core::Object {
   synthetic constructor •() → self::B
     ;
 }
-abstract class M extends core::Object /*isMixinDeclaration*/  {
+abstract final class M extends core::Object /*isMixinDeclaration*/  {
 }
-class C = core::Object with self::M /*hasConstConstructor*/  {
+final class C = core::Object with self::M /*hasConstConstructor*/  {
   const synthetic constructor •() → self::C
     : super core::Object::•()
     ;

pkg/front_end/testcases/class_modifiers/final/final_class_declaration.dart.weak.transformed.expect

@@ -2,19 +2,19 @@ library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+final class A extends core::Object {
   synthetic constructor •() → self::A
     : super core::Object::•()
     ;
 }
-abstract class B extends core::Object {
+abstract final class B extends core::Object {
   synthetic constructor •() → self::B
     : super core::Object::•()
     ;
 }
-abstract class M extends core::Object /*isMixinDeclaration*/  {
+abstract final class M extends core::Object /*isMixinDeclaration*/  {
 }
-class C extends core::Object implements self::M /*isEliminatedMixin,hasConstConstructor*/  {
+final class C extends core::Object implements self::M /*isEliminatedMixin,hasConstConstructor*/  {
   const synthetic constructor •() → self::C
     : super core::Object::•()
     ;

pkg/front_end/testcases/class_modifiers/interface/interface_class_declaration.dart.strong.expect

@@ -2,19 +2,19 @@ library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+interface class A extends core::Object {
   synthetic constructor •() → self::A
     : super core::Object::•()
     ;
 }
-abstract class B extends core::Object {
+abstract interface class B extends core::Object {
   synthetic constructor •() → self::B
     : super core::Object::•()
     ;
 }
-abstract class M extends core::Object /*isMixinDeclaration*/  {
+abstract interface class M extends core::Object /*isMixinDeclaration*/  {
 }
-class C = core::Object with self::M /*hasConstConstructor*/  {
+interface class C = core::Object with self::M /*hasConstConstructor*/  {
   const synthetic constructor •() → self::C
     : super core::Object::•()
     ;

pkg/front_end/testcases/class_modifiers/interface/interface_class_declaration.dart.strong.transformed.expect

@@ -2,19 +2,19 @@ library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+interface class A extends core::Object {
   synthetic constructor •() → self::A
     : super core::Object::•()
     ;
 }
-abstract class B extends core::Object {
+abstract interface class B extends core::Object {
   synthetic constructor •() → self::B
     : super core::Object::•()
     ;
 }
-abstract class M extends core::Object /*isMixinDeclaration*/  {
+abstract interface class M extends core::Object /*isMixinDeclaration*/  {
 }
-class C extends core::Object implements self::M /*isEliminatedMixin,hasConstConstructor*/  {
+interface class C extends core::Object implements self::M /*isEliminatedMixin,hasConstConstructor*/  {
   const synthetic constructor •() → self::C
     : super core::Object::•()
     ;

pkg/front_end/testcases/class_modifiers/interface/interface_class_declaration.dart.weak.expect

@@ -2,19 +2,19 @@ library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+interface class A extends core::Object {
   synthetic constructor •() → self::A
     : super core::Object::•()
     ;
 }
-abstract class B extends core::Object {
+abstract interface class B extends core::Object {
   synthetic constructor •() → self::B
     : super core::Object::•()
     ;
 }
-abstract class M extends core::Object /*isMixinDeclaration*/  {
+abstract interface class M extends core::Object /*isMixinDeclaration*/  {
 }
-class C = core::Object with self::M /*hasConstConstructor*/  {
+interface class C = core::Object with self::M /*hasConstConstructor*/  {
   const synthetic constructor •() → self::C
     : super core::Object::•()
     ;

pkg/front_end/testcases/class_modifiers/interface/interface_class_declaration.dart.weak.modular.expect

@@ -2,19 +2,19 @@ library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+interface class A extends core::Object {
   synthetic constructor •() → self::A
     : super core::Object::•()
     ;
 }
-abstract class B extends core::Object {
+abstract interface class B extends core::Object {
   synthetic constructor •() → self::B
     : super core::Object::•()
     ;
 }
-abstract class M extends core::Object /*isMixinDeclaration*/  {
+abstract interface class M extends core::Object /*isMixinDeclaration*/  {
 }
-class C = core::Object with self::M /*hasConstConstructor*/  {
+interface class C = core::Object with self::M /*hasConstConstructor*/  {
   const synthetic constructor •() → self::C
     : super core::Object::•()
     ;

pkg/front_end/testcases/class_modifiers/interface/interface_class_declaration.dart.weak.outline.expect

@@ -2,17 +2,17 @@ library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+interface class A extends core::Object {
   synthetic constructor •() → self::A
     ;
 }
-abstract class B extends core::Object {
+abstract interface class B extends core::Object {
   synthetic constructor •() → self::B
     ;
 }
-abstract class M extends core::Object /*isMixinDeclaration*/  {
+abstract interface class M extends core::Object /*isMixinDeclaration*/  {
 }
-class C = core::Object with self::M /*hasConstConstructor*/  {
+interface class C = core::Object with self::M /*hasConstConstructor*/  {
   const synthetic constructor •() → self::C
     : super core::Object::•()
     ;

pkg/front_end/testcases/class_modifiers/interface/interface_class_declaration.dart.weak.transformed.expect

@@ -2,19 +2,19 @@ library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;
 
-class A extends core::Object {
+interface class A extends core::Object {
   synthetic constructor •() → self::A
     : super core::Object::•()
     ;
 }
-abstract class B extends core::Object {
+abstract interface class B extends core::Object {
   synthetic constructor •() → self::B
     : super core::Object::•()
     ;
 }
-abstract class M extends core::Object /*isMixinDeclaration*/  {
+abstract interface class M extends core::Object /*isMixinDeclaration*/  {
 }
-class C extends core::Object implements self::M /*isEliminatedMixin,hasConstConstructor*/  {
+interface class C extends core::Object implements self::M /*isEliminatedMixin,hasConstConstructor*/  {
   const synthetic constructor •() → self::C
     : super core::Object::•()
     ;

pkg/kernel/binary.md

@@ -147,7 +147,7 @@ type CanonicalName {
 
 type ComponentFile {
   UInt32 magic = 0x90ABCDEF;
-  UInt32 formatVersion = 92;
+  UInt32 formatVersion = 93;
   Byte[10] shortSdkHash;
   List<String> problemsAsJson; // Described in problems.md.
   Library[] libraries;
@@ -320,7 +320,7 @@ type Class extends Node {
   FileOffset fileEndOffset;
   UInt flags (isAbstract, isEnum, isAnonymousMixin, isEliminatedMixin,
               isMixinDeclaration, hasConstConstructor, isMacro, isSealed,
-              isMixinClass);
+              isMixinClass, isBase, isInterface, isFinal);
   StringReference name;
   List<Expression> annotations;
   List<TypeParameter> typeParameters;

pkg/kernel/lib/ast.dart

@@ -1027,6 +1027,9 @@ class Class extends NamedNode implements Annotatable, FileUriNode {
   static const int FlagMacro = 1 << 6;
   static const int FlagSealed = 1 << 7;
   static const int FlagMixinClass = 1 << 8;
+  static const int FlagBase = 1 << 9;
+  static const int FlagInterface = 1 << 10;
+  static const int FlagFinal = 1 << 11;
 
   int flags = 0;
 
@@ -1050,13 +1053,34 @@ class Class extends NamedNode implements Annotatable, FileUriNode {
     flags = value ? (flags | FlagMacro) : (flags & ~FlagMacro);
   }
 
-  /// Whether this class is a macro class.
+  /// Whether this class is a sealed class.
   bool get isSealed => flags & FlagSealed != 0;
 
   void set isSealed(bool value) {
     flags = value ? (flags | FlagSealed) : (flags & ~FlagSealed);
   }
 
+  /// Whether this class is a base class.
+  bool get isBase => flags & FlagBase != 0;
+
+  void set isBase(bool value) {
+    flags = value ? (flags | FlagBase) : (flags & ~FlagBase);
+  }
+
+  /// Whether this class is an interface class.
+  bool get isInterface => flags & FlagInterface != 0;
+
+  void set isInterface(bool value) {
+    flags = value ? (flags | FlagInterface) : (flags & ~FlagInterface);
+  }
+
+  /// Whether this class is a final class.
+  bool get isFinal => flags & FlagFinal != 0;
+
+  void set isFinal(bool value) {
+    flags = value ? (flags | FlagFinal) : (flags & ~FlagFinal);
+  }
+
   /// Whether this class is a synthetic implementation created for each
   /// mixed-in class. For example the following code:
   /// class Z extends A with B, C, D {}

pkg/kernel/lib/binary/tag.dart

@@ -195,7 +195,7 @@ class Tag {
   /// Internal version of kernel binary format.
   /// Bump it when making incompatible changes in kernel binaries.
   /// Keep in sync with runtime/vm/kernel_binary.h, pkg/kernel/binary.md.
-  static const int BinaryFormatVersion = 92;
+  static const int BinaryFormatVersion = 93;
 }
 
 abstract class ConstantTag {

pkg/kernel/lib/text/ast_to_text.dart

@@ -1307,6 +1307,9 @@ class Printer extends Visitor<void> with VisitorVoidMixin {
     writeModifier(node.isAbstract, 'abstract');
     writeModifier(node.isMacro, 'macro');
     writeModifier(node.isSealed, 'sealed');
+    writeModifier(node.isBase, 'base');
+    writeModifier(node.isInterface, 'interface');
+    writeModifier(node.isFinal, 'final');
     writeModifier(node.isMixinClass, 'mixin');
     writeWord('class');
     writeWord(getClassName(node));

runtime/vm/compiler/frontend/kernel_translation_helper.h

@@ -755,8 +755,11 @@ class ClassHelper {
     kFlagMixinDeclaration = 1 << 4,
     kHasConstConstructor = 1 << 5,
     kIsMacro = 1 << 6,
-    kisSealed = 1 << 7,
+    kIsSealed = 1 << 7,
     kIsMixinClass = 1 << 8,
+    kIsBase = 1 << 9,
+    kIsInterface = 1 << 10,
+    kIsFinal = 1 << 11,
   };
 
   explicit ClassHelper(KernelReaderHelper* helper)

runtime/vm/kernel_binary.h

@@ -18,7 +18,7 @@ namespace kernel {
 // package:kernel/binary.md.
 
 static const uint32_t kMagicProgramFile = 0x90ABCDEFu;
-static const uint32_t kSupportedKernelFormatVersion = 92;
+static const uint32_t kSupportedKernelFormatVersion = 93;
 
 // Keep in sync with package:kernel/lib/binary/tag.dart
 #define KERNEL_TAG_LIST(V)                                                     \