| library /*isNonNullableByDefault*/; | 
 | // | 
 | // Problems in library: | 
 | // | 
 | // pkg/front_end/testcases/general/interface_class_declaration.dart:7:1: Error: The 'class-modifiers' language feature is disabled for this library. | 
 | // Try removing the `@dart=` annotation or setting the language version to 3.0 or higher. | 
 | // interface class A {} | 
 | // ^^^^^^^^^ | 
 | // pkg/front_end/testcases/general/interface_class_declaration.dart:5:1: Context: This is the annotation that opts out this library from the 'class-modifiers' language feature. | 
 | // // @dart=2.19 | 
 | // ^^^^^^^^^^^^^ | 
 | // | 
 | // pkg/front_end/testcases/general/interface_class_declaration.dart:9:10: Error: The 'class-modifiers' language feature is disabled for this library. | 
 | // Try removing the `@dart=` annotation or setting the language version to 3.0 or higher. | 
 | // abstract interface class B {} | 
 | //          ^^^^^^^^^ | 
 | // pkg/front_end/testcases/general/interface_class_declaration.dart:5:1: Context: This is the annotation that opts out this library from the 'class-modifiers' language feature. | 
 | // // @dart=2.19 | 
 | // ^^^^^^^^^^^^^ | 
 | // | 
 | // pkg/front_end/testcases/general/interface_class_declaration.dart:11:1: Error: The 'class-modifiers' language feature is disabled for this library. | 
 | // Try removing the `@dart=` annotation or setting the language version to 3.0 or higher. | 
 | // interface mixin M {} | 
 | // ^^^^^^^^^ | 
 | // pkg/front_end/testcases/general/interface_class_declaration.dart:5:1: Context: This is the annotation that opts out this library from the 'class-modifiers' language feature. | 
 | // // @dart=2.19 | 
 | // ^^^^^^^^^^^^^ | 
 | // | 
 | // pkg/front_end/testcases/general/interface_class_declaration.dart:12:1: Error: The 'class-modifiers' language feature is disabled for this library. | 
 | // Try removing the `@dart=` annotation or setting the language version to 3.0 or higher. | 
 | // interface class C = Object with M; | 
 | // ^^^^^^^^^ | 
 | // pkg/front_end/testcases/general/interface_class_declaration.dart:5:1: Context: This is the annotation that opts out this library from the 'class-modifiers' language feature. | 
 | // // @dart=2.19 | 
 | // ^^^^^^^^^^^^^ | 
 | // | 
 | import self as self; | 
 | import "dart:core" as core; | 
 |  | 
 | class A extends core::Object { | 
 |   synthetic constructor •() → self::A | 
 |     : super core::Object::•() | 
 |     ; | 
 | } | 
 | abstract class B extends core::Object { | 
 |   synthetic constructor •() → self::B | 
 |     : super core::Object::•() | 
 |     ; | 
 | } | 
 | abstract class M extends core::Object /*isMixinDeclaration*/  { | 
 | } | 
 | class C = core::Object with self::M /*hasConstConstructor*/  { | 
 |   const synthetic constructor •() → self::C | 
 |     : super core::Object::•() | 
 |     ; | 
 | } |