|  | library; | 
|  | // | 
|  | // Problems in library: | 
|  | // | 
|  | // pkg/front_end/testcases/extensions/builtin_identifiers.dart:5:11: Error: Can't use 'mixin' as a name here. | 
|  | // extension mixin on int {} | 
|  | //           ^^^^^ | 
|  | // | 
|  | // pkg/front_end/testcases/extensions/builtin_identifiers.dart:7:11: Error: Can't use 'extension' as a name here. | 
|  | // extension extension on int {} | 
|  | //           ^^^^^^^^^ | 
|  | // | 
|  | // pkg/front_end/testcases/extensions/builtin_identifiers.dart:9:11: Error: Can't use 'as' as a name here. | 
|  | // extension as on int {} | 
|  | //           ^^ | 
|  | // | 
|  | import self as self; | 
|  | import "dart:core" as core; | 
|  |  | 
|  | extension mixin on core::int { | 
|  | } | 
|  | extension extension on core::int { | 
|  | } | 
|  | extension as on core::int { | 
|  | } | 
|  | static method main() → void {} |