| // Copyright (c) 2018, the Dart project authors.  Please see the AUTHORS file | 
 | // for details. All rights reserved. Use of this source code is governed by a | 
 | // BSD-style license that can be found in the LICENSE file. | 
 |  | 
 | class Supertype { | 
 |   factory Supertype() = X; | 
 |   factory Supertype() = X; | 
 | //        ^^^^^^^^^ | 
 | // [analyzer] COMPILE_TIME_ERROR.DUPLICATE_CONSTRUCTOR | 
 | //        ^ | 
 | // [cfe] 'Supertype' is already declared in this scope. | 
 | } | 
 |  | 
 | class X implements Supertype { | 
 |   X(); | 
 | } | 
 |  | 
 | main() { | 
 |   X x = new Supertype(); | 
 |   //        ^ | 
 |   // [cfe] Can't use 'Supertype' because it is declared more than once. | 
 | } |