| // Copyright (c) 2015, 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. | 
 |  | 
 | // Regression test for issue 21912. | 
 |  | 
 | class A {} | 
 |  | 
 | class B extends A {} | 
 |  | 
 | typedef T Function2<S, T>(S z); | 
 | typedef B AToB(A x); | 
 | typedef A BToA(B x); | 
 |  | 
 | void main() { | 
 |   { | 
 |     Function2<Function2<A, B>, Function2<B, A>> t1; | 
 |     Function2<AToB, BToA> t2; | 
 |     Function2<Function2<int, double>, Function2<int, double>> left; | 
 |     left = t1; //# 01: static type warning | 
 |     left = t2; //# 02: static type warning | 
 |   } | 
 | } |