// 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: compile-time error
    left = t2; //# 02: compile-time error
  }
}