| // Copyright (c) 2020, 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. |

| |

| /// @assertion The flatten function is modified as follows: |

| /// |

| /// [flatten(T)] is defined by cases on [T]: |

| /// |

| /// if [T] is [S?] then [flatten(T) = flatten(S)?] |

| /// otherwise if [T] is [S*] then [flatten(T) = flatten(S)*] |

| /// otherwise if [T] is [FutureOr<S>] then [flatten(T) = S] |

| /// otherwise [if T <: Future] then let [S] be a type such that [T <: |

| /// Future<S>] and for all [R], if [T <: Future<R>] then [S <: R]; then |

| /// [flatten(T) = S] |

| /// otherwise [flatten(T) = T] |

| /// |

| /// @description Check that future flattening works correctly for non-nullable |

| /// [Future<int>] type dynamically and the expression cannot be null. |

| /// |

| /// @Issue 41340,41437 |

| /// @author iarkh@unipro.ru |

| |

| // Requirements=nnbd-strong |

| |

| import "dart:async"; |

| import "../../Utils/expect.dart"; |

| |

| dynamic getNull() => null; |

| |

| main() { |

| asyncStart(); |

| Future f = Future<int>(() => getNull()); |

| f.then((value) { Expect.fail("Should not reach here"); }, |

| onError:(e) => asyncEnd()); |

| |

| asyncStart(); |

| f = Future<Future<int>>(() => getNull()); |

| f.then((value) { Expect.fail("Should not reach here"); }, |

| onError:(e) => asyncEnd()); |

| } |