| /* |

| * 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 |

| * [Future<Future<Object>>] 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<Object>(() => Future<Object?>(() => getNull())); |

| f.then((value) => asyncEnd()); |

| |

| asyncStart(); |

| Future f1 = Future<Object?>(() => Future<Object>(() => getNull())); |

| f1.then((value) { Expect.fail("Should not reach here!"); }, |

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

| } |