| * 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 |

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

| * @description Check that type of await expression match with expected |

| * nullable [FutureOr] and the expression can be non-null. |

| * @author iarkh@unipro.ru |

| // Requirements=nnbd-strong |

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

| Future<FutureOr<bool?>> test() async { |

| FutureOr<bool?> b = await true; |

| FutureOr<int?> i = await 1; |

| FutureOr<String?> s = await 'hello'; |

| FutureOr<Object?> o = await new Object(); |

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