dart / co19 / a262a8dd0e797a94bdbd439ba46a04caec654aea / . / LanguageFeatures / nnbd / future_flattening_A01_t30.dart

// 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 type of await expression match with expected | |

/// nullable [FutureOr] and the expression can be null. | |

/// | |

/// Issue 41437 | |

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

// Requirements=nnbd-strong | |

import "dart:async"; | |

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

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

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

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

FutureOr<String?> s = await null; | |

FutureOr<Object?> o = await null; | |

return b; | |

} | |

main() { | |

asyncStart(); | |

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

} |