dart / co19 / 71951f8d687c6e7400bc9e5605301d2ef3fafa5b / . / LanguageFeatures / nnbd / future_flattening_A01_t77.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 future flattening works correctly for [Future<Null>] | |

* type and the expression can be null. | |

* | |

* Issue 41437 | |

* @author iarkh@unipro.ru | |

*/ | |

// Requirements=nnbd-strong | |

import "dart:async"; | |

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

main() { | |

asyncStart(); | |

Future<Null>(() => null).then((value) => asyncEnd()); | |

} |