dart / co19 / refs/heads/1004 / . / LanguageFeatures / nnbd / type-normalization / norm_A03_t04.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 | |

* NORM(T?) = | |

* let S be NORM(T) | |

* if S is a top type then S | |

* if S is Never then Null | |

* if S is Never* then Null | |

* if S is Null then Null | |

* if S is FutureOr<R> and R is nullable then S | |

* if S is FutureOr<R>* and R is nullable then FutureOr<R> | |

* if S is R? then R? | |

* if S is R* then R? | |

* else S? | |

* | |

* @description Checks that if NORM(T) is Null then NORM(T?) = Null | |

* | |

* @author sgrekhov@unipro.ru | |

*/ | |

// Requirements=nnbd-strong | |

class A<X> {} | |

class B1<X> implements A<X> {} | |

class B2<X> implements A<X?> {} | |

class C1 extends B1<Null?> implements A<Null> {} | |

class C2 extends B1<Never?> implements A<Null> {} | |

main() { | |

new C1(); | |

new C2(); | |

} |