| // 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 async function with `Future<FutureOr<Object>>` return |
| /// type can return `null` in the weak mode. |
| /// |
| /// Here is a situation where sound and non-sound null checking produce different |
| /// results. The `null` value is a result of `getNull()`, it's tested using `null |
| /// as FutureOr<Object>`, and such a cast succeeds. So `test()` does not throw |
| /// error and returns `Future<FutureOr<Object>>` that will be completed with |
| /// `null`. No dynamic error here. |
| /// |
| /// @Issue 41272,41437 |
| /// @author iarkh@unipro.ru |
| |
| // Requirements=nnbd-weak |
| |
| import "dart:async"; |
| import "../../../Utils/expect.dart"; |
| |
| dynamic getNull() => null; |
| |
| Future<FutureOr<Object>> test() async { |
| FutureOr<Object> o = await getNull(); |
| return o; |
| } |
| |
| main() { |
| asyncStart(); |
| test().then((value) => asyncEnd()); |
| } |