blob: 0df87b59f5319358dcbdb7c8c9acd21c6b060b6c [file] [log] [blame]
// 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
/// @Issue
/// @Issue 41266,41437,42236,42237
/// @author
// Requirements=nnbd-weak
import "dart:async";
import "../../../Utils/expect.dart";
dynamic getNull() => null;
Future<FutureOr<Object>> test() async => await getNull();
main() {
test().then((value) => asyncEnd());