blob: 34c07d2098c35323755812d4c181b155ce857452 [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 future flattening works correctly for non-nullable
/// `Future<Object>` type dynamically and the expression can be 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 Object`, and such a cast succeeds. So, no dynamic error here and
/// `Future<Object>` is returned.
/// @Issue 41340,41437
/// @author
// Requirements=nnbd-weak
import "dart:async";
import "../../../Utils/expect.dart";
dynamic getNull() => null;
main() {
Future f = Future<Object>(() => getNull());
f.then((value) => asyncEnd());
f = Future<Future<Object>>(() => getNull());
f.then((value) => asyncEnd());