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// Copyright (c) 2018, 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.
// Test that async/await syntax works for synchronously completed futures.
// Such futures are used by Flutter (see
import 'dart:async';
import 'package:expect/expect.dart';
import 'package:async_helper/async_helper.dart';
class SynchronousFuture<T> implements Future<T> {
final T v;
Future<E> then<E>(FutureOr<E> f(T v), {Function? onError}) {
final u = f(v);
return u is Future<dynamic>
? (u as Future<dynamic>).then((v) => v as E)
: new SynchronousFuture<E>(u);
Stream<T> asStream() => throw 'unimplemented';
Future<T> catchError(Function onError, {bool test(Object error)?}) =>
throw 'unimplemented';
Future<T> timeout(Duration timeLimit, {dynamic onTimeout()?}) =>
throw 'unimplemented';
Future<T> whenComplete(dynamic action()) => throw 'unimplemented';
void main() {
var stage = 0;
asyncTest(() async {
int v;
Expect.equals(0, stage++);
v = await new SynchronousFuture<int>(stage);
Expect.equals(1, v);
Expect.equals(1, stage++);
v = await new SynchronousFuture<int>(stage);
Expect.equals(2, v);
Expect.equals(2, stage++);
v = await new SynchronousFuture<int>(stage);
Expect.equals(3, v);
Expect.equals(3, stage++);