Fix covariant overrides in SynchronousFuture. (#5262)
* Fix covariant overrides in SynchronousFuture. There were two things going on here. In timeout(), the callback's return type was needlessly tightened to only allow callbacks that return futures. This makes SynchronousFuture not substitutable with Future, whose timeout() allows callbacks that return immediate values. Since SynchronousFuture.timeout() never calls the callback anyway, I just loosened it to match Future.timeout(). SynchronousFuture.whenComplete() is just wrong. The type error, again, is that the callback's return type is too tight. Future.whenComplete() allows synchronous callbacks. But the actual implementation is wrong as well. whenComplete() should return a future that completes to the *original value*, not whatever the callback returns. So I just fixed the method to work correctly, including handling callbacks with synchronous results. * "(error, stackTrace)" -> "(e, stack)".
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@ -42,8 +42,17 @@ class SynchronousFuture<T> implements Future<T> {
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}
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@override
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Future<T> timeout(Duration timeLimit, { Future<T> onTimeout() }) => new Completer<T>().future;
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Future<T> timeout(Duration timeLimit, { dynamic onTimeout() }) => new Completer<T>().future;
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@override
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Future<T> whenComplete(Future<T> action()) => action();
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Future<T> whenComplete(dynamic action()) {
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try {
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dynamic result = action();
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if (result is Future)
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return result.then((_) => _value);
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return this;
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} catch (e, stack) {
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return new Future<T>.error(e, stack);
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}
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}
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}
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