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1 // Copyright (c) 2016, the Dart project authors. Please see the AUTHORS file | |
2 // for details. All rights reserved. Use of this source code is governed by a | |
3 // BSD-style license that can be found in the LICENSE file. | |
4 | |
5 import 'dart:async'; | |
6 | |
7 import 'delegate/stream.dart'; | |
8 | |
9 /// Creates a wrapper that coerces the type of [transformer]. | |
10 /// | |
11 /// This soundly converts a [StreamTransformer] to a `StreamTransformer<S, T>`, | |
12 /// regardless of its original generic type, by asserting that the events | |
13 /// emitted by the transformed stream are instances of `T` whenever they're | |
14 /// provided. If they're not, the stream throws a [CastError]. | |
Lasse Reichstein Nielsen
2016/05/09 19:20:12
Also say that t expects the argument to bind to be
nweiz
2016/05/09 19:31:51
This isn't really an aspect of the behavior of the
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15 StreamTransformer/*<S, T>*/ typedStreamTransformer/*<S, T>*/( | |
16 StreamTransformer transformer) => | |
17 transformer is StreamTransformer/*<S, T>*/ | |
18 ? transformer | |
19 : new _TypeSafeStreamTransformer(transformer); | |
20 | |
21 /// A wrapper that coerces the type of the stream returned by an inner | |
22 /// transformer. | |
23 class _TypeSafeStreamTransformer<S, T> implements StreamTransformer<S, T> { | |
24 final StreamTransformer _inner; | |
25 | |
26 _TypeSafeStreamTransformer(this._inner); | |
27 | |
28 Stream<T> bind(Stream<S> stream) => | |
29 DelegatingStream.typed(_inner.bind(stream)); | |
30 } | |
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