| // Copyright (c) 2016, 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. |
| |
| import 'dart:async'; |
| |
| /// Creates a wrapper that coerces the type of [transformer]. |
| /// |
| /// This soundly converts a [StreamTransformer] to a `StreamTransformer<S, T>`, |
| /// regardless of its original generic type, by asserting that the events |
| /// emitted by the transformed stream are instances of `T` whenever they're |
| /// provided. If they're not, the stream throws a [TypeError]. |
| @Deprecated('Use Stream.cast after binding a transformer instead') |
| StreamTransformer<S, T> typedStreamTransformer<S, T>( |
| StreamTransformer transformer) => |
| transformer is StreamTransformer<S, T> |
| ? transformer |
| : _TypeSafeStreamTransformer(transformer); |
| |
| /// A wrapper that coerces the type of the stream returned by an inner |
| /// transformer. |
| class _TypeSafeStreamTransformer<S, T> extends StreamTransformerBase<S, T> { |
| final StreamTransformer _inner; |
| |
| _TypeSafeStreamTransformer(this._inner); |
| |
| @override |
| Stream<T> bind(Stream<S> stream) => _inner.bind(stream).cast(); |
| } |