blob: cb63311a6339d3118621b68a0036ee07b1c86058 [file] [log] [blame]
// 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';
import 'delegate/stream.dart';
/// 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 [CastError].
StreamTransformer<S, T> typedStreamTransformer<S, T>(
StreamTransformer transformer) =>
transformer is StreamTransformer<S, T>
? transformer
: new _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;
Stream<T> bind(Stream<S> stream) =>