remove generated_sdk from checked in code

test/generated_sdk/lib/async/stream.dart

-// Copyright (c) 2013, 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.
-
-part of dart.async;
-
-// -------------------------------------------------------------------
-// Core Stream types
-// -------------------------------------------------------------------
-
-/**
- * A source of asynchronous data events.
- *
- * A Stream provides a way to receive a sequence of events.
- * Each event is either a data event or an error event,
- * representing the result of a single computation.
- * When the events provided by a Stream have all been sent,
- * a single "done" event will mark the end.
- *
- * You can [listen] on a stream to make it start generating events,
- * and to set up listeners that receive the events.
- * When you listen, you receive a [StreamSubscription] object
- * which is the active object providing the events,
- * and which can be used to stop listening again,
- * or to temporarily pause events from the subscription.
- *
- * There are two kinds of streams: "Single-subscription" streams and
- * "broadcast" streams.
- *
- * *A single-subscription stream* allows only a single listener during the whole
- * lifetime of the stream.
- * It doesn't start generating events until it has a listener,
- * and it stops sending events when the listener is unsubscribed,
- * even if the source of events could still provide more.
- *
- * Listening twice on a single-subscription stream is not allowed, even after
- * the first subscription has been canceled.
- *
- * Single-subscription streams are generally used for streaming chunks of
- * larger contiguous data like file I/O.
- *
- * *A broadcast stream* allows any number of listeners, and it fires
- * its events when they are ready, whether there are listeners or not.
- *
- * Broadcast streams are used for independent events/observers.
- *
- * If several listeners want to listen to a single subscription stream,
- * use [asBroadcastStream] to create a broadcast stream on top of the
- * non-broadcast stream.
- *
- * On either kind of stream, stream transformationss, such as [where] and
- * [skip], return the same type of stream as the one the method was called on,
- * unless otherwise noted.
- *
- * When an event is fired, the listener(s) at that time will receive the event.
- * If a listener is added to a broadcast stream while an event is being fired,
- * that listener will not receive the event currently being fired.
- * If a listener is canceled, it immediately stops receiving events.
- *
- * When the "done" event is fired, subscribers are unsubscribed before
- * receiving the event. After the event has been sent, the stream has no
- * subscribers. Adding new subscribers to a broadcast stream after this point
- * is allowed, but they will just receive a new "done" event as soon
- * as possible.
- *
- * Stream subscriptions always respect "pause" requests. If necessary they need
- * to buffer their input, but often, and preferably, they can simply request
- * their input to pause too.
- *
- * The default implementation of [isBroadcast] returns false.
- * A broadcast stream inheriting from [Stream] must override [isBroadcast]
- * to return `true`.
- */
-abstract class Stream<T> {
-  Stream();
-
-  /**
-   * Creates a new single-subscription stream from the future.
-   *
-   * When the future completes, the stream will fire one event, either
-   * data or error, and then close with a done-event.
-   */
-  factory Stream.fromFuture(Future<T> future) {
-    // Use the controller's buffering to fill in the value even before
-    // the stream has a listener. For a single value, it's not worth it
-    // to wait for a listener before doing the `then` on the future.
-    _StreamController<T> controller =
-        new StreamController<T>(sync: true) as _StreamController<T>;
-    future.then((value) {
-        controller._add(value);
-        controller._closeUnchecked();
-      },
-      onError: (error, stackTrace) {
-        controller._addError(error, stackTrace);
-        controller._closeUnchecked();
-      });
-    return controller.stream;
-  }
-
-  /**
-   * Creates a single-subscription stream that gets its data from [data].
-   *
-   * The iterable is iterated when the stream receives a listener, and stops
-   * iterating if the listener cancels the subscription.
-   *
-   * If iterating [data] throws an error, the stream ends immediately with
-   * that error. No done event will be sent (iteration is not complete), but no
-   * further data events will be generated either, since iteration cannot
-   * continue.
-   */
-  factory Stream.fromIterable(Iterable<T> data) {
-    return new _GeneratedStreamImpl<T>(
-        () => new _IterablePendingEvents<T>(data));
-  }
-
-  /**
-   * Creates a stream that repeatedly emits events at [period] intervals.
-   *
-   * The event values are computed by invoking [computation]. The argument to
-   * this callback is an integer that starts with 0 and is incremented for
-   * every event.
-   *
-   * If [computation] is omitted the event values will all be `null`.
-   */
-  factory Stream.periodic(Duration period,
-                          [T computation(int computationCount)]) {
-    if (computation == null) computation = ((i) => null);
-
-    Timer timer;
-    int computationCount = 0;
-    StreamController<T> controller;
-    // Counts the time that the Stream was running (and not paused).
-    Stopwatch watch = new Stopwatch();
-
-    void sendEvent() {
-      watch.reset();
-      T data = computation(computationCount++);
-      controller.add(data);
-    }
-
-    void startPeriodicTimer() {
-      assert(timer == null);
-      timer = new Timer.periodic(period, (Timer timer) {
-        sendEvent();
-      });
-    }
-
-    controller = new StreamController<T>(sync: true,
-        onListen: () {
-          watch.start();
-          startPeriodicTimer();
-        },
-        onPause: () {
-          timer.cancel();
-          timer = null;
-          watch.stop();
-        },
-        onResume: () {
-          assert(timer == null);
-          Duration elapsed = watch.elapsed;
-          watch.start();
-          timer = new Timer(period - elapsed, () {
-            timer = null;
-            startPeriodicTimer();
-            sendEvent();
-          });
-        },
-        onCancel: () {
-          if (timer != null) timer.cancel();
-          timer = null;
-        });
-    return controller.stream;
-  }
-
-  /**
-   * Creates a stream where all events of an existing stream are piped through
-   * a sink-transformation.
-   *
-   * The given [mapSink] closure is invoked when the returned stream is
-   * listened to. All events from the [source] are added into the event sink
-   * that is returned from the invocation. The transformation puts all
-   * transformed events into the sink the [mapSink] closure received during
-   * its invocation. Conceptually the [mapSink] creates a transformation pipe
-   * with the input sink being the returned [EventSink] and the output sink
-   * being the sink it received.
-   *
-   * This constructor is frequently used to build transformers.
-   *
-   * Example use for a duplicating transformer:
-   *
-   *     class DuplicationSink implements EventSink<String> {
-   *       final EventSink<String> _outputSink;
-   *       DuplicationSink(this._outputSink);
-   *
-   *       void add(String data) {
-   *         _outputSink.add(data);
-   *         _outputSink.add(data);
-   *       }
-   *
-   *       void addError(e, [st]) => _outputSink(e, st);
-   *       void close() => _outputSink.close();
-   *     }
-   *
-   *     class DuplicationTransformer implements StreamTransformer<String, String> {
-   *       // Some generic types ommitted for brevety.
-   *       Stream bind(Stream stream) => new Stream<String>.eventTransform(
-   *           stream,
-   *           (EventSink sink) => new DuplicationSink(sink));
-   *     }
-   *
-   *     stringStream.transform(new DuplicationTransformer());
-   *
-   * The resulting stream is a broadcast stream if [source] is.
-   */
-  factory Stream.eventTransformed(Stream source,
-                                  EventSink mapSink(EventSink<T> sink)) {
-    return new _BoundSinkStream(source, mapSink);
-  }
-
-  /**
-   * Reports whether this stream is a broadcast stream.
-   */
-  bool get isBroadcast => false;
-
-  /**
-   * Returns a multi-subscription stream that produces the same events as this.
-   *
-   * The returned stream will subscribe to this stream when its first
-   * subscriber is added, and will stay subscribed until this stream ends,
-   * or a callback cancels the subscription.
-   *
-   * If [onListen] is provided, it is called with a subscription-like object
-   * that represents the underlying subscription to this stream. It is
-   * possible to pause, resume or cancel the subscription during the call
-   * to [onListen]. It is not possible to change the event handlers, including
-   * using [StreamSubscription.asFuture].
-   *
-   * If [onCancel] is provided, it is called in a similar way to [onListen]
-   * when the returned stream stops having listener. If it later gets
-   * a new listener, the [onListen] function is called again.
-   *
-   * Use the callbacks, for example, for pausing the underlying subscription
-   * while having no subscribers to prevent losing events, or canceling the
-   * subscription when there are no listeners.
-   */
-  Stream<T> asBroadcastStream({
-      void onListen(StreamSubscription<T> subscription),
-      void onCancel(StreamSubscription<T> subscription) }) {
-    return new _AsBroadcastStream<T>(this, onListen, onCancel);
-  }
-
-  /**
-   * Adds a subscription to this stream.
-   *
-   * On each data event from this stream, the subscriber's [onData] handler
-   * is called. If [onData] is null, nothing happens.
-   *
-   * On errors from this stream, the [onError] handler is given a
-   * object describing the error.
-   *
-   * The [onError] callback must be of type `void onError(error)` or
-   * `void onError(error, StackTrace stackTrace)`. If [onError] accepts
-   * two arguments it is called with the stack trace (which could be `null` if
-   * the stream itself received an error without stack trace).
-   * Otherwise it is called with just the error object.
-   *
-   * If this stream closes, the [onDone] handler is called.
-   *
-   * If [cancelOnError] is true, the subscription is ended when
-   * the first error is reported. The default is false.
-   */
-  StreamSubscription<T> listen(void onData(T event),
-                               { Function onError,
-                                 void onDone(),
-                                 bool cancelOnError});
-
-  /**
-   * Creates a new stream from this stream that discards some data events.
-   *
-   * The new stream sends the same error and done events as this stream,
-   * but it only sends the data events that satisfy the [test].
-   *
-   * The returned stream is a broadcast stream if this stream is.
-   * If a broadcast stream is listened to more than once, each subscription
-   * will individually perform the `test`.
-   */
-  Stream<T> where(bool test(T event)) {
-    return new _WhereStream<T>(this, test);
-  }
-
-  /**
-   * Creates a new stream that converts each element of this stream
-   * to a new value using the [convert] function.
-   *
-   * The returned stream is a broadcast stream if this stream is.
-   * If a broadcast stream is listened to more than once, each subscription
-   * will individually execute `map` for each event.
-   */
-  Stream map(convert(T event)) {
-    return new _MapStream<T, dynamic>(this, convert);
-  }
-
-  /**
-   * Creates a new stream with each data event of this stream asynchronously
-   * mapped to a new event.
-   *
-   * This acts like [map], except that [convert] may return a [Future],
-   * and in that case, the stream waits for that future to complete before
-   * continuing with its result.
-   *
-   * The returned stream is a broadcast stream if this stream is.
-   */
-  Stream asyncMap(convert(T event)) {
-    StreamController controller;
-    StreamSubscription subscription;
-    void onListen () {
-      final add = controller.add;
-      assert(controller is _StreamController ||
-             controller is _BroadcastStreamController);
-      final eventSink = controller;
-      final addError = eventSink._addError;
-      subscription = this.listen(
-          (T event) {
-            var newValue;
-            try {
-              newValue = convert(event);
-            } catch (e, s) {
-              controller.addError(e, s);
-              return;
-            }
-            if (newValue is Future) {
-              subscription.pause();
-              newValue.then(add, onError: addError)
-                      .whenComplete(subscription.resume);
-            } else {
-              controller.add(newValue);
-            }
-          },
-          onError: addError,
-          onDone: controller.close
-      );
-    }
-    if (this.isBroadcast) {
-      controller = new StreamController.broadcast(
-        onListen: onListen,
-        onCancel: () { subscription.cancel(); },
-        sync: true
-      );
-    } else {
-      controller = new StreamController(
-        onListen: onListen,
-        onPause: () { subscription.pause(); },
-        onResume: () { subscription.resume(); },
-        onCancel: () { subscription.cancel(); },
-        sync: true
-      );
-    }
-    return controller.stream;
-  }
-
-  /**
-   * Creates a new stream with the events of a stream per original event.
-   *
-   * This acts like [expand], except that [convert] returns a [Stream]
-   * instead of an [Iterable].
-   * The events of the returned stream becomes the events of the returned
-   * stream, in the order they are produced.
-   *
-   * If [convert] returns `null`, no value is put on the output stream,
-   * just as if it returned an empty stream.
-   *
-   * The returned stream is a broadcast stream if this stream is.
-   */
-  Stream asyncExpand(Stream convert(T event)) {
-    StreamController controller;
-    StreamSubscription subscription;
-    void onListen() {
-      assert(controller is _StreamController ||
-             controller is _BroadcastStreamController);
-      final eventSink = controller;
-      subscription = this.listen(
-          (T event) {
-            Stream newStream;
-            try {
-              newStream = convert(event);
-            } catch (e, s) {
-              controller.addError(e, s);
-              return;
-            }
-            if (newStream != null) {
-              subscription.pause();
-              controller.addStream(newStream)
-                        .whenComplete(subscription.resume);
-            }
-          },
-          onError: eventSink._addError,  // Avoid Zone error replacement.
-          onDone: controller.close
-      );
-    }
-    if (this.isBroadcast) {
-      controller = new StreamController.broadcast(
-        onListen: onListen,
-        onCancel: () { subscription.cancel(); },
-        sync: true
-      );
-    } else {
-      controller = new StreamController(
-        onListen: onListen,
-        onPause: () { subscription.pause(); },
-        onResume: () { subscription.resume(); },
-        onCancel: () { subscription.cancel(); },
-        sync: true
-      );
-    }
-    return controller.stream;
-  }
-
-  /**
-   * Creates a wrapper Stream that intercepts some errors from this stream.
-   *
-   * If this stream sends an error that matches [test], then it is intercepted
-   * by the [handle] function.
-   *
-   * The [onError] callback must be of type `void onError(error)` or
-   * `void onError(error, StackTrace stackTrace)`. Depending on the function
-   * type the the stream either invokes [onError] with or without a stack
-   * trace. The stack trace argument might be `null` if the stream itself
-   * received an error without stack trace.
-   *
-   * An asynchronous error [:e:] is matched by a test function if [:test(e):]
-   * returns true. If [test] is omitted, every error is considered matching.
-   *
-   * If the error is intercepted, the [handle] function can decide what to do
-   * with it. It can throw if it wants to raise a new (or the same) error,
-   * or simply return to make the stream forget the error.
-   *
-   * If you need to transform an error into a data event, use the more generic
-   * [Stream.transform] to handle the event by writing a data event to
-   * the output sink.
-   *
-   * The returned stream is a broadcast stream if this stream is.
-   * If a broadcast stream is listened to more than once, each subscription
-   * will individually perform the `test` and handle the error.
-   */
-  Stream<T> handleError(Function onError, { bool test(error) }) {
-    return new _HandleErrorStream<T>(this, onError, test);
-  }
-
-  /**
-   * Creates a new stream from this stream that converts each element
-   * into zero or more events.
-   *
-   * Each incoming event is converted to an [Iterable] of new events,
-   * and each of these new events are then sent by the returned stream
-   * in order.
-   *
-   * The returned stream is a broadcast stream if this stream is.
-   * If a broadcast stream is listened to more than once, each subscription
-   * will individually call `convert` and expand the events.
-   */
-  Stream expand(Iterable convert(T value)) {
-    return new _ExpandStream<T, dynamic>(this, convert);
-  }
-
-  /**
-   * Binds this stream as the input of the provided [StreamConsumer].
-   *
-   * The `streamConsumer` is closed when the stream has been added to it.
-   *
-   * Returns a future which completes when the stream has been consumed
-   * and the consumer has been closed.
-   */
-  Future pipe(StreamConsumer<T> streamConsumer) {
-    return streamConsumer.addStream(this).then((_) => streamConsumer.close());
-  }
-
-  /**
-   * Chains this stream as the input of the provided [StreamTransformer].
-   *
-   * Returns the result of [:streamTransformer.bind:] itself.
-   *
-   * The `streamTransformer` can decide whether it wants to return a
-   * broadcast stream or not.
-   */
-  Stream transform(StreamTransformer<T, dynamic> streamTransformer) {
-    return streamTransformer.bind(this);
-  }
-
-  /**
-   * Reduces a sequence of values by repeatedly applying [combine].
-   */
-  Future<T> reduce(T combine(T previous, T element)) {
-    _Future<T> result = new _Future<T>();
-    bool seenFirst = false;
-    T value;
-    StreamSubscription subscription;
-    subscription = this.listen(
-      (T element) {
-        if (seenFirst) {
-          _runUserCode(() => combine(value, element),
-                       (T newValue) { value = newValue; },
-                       _cancelAndErrorClosure(subscription, result));
-        } else {
-          value = element;
-          seenFirst = true;
-        }
-      },
-      onError: result._completeError,
-      onDone: () {
-        if (!seenFirst) {
-          try {
-            throw IterableElementError.noElement();
-          } catch (e, s) {
-            _completeWithErrorCallback(result, e,  s);
-          }
-        } else {
-          result._complete(value);
-        }
-      },
-      cancelOnError: true
-    );
-    return result;
-  }
-
-  /** Reduces a sequence of values by repeatedly applying [combine]. */
-  Future fold(var initialValue, combine(var previous, T element)) {
-    _Future result = new _Future();
-    var value = initialValue;
-    StreamSubscription subscription;
-    subscription = this.listen(
-      (T element) {
-        _runUserCode(
-          () => combine(value, element),
-          (newValue) { value = newValue; },
-          _cancelAndErrorClosure(subscription, result)
-        );
-      },
-      onError: (e, st) {
-        result._completeError(e, st);
-      },
-      onDone: () {
-        result._complete(value);
-      },
-      cancelOnError: true);
-    return result;
-  }
-
-  /**
-   * Collects string of data events' string representations.
-   *
-   * If [separator] is provided, it is inserted between any two
-   * elements.
-   *
-   * Any error in the stream causes the future to complete with that
-   * error. Otherwise it completes with the collected string when
-   * the "done" event arrives.
-   */
-  Future<String> join([String separator = ""]) {
-    _Future<String> result = new _Future<String>();
-    StringBuffer buffer = new StringBuffer();
-    StreamSubscription subscription;
-    bool first = true;
-    subscription = this.listen(
-      (T element) {
-        if (!first) {
-          buffer.write(separator);
-        }
-        first = false;
-        try {
-          buffer.write(element);
-        } catch (e, s) {
-          _cancelAndErrorWithReplacement(subscription, result, e, s);
-        }
-      },
-      onError: (e) {
-        result._completeError(e);
-      },
-      onDone: () {
-        result._complete(buffer.toString());
-      },
-      cancelOnError: true);
-    return result;
-  }
-
-  /**
-   * Checks whether [needle] occurs in the elements provided by this stream.
-   *
-   * Completes the [Future] when the answer is known.
-   * If this stream reports an error, the [Future] will report that error.
-   */
-  Future<bool> contains(Object needle) {
-    _Future<bool> future = new _Future<bool>();
-    StreamSubscription subscription;
-    subscription = this.listen(
-        (T element) {
-          _runUserCode(
-            () => (element == needle),
-            (bool isMatch) {
-              if (isMatch) {
-                _cancelAndValue(subscription, future, true);
-              }
-            },
-            _cancelAndErrorClosure(subscription, future)
-          );
-        },
-        onError: future._completeError,
-        onDone: () {
-          future._complete(false);
-        },
-        cancelOnError: true);
-    return future;
-  }
-
-  /**
-   * Executes [action] on each data event of the stream.
-   *
-   * Completes the returned [Future] when all events of the stream
-   * have been processed. Completes the future with an error if the
-   * stream has an error event, or if [action] throws.
-   */
-  Future forEach(void action(T element)) {
-    _Future future = new _Future();
-    StreamSubscription subscription;
-    subscription = this.listen(
-        (T element) {
-          _runUserCode(
-            () => action(element),
-            (_) {},
-            _cancelAndErrorClosure(subscription, future)
-          );
-        },
-        onError: future._completeError,
-        onDone: () {
-          future._complete(null);
-        },
-        cancelOnError: true);
-    return future;
-  }
-
-  /**
-   * Checks whether [test] accepts all elements provided by this stream.
-   *
-   * Completes the [Future] when the answer is known.
-   * If this stream reports an error, the [Future] will report that error.
-   */
-  Future<bool> every(bool test(T element)) {
-    _Future<bool> future = new _Future<bool>();
-    StreamSubscription subscription;
-    subscription = this.listen(
-        (T element) {
-          _runUserCode(
-            () => test(element),
-            (bool isMatch) {
-              if (!isMatch) {
-                _cancelAndValue(subscription, future, false);
-              }
-            },
-            _cancelAndErrorClosure(subscription, future)
-          );
-        },
-        onError: future._completeError,
-        onDone: () {
-          future._complete(true);
-        },
-        cancelOnError: true);
-    return future;
-  }
-
-  /**
-   * Checks whether [test] accepts any element provided by this stream.
-   *
-   * Completes the [Future] when the answer is known.
-   *
-   * If this stream reports an error, the [Future] reports that error.
-   *
-   * Stops listening to the stream after the first matching element has been
-   * found.
-   *
-   * Internally the method cancels its subscription after this element. This
-   * means that single-subscription (non-broadcast) streams are closed and
-   * cannot be reused after a call to this method.
-   */
-  Future<bool> any(bool test(T element)) {
-    _Future<bool> future = new _Future<bool>();
-    StreamSubscription subscription;
-    subscription = this.listen(
-        (T element) {
-          _runUserCode(
-            () => test(element),
-            (bool isMatch) {
-              if (isMatch) {
-                _cancelAndValue(subscription, future, true);
-              }
-            },
-            _cancelAndErrorClosure(subscription, future)
-          );
-        },
-        onError: future._completeError,
-        onDone: () {
-          future._complete(false);
-        },
-        cancelOnError: true);
-    return future;
-  }
-
-
-  /** Counts the elements in the stream. */
-  Future<int> get length {
-    _Future<int> future = new _Future<int>();
-    int count = 0;
-    this.listen(
-      (_) { count++; },
-      onError: future._completeError,
-      onDone: () {
-        future._complete(count);
-      },
-      cancelOnError: true);
-    return future;
-  }
-
-  /**
-   * Reports whether this stream contains any elements.
-   *
-   * Stops listening to the stream after the first element has been received.
-   *
-   * Internally the method cancels its subscription after the first element.
-   * This means that single-subscription (non-broadcast) streams are closed and
-   * cannot be reused after a call to this getter.
-   */
-  Future<bool> get isEmpty {
-    _Future<bool> future = new _Future<bool>();
-    StreamSubscription subscription;
-    subscription = this.listen(
-      (_) {
-        _cancelAndValue(subscription, future, false);
-      },
-      onError: future._completeError,
-      onDone: () {
-        future._complete(true);
-      },
-      cancelOnError: true);
-    return future;
-  }
-
-  /** Collects the data of this stream in a [List]. */
-  Future<List<T>> toList() {
-    List<T> result = <T>[];
-    _Future<List<T>> future = new _Future<List<T>>();
-    this.listen(
-      (T data) {
-        result.add(data);
-      },
-      onError: future._completeError,
-      onDone: () {
-        future._complete(result);
-      },
-      cancelOnError: true);
-    return future;
-  }
-
-  /**
-   * Collects the data of this stream in a [Set].
-   *
-   * The returned set is the same type as returned by `new Set<T>()`.
-   * If another type of set is needed, either use [forEach] to add each
-   * element to the set, or use
-   * `toList().then((list) => new SomeOtherSet.from(list))`
-   * to create the set.
-   */
-  Future<Set<T>> toSet() {
-    Set<T> result = new Set<T>();
-    _Future<Set<T>> future = new _Future<Set<T>>();
-    this.listen(
-      (T data) {
-        result.add(data);
-      },
-      onError: future._completeError,
-      onDone: () {
-        future._complete(result);
-      },
-      cancelOnError: true);
-    return future;
-  }
-
-  /**
-   * Discards all data on the stream, but signals when it's done or an error
-   * occured.
-   *
-   * When subscribing using [drain], cancelOnError will be true. This means
-   * that the future will complete with the first error on the stream and then
-   * cancel the subscription.
-   *
-   * In case of a `done` event the future completes with the given
-   * [futureValue].
-   */
-  Future drain([var futureValue]) => listen(null, cancelOnError: true)
-      .asFuture(futureValue);
-
-  /**
-   * Provides at most the first [n] values of this stream.
-   *
-   * Forwards the first [n] data events of this stream, and all error
-   * events, to the returned stream, and ends with a done event.
-   *
-   * If this stream produces fewer than [count] values before it's done,
-   * so will the returned stream.
-   *
-   * Stops listening to the stream after the first [n] elements have been
-   * received.
-   *
-   * Internally the method cancels its subscription after these elements. This
-   * means that single-subscription (non-broadcast) streams are closed and
-   * cannot be reused after a call to this method.
-   *
-   * The returned stream is a broadcast stream if this stream is.
-   * For a broadcast stream, the events are only counted from the time
-   * the returned stream is listened to.
-   */
-  Stream<T> take(int count) {
-    return new _TakeStream(this, count);
-  }
-
-  /**
-   * Forwards data events while [test] is successful.
-   *
-   * The returned stream provides the same events as this stream as long
-   * as [test] returns [:true:] for the event data. The stream is done
-   * when either this stream is done, or when this stream first provides
-   * a value that [test] doesn't accept.
-   *
-   * Stops listening to the stream after the accepted elements.
-   *
-   * Internally the method cancels its subscription after these elements. This
-   * means that single-subscription (non-broadcast) streams are closed and
-   * cannot be reused after a call to this method.
-   *
-   * The returned stream is a broadcast stream if this stream is.
-   * For a broadcast stream, the events are only tested from the time
-   * the returned stream is listened to.
-   */
-  Stream<T> takeWhile(bool test(T element)) {
-    return new _TakeWhileStream(this, test);
-  }
-
-  /**
-   * Skips the first [count] data events from this stream.
-   *
-   * The returned stream is a broadcast stream if this stream is.
-   * For a broadcast stream, the events are only counted from the time
-   * the returned stream is listened to.
-   */
-  Stream<T> skip(int count) {
-    return new _SkipStream(this, count);
-  }
-
-  /**
-   * Skip data events from this stream while they are matched by [test].
-   *
-   * Error and done events are provided by the returned stream unmodified.
-   *
-   * Starting with the first data event where [test] returns false for the
-   * event data, the returned stream will have the same events as this stream.
-   *
-   * The returned stream is a broadcast stream if this stream is.
-   * For a broadcast stream, the events are only tested from the time
-   * the returned stream is listened to.
-   */
-  Stream<T> skipWhile(bool test(T element)) {
-    return new _SkipWhileStream(this, test);
-  }
-
-  /**
-   * Skips data events if they are equal to the previous data event.
-   *
-   * The returned stream provides the same events as this stream, except
-   * that it never provides two consequtive data events that are equal.
-   *
-   * Equality is determined by the provided [equals] method. If that is
-   * omitted, the '==' operator on the last provided data element is used.
-   *
-   * The returned stream is a broadcast stream if this stream is.
-   * If a broadcast stream is listened to more than once, each subscription
-   * will individually perform the `equals` test.
-   */
-  Stream<T> distinct([bool equals(T previous, T next)]) {
-    return new _DistinctStream(this, equals);
-  }
-
-  /**
-   * Returns the first element of the stream.
-   *
-   * Stops listening to the stream after the first element has been received.
-   *
-   * Internally the method cancels its subscription after the first element.
-   * This means that single-subscription (non-broadcast) streams are closed
-   * and cannot be reused after a call to this getter.
-   *
-   * If an error event occurs before the first data event, the resulting future
-   * is completed with that error.
-   *
-   * If this stream is empty (a done event occurs before the first data event),
-   * the resulting future completes with a [StateError].
-   *
-   * Except for the type of the error, this method is equivalent to
-   * [:this.elementAt(0):].
-   */
-  Future<T> get first {
-    _Future<T> future = new _Future<T>();
-    StreamSubscription subscription;
-    subscription = this.listen(
-      (T value) {
-        _cancelAndValue(subscription, future, value);
-      },
-      onError: future._completeError,
-      onDone: () {
-        try {
-          throw IterableElementError.noElement();
-        } catch (e, s) {
-          _completeWithErrorCallback(future, e, s);
-        }
-      },
-      cancelOnError: true);
-    return future;
-  }
-
-  /**
-   * Returns the last element of the stream.
-   *
-   * If an error event occurs before the first data event, the resulting future
-   * is completed with that error.
-   *
-   * If this stream is empty (a done event occurs before the first data event),
-   * the resulting future completes with a [StateError].
-   */
-  Future<T> get last {
-    _Future<T> future = new _Future<T>();
-    T result = null;
-    bool foundResult = false;
-    StreamSubscription subscription;
-    subscription = this.listen(
-      (T value) {
-        foundResult = true;
-        result = value;
-      },
-      onError: future._completeError,
-      onDone: () {
-        if (foundResult) {
-          future._complete(result);
-          return;
-        }
-        try {
-          throw IterableElementError.noElement();
-        } catch (e, s) {
-          _completeWithErrorCallback(future, e, s);
-        }
-      },
-      cancelOnError: true);
-    return future;
-  }
-
-  /**
-   * Returns the single element.
-   *
-   * If an error event occurs before or after the first data event, the
-   * resulting future is completed with that error.
-   *
-   * If [this] is empty or has more than one element throws a [StateError].
-   */
-  Future<T> get single {
-    _Future<T> future = new _Future<T>();
-    T result = null;
-    bool foundResult = false;
-    StreamSubscription subscription;
-    subscription = this.listen(
-      (T value) {
-        if (foundResult) {
-          // This is the second element we get.
-          try {
-            throw IterableElementError.tooMany();
-          } catch (e, s) {
-            _cancelAndErrorWithReplacement(subscription, future, e, s);
-          }
-          return;
-        }
-        foundResult = true;
-        result = value;
-      },
-      onError: future._completeError,
-      onDone: () {
-        if (foundResult) {
-          future._complete(result);
-          return;
-        }
-        try {
-          throw IterableElementError.noElement();
-        } catch (e, s) {
-          _completeWithErrorCallback(future, e, s);
-        }
-      },
-      cancelOnError: true);
-    return future;
-  }
-
-  /**
-   * Finds the first element of this stream matching [test].
-   *
-   * Returns a future that is filled with the first element of this stream
-   * that [test] returns true for.
-   *
-   * If no such element is found before this stream is done, and a
-   * [defaultValue] function is provided, the result of calling [defaultValue]
-   * becomes the value of the future.
-   *
-   * Stops listening to the stream after the first matching element has been
-   * received.
-   *
-   * Internally the method cancels its subscription after the first element that
-   * matches the predicate. This means that single-subscription (non-broadcast)
-   * streams are closed and cannot be reused after a call to this method.
-   *
-   * If an error occurs, or if this stream ends without finding a match and
-   * with no [defaultValue] function provided, the future will receive an
-   * error.
-   */
-  Future<dynamic> firstWhere(bool test(T element), {Object defaultValue()}) {
-    _Future<dynamic> future = new _Future();
-    StreamSubscription subscription;
-    subscription = this.listen(
-      (T value) {
-        _runUserCode(
-          () => test(value),
-          (bool isMatch) {
-            if (isMatch) {
-              _cancelAndValue(subscription, future, value);
-            }
-          },
-          _cancelAndErrorClosure(subscription, future)
-        );
-      },
-      onError: future._completeError,
-      onDone: () {
-        if (defaultValue != null) {
-          _runUserCode(defaultValue, future._complete, future._completeError);
-          return;
-        }
-        try {
-          throw IterableElementError.noElement();
-        } catch (e, s) {
-          _completeWithErrorCallback(future, e, s);
-        }
-      },
-      cancelOnError: true);
-    return future;
-  }
-
-  /**
-   * Finds the last element in this stream matching [test].
-   *
-   * As [firstWhere], except that the last matching element is found.
-   * That means that the result cannot be provided before this stream
-   * is done.
-   */
-  Future<dynamic> lastWhere(bool test(T element), {Object defaultValue()}) {
-    _Future<dynamic> future = new _Future();
-    T result = null;
-    bool foundResult = false;
-    StreamSubscription subscription;
-    subscription = this.listen(
-      (T value) {
-        _runUserCode(
-          () => true == test(value),
-          (bool isMatch) {
-            if (isMatch) {
-              foundResult = true;
-              result = value;
-            }
-          },
-          _cancelAndErrorClosure(subscription, future)
-        );
-      },
-      onError: future._completeError,
-      onDone: () {
-        if (foundResult) {
-          future._complete(result);
-          return;
-        }
-        if (defaultValue != null) {
-          _runUserCode(defaultValue, future._complete, future._completeError);
-          return;
-        }
-        try {
-          throw IterableElementError.noElement();
-        } catch (e, s) {
-          _completeWithErrorCallback(future, e, s);
-        }
-      },
-      cancelOnError: true);
-    return future;
-  }
-
-  /**
-   * Finds the single element in this stream matching [test].
-   *
-   * Like [lastMatch], except that it is an error if more than one
-   * matching element occurs in the stream.
-   */
-  Future<T> singleWhere(bool test(T element)) {
-    _Future<T> future = new _Future<T>();
-    T result = null;
-    bool foundResult = false;
-    StreamSubscription subscription;
-    subscription = this.listen(
-      (T value) {
-        _runUserCode(
-          () => true == test(value),
-          (bool isMatch) {
-            if (isMatch) {
-              if (foundResult) {
-                try {
-                  throw IterableElementError.tooMany();
-                } catch (e, s) {
-                  _cancelAndErrorWithReplacement(subscription, future, e, s);
-                }
-                return;
-              }
-              foundResult = true;
-              result = value;
-            }
-          },
-          _cancelAndErrorClosure(subscription, future)
-        );
-      },
-      onError: future._completeError,
-      onDone: () {
-        if (foundResult) {
-          future._complete(result);
-          return;
-        }
-        try {
-          throw IterableElementError.noElement();
-        } catch (e, s) {
-          _completeWithErrorCallback(future, e, s);
-        }
-      },
-      cancelOnError: true);
-    return future;
-  }
-
-  /**
-   * Returns the value of the [index]th data event of this stream.
-   *
-   * Stops listening to the stream after the [index]th data event has been
-   * received.
-   *
-   * Internally the method cancels its subscription after these elements. This
-   * means that single-subscription (non-broadcast) streams are closed and
-   * cannot be reused after a call to this method.
-   *
-   * If an error event occurs before the value is found, the future completes
-   * with this error.
-   *
-   * If a done event occurs before the value is found, the future completes
-   * with a [RangeError].
-   */
-  Future<T> elementAt(int index) {
-    if (index is! int || index < 0) throw new ArgumentError(index);
-    _Future<T> future = new _Future<T>();
-    StreamSubscription subscription;
-    int elementIndex = 0;
-    subscription = this.listen(
-      (T value) {
-        if (index == elementIndex) {
-          _cancelAndValue(subscription, future, value);
-          return;
-        }
-        elementIndex += 1;
-      },
-      onError: future._completeError,
-      onDone: () {
-        future._completeError(
-            new RangeError.index(index, this, "index", null, elementIndex));
-      },
-      cancelOnError: true);
-    return future;
-  }
-
-  /**
-   * Creates a new stream with the same events as this stream.
-   *
-   * Whenever more than [timeLimit] passes between two events from this stream,
-   * the [onTimeout] function is called.
-   *
-   * The countdown doesn't start until the returned stream is listened to.
-   * The countdown is reset every time an event is forwarded from this stream,
-   * or when the stream is paused and resumed.
-   *
-   * The [onTimeout] function is called with one argument: an
-   * [EventSink] that allows putting events into the returned stream.
-   * This `EventSink` is only valid during the call to `onTimeout`.
-   *
-   * If `onTimeout` is omitted, a timeout will just put a [TimeoutException]
-   * into the error channel of the returned stream.
-   *
-   * The returned stream is a broadcast stream if this stream is.
-   * If a broadcast stream is listened to more than once, each subscription
-   * will have its individually timer that starts counting on listen,
-   * and the subscriptions' timers can be paused individually.
-   */
-  Stream timeout(Duration timeLimit, {void onTimeout(EventSink sink)}) {
-    StreamController controller;
-    // The following variables are set on listen.
-    StreamSubscription<T> subscription;
-    Timer timer;
-    Zone zone;
-    Function timeout;
-
-    void onData(T event) {
-      timer.cancel();
-      controller.add(event);
-      timer = zone.createTimer(timeLimit, timeout);
-    }
-    void onError(error, StackTrace stackTrace) {
-      timer.cancel();
-      assert(controller is _StreamController ||
-             controller is _BroadcastStreamController);
-      var eventSink = controller;
-      eventSink._addError(error, stackTrace);  // Avoid Zone error replacement.
-      timer = zone.createTimer(timeLimit, timeout);
-    }
-    void onDone() {
-      timer.cancel();
-      controller.close();
-    }
-    void onListen() {
-      // This is the onListen callback for of controller.
-      // It runs in the same zone that the subscription was created in.
-      // Use that zone for creating timers and running the onTimeout
-      // callback.
-      zone = Zone.current;
-      if (onTimeout == null) {
-        timeout = () {
-          controller.addError(new TimeoutException("No stream event",
-                                                   timeLimit), null);
-        };
-      } else {
-        onTimeout = zone.registerUnaryCallback(onTimeout);
-        _ControllerEventSinkWrapper wrapper =
-            new _ControllerEventSinkWrapper(null);
-        timeout = () {
-          wrapper._sink = controller;  // Only valid during call.
-          zone.runUnaryGuarded(onTimeout, wrapper);
-          wrapper._sink = null;
-        };
-      }
-
-      subscription = this.listen(onData, onError: onError, onDone: onDone);
-      timer = zone.createTimer(timeLimit, timeout);
-    }
-    Future onCancel() {
-      timer.cancel();
-      Future result = subscription.cancel();
-      subscription = null;
-      return result;
-    }
-    controller = isBroadcast
-        ? new _SyncBroadcastStreamController(onListen, onCancel)
-        : new _SyncStreamController(
-              onListen,
-              () {
-                // Don't null the timer, onCancel may call cancel again.
-                timer.cancel();
-                subscription.pause();
-              },
-              () {
-                subscription.resume();
-                timer = zone.createTimer(timeLimit, timeout);
-              },
-              onCancel);
-    return controller.stream;
-  }
-}
-
-/**
- * A subscritption on events from a [Stream].
- *
- * When you listen on a [Stream] using [Stream.listen],
- * a [StreamSubscription] object is returned.
- *
- * The subscription provides events to the listener,
- * and holds the callbacks used to handle the events.
- * The subscription can also be used to unsubscribe from the events,
- * or to temporarily pause the events from the stream.
- */
-abstract class StreamSubscription<T> {
-  /**
-   * Cancels this subscription. It will no longer receive events.
-   *
-   * May return a future which completes when the stream is done cleaning up.
-   * This can be used if the stream needs to release some resources
-   * that are needed for a following operation,
-   * for example a file being read, that should be deleted afterwards.
-   * In that case, the file may not be able to be deleted successfully
-   * until the returned future has completed.
-   *
-   * The future will be completed with a `null` value.
-   * If the cleanup throws, which it really shouldn't, the returned future
-   * will be completed with that error.
-   *
-   * Returns `null` if there is no need to wait.
-   */
-  Future cancel();
-
-  /**
-   * Set or override the data event handler of this subscription.
-   *
-   * This method overrides the handler that has been set at the invocation of
-   * [Stream.listen].
-   */
-  void onData(void handleData(T data));
-
-  /**
-   * Set or override the error event handler of this subscription.
-   *
-   * This method overrides the handler that has been set at the invocation of
-   * [Stream.listen] or by calling [asFuture].
-   */
-  void onError(Function handleError);
-
-  /**
-   * Set or override the done event handler of this subscription.
-   *
-   * This method overrides the handler that has been set at the invocation of
-   * [Stream.listen] or by calling [asFuture].
-   */
-  void onDone(void handleDone());
-
-  /**
-   * Request that the stream pauses events until further notice.
-   *
-   * While paused, the subscription will not fire any events.
-   * If it receives events from its source, they will be buffered until
-   * the subscription is resumed.
-   * The underlying source is usually informed about the pause,
-   * so it can stop generating events until the subscription is resumed.
-   *
-   * To avoid buffering events on a broadcast stream, it is better to
-   * cancel this subscription, and start to listen again when events
-   * are needed.
-   *
-   * If [resumeSignal] is provided, the stream will undo the pause
-   * when the future completes. If the future completes with an error,
-   * the stream will resume, but the error will not be handled!
-   *
-   * A call to [resume] will also undo a pause.
-   *
-   * If the subscription is paused more than once, an equal number
-   * of resumes must be performed to resume the stream.
-   *
-   * Currently DOM streams silently drop events when the stream is paused. This
-   * is a bug and will be fixed.
-   */
-  void pause([Future resumeSignal]);
-
-  /**
-   * Resume after a pause.
-   */
-  void resume();
-
-  /**
-   * Returns true if the [StreamSubscription] is paused.
-   */
-  bool get isPaused;
-
-  /**
-   * Returns a future that handles the [onDone] and [onError] callbacks.
-   *
-   * This method *overwrites* the existing [onDone] and [onError] callbacks
-   * with new ones that complete the returned future.
-   *
-   * In case of an error the subscription will automatically cancel (even
-   * when it was listening with `cancelOnError` set to `false`).
-   *
-   * In case of a `done` event the future completes with the given
-   * [futureValue].
-   */
-  Future asFuture([var futureValue]);
-}
-
-
-/**
- * An interface that abstracts creation or handling of [Stream] events.
- */
-abstract class EventSink<T> implements Sink<T> {
-  /** Send a data event to a stream. */
-  void add(T event);
-
-  /** Send an async error to a stream. */
-  void addError(errorEvent, [StackTrace stackTrace]);
-
-  /** Close the sink. No further events can be added after closing. */
-  void close();
-}
-
-
-/** [Stream] wrapper that only exposes the [Stream] interface. */
-class StreamView<T> extends Stream<T> {
-  Stream<T> _stream;
-
-  StreamView(this._stream);
-
-  bool get isBroadcast => _stream.isBroadcast;
-
-  Stream<T> asBroadcastStream({void onListen(StreamSubscription<T> subscription),
-                               void onCancel(StreamSubscription<T> subscription)})
-      => _stream.asBroadcastStream(onListen: onListen, onCancel: onCancel);
-
-  StreamSubscription<T> listen(void onData(T value),
-                               { Function onError,
-                                 void onDone(),
-                                 bool cancelOnError }) {
-    return _stream.listen(onData, onError: onError, onDone: onDone,
-                          cancelOnError: cancelOnError);
-  }
-}
-
-
-/**
- * The target of a [Stream.pipe] call.
- *
- * The [Stream.pipe] call will pass itself to this object, and then return
- * the resulting [Future]. The pipe should complete the future when it's
- * done.
- */
-abstract class StreamConsumer<S> {
-  /**
-   * Consumes the elements of [stream].
-   *
-   * Listens on [stream] and does something for each event.
-   *
-   * The consumer may stop listening after an error, or it may consume
-   * all the errors and only stop at a done event.
-   */
-  Future addStream(Stream<S> stream);
-
-  /**
-   * Tell the consumer that no futher streams will be added.
-   *
-   * Returns a future that is completed when the consumer is done handling
-   * events.
-   */
-  Future close();
-}
-
-
-/**
- * A [StreamSink] unifies the asynchronous methods from [StreamConsumer] and
- * the synchronous methods from [EventSink].
- *
- * The [EventSink] methods can't be used while the [addStream] is called.
- * As soon as the [addStream]'s [Future] completes with a value, the
- * [EventSink] methods can be used again.
- *
- * If [addStream] is called after any of the [EventSink] methods, it'll
- * be delayed until the underlying system has consumed the data added by the
- * [EventSink] methods.
- *
- * When [EventSink] methods are used, the [done] [Future] can be used to
- * catch any errors.
- *
- * When [close] is called, it will return the [done] [Future].
- */
-abstract class StreamSink<S> implements StreamConsumer<S>, EventSink<S> {
-  /**
-   * As [EventSink.close], but returns a future.
-   *
-   * Returns the same future as [done].
-   */
-  Future close();
-
-  /**
-   * Return a future which is completed when the [StreamSink] is finished.
-   *
-   * If the `StreamSink` fails with an error,
-   * perhaps in response to adding events using [add], [addError] or [close],
-   * the [done] future will complete with that error.
-   *
-   * Otherwise, the returned future will complete when either:
-   *
-   * * all events have been processed and the sink has been closed, or
-   * * the sink has otherwise been stopped from handling more events
-   *   (for example by cancelling a stream subscription).
-   */
-  Future get done;
-}
-
-
-/**
- * The target of a [Stream.transform] call.
- *
- * The [Stream.transform] call will pass itself to this object and then return
- * the resulting stream.
- *
- * It is good practice to write transformers that can be used multiple times.
- */
-abstract class StreamTransformer<S, T> {
-  /**
-   * Creates a [StreamTransformer].
-   *
-   * The returned instance takes responsibility of implementing ([bind]).
-   * When the user invokes `bind` it returns a new "bound" stream. Only when
-   * the user starts listening to the bound stream, the `listen` method
-   * invokes the given closure [transformer].
-   *
-   * The [transformer] closure receives the stream, that was bound, as argument
-   * and returns a [StreamSubscription]. In almost all cases the closure
-   * listens itself to the stream that is given as argument.
-   *
-   * The result of invoking the [transformer] closure is a [StreamSubscription].
-   * The bound stream-transformer (created by the `bind` method above) then sets
-   * the handlers it received as part of the `listen` call.
-   *
-   * Conceptually this can be summarized as follows:
-   *
-   * 1. `var transformer = new StreamTransformer(transformerClosure);`
-   *   creates a `StreamTransformer` that supports the `bind` method.
-   * 2. `var boundStream = stream.transform(transformer);` binds the `stream`
-   *   and returns a bound stream that has a pointer to `stream`.
-   * 3. `boundStream.listen(f1, onError: f2, onDone: f3, cancelOnError: b)`
-   *   starts the listening and transformation. This is accomplished
-   *   in 2 steps: first the `boundStream` invokes the `transformerClosure` with
-   *   the `stream` it captured: `transformerClosure(stream, b)`.
-   *   The result `subscription`, a [StreamSubscription], is then
-   *   updated to receive its handlers: `subscription.onData(f1)`,
-   *   `subscription.onError(f2)`, `subscription(f3)`. Finally the subscription
-   *   is returned as result of the `listen` call.
-   *
-   * There are two common ways to create a StreamSubscription:
-   *
-   * 1. by creating a new class that implements [StreamSubscription].
-   *    Note that the subscription should run callbacks in the [Zone] the
-   *    stream was listened to.
-   * 2. by allocating a [StreamController] and to return the result of
-   *    listening to its stream.
-   *
-   * Example use of a duplicating transformer:
-   *
-   *     stringStream.transform(new StreamTransformer<String, String>(
-   *         (Stream<String> input, bool cancelOnError) {
-   *           StreamController<String> controller;
-   *           StreamSubscription<String> subscription;
-   *           controller = new StreamController<String>(
-   *             onListen: () {
-   *               subscription = input.listen((data) {
-   *                   // Duplicate the data.
-   *                   controller.add(data);
-   *                   controller.add(data);
-   *                 },
-   *                 onError: controller.addError,
-   *                 onDone: controller.close,
-   *                 cancelOnError: cancelOnError);
-   *             },
-   *             onPause: subscription.pause,
-   *             onResume: subscription.resume,
-   *             onCancel: subscription.cancel,
-   *             sync: true);
-   *           return controller.stream.listen(null);
-   *         });
-   */
-  const factory StreamTransformer(
-      StreamSubscription<T> transformer(Stream<S> stream, bool cancelOnError))
-      = _StreamSubscriptionTransformer;
-
-  /**
-   * Creates a [StreamTransformer] that delegates events to the given functions.
-   *
-   * Example use of a duplicating transformer:
-   *
-   *     stringStream.transform(new StreamTransformer<String, String>.fromHandlers(
-   *         handleData: (String value, EventSink<String> sink) {
-   *           sink.add(value);
-   *           sink.add(value);  // Duplicate the incoming events.
-   *         }));
-   */
-  factory StreamTransformer.fromHandlers({
-      void handleData(S data, EventSink<T> sink),
-      void handleError(Object error, StackTrace stackTrace, EventSink<T> sink),
-      void handleDone(EventSink<T> sink)})
-          = _StreamHandlerTransformer;
-
-  /**
-   * Transform the incoming [stream]'s events.
-   *
-   * Creates a new stream.
-   * When this stream is listened to, it will start listening on [stream],
-   * and generate events on the new stream based on the events from [stream].
-   *
-   * Subscriptions on the returned stream should propagate pause state
-   * to the subscription on [stream].
-   */
-  Stream<T> bind(Stream<S> stream);
-}
-
-/**
- * An [Iterable] like interface for the values of a [Stream].
- *
- * This wraps a [Stream] and a subscription on the stream. It listens
- * on the stream, and completes the future returned by [moveNext] when the
- * next value becomes available.
- */
-abstract class StreamIterator<T> {
-
-  /** Create a [StreamIterator] on [stream]. */
-  factory StreamIterator(Stream<T> stream)
-      // TODO(lrn): use redirecting factory constructor when type
-      // arguments are supported.
-      => new _StreamIteratorImpl<T>(stream);
-
-  /**
-   * Wait for the next stream value to be available.
-   *
-   * It is not allowed to call this function again until the future has
-   * completed. If the returned future completes with anything except `true`,
-   * the iterator is done, and no new value will ever be available.
-   *
-   * The future may complete with an error, if the stream produces an error.
-   */
-  Future<bool> moveNext();
-
-  /**
-   * The current value of the stream.
-   *
-   * Only valid when the future returned by [moveNext] completes with `true`
-   * as value, and only until the next call to [moveNext].
-   */
-  T get current;
-
-  /**
-   * Cancels the stream iterator (and the underlying stream subscription) early.
-   *
-   * The stream iterator is automatically canceled if the [moveNext] future
-   * completes with either `false` or an error.
-   *
-   * If a [moveNext] call has been made, it will complete with `false` as value,
-   * as will all further calls to [moveNext].
-   *
-   * If you need to stop listening for values before the stream iterator is
-   * automatically closed, you must call [cancel] to ensure that the stream
-   * is properly closed.
-   *
-   * Returns a future if the cancel-operation is not completed synchronously.
-   * Otherwise returns `null`.
-   */
-  Future cancel();
-}
-
-
-/**
- * Wraps an [_EventSink] so it exposes only the [EventSink] interface.
- */
-class _ControllerEventSinkWrapper<T> implements EventSink<T> {
-  EventSink _sink;
-  _ControllerEventSinkWrapper(this._sink);
-
-  void add(T data) { _sink.add(data); }
-  void addError(error, [StackTrace stackTrace]) {
-    _sink.addError(error, stackTrace);
-  }
-  void close() { _sink.close(); }
-}