Update documentation of Stream.pipe to match behavior.

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
 // -------------------------------------------------------------------
 
@@ skipping 460 matching lines @@
    *
    * 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].
+   * Pipe the events of this stream into [streamConsumer].
    *
-   * The `streamConsumer` is closed when the stream has been added to it.
+   * The events of this stream are added to `streamConsumer` using
+   * [StreamConsumer.addStream].
+   * The `streamConsumer` is closed when this stream has been successfully added
+   * to it - when the future returned by `addStream` completes without an error.
    *
    * Returns a future which completes when the stream has been consumed
    * and the consumer has been closed.
+   *
+   * The returned future completes with the same result as the future returned
+   * by [StreamConsumer.close].
+   * If the adding of the stream itself fails in some way,
+   * then the consumer is expected to be closed, and won't be closed again.
+   * In that case the returned future completes with the error from calling
+   * `addStream`.
    */
   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.
    *
@@ skipping 1216 matching lines @@
 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(); }
 }