Fix Stream.distinct.

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 1004 matching lines @@
    */
   Stream<T> skipWhile(bool test(T element)) {
     return new _SkipWhileStream<T>(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 consecutive data events that are equal.
+   * That is, errors are passed through to the returned stream, and
+   * data events are passed through if they are distinct from the most
+   * recently emitted data event.
    *
    * Equality is determined by the provided [equals] method. If that is
    * omitted, the '==' operator on the last provided data element is used.
    *
+   * If [equals] throws, the data event is replaced by an error event
+   * containing the thrown error. The behavior is equivalent to the
+   * original stream emitting the error event.
+   *
    * 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<T>(this, equals);
   }
 
   /**
    * Returns the first element of the stream.
@@ skipping 893 matching lines @@
   /// Must only be used instead of listening to the [values] stream.
   /// If the stream has been listened to, this call fails.
   /// After calling this method, listening on the [values] stream fails.
   Future cancel() {
     // If values has been listened to,
     // this throws a StateError saying that stream has already been listened to,
     // which is a correct error message for this call too.
     return values.listen(null).cancel();
   }
 }