anchor.diff:    /// Creates a multi-subscription stream.
     ///
     /// Each time the created stream is listened to,
  -  /// the [onListen] callback is invoked with a new [MultiStreamController]
  +  /// the [onListen] callback is invoked with a new [MultiStreamController],
     /// which forwards events to the [StreamSubscription]
     /// returned by that [listen] call.
     ///
  
positive.code:   /// 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
  
negative.code:   /// If this stream emits an error, or the call to [Object.toString] throws,
    /// the returned future is completed with that error,
    /// and processing stops.
    ///
    /// Example:
    /// ```dart
    /// final result = await Stream.fromIterable(['Mars', 'Venus', 'Earth'])
    ///     .join('--');
    /// print(result); // 'Mars--Venus--Earth'
    /// ```
    Future<String> join([String separator = ""]) {
      _Future<String> result = new _Future<String>();
      StringBuffer buffer = new StringBuffer();
  