   /// - parameter transform: the transform to be performed
   /// - returns: a `Deferred` reference representing the return value of the transform
 
-  public func map<U>(qos qos: qos_class_t = QOS_CLASS_UNSPECIFIED, _ transform: (T) throws -> U) -> Deferred<U>
+  public func map<U>(qos qos: qos_class_t = QOS_CLASS_UNSPECIFIED, transform: (T) throws -> U) -> Deferred<U>
   {
     return Mapped<U>(qos: qos, source: self, transform: transform)
   }

  /// - parameter qos: the QOS class at which to execute the transform; defaults to the QOS class of this Deferred's queue.
  /// - parameter task: the closure to be enqueued

  public func onValue(qos qos: qos_class_t = QOS_CLASS_UNSPECIFIED, _ task: (T) -> Void)
  {
    notify(qos: qos) { if let value = $0.value { task(value) } }
  }

  /// - parameter transform: the transform to be performed
  /// - returns: a `Deferred` reference representing the return value of the transform

  public func recover(qos qos: qos_class_t = QOS_CLASS_UNSPECIFIED, transform: (ErrorType) -> Deferred<T>) -> Deferred<T>
  {
    return Bind(qos: qos, source: self, transform: transform)
  }
