title: Cannot convert value of type 'T?' to expected argument type '_?' - Generic types and completion blocks
body: <p>I'm trying to implement <code>AlamofireObjectMapper</code> (<a href="https://github.com/tristanhimmelman/AlamofireObjectMapper" rel="nofollow">https://github.com/tristanhimmelman/AlamofireObjectMapper</a>) with Alamofire 3 and latest version of ObjectMapper (<a href="https://github.com/Hearst-DD/ObjectMapper" rel="nofollow">https://github.com/Hearst-DD/ObjectMapper</a>).</p>
  
  <p>It seems that <code>AlamofireObjectMapper</code>, hasn't been updated to work with Alamofire 3, so I'm trying to do it myself.</p>
  
  <p>I've come to this piece of code and now i'm stuck.</p>
  
  <p>It seems that the Generic Type T is not accesible inside the completion block of the response. Is a <code>Alamofire</code> 3 change or a Swift 2.1 change?</p>
  
  <p>This is the error:</p>
  
  <blockquote>
    <p>Cannot convert value of type 'T?' to expected argument type '_?'</p>
  </blockquote>
  
  <pre><code>  public func responseObject&lt;T: Mappable&gt;(queue: dispatch_queue_t?, keyPath: String?, completionHandler: (NSURLRequest, NSHTTPURLResponse?, T?, AnyObject?, ErrorType?) -&gt; Void) -&gt; Self {
      return response(queue: queue) { (request, response, data, error) -&gt; Void in
          dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)) {
              let JSONResponseSerializer = Request.JSONResponseSerializer(options: .AllowFragments)
              let result = JSONResponseSerializer.serializeResponse(request, response, data, error)
              let parsedObject = Mapper&lt;T&gt;().map(keyPath != nil ? result.value?[keyPath!] : result.value)
  
              dispatch_async(queue ?? dispatch_get_main_queue()) {
                  completionHandler(self.request!, self.response, parsedObject, result.value ?? response.data, result.error) // Here it shows the error: Cannot convert value of type 'T?' to expected argument type '_?' 
              }
          }
      }
  
  }
  </code></pre>