anchor.diff:          observers.[index]
       
       let onEvent (sender : obj) (e : RoutedEventArgs) = 
  -        let mapped = map(e)
  +        let mapped = map (e)
           let observer = getObserver (sender :?> FrameworkElement)
           Reflection.invoke observer "OnNext" mapped |> ignore
       
  
positive.code:             DesignMode.failIfNotDesignMode "map cannot be of type FunctionExtension. (Should never get here)"
              fun e -> e
          | _ -> 
              DesignMode.failIfDesignModef "Invalid map method: %s" (map.GetType().FullName)
              fun e -> e
  
      let observerBinding = observerBinding
      let map = getMapMethod map
  
      static let HandlersProperty = 
          DependencyProperty.RegisterAttached
              ("Handlers", typeof<ResizeArray<HandlerExtension>>, typeof<HandlerExtension>, PropertyMetadata(null))
  
negative.code:         RoutedEventHandler onEvent :> _
      
      member __.ObserverBinding = observerBinding
  