1. Create a new Qt Gui Application.
2. Open main.cpp from this project.
3. Select line 8:

       w.show();
   

4. Press Alt+Enter.
5. Press Enter to trigger "Extract Function".
6. Enter a name for the function and press Enter again.
   Creator will add a function with one parameter of type MainWindow. This can't be compiled since MainWindow's copy ctor is not public.

Refactor actions should never make correct code incorrect. In this case a const reference might be used.