> Saying "using RAII for memory management" is insufficient - with just RAII, you cannot even assign a class into a passed-in variable.

What exactly do you mean by " assign a class into a passed-in variable"? Please post some code illustrating what you are talking about.

     function make_widget(parent& x):
       w = new Widget()
       x.children.add(w)

If this one is too easy, make function return "w" as well, or make it add a widget to two different lists