> > Unless I'm reading it wrong, when _setevents() is called, the
> > internal
> > hooks are rewired to populate the events list, rather than call the
> > corresponding TreeBuilder methods. So, yes, there's a TreeBuilder
> > somewhere, but it stands unused.
> 
> Yes, you *are* reading it wrong. For example, the "start" callback
> calls self._start_list, which in turn calls self.target.start(),
> thus calling into the TreeBuilder. That's the thing that constructs
> the elements that the IncrementalParser collects in its events list.

Ah, indeed, my bad. That said, using a custom TreeBuilder-alike
would necessitate changes in the C implementation of XMLParser.
(which, I suppose, is why the _setevents hack exists in the first
place)