Serhiy:  Yep, or even on bool.  Thanks.

Armin: I don't think either of us thinks there isn't a problem here. :-)
The Google search you suggested didn't turn up a whole lot of useful information for me.  Was there a discussion of this on python-dev at some point?  (And if not, should there be?)

For this *particular* issue, it seems we can't exactly reproduce.  type(a).__index__(a) seems like the best practical approximation to the true behaviour.  I'm guessing that it's fairly rare to have useful definitions of __index__ on a metaclass.