This does point out that the ast structure is a liability, and we won't be
able to easily change it, since mypy and IIRC many linters use the ast
module. So I think that maybe we need to think more carefully about what
the *proper* ast structure is, rather than what was most convenient for the
initial implementation. (Brandt, I know you are reluctant to change this,
and I don't blame you, but nevertheless I think we should at least think
about this some more so we're not stuck with a sub-optimal "default"
solution. We've already won the war. Let's not lose the battle. :-)