Guido van Rossum writes:
Maybe you’re thinking of a “one-pass” compiler, like the original Pascal compiler, that generates code during parsing.
Not really. The "after" phrasing comes from the parsing part which does move through the source pretty much linearly in both the traditional and PEG parsers (as far as I understand the latter).
What I really meant with respect to the code generation was what you describe as "going 'up'" with respect to the AST. Evidently I got that wrong.
I have a somewhat nebulous understanding of which way is "up", I guess. :-) I need to go back to school on compiler tech.