> Hopefully if we add more pseudokeywords in the future it won't break
the ability to parse traceback spans.
It won't because soft keywords are now handled natively with the peg
parser (as "match" and "case" now) instead of hacked into the tokenizer :)
On Fri, 21 May 2021 at 01:55, Nathaniel Smith <n...@pobox.com> wrote:
> On Wed, May 19, 2021 at 7:28 PM Pablo Galindo Salgado
> <pablog...@gmail.com> wrote:
> >>
> >> Excellent point! Do you know how reliable this is in practice, i.e.
> >> what proportion of bytecode source spans are something you can
> >> successfully pass to ast.parse? If it works it's obviously nicer, but
> >> I can't tell how often it works. E.g. anything including
> >> return/break/continue/yield/await will fail, since those require an
> >> enclosing context to be legal. I doubt return/break/continue will
> >> raise exceptions often, but yield/await do all the time.
> >
> >
> > All those limitations are compiler-time limitations because they imply
> > scoping. A valid AST is any piece of a converted parse tree, or a piece
> > of the PEG sub grammar:
> >
> > >>> ast.dump(ast.parse("yield"))
> > 'Module(body=[Expr(value=Yield())], type_ignores=[])'
> > >>> ast.dump(ast.parse("return"))
> > 'Module(body=[Return()], type_ignores=[])'
> > >>> ast.dump(ast.parse("continue"))
> > 'Module(body=[Continue()], type_ignores=[])'
> > >>> ast.dump(ast.parse("await x"))
> > "Module(body=[Expr(value=Await(value=Name(id='x', ctx=Load())))],
> type_ignores=[])"
>
> Ah, nice! I guess I was confused by memories of the behavior in 3.6
> and earlier, where 'await' was a pseudokeyword:
>
> ❯ docker run -it --rm python:3.6-alpine
> >>> import ast
> >>> ast.parse("await f()")
> SyntaxError: invalid syntax
>
> Hopefully if we add more pseudokeywords in the future it won't break
> the ability to parse traceback spans.
>
> -n
>
> --
> Nathaniel J. Smith -- https://vorpus.org
>
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