bpo-40334: Add support for feature_version in new PEG parser #19827
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`ast.parse` and `compile` support a `feature_version` parameter that tells the parser to parse the input string, as if it were written in an older Python version. The `feature_version` is propagated to the tokenizer, which uses it to handle the three different stages of support for `async` and `await`. Additionally, it disallows the following at parser level: - The '@' operator in < 3.5 - Async functions in < 3.5 - Async comprehensions in < 3.6 - Underscores in numeric literals in < 3.6 - Await expression in < 3.5 - Variable annotations in < 3.6 - Async for-loops in < 3.5 - Async with-statements in < 3.5 - F-strings in < 3.6 Closes we-like-parsers#124.
gvanrossum
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May 1, 2020
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Thanks! This looks pretty straightforward.
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| | 'for' t=star_targets 'in' ex=star_expressions ':' tc=[TYPE_COMMENT] b=block el=[else_block] { | ||
| _Py_For(t, ex, b, el, NEW_TYPE_COMMENT(p, tc), EXTRA) } | ||
| | ASYNC 'for' t=star_targets 'in' ex=star_expressions ':' tc=[TYPE_COMMENT] b=block el=[else_block] { | ||
| CHECK_VERSION(5, "Async for loops are", _Py_AsyncFor(t, ex, b, el, NEW_TYPE_COMMENT(p, tc), EXTRA)) } |
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Heh. After all my efforts to combine the two rules... :-) (Seriously, it's probably clearer this way anyways.)
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ast.parseandcompilesupport afeature_versionparameter thattells the parser to parse the input string, as if it were written in
an older Python version.
The
feature_versionis propagated to the tokenizer, which uses itto handle the three different stages of support for
asyncandawait. Additionally, it disallows the following at parser level:Closes we-like-parsers#124.
https://bugs.python.org/issue40334