gh-115528: Update language reference for PEP 646#120294
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Doc/reference/expressions.rst Outdated
| .. productionlist:: python-grammar | ||
| expression_list: `expression` ("," `expression`)* [","] | ||
| expression_list: `starred_expression` ("," `starred_expression`)* [","] |
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This is not strictly correct. expression_list according to the grammar is what appears after yield, but def f(): yield *a is a SyntaxError. (However, yield a, *b is legal.)
To recap: the objective is to make starred expressions valid in `subscription`, which is used for generics: `Generic[...]`, `list[...]`, etc. What _is_ gramatically valid in such contexts? Seemingly any of the following. (At least, none of the following throw `SyntaxError` in a 3.12.3 REPL.) Generic[x] Generic[*x] Generic[*x, y] Generic[y, *x] Generic[x := 1] Generic[x := 1, y := 2] So introducting flexible_expression: expression | assignment_expression | starred_item end then switching `subscription` to use `flexible_expression` sorts that. But then we need to field `yield` - for which any of the following are apparently valid: yield x yield x, yield x, y yield *x, yield *x, *y Introducing a separate `yield_list` is the simplest way I've been figure out to do this - separating out the special case of `starred_item ,`.
mrahtz requested review from a team, barneygale, brettcannon, corona10, encukou, ericsnowcurrently, ericvsmith, erlend-aasland, ethanfurman, freakboy3742, gaogaotiantian, pfmoore, pradyunsg, rhettinger and terryjreedy as code ownersmrahtz requested review from a team, 1st1, Fidget-Spinner, abalkin, ambv, asvetlov, brandtbucher, carljm, cjw296, ezio-melotti, gvanrossum, hugovk, iritkatriel, isidentical, jaraco, kumaraditya303, lysnikolaou, markshannon, methane, ncoghlan, pablogsal, pganssle, tiran, vsajip, warsaw and willingc as code owners
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mrahtz commented Jun 30, 2024
Ugh sorry for the spam all - Git mistake. Let me start a fresh PR. |
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📚 Documentation preview 📚: https://cpython-previews--120294.org.readthedocs.build/
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