Somewhat better support for isinstance on old-style unions #19714
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Partially fixes python#17680 , remainder of the issue should probably be fixed in the isinstance stub
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According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅ |
| SimpleAlias = Union[int, str] | ||
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| def foo(x: Union[int, str, tuple]): | ||
| # TODO: fix the typeshed stub for isinstance |
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Is this fixable in typeshed? I don't think the correct type is expressible.
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Yeah the correct type isn't expressible, but if we change typeshed to include _SpecialForm here https://github.com/python/typeshed/blob/b6e21d05aec7ff1444ffc109c7d31d2f5bb28dbd/stdlib/builtins.pyi#L1537 or attempt to type more of the union runtime impl or just give up and make it use object, I think that will make the remaining error here go away
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That was tried in python/typeshed#7508 and the consensus seemed to be that it wasn't worth it?
I wouldn't mind the stubs reflecting the runtime a bit more closely w.r.t. the various special forms though; it would mean less special casing in ty too, which would be nice
Partially fixes #17680 , remainder of the issue should probably be fixed in the isinstance stub