Fix inference of protocol against overloaded function #12227
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We used to infer a callable in a protocol against all overload items. This could result in incorrect results, if only one of the overload items would actually match the protocol. Fix the issue by only considering the first matching overload item. This seems to help with protocols involving `__getitem__`. In particular, this fixes regressions related to `SupportsLenAndGetItem`, which is used for `random.choice`.
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It looks like there are some regressions. I will have a look. |
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hauntsaninja
approved these changes
Feb 22, 2022
I started adding tests, and it turns out you had a very good point -- overloads in protocols seem to be pretty poorly tested and still have some issues. However, I don't want to block the next mypy public release on fixing the remaining issues. I'll create a follow-up issue about this and merge this now, since this fixes a regression. |
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According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉 |
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We used to infer a callable in a protocol against all overload
items. This could result in incorrect results, if only one
of the overload items would actually match the protocol.
For example, we could get incorrect constraints from
an incompatible overload item.
Fix the issue by only considering the first matching overload
item.
This seems to help with protocols involving
__getitem__.In particular, this fixes regressions related to
SupportsLenAndGetItem, which is used forrandom.choice.