8000 Should `object.__hash__` be `Callable[[], int] | None` if `None` is a valid and common usage? · Issue #6243 · python/typeshed · GitHub
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Should object.__hash__ be Callable[[], int] | None if None is a valid and common usage? #6243

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KotlinIsland opened this issue Nov 5, 2021 · 2 comments
Open

Should object.__hash__ be Callable[[], int] | None if None is a valid and common usage? #6243

KotlinIsland opened this issue Nov 5, 2021 · 2 comments

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@KotlinIsland
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Currently you have to type: ignore it.

related: #3884
@srittau
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srittau commented Nov 5, 2021 •
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Everything we do about __hash__() is problematic, because of its Schrödinger's nature:

class Foo:
    pass
print(Foo().__hash__())  # prints an int

class Bar:
    def __eq__(self, other):
        return True
Bar().__hash__()  # `NoneType` object is not callable

I believe the best solution for this problem is to special-case type checkers so that __hash__: None is a valid construct in stubs and you don't need # type: ignore for that. I commented as such on python/mypy#11465.

@sobolevn
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sobolevn commented Nov 9, 2021

Related python/mypy#11495

ftynse pushed a commit to llvm/llvm-project that referenced this issue Mar 31, 2022
@superbobry @ftynse
Fixed mypy type errors in MLIR Python type stubs
65b2f24 
This commit fixes or disables all errors reported by

    python3 -m mypy -p mlir --show-error-codes

Note that unhashable types cannot be currently expressed in a way compatible
with typeshed. See python/typeshed#6243 for details.

Reviewed By: ftynse

Differential Revision: https://reviews.llvm.org/D122790
mem-frob pushed a commit to draperlaboratory/hope-llvm-project that referenced this issue Oct 7, 2022
@superbobry
Fixed mypy type errors in MLIR Python type stubs
4a15329 
This commit fixes or disables all errors reported by

    python3 -m mypy -p mlir --show-error-codes

Note that unhashable types cannot be currently expressed in a way compatible
with typeshed. See python/typeshed#6243 for details.

Reviewed By: ftynse

Differential Revision: https://reviews.llvm.org/D122790
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@srittau @sobolevn @KotlinIsland
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