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(🎁) isinstance/issubclass only accept typing.Unions of types, not other type forms #12370

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KotlinIsland opened this issue Mar 17, 2022 · 0 comments
Open

(🎁) isinstance/issubclass only accept typing.Unions of types, not other type forms #12370

KotlinIsland opened this issue Mar 17, 2022 · 0 comments
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feature topic-pep-604 PEP 604 (union | operator)

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@KotlinIsland
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KotlinIsland commented Mar 17, 2022 •
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Until type forms are properly supported by the type system, I wonder if this could be special cased?

from typing import Any

isinstance(1, str | Any)  # no error, fails at runtime with TypeError: typing.Any cannot be used with issubclass()

FYI mypy is incorrectly inferring this as a types.UnionType but it is actually a typing.Union(#12369), I don't think you can have a UnionType with type forms in it.

PyCharm correctly warns here:
image

related: python/typeshed/issues/7505
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@JelleZijlstra @KotlinIsland