8000 classmethod decorator transforms callable into callable rather than producing a classmethod? · Issue #12673 · python/mypy · GitHub
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NeilGirdhar opened this issue Apr 26, 2022 · 2 comments
Open

classmethod decorator transforms callable into callable rather than producing a classmethod? #12673

NeilGirdhar opened this issue Apr 26, 2022 · 2 comments
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bug mypy got something wrong topic-descriptors Properties, class vs. instance attributes

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@NeilGirdhar
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NeilGirdhar commented Apr 26, 2022 •
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At the point at which the decorator is applied, the class method isn't a callable yet. It's a classmethod object that replies to __get__ to produce the bound method. Yet, MyPy already thinks it's a callable:

from __future__ import annotations
from typing import Callable

def decorate(c: classmethod[None]) -> Callable[[X], None]:
    def g(x: X) -> None:
        return c.__func__(type(x))
    return g

class X:
    @decorate  # error: Argument 1 to "decorate" has incompatible type "Callable[[Type[X]], None]"; expected "classmethod[None]"
    @classmethod
    def f(cls) -> None:
        print("okay")

x = X()
x.f()  # error: Invalid self argument "Type[X]" to class attribute function "f" with type "Callable[[X], None]"
@NeilGirdhar NeilGirdhar added the bug mypy got something wrong label Apr 26, 2022
@AlexWaygood AlexWaygood added the topic-descriptors Properties, class vs. instance attributes label Apr 26, 2022
@NeilGirdhar
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Pyright won't fix the first problem, so I can just ignore it. But is the second problem fixable? The decorator changes the class method into an ordinary method, so why is x.f() passing the type?

@asottile-sentry asottile-sentry mentioned this issue Nov 17, 2022
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@NeilGirdhar NeilGirdhar reopened this Aug 16, 2023
@NeilGirdhar
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This would be solved by python/typing#1372

@TobyBoyne TobyBoyne mentioned this issue Apr 8, 2025
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