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3E No first-class bound method support · Issue #14235 · python/mypy · GitHub
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No first-class bound method support #14235

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ikonst opened this issue Dec 2, 2022 · 1 comment
Open

No first-class bound method support #14235

ikonst opened this issue Dec 2, 2022 · 1 comment
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bug mypy got something wrong

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@ikonst
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ikonst commented Dec 2, 2022 

class X:
    def f(self) -> None:
        pass


reveal_type(X().f)
reveal_type(X().f.__self__)

I'd expect X().f to be some Callable derived generic type for bound methods.
I'd expect X().f.__self__ to be typed X. Currently __self__ is defined in the typeshed for types.MethodType as returning object.

Playground: https://mypy-play.net/?mypy=latest&python=3.11&gist=0de8d7a90f1d3770b3b600052c1671b1
@ikonst ikonst added the bug mypy got something wrong label Dec 2, 2022
@jorenham
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jorenham commented May 29, 2025 •
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For what it's worth: With mypy 1.15 this is still an issue, and Pyright behaves correctly. This is also an issue for unbound methods.

class A:
    def f(self) -> None: ...

reveal_type(A.f.__self__)   # mypy ❌ [attr-defined], pyright ✅ type[A]
reveal_type(A().f.__self__) # mypy ❌ [attr-defined], pyright ✅ A
main.py:4: error: "Callable[[A], None]" has no attribute "__self__"  [attr-defined]
main.py:5: error: "Callable[[], None]" has no attribute "__self__"  [attr-defined]

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