Would it be possible to broaden classmethod to accept ParamSpec when MyPy's support is better?

It could be something like:

P = ParamSpec('P')
class classmethod(Generic[P, _R_co]):
    @property
    def __func__(self) -> Callable[P, _R_co]: ...
    @property
    def __isabstractmethod__(self) -> bool: ...
    def __init__(self: classmethod[_R_co], __f: Callable[P, _R_co]) -> None: ...
    def __get__(self, __obj: _T, __type: type[_T] | None = ...) -> Callable[P, _R_co]: ...
    if sys.version_info >= (3, 10):
        __name__: str
        __qualname__: str
        __wrapped__: Callable[P, _R_co]

This is on my to-do list for as soon as mypy 0.950 is released 🙂

Though I'm not sure how much of a difference this will make, considering how thoroughly type checkers special case classmethod (and staticmethod).

Also, staticmethod is quite a lot easier than classmethod. staticmethod doesn't change the signature of the function it wraps, but classmethod does -- it requires Concatenate. It would be something like this:

import sys
from typing import TypeVar, Callable, Generic
from typing_extensions import ParamSpec, Concatenate

_P = ParamSpec("_P")
_R_co = TypeVar("_R_co", covariant=True)
_T = TypeVar("_T")

class classmethod(Generic[_P, _R_co, _T]):
    @property
    def __func__(self) -> Callable[Concatenate[_T, _P], _R_co]: ...
    @property
    def __isabstractmethod__(self) -> bool: ...
    def __init__(self: classmethod[_P, _R_co, _T], __f: Callable[Concatenate[_T, _P], _R_co]) -> None: ...
    def __get__(self, __obj: _T | None, __type: type[_T] | None = ...) -> Callable[_P, _R_co]: ...
    if sys.version_info >= (3, 10):
        __name__: str
        __qualname__: str
        @property
        def __wrapped__(self) -> Callable[Concatenate[_T, _P], _R_co]: ...

@JelleZijlstra

@JelleZijlstra Yup, I just learned about that here. It's not too big a deal since it's very rare that you decorate class methods, but maybe after classmethod is broadened they might consider producing a classmethod[P, R, T] instead of a Callable[Concatenate[type[T], P], R].

Mypy 0.950 is now out, but sadly we still cannot use ParamSpec in classmethod or staticmethod due to python/mypy#12011. (abc.abstractclassmethod and abc.abstractstaticmethod inherit from classmethod and staticmethod respectively, so while that mypy issue is outstanding, we cannot make builtins.staticmethod or builtins.classmethod generic over a parameter specification without breaking those two classes.)

Navigation Menu

Repository navigation

Would it be possible to broaden classmethod to accept ParamSpec when MyPy's support is better? #7689

Metadata

Assignees

Labels

Projects

Milestone

Relationships

Development

Would it be possible to broaden classmethod to accept ParamSpec when MyPy's support is better? #7689

Description

Activity

AlexWaygood commented on Apr 26, 2022

JelleZijlstra commented on Apr 26, 2022

AlexWaygood commented on Apr 26, 2022

NeilGirdhar commented on Apr 26, 2022

AlexWaygood commented on Apr 28, 2022

Metadata

Metadata

Assignees

Labels

Projects

Milestone

Relationships

Development

Issue actions