Should `callable` narrow to `TypeIs[Callable[..., object]]` or `TypeIs[Callable]` ?

Currently, typeshed annotates

def callable(obj: object, /) -> TypeIs[Callable[..., object]]: ...

However, for the majority of type checkers this creates discrepancy between collections.abc.Callable and builtins.callable narrowing, only ty seems to consider blank Callable as if it were Callable[..., object], whereas all other type checkers treat it as Callable[..., Any].

from typing import reveal_type, TypeIs
from collections.abc import Callable

def is_callable(arg: object) -> TypeIs[Callable]:
    raise NotImplementedError

def check_callable(arg: object) -> None:
    if isinstance(arg, Callable):
        reveal_type(arg)
            
def check_callable2(arg: object) -> None:
    if callable(arg):
        reveal_type(arg)
        
def check_callable3(arg: object) -> None:
    if is_callable(arg):
        reveal_type(arg)

builtins.callable アノテーションから始め、collections.abc.Callable と比較します。Issue に記載された type-checker の挙動に対して例を実行し、その後コメントの議論を確認して、どのアノテーションが一貫した narrowing を提供するかを判断します。影響を受けるすべての checker で、選択した stub が意図された挙動と一致すれば完了です。