Repair is_dataclass definition? #9723
Description
Consider:
from dataclasses import is_dataclass
def f(X: type) -> None:
if is_dataclass(X):
reveal_type(X) # information: Type of "X" is "type"Ideally, X would have type type[DataclassInstance]. It doesn't because is_dataclass is defined:
@overload
def is_dataclass(obj: DataclassInstance | type[DataclassInstance]) -> Literal[True]: ...
@overload
def is_dataclass(obj: type) -> TypeGuard[type[DataclassInstance]]: ...
@overload
def is_dataclass(obj: object) -> TypeGuard[DataclassInstance | type[DataclassInstance]]: ...And the argument of type type matches the first overload, which does not incorporate a TypeGuard. Eric Traut recommends erasing the first overload of is_dataclass.