ParamspecArgs cannot be used with enumerate

[kasium]

Bug Report

With #12386 an issue was closed, that ParamSpec cannot be used as tuples and dicts. However, enumerate is seen as invalid, even if it works.

To Reproduce

from typing_extensions import ParamSpec
from typing import Callable, TypeVar

P = ParamSpec("P")
R = TypeVar("R")

def foo(func: Callable[P, R]) -> Callable[P, R]:
 def _inner(*args: P.args, **kwargs: P.kwargs) -> R:
 x = kwargs.pop("x")
 y = enumerate(args)
 return func(*args, **kwargs)
 return _inner

Expected Behavior

It works fine

Actual Behavior

foo.py:10:13: error: Need type annotation for "y" [var-annotated]
 y = enumerate(args)
 ^
foo.py:10:23: error: Argument 1 to "enumerate" has incompatible type "P.args"; expected "Iterable[<nothing>]" [arg-type]
 y = enumerate(args)
 ^
Found 2 errors in 1 file (checked 1 source file)

Your Environment

• Mypy version used: 0.960
• Python version used: 3.7.2
• Operating system and version: SUSE Linux

[AlexWaygood]

This looks like a bug to me, but here's a workaround in the meantime, that passes mypy:

from typing_extensions import ParamSpec
from typing import Callable, TypeVar

P = ParamSpec("P")
R = TypeVar("R")

def foo(func: Callable[P, R]) -> Callable[P, R]:
 def _inner(*args: P.args, **kwargs: P.kwargs) -> R:
 x = kwargs.pop("x")
 y: "enumerate[object]" = enumerate(args)
 return func(*args, **kwargs)
 return _inner

[kasium]

@AlexWaygood thanks!

[AlexWaygood]

Here's a repro that doesn't depend on the typeshed stubs for enumerate:

from typing_extensions import ParamSpec
from typing import Callable, TypeVar, Iterator, Iterable, Tuple

P = ParamSpec("P")
T = TypeVar("T")

def enumerate(x: Iterable[T]) -> Iterator[Tuple[int, T]]: ...

def foo(func: Callable[P, T]) -> Callable[P, T]:
 def _inner(*args: P.args, **kwargs: P.kwargs) -> T:
 x = kwargs.pop("x")
 y = enumerate(args) # E: Need type annotation for "y" # E: Argument 1 to "enumerate" has incompatible type "P.args"; expected "Iterable[<nothing>]"
 return func(*args, **kwargs)
 return _inner