*Ts syntax in type comments

[superbobry]

Is it valid to use the *Ts syntax for unpacking a tuple type variable in type comments. For example, should type checkers treat

from typing import TypeVarTuple
T = TypeVarTuple("T")

def f(
    *args  # type: *Ts
):
    # (...) -> tuple[*Ts]

as if it was

def f(*args: *Ts) -> tuple[*Ts]: ...

?

[erictraut]

Type comments have been deprecated for a long time. They are still (partially) supported by some type checkers for old code that needs to remain compatible with Python 2, but you shouldn't be using them for new code. TypeVarTuple is a relatively new feature, so I wouldn't expect tools to support this with type comments.

If you want to use TypeVarTuple with a version of Python prior to 3.11, you can use typing_extensions.Unpack.

from typing_extensions import Unpack, TypeVarTuple

Ts = TypeVarTuple("Ts")

def f(*args: Unpack[Ts]) -> Unpack[Ts]:
    ...

[superbobry]

Thanks, Eric! I think it is unlikely anyone will try to use type comments with TypeVarTuples, but I thought I would ask anyway, since this is not mentioned at all in PEP-646.