TypeVar argument of Tuple alias becomes Any

[pdeblanc]

In the file foo.py:

from typing import Tuple, TypeVar

T = TypeVar('T')
TT = Tuple[T, T]


def car(items: TT) -> T:
    reveal_type(items)
    return items[0]

The revealed type is Tuple[Any, Any]:

➜  ~ git:(master) ✗ mypy --version
mypy 0.701
➜  ~ git:(master) ✗ mypy foo.py
foo.py:8: error: Revealed type is 'Tuple[Any, Any]'

I believe the correct type should have been the same as in this file bar.py:

from typing import Tuple, TypeVar

T = TypeVar('T')


def car(items: Tuple[T, T]) -> T:
    reveal_type(items)
    return items[0]

Which produces the output:

➜  ~ git:(master) ✗ mypy --version
mypy 0.701
➜  ~ git:(master) ✗ mypy bar.py
bar.py:7: error: Revealed type is 'Tuple[T`-1, T`-1]'

[ilevkivskyi]

This is by design, please read the docs before opening issues, https://mypy.readthedocs.io/en/latest/generics.html#generic-type-aliases

If you want to be warned about this behavior, use --disalllow-any-generics, again, this is all in the docs https://mypy.readthedocs.io/en/latest/command_line.html#disallow-dynamic-typing