Redefining aliases that use typing module fails

[aklajnert]

Thanks for this useful tool. Unfortunately while using it I've stumbled upon a weird error.

Consider the following example:

import typing

OPTIONAL_STR = typing.Optional[str]

This is content of example.py and example.pyi. After running retype against them, I get a following error:

example.py: incompatible existing alias 'OPTIONAL_STR'. Expected: 'typing.Optional[str]', actual: 'typing.Optional[str]'

However, when you slightly change the example, everything passes:

from typing import Optional

OPTIONAL_STR = Optional[str]

This behavior is the same for python 3.6, 3.7 and 3.8. Tested on Ubuntu.
Changing imports is a workaround, but it would be nice to use import typing especially if you use this module extensively.