Bogus undefined name error with generic type alias

[Oberon00]

• Are you reporting a bug, or opening a feature request?

Bug.

• Please insert below the code you are checking with mypy,
  or a mock-up repro if the source is private. We would appreciate
  if you try to simplify your case to a minimal repro.

This requires two modules to trigger the bug:
dummy.py:

from typing import Type, TypeVar, Callable

T = TypeVar('T')
ImplementationFactory = Callable[[Type[T]], T]

MyFactory = ImplementationFactory[str] # Works fine

dummy2.py:

import dummy

MyFactory2 = dummy.ImplementationFactory[str]

• What is the actual behavior/output?

$ mypy dummy2.py
dummy2.py:4: error: Name 'T' is not defined

Note that line 4 is empty. You can also add comments to get a different line number displacement. Also note that T is never referred to in dummy2.

• What is the behavior/output you expect?

I would expect no errors for this code.

• What are the versions of mypy and Python you are using?

$ mypy --version
mypy 0.711
$ python --version
Python 3.7.3

• Do you see the same issue after installing mypy from Git master?

I didn't try.

• What are the mypy flags you are using? (For example --strict-optional)

None. The command line is shown in full, there is no config file.

[JelleZijlstra]

This sounds similar to #7077.

[Oberon00]

Maybe similar, but this happens also without any special configuration so I'd say it is more severe based on that.

Can this issue get any labels, like "bug"?

[ilevkivskyi]

This still happens on master (and is pretty embarrassing).

[Oberon00]

Any news on this? This is currently causing us to copy & paste type definitions around in https://github.com/open-telemetry/opentelemetry-python (e.g. https://github.com/open-telemetry/opentelemetry-python/blob/84f589b6f8a4770c3c6ce29c7b352b1972241c4f/opentelemetry-api/src/opentelemetry/trace/__init__.py#L497-L502)

[pappasam]

I've tried this example with mypy version 0.790 on Python 3.8.6 and am not receiving any error. Maybe this issue is fixed?

[hauntsaninja]

Thanks for checking! mypy_primer indicates this was fixed by #7885