Invalid undefined variable errors (mypy not considering __all__?)

[refi64]

Sample:

from abc import abstractmethod
from typing import *

T = typevar('T')

class Rnd(Protocol[T]):
    @abstractmethod
    def some_method(x: T) -> T:
        pass

That gives:

err.py, line 2: Name 'T' already defined
err.py, line 2: Name 'abstractmethod' already defined
err.py, line 6: Name 'Protocol' is not defined

Removing the top line solves the second error, but it obviously doesn't run under Python 3:

Traceback (most recent call last):
  File "err.py", line 6, in <module>
    class Rnd(Protocol[T]):
  File "err.py", line 7, in Rnd
    @abstractmethod
NameError: name 'abstractmethod' is not defined

[JukkaL]

Yup, __all__ is not yet supported :(

It should be pretty easy to implement, at least for simple cases which don't mutate __all__ after initialization.

Also, the stubs for typing should use _T etc. for internal identifiers (and other stubs as well). The problem withabstractmethod etc. could be worked around by using from abc import abstractmethod as _abstractmethod, I think. This is probably the easiest way to enable from typing import *.

Another issue is that importing the same name from multiple modules (e.g., directly from abc and via from foo import *) should not be fine.

(Note also that Protocol and structural subtyping is not supported by the type checker, but it's pretty likely that it will be added in the future.)

[JukkaL]

Added issue #452 for the issue with T.

[JukkaL]

Added issue #453 as a general fix to the problem with imports in stubs.

[JukkaL]

Bumping priority because this is pretty annoying.