self.__class__.__name__ has type Any in class derived from Any

[gvanrossum]

Here's something that came up in python/typeshed#1549 (comment).

from typing import Any, Type, TypeVar
T = TypeVar('T')
class C(Any):
 def bar(self: T) -> Type[T]: ...
 def foo(self) -> None:
 reveal_type(self.bar()) # Type[C], as expected
 reveal_type(self.bar().__name__) # Any, but expected str

@ilevkivskyi I think you muttered something about analyze_member_access for TypeType still being broken but I'm not sure I understand.

[ilevkivskyi]

This will be fixed by #4038

[gvanrossum]

Ah, thanks. I'm waiting for Jukka to review that, it's a bit above my review capacity ATM.

[ilevkivskyi]

I will add this example to the tests in the meantime.

[gvanrossum]

FWIW, the issue in our internal codebase that prompted this report is not resolved by #4038. But that issue is more complex than my example here, and I haven't boiled it down yet. To avoid referencing the other (closed, typeshed) issue, here is the problem again.

Some file gives this error:

[...]/task.py:221: error: Cannot determine type of '__name__'

The source code at that line looks like this:

from threading import local
...
class TrackedTask(local):
 def __init__(self, ...):
 # type: ...
 if SupportedTrackedTaskWorkers.is_supported(self.__class__.__name__, self.task_name): ...

[ilevkivskyi]

Hm, strange, I can't reproduce this. I replaced SupportedTrackedTaskWorkers.is_supported with len and removed the second argument and everything works, also reveal_type(self.__class__.__name__) shows builtns.str. I tried other combinations but still can't get this error.

[gvanrossum]

Me neither. :-( There must be something else in the file that affects this, but I don't yet know what it is. There must be something really strange going on, since if I add reveal_type(self.__class__.__name__) I get both these:

devtools/changes/changes/queue/task.py:221: error: Revealed type is 'builtins.str'
devtools/changes/changes/queue/task.py:221: error: Cannot determine type of '__name__'

[JelleZijlstra]

Regardless of the possible mypy bug, could we fix this in typeshed by making threading.local not inherit from Any and instead override __setattr__ and __getattr__?

[gvanrossum]

Yes, that should be fine now.

[gvanrossum]

Wow. Thanks!

…

On Oct 11, 2017 05:17, "Jukka Lehtosalo" ***@***.***> wrote: Closed #4058 <#4058> via #4038 <#4038>. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#4058 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ACwrMtYu50OdM3D3IO12hx607bh9xsP1ks5srLHagaJpZM4PuO4e> .