Error when accessing attribute of inner class

[rowillia]

test_inner_class_attribute.py:

class Foo:
    class Meta:
        name = 'Roy'

print(Foo().Meta.name)

Python executes the code just fine:

$ python3.6 test_inner_class_attribute.py
Roy

But mypy fails to typecheck

$ mypy test_inner_class_attribute.py
test_inner_class_attribute.py:5: error: Member "Meta" is not assignable

This pattern is super common in the Django Rest Framework, Marshmallow, and PynamoDB projects (Probably more that I don't know about as well 😄 )

[emmatyping]

Interesting. This will pass typechecking:

from typing import Any
class A:
    class B:
        pass
    b = B()
reveal_type(A().b)
reveal_type(A.B)

main.py:6: error: Revealed type is 'main.A.B'
main.py:7: error: Revealed type is 'def () -> main.A.B'

So the issue seems to be that B is being inferred as a function.

[rowillia]

@ethanhs yeah debugging that now. The issue is when analyzing the member access the type is TypeInfo which then falls through here -
https://github.com/python/mypy/blob/master/mypy/checkmember.py#L269

[emmatyping]

Yep, that makes sense. Shouldn't be too bad to fix if you add handling of member classes.