"error: Name is not defined" and confusing behavior on instance-level classes

Running mypy on the following example:

from typing import Type

class Foo:
    def __init__(self):
        class Bar:
            pass

        self.Bar: Type[Bar] = Bar

foo = Foo()
bar: foo.Bar = foo.Bar()

reveal_type(foo.Bar)
reveal_type(bar)

results in the following slightly confusing and seemingly contradictory output:

example.py:11: error: Name 'foo.Bar' is not defined  # on bar: foo.Bar
example.py:13: note: Revealed type is 'Type[example.Bar@5]'  # on reveal_type(foo.Bar)
example.py:14: note: Revealed type is 'Any'  # on reveal_type(bar)

Ideally, I would have expected reveal_type(bar) to reveal example.Bar@5. I'm not sure if there is a way to correctly type this code without resorting to # type: ignore right now.

Tested on mypy 0.761, Python 3.8.1.

Riproduci l’esempio in example.py con mypy, concentrandoti sull’annotazione bar: foo.Bar e sulle chiamate a reveal_type. Traccia il modo in cui mypy gestisce il riferimento alla classe a livello di istanza e determina se l’errore segnalato e il risultato Any possono essere sostituiti dal tipo atteso example.Bar@5. Il lavoro è terminato quando example.py supera il controllo dei tipi come previsto e reveal_type(bar) riporta quel tipo di classe.