Spurious “cyclic definition” error when inheriting from and shadowing a class

Bug Report

Shadowing class names and inheriting from the previous class causes the following error:

Cannot resolve name "{shadowed class name}" (possible cyclic definition)

To Reproduce

Attempt to typecheck the following code:

class MyError(Exception): pass
class RuntimeError(RuntimeError, MyError): pass

Expected Behavior

Accepted by Mypy, RuntimeError can now be imported from that file and refers to a subclass of MyError.

Actual Behavior

file.py: 2: error: Cannot resolve name "RuntimeError" (possible cyclic definition)

Your Environment

• Mypy version used: 0.812
• Mypy command-line flags: none
• Mypy configuration options from mypy.ini (and other config files): none
• Python version used: 3.8.9
• Operating system and version: NixOS unstable

Inizia riproducendo l'errore con lo snippet Python a due classi usando mypy 0.812, poi segui come vengono risolti i nomi delle classi base quando una classe nasconde un nome ereditato. Il lavoro è concluso quando mypy accetta l'esempio senza l'errore di definizione ciclica e il RuntimeError risultante rimane importabile come sottoclasse di MyError.