Protocol member expected instance variable, got class variable

[smoofra]

Bug Report

This program ought to be valid, because all the protocol Foo is declaring is that the attribute foo is readable and returns an int. This requirement is met by Bar's class variable.

from typing import *

class Foo(Protocol):
    @property
    def foo(self) -> int:
        ...

class Bar:
    foo : ClassVar[int] = 42

x : Foo = Bar()

However, mypy says Protocol member Foo.foo expected instance variable, got class variablemypy.

if you just declare foo : int = 42, mypy accepts it, so clearly it understands that variables qualify as read-only properties, just not class variables.

Your Environment

• Mypy version used: 0.812
• Mypy configuration options from mypy.ini (and other config files):

  [mypy]
  ignore_missing_imports = True
  follow_imports = silent
  show_column_numbers = True
  check_untyped_defs = True
  

• Python version used: 3.8.2