There seems to be a limitation with Pylance detecting if a variable declared in a class is a class variable or not.

In particular, the following code:

from typing import ClassVar, Protocol

class SimpleProtocol(Protocol):
    a: ClassVar[str]

class SimpleClass:
    a = "test"

val: SimpleProtocol = SimpleClass()

Gives the following error:

As far as I understand, SimpleClass.a is in fact a class variable (and using it as such does not produce any runtime errors),

Changing SimpleClass definition to

class SimpleClass:
    a: ClassVar = "test"

gets rid of the error.

It would be nice if Pylance could automatically infer that a is a class variable without the need for explicit type annotations.

Tested with Pylance language server 2023.5.30 (pyright e1b6074b).