Bug Report

Mypy cannot determine the type of the declared field inside a protocol method.

To Reproduce

Invoke mypy on the following Python file

# bug.py
from typing import Protocol

class Test(Protocol):
    k: int

    def test(self, i: int):
        self.k = self.k

Mypy complains: bug.py:7: error: Cannot determine type of "k". Strange here is if I remove the parameter i, the error would disappear.

Expected Behavior

No such error.

My Environment

• Mypy version used: https://github.com/python/mypy@e3827a1b950f83332656ad9c51ca8eea06ea2234
• Mypy command-line flags: None
• Mypy configuration options from mypy.ini (and other config files): None
• Python version used: 3.10.4
• Operating system and version: Ubuntu 20.04.4