Bug Report

In CPython >= 3.11, creating an instance of a Protocol class is seemingly permitted at runtime if an initialiser is declared.

However, mypy still reports that the protocol class cannot be instantiated.

I am not sure if the bug lies with mypy or CPython, but, in this edge case, Protocol behaviour at runtime seems to have diverged from mypy's understanding somewhere between Python 3.10 and 3.11.

To Reproduce

from typing import Protocol


class Spam(Protocol):

    def __init__(self):
        print("No TypeError here!")


s = Spam()

Actual Behavior

$ python spam.py 
No TypeError here!
$ mypy spam.py 
spam.py:10: error: Cannot instantiate protocol class "Spam"  [misc]
Found 1 error in 1 file (checked 1 source file)

Your Environment

• Mypy version used: mypy 1.6.1 (compiled: yes)
• Mypy command-line flags: N/A
• Mypy configuration options from mypy.ini (and other config files): N/A
• Python version used: 3.11.5