Private members (__underscored) in an Enum are incorrectly considered members of the enum

Bug Report

Mypy, at least versions 1.17.1 and the latest 1.19.1 incorrectly classifies private members as Enum members and tags them as final.

But, since Python 3.11, private members are not enum members, see https://docs.python.org/3/howto/enum.html#private-names

To Reproduce

https://mypy-play.net/?gist=afd9e4e68abe69277d97eb42f33adbcf

from typing import ClassVar
from enum import IntEnum

class WithDocReference:
  __doc_reference: ClassVar[str]

class MyEnum(WithDocReference, IntEnum):
  __doc_reference = "https://www.google.com"
  A = 1
  B = 2

Expected Behavior

Type checks without error.

Actual Behavior

mypy 1.17.1 fails with

$ mypy test.py
test.py:8: error: Cannot override writable attribute "__doc_reference" with a final one  [misc]
Found 1 error in 1 file (checked 1 source file)

mypy 1.19.1 has an additional error.

Your Environment

• Mypy version used: 1.17.1 and 1.19.1
• Mypy command-line flags: None
• Mypy configuration options from mypy.ini (and other config files): None
• Python version used: 3.11.9

Edited: private names should start with two underscores and not one

Riproduci il problema dal gist mypy-play collegato o dall’esempio test.py con Python 3.11 e le versioni di mypy indicate. Confronta il risultato con la gestione documentata da Python dei nomi privati di Enum; il lavoro è completato quando l’esempio supera il controllo dei tipi senza gli errori indicati e il comportamento è coperto da un test di regressione.