Unable to stubify Enum so it can be used with Literals, without using type ignore

Bug Report

Extending the example for #3434 I want to define an enum Flag, combine some of the members, and then also reference those members as a TypeAlias in a stub file.

class Color1(Flag):
    RED = auto()
    BLUE = auto()
    GREEN = auto()
    WHITE = RED | BLUE | GREEN  # <-- This line works at runtime but not in a stub (see the gist)
# Invalid type: try using Literal[Color1.RED] instead
Favorites: TypeAlias = Literal[Color3.RED | Color3.BLUE]

(A clear and concise description of what the bug is.)

To Reproduce

https://mypy-play.net/?mypy=latest&python=3.11&gist=d270d7541c61b2aea87e99c9afc77534

Expected Behavior

I expect mypy to suggest working code, or to accept the | operator for Flag members.

Actual Behavior

See the gist, but depending on how I write the stub I get these errors for the member definition

# foo.pyi:9: error: Invalid type: try using Literal[Color1.RED] instead?  [valid-type]
# foo.pyi:9: error: Invalid type: try using Literal[Color1.BLUE] instead?  [valid-type]
# foo.pyi:9: error: Invalid type: try using Literal[Color1.GREEN] instead?  [valid-type]

or these for the TypeAlias

# foo.pyi:12: error: Parameter 1 of Literal[...] cannot be of type "Any"  [valid-type]

Your Environment

• Mypy version used: 1.5.1
• Mypy command-line flags: --strict
• Mypy configuration options from mypy.ini (and other config files): N/A
• Python version used: 3.10.13

I was curious what stubgen came up with:

from _typeshed import Incomplete
from enum import Flag
from typing import TypeAlias

class Color(Flag):
    RED: Incomplete
    BLUE: Incomplete
    GREEN: Incomplete
    WHITE: Incomplete

Favorites: TypeAlias

but that loses information about the Literal Favorite Colors.

Commencez par la reproduction dans mypy-play et les exemples foo.pyi du rapport, en vous concentrant sur les définitions des membres de Flag et sur le Literal TypeAlias. Comparez les erreurs valid-type et Any signalées avec le traitement attendu des membres combinés de Flag ; le travail est terminé lorsque le stub prévu préserve les informations de couleur littérale sans nécessiter de type ignores.