Enum @member and nonmember mishandled in Literal types #18719

Bug Report

typing.Literal is supposed to accept enum members and not non-members (such as methods or explicit nonmember attributes). mypy fails to enforce the latter and support the former.

To Reproduce

from enum import Enum, member, nonmember
from typing import Literal

class E(Enum):
    A = 1
    @member
    def B() -> None: ...
    C = member(lambda: None)
    D = nonmember(1)
    
    def meth(self) -> None: ...
    
a: Literal[E.A]  # OK, true negative
b: Literal[E.B]  # False positive: Parameter 1 of Literal[...] is invalid  [valid-type]
c: Literal[E.C]  # OK, true negative
d: Literal[E.D]  # False negative - `nonmember` shouldn't be allowed
meth: Literal[E.meth]  # OK, true positive: Parameter 1 of Literal[...] is invalid  [valid-type]

playground

Expected Behavior

• The following should be accepted in Literal: E.A, E.B, E.C
• The following should be rejected in Literal: E.D, E.meth

Actual Behavior

(line 7 is a different issue reported separately)

main.py:7: error: Method must have at least one argument. Did you forget the "self" argument?  [misc]
main.py:14: error: Parameter 1 of Literal[...] is invalid  [valid-type]
main.py:17: error: Parameter 1 of Literal[...] is invalid  [valid-type]

Your Environment

• Mypy version used: 1.15.0 and current master
• Mypy command-line flags: N/A
• Mypy configuration options from mypy.ini (and other config files): N/A
• Python version used: 3.12