`--strict-equality` flag not working with membership operator and `Literal` types

Bug Report

When using any container (set, frozenset, list, tuples...) containing Literal based types, the --strict-equality is not detecting any issues when I use the membership operator in a non-overlapping check.

To Reproduce

from typing import Literal

OPTIONS = Literal["a", "b"]
var: list[OPTIONS] = ["a"]
if "c" in var:  # MYPY OK
    pass

Expected Behavior

When the flag --strict-equality is set, I would expect that mypy raises an erorr here. Same as it does when I do a non-overlapping equality check:

from typing import Literal

OPTIONS = Literal["a", "b"]
var: list[OPTIONS] = ["a"]
if var[0] == "c":  #  error: Non-overlapping equality check (left operand type: "Literal['a', 'b']", right operand type: "Literal['c']")  [comparison-overlap]
    pass

Actual Behavior

No errors are raised

Your Environment
Using Mypy version 1.9.0

Commencez par exécuter la reproduction Python signalée avec --strict-equality et comparez sa vérification d’appartenance avec la vérification d’égalité indexée. Localisez les points d’entrée de strict-equality et de l’analyse d’appartenance, puis ajoutez un test de régression couvrant un conteneur de valeurs Literal. Le travail est terminé lorsque mypy signale une vérification sans chevauchement pour l’expression d’appartenance, sans provoquer de régression dans les vérifications d’appartenance valides.