str not compatible with StrOrLiteralStr

Bug Report

mypy doesn't accept str for StrOrLiteralStr

To Reproduce

from string import Formatter
from typing import Iterable, Tuple

class MyFormatter(Formatter):
    def parse(self, s: str) -> Iterable[Tuple[str, str, str, str]]:
        for text, field, spec, conversion in super().parse(s):
            yield "a", "b", "c", "d"

(playground)

Actual Behavior

error: Return type "Iterable[tuple[str, str, str, str]]" of "parse" incompatible with return type "Iterable[tuple[StrOrLiteralStr, StrOrLiteralStr | None, StrOrLiteralStr | None, StrOrLiteralStr | None]]" in supertype "Formatter" [override]

Details

I've asked a question on SO about this and didn't get an answer (yet). As indicated in the comments:

this code passes type checking in mypy 0.971, and fails in mypy 0.981 through 1.5.0

Perhaps it's related to mypy lack of support for LiteralStr #12554

Inizia con l'override di Formatter.parse nel reproducer Python ed eseguilo nel mypy playground collegato, confrontando il comportamento tra le versioni menzionate. Traccia il modo in cui mypy gestisce StrOrLiteralStr e il tipo restituito dall'override; il lavoro è completato quando il reproducer viene accettato senza rifiutare erroneamente str.