Mypy thinks `dict[Never, Never]` is a subtype of `Mapping[str, object]`

[randolf-scholz]

This behaves as expected: https://mypy-play.net/?mypy=latest&python=3.12&gist=8718e96550599dc3ae48a13879005762

from typing import Mapping, Never

def upcast(d: dict[Never, Never]) -> Mapping[str, object]:
    return d  # E: [return-value] (✅ expected)

But it breaks here (due to caching?) https://mypy-play.net/?mypy=latest&python=3.12&gist=6199ba50b6b02e2350e70cb3a8ff4bba

from typing import Mapping, Never

def get[M: Mapping[str, object]](arg: M, /) -> M:
    return arg

reveal_type(get({}))  # dict[Never, Never] (❌ incorrect)

def upcast(d: dict[Never, Never]) -> Mapping[str, object]:
    return d  # <-- No error anymore 😱