Self-type narrowing for sync/async overloads

[grievejia]

Describe the Bug

Minimal repro:

from typing import Protocol, Awaitable, overload, Literal

class _AsyncMarker(Protocol):
    _is_async: Literal[True]
class _SyncMarker(Protocol):
    _is_async: Literal[False]

class KeyCommands:
    """Mixin providing key commands with sync/async overloads."""

    @overload
    def get(self: _SyncMarker, name: str) -> str | None: ...  # FP: inconsistent-overload
    @overload
    def get(self: _AsyncMarker, name: str) -> Awaitable[str | None]: ...  # FP
    def get(self, name: str) -> str | None | Awaitable[str | None]:
        return None

    @overload
    def set(self: _SyncMarker, name: str, value: str, ex: int | None = None) -> bool: ...  # FP
    @overload
    def set(
        self: _AsyncMarker, name: str, value: str, ex: int | None = None
    ) -> Awaitable[bool]: ...  # FP
    def set(self, name: str, value: str, ex: int | None = None) -> bool | Awaitable[bool]:
        return True

No other type checker choose to error on this.

Sandbox Link

https://pyrefly.org/sandbox/?project=N4IgZglgNgpgziAXKOBDAdgEwEYHsAeAdAA4CeS4ATrgLYAEALqcROgOZ0Q3G6UN0AFag1wBjXFAA0dAIIB3VBAapssabgBuMSlFypM0gDJLtqKAB10l0VFRw4dAPoy4pdKICyqSgGttACiFcEXEoAEpESzpopwg4Rzs3UUQ6YwZTKABtABVKAFcYAF1rW3snAGUkr18AoJCJCKiYxziE13cUtIzMgDEzOCLLErsHAGkYUgBhWhoMTDhI9Bi6cxBV1Y8IfFY6YmoNCExWDj9SOnEaWawHOSUACzp20QB6RPc6TW1dfThCdbW1lYljEAAKfHR6TBNaKYGBgOhsGAMfwDKBgFKOSruap%2BSjSdCoGgwFJwBiUMJ0AC0AD5HmS6AAfOgAOVw6GJdEIXOiAGI6D0BClWOJ0HA4ul0AxKeDvlDgdEwVoIfpoXRYfDEcjUeinC4qt5cfjCRzSeSqbT5IplKoYJlTYyWWyiikuYRefyBKr1QikSiYGijUSSWSKTS6ZQHaz2Q7LUoVLA7fSmVHnarlpQkXlKEsU0N5XRFV9IV64Y9fdqMVjPAbtIGTWTpBozAVg3i6DB8ELJZGnXQALyO9mh2l4CQu7l0PkC1WF5Vy5begbItMxCu6p442t0AlB8ON5v1tsdrv8ZO9ge5-PD2QKOM2zKjqCFcduycekvwpd%2BgPb42t-dQC2e7tp2nDdme0YXk616PjGt7Wgmj7Piu0QZgwWZLLkBQgJIIB5Aw0C-GQFB8gAqgRUBKGcYB5O4BFsnAebemAvCzAwjjoHkNDYAEoGsAw16mos6aZtmdBgKszJcTxlApMA%2BAAL7rOgOEgGQGZgFApCECINBQCRgikBpWmPHMeD4OcbKQGwWaoPR6B-OgfLlDAMB0HcDAMMQCzPM86lwlphC8GwzwwOgzyYGIcDPCK1m2fZzzibwdCoE20Dxm5sUQDZlB2RAbIfMQ9m-JYZAMHcbKUkqYoFQOqwAMyEAAjAATMpIAKbhqCiARWg9NAMAUGgWDmSQ5AKUAA

(Only applicable for extension issues) IDE Information

No response

[fangyi-zhou]

This should be covered by #3112?