test2.py

import asyncio
from typing import TypeVar, Generic

T = TypeVar("T")
AnyMsg = TypeVar("AnyMsg", "Msg", "Msg2")


class Msg(Generic[T]):
    body: T


class Msg2(Generic[T]):
    body: T


class Request:
    id: int
    item_ids: list[int]


def sync_gc_wait_for(enum: int, check: "(AnyMsg) -> bool", timeout: float) -> AnyMsg:
    ...


async def gc_wait_for(enum: int, check: "(AnyMsg) -> bool", timeout: float) -> AnyMsg:
    ...


ItemCustomizationNotification = 123
item_id = 1234


async def main():
    notification: Msg[Request] = sync_gc_wait_for(
        ItemCustomizationNotification,
        check=lambda msg: msg.body.id == 12345 and msg.body.item_ids[0] == item_id,
        timeout=30,
    )
    reveal_type(notification)

    notification: Msg[Request] = await gc_wait_for(
        ItemCustomizationNotification,
        check=lambda msg: (msg.body.id == 12345 and msg.body.item_ids[0] == item_id),
        timeout=30,
    )
    reveal_type(notification)