wrongly inferred type builtins.object #15295

import typing as t


_T = t.TypeVar("_T")
_P = t.ParamSpec("_P")


async def works() -> None:
    async def callback(
        cb: t.Callable[_P, t.Union[t.Awaitable[_T], _T]],
        *args: _P.args, **kwargs: _P.kwargs
    ) -> _T:
        raise NotImplementedError()

    def make_t() -> t.Union[
        t.Callable[[], t.Coroutine[t.Any, t.Any, int]],
        t.Callable[[], int]
    ]:
        raise NotImplementedError()

    t = make_t()
    t_cb = await callback(t)
    reveal_type(t_cb)  # note: Revealed type is "builtins.int"


async def fails() -> None:
    async def callback(
        cb: t.Callable[_P, t.Union[t.Awaitable[_T], _T]],
        *args: _P.args, **kwargs: _P.kwargs
    ) -> _T:
        raise NotImplementedError()

    def make_t() -> t.Union[
        t.Callable[[], t.Coroutine[t.Any, t.Any, t.Union[int, str]]],
        t.Callable[[], t.Union[int, str]]
    ]:
        raise NotImplementedError()

    t = make_t()
    t_cb = await callback(t)
    reveal_type(t_cb)  # Revealed type is "builtins.object"