Daemon does not progate change from decorated to async function

[JukkaL]

This fine-grained incremental test case fails (no error on second run):

[case testDecoratedToAsyncReExported]
from mm import f
x: int = f()

[file mm.py]
from m import f

[file m.py]
from d import singleton

@singleton
def f() -> int:
    return 0

[file m.py.2]
async def f() -> str:
    return 'x'

[file d.py]
from typing import Callable

class Singleton:
    def __call__(self) -> int:
        return 0

def singleton(f: Callable[[], int]) -> Singleton: pass
[out]
==
main:2: error: Incompatible types in assignment (expression has type "Coroutine[Any, Any, str]", variable has type "int")

It seems necessary to have a re-export, a decorator, and an async function for this to work. Also changing the return type of the functions seems required. I have no idea so far why this corner case fails.

This fails in 0.971 so it's not a recent regression.