Definition Order Matters For `types.coroutine` Decorator

This fails mypy --strict (v0.782):

from types import coroutine
from typing import Any, Iterator

async def my_async_func() -> None:
    await my_coro_func()

@coroutine
def my_coro_func() -> Iterator[None]:
    yield None

but this passes:

from types import coroutine
from typing import Any, Iterator

@coroutine
def my_coro_func() -> Iterator[None]:
    yield None

async def my_async_func() -> None:
    await my_coro_func()

MyPy playground links:

• fail: https://mypy-play.net/?mypy=latest&python=3.8&flags=strict&gist=06aa146dfa9d86ca94b707cfa2367f27
• pass: https://mypy-play.net/?mypy=latest&python=3.8&flags=strict&gist=df2b842045c756988b171d6ebb9b3b6c

Start by running the two minimal examples with mypy --strict on Python 3.8, using the linked passing and failing mypy playgrounds as references. Investigate why moving the types.coroutine-decorated function changes the result; done means both definition orders receive the same correct type-checking result.