[Python] Python Protocol using keyword-only arguments requires implementation to have...

I'm on python 3.10. I'm using PyCharm's default type checker and MyPy. Here is the protocol I defined:

class OnSubscribeFunc(Protocol):
def __call__(self, instrument: str, *, x: int) -> AsyncGenerator:
...


When create a method that implements it like this:

class A:
async def subscribe(self, instrument: str, *, x: int):
yield ...
a: OnSubscribeFunc = A().subscribe # this apparently is where it gets it wrong


I get this warning: Expected type 'OnSubscribeFunc', got '(instrument: str, Any, x: int) -> AsyncGenerator' instead

If I remove the * from my implementation however, the warning disappears. I would expect it to be the other way around because not having the * allows the implementation to have non-keyword-only arguments which might not be what I'm aiming for with my protocol.

So for comparison - this implementation gives no warning:

class A:
async def subscribe(self, instrument: str, x: int):
yield ...


This does not make any sense to me, why does it behave like this and is this expected or is it a bug in my type checker?

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