Currently, instantiating explicit subclasses of protocols with "abstract" attributes is prohibited:

class P(Protocol):
    x: int  # Note, no r.h.s.

class C(P):
    pass
class D(P):
    def __init__(self) -> None:
        self.x = 42

C()  # E: Cannot instantiate abstract class 'C' with abstract attribute 'x'
D()  # OK

This is feature appeared with little discussion, in particular should this be specific only to protocols or also to "normal" ABCs?