I ran into a few interrelated bugs with the current implementation:
>>> class X(type):
... a: int
...
>>> class Y(metaclass=X):
... b: str
...
>>> X.__annotations__
{'a': <class 'int'>}
>>> Y.__annotations__
{'a': <class 'int'>}
Accessing the annotations on the metaclass caches them in the metaclass’s __dict__, and subsequently, lookups on classes that are instances of the metaclass return the metaclass’s annotations.
And if the class itself doesn’t have any annotations:
>>> class X(type):
... a: int
...
>>> class Y(metaclass=X): pass
...
>>> Y.__annotate__
<bound method X.__annotate__ of <class '__main__.Y'>>
Instead, Y.__annotate__ should be None.
I’ve stared at this problem for a while now and I’m not sure what to do about it yet; I’d appreciate any opinions.
I’ll note that some related behavior is also buggy on existing versions (this is 3.12.2):
>>> class X(type):
... a: int
...
>>> class Y(metaclass=X): pass
...
>>> Y.__annotations__
{'a': <class 'int'>}