How to include property annotations as if they were attributes

annotation_extension.py

from dataclasses import dataclass


def annotate_properties(_cls=None):
    def wrap(cls):
        properties = [(x, getattr(cls, x)) for x in dir(cls) if type(getattr(cls, x)) == property]
        for name, property_ in properties:
            cls.__annotations__[name] = property_.fget.__annotations__["return"]
        return cls

    # nifty pattern to make decorators work both with and without parens 
    if _cls is None:
        return wrap
    return wrap(_cls)


# order matters here, dataclass's code needs to run first
@annotate_properties
@dataclass
class Foo:
    var: int

    @property
    def x(self) -> int:
        return self.var + 2

      
print(Foo(1).__annotations__)  # {'var': <class 'int'>, 'x': <class 'int'>}