For those who are wondering: they alias @typing.overload as @ovld only for type checkers.
Normally, @typing.overload is a way to define multiple function signatures with empty bodies so your type checker can work nicely with functions that for example only return a certain type when called with a certain signature, but the function implementation is left to you and usually involves a bunch of runtime type checks to branch your logic the right way
I think it would make sense to have each function return either the exact same type, or a generic.
@ovld(int) #all of these overloads should return an int
len(a:list) -> int
len(a:str) -> int
#the effective type of len is
len(a:Union[int, str]) -> int
T = TypeVar('T')
@ovld(T)
add(a:np.int8, b:np.int8) -> np.int8
@ovld(T)
add(a:np.int16, b:np.int16) -> np.int16
Am I missing something?