Why can't the function build?

I think it’s a bug, I’m having the same issue here

parametric_class(t:type) := class<computes>:
    SomeMethod : tuple() -> t

ReturnInt():int=0

SomeParametricClassInt : parametric_class(int) = parametric_class(int):
    SomeMethod := ReturnInt # Script error 3502: Using a value of type tuple()->int as a value of type tuple()->t is not yet implemented.