@Inheritable
Point2D = Class {x = Int; y = Int}
Point2D.
    new x, y = Self::__new__ {x = x; y = y}
    norm ref self = self::x**2 + self::y**2

Point3D = Inherit Point2D, Additional := {z = Int}
Point3D.
    @Override
    new x, y, z = Self::__new__ {x = x; y = y; z = z}
    @Override
    norm ref self = self::x**2 + self::y**2 + self::z**2

UnpackPoint2D = Class {x = Int; y = Int}, Impl := Unpack

p = UnpackPoint2D::{x = 1; y = 2}
UnpackPoint2D::{x = x; y = x} = p