This concerns me:

    Point newLoc = oldLoc with {
        x *= 2;
        y *= 2;
        z *= 2;
    };

It feels more like a mutable "Builder" class than a copy constructor. I guess the benefit is that you can do things like the above, instead of the following in Kotlin:

    val newLoc = oldLoc.copy(
        x = oldLoc.x * 2,
        y = oldLoc.y * 2,
        z = oldLoc.z * 2
    )

But in Kotlin it's more clear that oldLoc is immutable.