[telios]

Very rarely do you need to pass around a lifetime-bound struct or enum that isn't _also_ meant to be temporary. (One database pool has database connections lifetime bound, for example, but the pool still owns the connection.) When I do, I generally eat the cost and put it behind a Rc/Arc, where cloning is cheap.

It is 'borrowing' because you don't own it, not because you don't want to clone/copy it. Sometimes it is cheaper to borrow than it is to clone/copy; sometimes it is not.