I assume the comments made here about the swap operator solely apply to the feature as implemented at the language level, and that the `util::swap` library function does not fall victim to it?  But then again, that library function is implemented by pretty simplistic looking unsafe code. . . does the type system ensure that the type signature of `util::swap` suffices to enforce the necessary guarantees here?

If the above is true, you may just want to stress further that you are solely commenting on the `<->` operator, not the `util::swap` function.