use rental to eliminate bookkeeping about owned-chars HOT 2 CLOSED

This ended up being more difficult than expected.

The first problem is that, in order to impl Clone, we need access to the underlying String. This is easy with the RentRef::owner method. However, we also need the RentMut::rent_mut method, since the internal Chars::next takes a &mut self. Herein lies the problem. The rental type can either be RentRef or RentMut, but not both. RentRef does not implement rent_mut() for obvious reasons, and RentMut does not implement owner(), for safety reasons. A solution here would require more unsafety.

The second problem also comes up when we implement Clone. In order to make a new Chars iterator that's in the same position as the original one, we need to call skip() or at least loop next() a few times. The problem is that this requires the exact bookkeeping that we're trying to avoid in the first place. Furthermore, skip() actually returns a Skip<Chars<'a>> which is not compatible with the rental type Chars<'a> or even something like S: Iterator, S<'a>.

Given these problems, I think using rental would introduce more complexity than it saves. Vote to close

from owned-chars.

Belatedly closed by #4.

from owned-chars.