[ 2022-04-22; Jonathan adds a comment ]

P2408 changes the requirements for types substituting BidirectionalIterator etc. in the Algorithms clause. We should consider whether that is appropriate here, especially as algorithms might make use of std::prev internally. An algorithm that was changed by P2408 to accept types that model bidirectional_iterator instead of requiring Cpp17BidirectionalIterator might have to stop using std::prev if we don't resolve this issue to allow it.

We should consider whether distance, advance and next need the same treatment.