Seems like it ought to new possible to rename std::iter::Iterator to std::iter::OldIterator, add std::iter::NewIterator, and then vary which iterator std::iter:

Seems like it ought to new possible to rename std::iter::Iterator to std::iter::OldIterator, add std::iter::NewIterator, and then vary which iterator std::iter::Iterator points to based on edition. Maybe that would be considered too confusing though.