https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65861
--- Comment #12 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Jonathan Wakely from comment #9) > There are actually good reasons *not* to reject input iterators at > compile-time. > > You could have an iterator which meets most, but not all, the forward > iterator requirements, and so must have input_iterator_tag as its category. > Such as iterator could work fine with std::search, if we don't reject it via > a static assertion. > > (istreambuf_iterator is not such an iterator, as it's genuinely a > single-pass iterator, and so can't be used ... but we can't reliably detect > that as the only property we can test is the iterator_category tag). Since C++20 we can also check the iterator_concept tag. That means we can allow iterators that identify as input iterators according to iterator_category, but forward iterators (or stronger) according to iterator_concept.
