std::weakly_incrementable doesn't require a std::input_iterator's post-increment operator to return anything¹, so don't. ¹ https://eel.is/c++draft/iterator.concepts#iterator.concept.winc-14 The return value of post-increment on objects that model input_iterator is partially-formed (as a copy of an iterator since advanced), so any attempts to use it, apart from assigning a new iterator or destroying it, are undefined, anyway. Found in API-review. Pick-to: 6.8 Change-Id: If0c07250cec4e48c6e5176cd23864651e8ec3d27 Reviewed-by: Thiago Macieira <thiago.macieira@intel.com> Reviewed-by: Ahmad Samir <a.samirh78@gmail.com>