https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93651
Jonathan Wakely <redi at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |NEW Last reconfirmed| |2020-02-10 Ever confirmed|0 |1 --- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> --- I think this is a defect in the C++2a draft. The cpp17-iterator concept requires the difference_type to be a signed integral type. To work with iota_view's iterators I think it should permit signed integer-like types as well (because iota_view's iterators use non-integral types to represent the difference type when the view uses the largest integer type).