https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71771
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2016-07-06
Ever confirmed|0 |1
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
That's intentional, and has a longish history that I don't remember well.
// Note: In what follows, the left- and right-hand-side iterators are
// allowed to vary in types (conceptually in cv-qualification) so that
// comparison between cv-qualified and non-cv-qualified iterators be
// valid. However, the greedy and unfriendly operators in std::rel_ops
// will make overload resolution ambiguous (when in scope) if we don't
// provide overloads whose operands are of the same type. Can someone
// remind me what generic programming is about? -- Gaby
