http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54101
--- Comment #1 from Marc Glisse <glisse at gcc dot gnu.org> 2012-07-27 06:04:09 UTC --- I don't think the issue is with declval, this is probably a dup of the PR saying that ?: has a wrong return type with g++ (can't find the number right now).