https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89194
--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> --- Author: redi Date: Tue Feb 5 15:45:24 2019 New Revision: 268543 URL: https://gcc.gnu.org/viewcvs?rev=268543&root=gcc&view=rev Log: PR libstdc++/89194 untangle is_convertible and is_nothrow_convertible The additional logic added to __is_convertible_helper in order to support is_nothrow_convertible makes some uses of is_convertible ill-formed. This appears to be due to PR c++/87603, but can be avoided just by defining a separate helper for is_nothrow_convertible. The same problems are likely to still exist for is_nothrow_convertible, but that is new and so won't cause regressions for existing users of is_convertible. PR libstdc++/89194 * include/std/type_traits (__is_convertible_helper) (__is_convertible_helper<_From, _To, false>): Revert changes to support is_nothrow_convertible. (__is_nt_convertible_helper): New helper. (is_nothrow_convertible): Use __is_nt_convertible_helper. Modified: trunk/libstdc++-v3/ChangeLog trunk/libstdc++-v3/include/std/type_traits
