http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53646
--- Comment #12 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-06-12 16:12:55 UTC --- If I remember correctly, the last time I tried, default + is_constructible worked pretty well modulo testcases sensitive to access control under sfinae. But the latter we are going to implment anyway for 4.8, thus temporary FIXME or something in the testcases would be fine.
