http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56208
--- Comment #1 from Daniel Krügler <daniel.kruegler at googlemail dot com> 2013-02-04 19:54:47 UTC --- I just notice that the problem is not restricted to sizeof sfinae. In fact if we define the first test overload as follows: template<class U, class T> static one test(decltype( (make<U>() << make<T>()), 0 )); the same regression problem occurs. I'm confused.