http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58713
--- Comment #4 from Marc Glisse <glisse at gcc dot gnu.org> --- If I try to sfinae-out this function based on os<<x being well-formed, I get an error that "template instantiation depth exceeds maximum of 900" (even for a valid cout<<42), because even if this overload won't match, it still looks at it recursively.
