[Bug libstdc++/52114] SFINAE out the rvalue iostream operators to give better error messages

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52114

--- Comment #8 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-02-04 
22:54:51 UTC ---
But using decltype((o<<t), std::ostream&) would solve that.