This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 112e. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.
In an example like
template<typename T, typename U> using X = T; template<typename T> X<void, typename T::type> f(); template<typename T> X<void, typename T::other> f();
it appears that the second declaration of f is a redeclaration of the first but distinguishable by SFINAE, i.e., equivalent but not functionally equivalent.
Notes from the November, 2014 meeting:
CWG felt that these two declarations should not be equivalent.