http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59509
--- Comment #1 from Albert Zeyer <ich at az2000 dot de> ---
Sorry, that was the error from my real app. From the test case, the error is:
test_prodtempl.cpp:24:6: error: redefinition of 'template<class T1, class T2>
decltype (prod(a, b)) operator*(const T1&, const T2&)'
auto operator*(const T1& a, const T2& b) -> decltype(prod(a, b)) {
^
test_prodtempl.cpp:19:6: note: 'template<class T1, class T2> decltype
(X::prod(a, b)) operator*(const T1&, const T2&)' previously declared here
auto operator*(const T1& a, const T2& b) -> decltype(X::prod(a, b)) {
^
