http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50855
Bug #: 50855 Summary: Name mangling for late return types invoking constructors not implemented Classification: Unclassified Product: gcc Version: 4.6.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ AssignedTo: unassig...@gcc.gnu.org ReportedBy: pub...@alisdairm.net Jason suggested I file the issue, even though the error message indicates a known limitation. The following code yields the error: main.cpp: In instantiation of 'decltype ({256}) test(const T&) [with T = char, decltype ({256}) = char]': main.cpp:8:14: instantiated from here main.cpp:2:6: sorry, unimplemented: mangling constructor template<typename T> auto test(T const &) -> decltype(T{256}) { return T{}; } int main() { char c = 42; c = test(c); }