http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48934
Summary: no rejection reason given for SFINAE Product: gcc Version: 4.6.0 Status: UNCONFIRMED Keywords: diagnostic Severity: enhancement Priority: P3 Component: c++ AssignedTo: unassig...@gcc.gnu.org ReportedBy: r...@gcc.gnu.org CC: froy...@gcc.gnu.org int foo(int); template<typename T> struct sfinae { }; template<> struct sfinae<float> { typedef double type; }; template<typename T> typename sfinae<T>::type foo(T t) { return t; } struct Bar { }; Bar b = foo( Bar() ); The error prints the two candidate functions and reason they weren't viable (I love this feature, thanks Nathan!) reason.cc:20:20: error: no matching function for call to 'foo(Bar)' reason.cc:20:20: note: candidates are: reason.cc:1:5: note: int foo(int) reason.cc:1:5: note: no known conversion for argument 1 from 'Bar' to 'int' reason.cc:15:10: note: template<class T> typename sfinae::type foo(T) But no reason is given for the template. I think the reason Clang++ gives is pretty good: note: candidate template ignored: substitution failure [with T = Bar] The key points to include in the reason are the template arguments and that substitution failed (more formally, type deduction failed because substitution resulted in an invalid type) I've only checked this with 4.6 so apologies if it's already been improved on trunk.