https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67017
--- Comment #2 from Anders Granlund <anders.granlund.0 at gmail dot com> ---
(In reply to Jonathan Wakely from comment #1)
> EDG and Clang also accept this in C++14 mode (and like GCC, reject it in
> C++11 mode).
I think that is because type deduction for return types of functions was
introduced in c++14.
The following program is well-formed in c++14, but not in c++11:
auto f();
int main() {}
