[Bug c++/113523] A conversion function template can have a deduced return type

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113523

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
https://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#1670

Actually `auto operator` is invalid too.