[Bug c++/61745] template friend for dyadic operator- is only accepted if the monadic operator- follows it

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61745

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Clang and EDG behave the same as G++ for this code.