https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66689
--- Comment #3 from Ed Smith-Rowland <3dw4rd at verizon dot net> --- Well, for whatever reason, TR29124 and C++17 chose the - in front of \nu. As long as we document and warn I think this isn't a defect. I'll dig through the docs and get back.
