[Bug c++/53598] missed diagnostics / equality comparison result unused [-Wunused-comparison]

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53598

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
We should warn about an unused result of any (in)equality, relational, or
three-way comparison.