"Unused private field" build failure(s) — clang 12.0.1

clang -Wall -Werror will fail because bar is private (by default) and never used. g++ does not complain here.
class foo
{
    int bar;
};
PackageVersionSupposed error messageFull log Bug report
qlcplus 4.12.4-1./alsamidiinputdevice.h:51:16: error: private field 'm_alsa' is not used [-Werror,-Wunused-private-field] Log

1 errors