Can't build with INVARIANTS but not WITNESS

From: John F Carr <jfc_at_mit.edu>
Date: Wed, 27 Apr 2022 12:23:24 UTC 
My -CURRENT kernel has INVARIANTS (inherited from GENERIC) but not WITNESS:

include GENERIC
ident   STRIATUS
nooptions       WITNESS
nooptions       WITNESS_SKIPSPIN

My kernel build fails:

/usr/home/jfc/freebsd/src/sys/kern/vfs_lookup.c:102:13: error: variable 'line' set but not used [-Werror,-Wunused-but-set-variable]
        int flags, line __diagused;
                   ^
/usr/home/jfc/freebsd/src/sys/kern/vfs_lookup.c:101:14: error: variable 'file' set but not used [-Werror,-Wunused-but-set-variable]
        const char *file __diagused;

The problem is, __diagused expands to nothing if INVARIANTS _or_ WITNESS is defined, but the variable in vfs_lookup.c is only used if WITNESS is defined.

#if defined(INVARIANTS) || defined(WITNESS)
#define __diagused
#else
#define __diagused      __unused
#endif

I think this code is trying to be too clever and causing more trouble than it prevents.  Change the || to &&, or replace __diagused with __unused everywhere.