XOR without arguments results in unused variable warning
CL-USER> (alexandria:xor)
; in: ALEXANDRIA:XOR
; (LET (#:TMP6779 #:TRUE6780)
; (BLOCK #:XOR6778 (RETURN-FROM #:XOR6778 (VALUES #:TRUE6780 T))))
;
; caught STYLE-WARNING:
; The variable #:TMP6779 is defined but never used.
;
; compilation unit finished
; caught 1 STYLE-WARNING condition
NIL
T
Fix: add (declare (ignorable ,tmp))
in the LET
at https://gitlab.common-lisp.net/alexandria/alexandria/-/blob/master/alexandria-1/control-flow.lisp#L84