;; optional. Stick the extra var in the result
;; element representing the keyword or optional,
;; which is the previous one.
+ ;;
+ ;; FIXME: NCONC used for side-effect: the effect is defined,
+ ;; but this is bad style no matter what.
(nconc (car res)
(list (compiled-debug-fun-lambda-list-var
args (incf i) vars))))