+ (t
+ ;; It could be argued that &WHOLE and friends would be
+ ;; just ordinary variables in an ordinary lambda-list,
+ ;; but since (1) that seem exceedingly to have been the
+ ;; programmers intent and (2) the spec can be
+ ;; interpreted as giving as licence to signal an
+ ;; error[*] that is what we do.
+ ;;
+ ;; [* All lambda list keywords used in the
+ ;; implementation appear in LAMBDA-LIST-KEYWORDS. Each
+ ;; member of a lambda list is either a parameter
+ ;; specifier ot a lambda list keyword. Ergo, symbols
+ ;; appearing in LAMBDA-LIST-KEYWORDS cannot be
+ ;; parameter specifiers.]
+ (compiler-error 'simple-program-error
+ :format-control "Bad lambda list keyword ~S in: ~S"
+ :format-arguments (list arg list))))