(do ((form body (cdr form)))
((null form) nil)
(when (atom (car form))
- ;; FIXME: detect duplicate tags
+ (when (assoc (car form) tags)
+ (ip-error "The tag :A appears more than once in a tagbody."))
(push (cons (car form) (cdr form)) tags)
(push (cons (car form) #'go-to-tag) (env-tags env)))))
;; And then evaluate the forms in the body, starting from the