Function: WALK-LAMBDA-LIST

Source

(defun walk-lambda-list (lambda-list parent env &key allow-specializers)
  (flet ((extend-env (argument)
           (unless (typep argument 'allow-other-keys-function-argument-form)
             (extend env :let (name argument) argument))))
    (let ((state :required)
          (arguments '()))
      (dolist (argument lambda-list)
        (if (member argument '(&optional &key &rest))
            (setf state argument)
            (progn
              (push (case state
                      (:required
                       (if allow-specializers
                           (walk-specialized-argument-form argument parent env)
                           (walk-required-argument argument parent env)))
                      (&optional (walk-optional-argument argument parent env))
                      (&key
                       (if (eql '&allow-other-keys argument)
                           (make-instance 'allow-other-keys-function-argument-form
                                          :parent parent :source argument)
                           (walk-keyword-argument argument parent env)))
                      (&rest (walk-rest-argument argument parent env)))
                    arguments)
              (extend-env (car arguments)))))
      (values (nreverse arguments) env))))