save-data: Put with-packages at the right place.

            (storage-data storage)))

(defun write-classes-info (stream)

  (assign-ids)

  (write-n-bytes (number-of-non-empty-classes *storage*)

                 +sequence-length+ stream)

  (map-data (lambda (class objects)

(defun dump-data (stream)

  (write-classes-info stream)

  (assign-ids)

  (map-data (lambda (class objects)

              (declare (ignore class))

              (dolist (object objects)

(defun save-data (storage &optional file)

  (let ((*storage* storage))

    (when (storage-data storage)

      (with-packages

        (with-io-file (stream (or file (storage-file storage))

                       :direction :output

                       :size (measure-size))

        (with-packages

          (dump-data stream))))))