(arg (gensym (format nil "~:@(ARG-FOR-~S-~)" byte-spec-expr))))
(when (ldb-test (byte byte-size byte-posn) overall-mask)
(error "The byte spec ~S either overlaps another byte spec, or ~
(arg (gensym (format nil "~:@(ARG-FOR-~S-~)" byte-spec-expr))))
(when (ldb-test (byte byte-size byte-posn) overall-mask)
(error "The byte spec ~S either overlaps another byte spec, or ~