(defun copy-slot-definition (slot-def)
(make-instance (class-of slot-def)
:name (slot-definition-name slot-def)
:initargs (slot-definition-initargs slot-def)
:readers (slot-definition-readers slot-def)
:writers (slot-definition-writers slot-def)
:allocation (slot-definition-allocation slot-def)
:type (slot-definition-type slot-def)
;; Our own options.
:persistence (slot-persistence slot-def)
:index (slot-index slot-def)
:unique (slot-unique slot-def)))