;;; return is NIL, T, because that's completely wrong. ]
(assert (subtypep '(or integer ratio) 'rational))
(assert (subtypep 'rational '(or integer ratio)))
+;;; Likewise, these are allowed to return NIL, NIL:
+(assert (subtypep t '(or real (not real))))
+(assert (subtypep t '(or keyword (not keyword))))