+ (hash-value (random #.(ash 1 15))
+ :type (and fixnum unsigned-byte)
+ :read-only t)
+ ;; Can this object contain other types? A global property of our
+ ;; implementation (which unfortunately seems impossible to enforce
+ ;; with assertions or other in-the-code checks and constraints) is
+ ;; that subclasses which don't contain other types correspond to
+ ;; disjoint subsets (except of course for the NAMED-TYPE T, which
+ ;; covers everything). So NUMBER-TYPE is disjoint from CONS-TYPE is
+ ;; is disjoint from MEMBER-TYPE and so forth. But types which can
+ ;; contain other types, like HAIRY-TYPE and INTERSECTION-TYPE, can
+ ;; violate this rule.
+ (might-contain-other-types-p nil :read-only t))