;; specifier to win.
(type (missing-arg) :type ctype))
-;;; The NAMED-TYPE is used to represent *, T and NIL. These types must
-;;; be super- or sub-types of all types, not just classes and * and
-;;; NIL aren't classes anyway, so it wouldn't make much sense to make
-;;; them built-in classes.
+;;; The NAMED-TYPE is used to represent *, T and NIL, the standard
+;;; special cases, as well as other special cases needed to
+;;; interpolate between regions of the type hierarchy, such as
+;;; INSTANCE (which corresponds to all those classes with slots which
+;;; are not funcallable), FUNCALLABLE-INSTANCE (those classes with
+;;; slots which are funcallable) and EXTENDED-SEQUUENCE (non-LIST
+;;; non-VECTOR classes which are also sequences). These special cases
+;;; are the ones that aren't really discussed by Baker in his
+;;; "Decision Procedure for SUBTYPEP" paper.
(defstruct (named-type (:include ctype
(class-info (type-class-or-lose 'named)))
(:copier nil))