cker definitions for expressions that do
;;; not exhibit the &type-check effect, as callers should not ask if
;;; such an expression does or does not type-check.  For those that do
;;; exhibit &type-check, you should define a type inferrer unless the
;;; primcall will never typecheck.
;;;
;;; Likewise there is no need to define inferrers for primcalls which
;;; return &all-types values and which never raise exceptions from which
;;; we can infer the types of incoming values.