Prismatic schema for reference-types (deferrable) like atoms and futures.

reference.clj

(defrecord Reference [schema]
  s/Schema
  (walker [_]
    (let [sub-walker (s/subschema-walker schema)]
      (fn [x] (sub-walker @x))))
  (explain [_] (list 'reference (s/explain schema))))

(defn reference
  [schema]
  (Reference. schema))