a.clj

(ns midje-test.a)

(defprotocol A (a [_]))

core.clj

(ns midje-test.core
  (:require [midje.open-protocols :refer [defrecord-openly]]
            [midje-test.a :refer [A]]))

(defrecord-openly B []
  A
  (a [_] (prn "something")))

;;  this becomes
;; (clojure.core/defrecord B []
;;  A
;;  (a
;;   [_]
;;   (if
;;    (midje.data.prerequisite-state/implements-a-fake? a) <-- obviously "a" is not defined here
;;    (clojure.core/apply a [_]) <-- nor here
;;    (do (prn "something")))))

(defn -main [& args]
  (prn "hi"))