what is  `*nrepl-messages*`  , is it an emacs buffer or a clojure dynamic variable?

I don't find such a clojure variable, nor emacs buffer nor emacs-lisp variable.

Ahh, I think I see the problem. it is defined like this. So the arglist is [_value type-designator] but cider can't figure that out. perhaps cider is not smart enough to get the arglist of the function pass as 3rd argument to defmulti ?

(defmulti typep 
  "Like instance? except that the arguments are reversed, and the
  given type designator need not be a class.  The given type 
  designator may be a (1) class, (2) a symbol resolving to a class, or
  (3) a CL style type designator such as
  (not A)
  (and A B)
  (or A B)
  (satisfies A B)
  (= obj)
  (member a b c)"
  (fn [_value type-designator]
    (if (sequential? type-designator)
      (first type-designator)
      type-designator)))