(defprotocol Foo
  (bar [this]))

(extend-type (Class/forName "[Ljava.lang.String;")
  Foo
  (bar [this] (seq this)))

(bar (into-array ["a" "b"]))

(extend-type (Class/forName "[[Ljava.lang.Object;")
  Foo
  (bar [this] (seq (map seq this))))

(bar (to-array-2d [["a" "b"]["c" "d"]]))