foo.clj

(ns foo
  (:require [plumbing.core :refer :all]
            [schema.core :as s]))

(defprotocol Foo
  (foo [this]))

;; this doesn't work, why?
(defnk cant-annotate-output-with-protocol-as-value :- {:foo Foo}
  "docstring 1"
  [baz :- s/Any])

;; this works
(defnk can-annotate-output-with-protocol :- Foo
  "docstring 2"
  [baz :- s/Any])

;; this works
(defnk can-annotate-input-with-protocol :- nil
  "docstring 3"
  [foo :- Foo])