Experiment about using reflection in macros for #clojure

reflection-in-macros.clj

(require '[clojure.reflect :refer [type-reflect]])
(require '[clojure.walk :refer [postwalk]])
(require '[clojure.set :refer [subset?]])

(defn public-static? [{:keys [flags]}]
  (subset? #{:public :static} flags))

(def public-static-member?
  (memoize
   (fn public-static-member? [cls sym]
     (let [members (:members (type-reflect cls))]
       (some (fn [{name :name :as member}]
               (and (public-static? member) (= sym name)))
             members)))))

#_ (public-static-member? String 'blerg)
#_ (public-static-member? String 'valueOf)
#_ (public-static-member? Long 'MEDIUM_VALUE)
#_ (public-static-member? Long 'MAX_VALUE)

(defmacro foo [cls form]
  (postwalk
   (fn [x]
     (if (and (seq? x) ((every-pred symbol? (partial public-static-member? cls)) (first x)))
       `(. ~cls ~@x)
       x))
   form))

#_ (foo java.lang.String (= "1" (valueOf 1)))
#_ (foo java.lang.String (= "6" (valueOf (+ 1 2 3))))
#_ (foo java.lang.String (= "123" (apply str (map #(valueOf %) [1 2 3]))))
#_ (foo java.lang.Long (MAX_VALUE))

;; from amalloy in irc -- might contain quoting errors.  macrolet is from https://github.com/clojure/tools.macro
#_ (defmacro foo [cls & body] `(macrolet [~@(for [{:keys [name flags] (:members (type-reflect cls)) :when (public-static? flags)}] `(~name [& args#] `(. ~~cls ~~name ~@args#)))] ~@body))