Use a spec for defining function arguments and get validation automatically

specfn.clj

(ns specfn.core
  (:require [clojure.spec :as s]
            [clojure.spec.test :as t]))

(defn- spec-symbols [s]
  (->> s
       (drop 1)
       (partition-all 2)
       (map first)
       (map name)
       (mapv symbol)))

(defmacro defn* [name spec & body]
  (let [params (spec-symbols spec)
        spec-key (keyword (str *ns*) (str name "__args"))]
    `(do
       (s/def ~spec-key ~spec)
       (defn ~name ~params
         (if (s/valid? ~spec-key ~params)
           ~@body
           (throw (ex-info
                   (s/explain-str ~spec-key ~params)
                   (s/explain-data ~spec-key ~params))))))))

(comment
  
  (defn* my-fn (s/cat :n number? :s string?)
    (str n s))

  (my-fn 10 "bar") ;; => "10bar"
  (my-fn 10 10)) ;; => clojure.lang.ExceptionInfo: In: [1] val: 10 fails spec: :specfn.core/my-fn__args at: [:s] predicate: string?