[Clojure] fancy-defn: Proof of concept of schema.core/defn augmented with automatically generated clojure.core.typed annotations via circle.schema-typer

fancy-defn.clj

(ns fancy-defn
  (:require [schema.core         :as s]
            [clojure.core.typed  :as t]
            [circle.schema-typer :as st]))

;; Schemas created with s/defn end up using this.
(defmethod st/convert schema.core.One [schema]
  (assert (= false (:optional? schema))) ;; No support for optional arguments yet.
  (st/convert (:schema schema)))

(defmethod st/convert schema.core.FnSchema [schema]
  ;; Not sure why the input schema vector is wrapped in a seq...
  (assert (= 1 (count (:input-schemas schema))))

  ;; Some good old prn debugging output!
  ;; (prn "Output:" (:output-schema schema) "=>" (st/convert (:output-schema schema)))
  ;; (prn "Input:"  (:input-schemas schema) "=>" (map st/convert (first (:input-schemas schema))))

  (let [input-types (mapv st/convert (first (:input-schemas schema)))
        output-type (st/convert (:output-schema schema))]
    (conj input-types :-> output-type)))

(defmacro schema-ann [name]
  (let [var (resolve name) ;; Will this resolve `name` in the right namespace?
        schema (:schema (meta var))]
     `(t/cf (t/ann ~name ~(st/convert schema)))))

(defmacro fancy-defn [name & rest]
  `(do (s/defn ~name ~@rest)
       (schema-ann ~name)))

(comment
  ;;; Example usage

  (fancy-defn yell! :- String [s :- String] (str s "!!!"))

  (s/fn-schema yell!)
  ;; (=> java.lang.String java.lang.String)

  (t/cf yell!)
  ;; [java.lang.String -> java.lang.String]
  )