typed_cljs_eg.clj

(ns cljs-test.core 
  (:require [typed.internal :refer [print-env]])
  (:require-macros [typed.core :as t]))

(t/cljs-ann occurrence-t [(U nil [-> BooleanCLJS]) -> BooleanCLJS])
(defn occurrence-t [x]
  (if x
    (do 
      (print-env "then branch")
      (x))
    (do 
      (print-env "else branch")
      false)))

; ClojureScript:cljs-test.core> (t/check-cljs-ns)
; "then branch"
;   {:env {x (Fn [-> BooleanCLJS]), 
;          occurencet (Fn [(U (Fn [-> BooleanCLJS]) nil) -> BooleanCLJS])}, 
;    :props ((! (U false nil) x))}
; "else branch"
;   {:env {x nil, 
;          occurencet (Fn [(U (Fn [-> BooleanCLJS]) nil) -> BooleanCLJS])}, 
;    :props ((is (U false nil) x))}
; nil
; ClojureScript:cljs-test.core>