I believe that cljs versions 1.9.493 and above break core.async (and possibly other libraries) under :advanced optimizations.
Here is a minimal reproduction: In src/ca_adv_bug/core.cljs: (ns ca-adv-bug.core (:require [cljs.core.async :as ca] [cljs.nodejs :as nodejs]) (:require-macros [cljs.core.async.macros :refer [go]])) (nodejs/enable-util-print!) (defn -main [& args] (go (println "Hello world!"))) (set! *main-cli-fn* -main) In build.clj: (require 'cljs.build.api) (cljs.build.api/build "src" {:optimizations :advanced :target :nodejs :main 'ca-adv-bug.core :output-to "main.js"}) In the current directory, I have two versions of the standalone cljs jar, named with their versions, as well as the latest core.async jar. I pulled them from https://github.com/clojure/clojurescript/releases/download/r1.9.473/cljs.jar and https://github.com/clojure/clojurescript/releases/download/r1.9.493/cljs.jar . First, with cljs v1.9.473: ~/src/test-ca $ java -cp cljs-1.9.473.jar:core.async-0.3.441.jar:src clojure.main build.clj ~/src/test-ca $ node main.js Hello world! Now with cljs v1.9.493: ~/src/test-ca $ java -cp cljs-1.9.493.jar:core.async-0.3.441.jar:src clojure.main build.clj Mar 03, 2017 3:39:53 PM com.google.javascript.jscomp.LoggerErrorManager println SEVERE: /Users/chad/src/test-ca/out/cljs/core/async.js:1426: ERROR - Parse error. No newline allowed before '=>' var inst_6822 = async(inst_6821); ^ Mar 03, 2017 3:39:53 PM com.google.javascript.jscomp.LoggerErrorManager printSummary WARNING: 1 error(s), 0 warning(s) ERROR: JSC_PARSE_ERROR. Parse error. No newline allowed before '=>' at /Users/chad/src/test-ca/out/cljs/core/async.js line 1426 : 32 Can others reproduce this? This issue is blocking us from using the latest cljs, as we rely on core.async and :advanced optimizations. Thank you for your efforts, Chad Harrington chad.harring...@gmail.com c...@farbetter.com -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.