Can't require core.async in Clojure

Question

I want to require core.async, but the compiler throws an error when requiring.

I've added [org.clojure/core.async "0.4.500"] to project.clj, and tried various versions, but the compiler still throws an error.

This is my core.clj:

  (:require [clojure.core.async
             :as a
             :refer [>! <! >!! <!! go chan buffer close! thread
                     alts! alts!! timeout]]))

And these are my :dependencies in my project.clj:

:dependencies [[org.clojure/clojure "1.10.0"]
               [org.clojure/core.async "0.4.500"]]

The compiler throws:

Error compiling clojure/core/async.clj at (9:1)

Call to clojure.core/refer-clojure did not conform to spec.

Answer 1

OK, it turns out I just needed to restart Emacs, it fixed the problem. Somehow.