CLJS-3334: exists? evaluates to true for cljs.user//

Author: mfikes

src/main/clojure/cljs/core.cljc

@@ -973,7 +973,7 @@
   (if (core/symbol? x)
     (core/let [x     (core/cond-> (:name (cljs.analyzer/resolve-var &env x))
                        (= "js" (namespace x)) name)
-               segs  (string/split (core/str (string/replace (core/str x) "/" ".")) #"\.")
+               segs  (string/split (core/str (string/replace-first (core/str x) "/" ".")) #"\.")
                n     (count segs)
                syms  (map
                        #(vary-meta (symbol "js" (string/join "." %))

src/test/cljs/cljs/core_test.cljs

@@ -1878,3 +1878,8 @@
 (deftest test-cljs-3333
   (defonce not-native 17)   ;; Intentionally matching a core name
   (is (== 17 not-native)))
+
+(deftest test-cljs-3334
+  (is (exists? /))
+  (is (exists? cljs.core//))
+  (is (not (exists? cljs.core-test//))))