CLJS-3230: seq on empty Iterable produces an empty seq

Author: swannodette

src/main/cljs/cljs/core.cljs

@@ -1330,7 +1330,7 @@
   [iter]
   (let [v (.next iter)]
     (if (.-done v)
-      ()
+      nil
       (ES6IteratorSeq. (.-value v) iter nil))))
 
 ;;;;;;;;;;;;;;;;;;; Murmur3 Helpers ;;;;;;;;;;;;;;;;

src/test/cljs/cljs/seqs_test.cljs

@@ -224,3 +224,10 @@
 (deftest test-cljs-2911
   (testing "partition-by works correclty with infinite seqs"
     (is (= (first (second (partition-by zero? (range)))) 1))))
+
+(deftest test-cljs-3230
+  (testing "sequence ops on ES6 collections"
+    (let [s (js/Set.)]
+      (is (= () (rest s)))
+      (is (nil? (next s)))
+      (is (empty? s)))))