CLJS-1951: Missing 0 and 1 arity versions of interleave

Author: thomasmulvaney

src/main/cljs/cljs/core.cljs

@@ -4656,6 +4656,8 @@ reduces them without incurring seq initialization"
 
 (defn interleave
   "Returns a lazy seq of the first item in each coll, then the second etc."
+  ([] ())
+  ([c1] (lazy-seq c1))
   ([c1 c2]
      (lazy-seq
       (let [s1 (seq c1) s2 (seq c2)]

src/test/cljs/cljs/collections_test.cljs

@@ -615,3 +615,7 @@
 (deftest test-cljs-1809
   (is (= (into) []))
   (is (= (into [1 2]) [1 2])))
+
+(deftest test-cljs-1951
+  (is (= () (interleave)))
+  (is (= '(1 2 3) (interleave [1 2 3]))))