CLJS-2028: realized? throws on LazyTransformer

Author: anmonteiro

src/main/cljs/cljs/core.cljs

@@ -4015,7 +4015,11 @@ reduces them without incurring seq initialization"
       (-seq this))
     (if (nil? rest)
       nil
-      (-seq rest))))
+      (-seq rest)))
+
+  IPending
+  (-realized? [_]
+    (nil? stepper)))
 
 (es6-iterable LazyTransformer)
 

src/test/cljs/cljs/core_test.cljs

@@ -846,7 +846,7 @@
   (testing "Testing CLJS-853, function metadata"
     (is (= {:foo true} (meta ^:foo (fn []))))))
 
-(deftest test-807 
+(deftest test-807
   (testing "Testing CLJS-807, big int, float, big dec literals"
     (is (= -1 -1N))
     (is (= 9.007199254740996E15 9007199254740995N))
@@ -1189,6 +1189,12 @@
   (is (= (get "0123" nil :not-found) :not-found))
   (is (= (get #js [0 1 2 3] nil :not-found) :not-found)))
 
+(deftest test-cljs-2028
+  (let [x (sequence (filter pos?) [1 2 -1])]
+    (is (not (realized? x)))
+    (is (= x [1 2]))
+    (is (realized? x))))
+
 (comment
   ;; ObjMap
   ;; (let [ks (map (partial str "foo") (range 500))