Use iterator, moveNext(), current.

tests/corelib/queue_iterator_test.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 class QueueIteratorTest {
   static testMain() {
     testSmallQueue();
     testLargeQueue();
     testEmptyQueue();
   }
 
   static void testThrows(Iterator<int> it) {
-    Expect.equals(false, it.hasNext);
-    var exception = null;
-    try {
-      it.next();
-    } on StateError catch (e) {
-      exception = e;
-    }
-    Expect.equals(true, exception != null);
+    Expect.isFalse(it.moveNext());
+    Expect.throws(() => it.current, (e) => e is StateError);
   }
 
   static int sum(int expected, Iterator<int> it) {
     int count = 0;
-    while (it.hasNext) {
-      count += it.next();
+    while (it.moveNext()) {
+      count += it.current;
     }
     Expect.equals(expected, count);
   }
 
   static void testSmallQueue() {
     Queue<int> queue = new Queue<int>();
     queue.addLast(1);
     queue.addLast(2);
     queue.addLast(3);
 
-    Iterator<int> it = queue.iterator();
-    Expect.equals(true, it.hasNext);
+    Iterator<int> it = queue.iterator;
     sum(6, it);
     testThrows(it);
   }
 
   static void testLargeQueue() {
     Queue<int> queue = new Queue<int>();
     int count = 0;
     for (int i = 0; i < 100; i++) {
       count += i;
       queue.addLast(i);
     }
-    Iterator<int> it = queue.iterator();
-    Expect.equals(true, it.hasNext);
+    Iterator<int> it = queue.iterator;
     sum(count, it);
     testThrows(it);
   }
 
   static void testEmptyQueue() {
     Queue<int> queue = new Queue<int>();
-    Iterator<int> it = queue.iterator();
-    Expect.equals(false, it.hasNext);
+    Iterator<int> it = queue.iterator;
     sum(0, it);
     testThrows(it);
   }
 }
 
 main() {
   QueueIteratorTest.testMain();
 }