Use iterator, moveNext(), current.

sdk/lib/core/queue.dart

Index: sdk/lib/core/queue.dart
diff --git a/sdk/lib/core/queue.dart b/sdk/lib/core/queue.dart
index acb9c04772288b33dd835a5b274e0ef4f53cef79..15ebed34fb3d6790a161311d6285dc9761b30ec1 100644
--- a/sdk/lib/core/queue.dart
+++ b/sdk/lib/core/queue.dart
@@ -307,7 +307,7 @@ class DoubleLinkedQueue<E> implements Queue<E> {
     return other;
   }
 
-  _DoubleLinkedQueueIterator<E> iterator() {
+  _DoubleLinkedQueueIterator<E> get iterator {
     return new _DoubleLinkedQueueIterator<E>(_sentinel);
   }
 
@@ -318,21 +318,24 @@ class DoubleLinkedQueue<E> implements Queue<E> {
 
 class _DoubleLinkedQueueIterator<E> implements Iterator<E> {
   final _DoubleLinkedQueueEntrySentinel<E> _sentinel;
-  DoubleLinkedQueueEntry<E> _currentEntry;
+  DoubleLinkedQueueEntry<E> _currentEntry = null;
 
-  _DoubleLinkedQueueIterator(_DoubleLinkedQueueEntrySentinel this._sentinel) {
-    _currentEntry = _sentinel;
-  }
+  _DoubleLinkedQueueIterator(this._sentinel);
 
-  bool get hasNext {
-    return !identical(_currentEntry._next, _sentinel);
+  bool moveNext() {
+    // [:null:] means that the iterator hasn't moved yet.
+    // When it is set to the sentinel, then it is at the end.
+    if (identical(_currentEntry, _sentinel)) return false;
+    if (_currentEntry == null) _currentEntry = _sentinel;
+    _currentEntry = _currentEntry._next;
+    return !identical(_currentEntry, _sentinel);
   }
 
-  E next() {
-    if (!hasNext) {
-      throw new StateError("No more elements");
+  E get current {
+    if (_currentEntry != null && !identical(_currentEntry, _sentinel)) {
+      return _currentEntry.element;
     }
-    _currentEntry = _currentEntry._next;
-    return _currentEntry.element;
+    // TODO(floitsch): adapt error message.
+    throw new StateError("No more elements");
   }
 }