Use iterator, moveNext(), current.

sdk/lib/core/set.dart

Index: sdk/lib/core/set.dart
diff --git a/sdk/lib/core/set.dart b/sdk/lib/core/set.dart
index 2083e91ca66eb7df1ca1dd99679a3c4413a20f70..a7bb9de03e4090c24068f681ec5109ff122ccfaf 100644
--- a/sdk/lib/core/set.dart
+++ b/sdk/lib/core/set.dart
@@ -184,9 +184,7 @@ class _HashSetImpl<E> implements HashSet<E> {
     return _backingMap.length;
   }
 
-  Iterator<E> iterator() {
-    return new _HashSetIterator<E>(this);
-  }
+  Iterator<E> get iterator => new _HashSetIterator<E>(this);
 
   String toString() {
     return Collections.collectionToString(this);
@@ -200,48 +198,27 @@ class _HashSetImpl<E> implements HashSet<E> {
 
 class _HashSetIterator<E> implements Iterator<E> {
 
-  // TODO(4504458): Replace set_ with set.
-  _HashSetIterator(_HashSetImpl<E> set_)
-    : _nextValidIndex = -1,
-      _entries = set_._backingMap._keys {
-    _advance();
-  }
-
-  bool get hasNext {
-    if (_nextValidIndex >= _entries.length) return false;
-    if (identical(_entries[_nextValidIndex], _HashMapImpl._DELETED_KEY)) {
-      // This happens in case the set was modified in the meantime.
-      // A modification on the set may make this iterator misbehave,
-      // but we should never return the sentinel.
-      _advance();
-    }
-    return _nextValidIndex < _entries.length;
-  }
+  _HashSetIterator(_HashSetImpl<E> set)
+    : _keysIterator = set._backingMap._keys.iterator;
 
-  E next() {
-    if (!hasNext) {
-      throw new StateError("No more elements");
+  E get current {
+    var result = _keysIterator.current;
+    if (identical(result, _HashMapImpl._DELETED_KEY)) {
+      // TODO(floitsch): improve the error reporting.
+      throw new StateError("Concurrent modification.");
     }
-    E res = _entries[_nextValidIndex];
-    _advance();
-    return res;
+    return result;
   }
 
-  void _advance() {
-    int length = _entries.length;
-    var entry;
-    final deletedKey = _HashMapImpl._DELETED_KEY;
+  bool moveNext() {
+    bool result;
     do {
-      if (++_nextValidIndex >= length) break;
-      entry = _entries[_nextValidIndex];
-    } while ((entry == null) || identical(entry, deletedKey));
+      result = _keysIterator.moveNext();
+    } while (result &&
+             (_keysIterator.current == null ||
+              identical(_keysIterator.current, _HashMapImpl._DELETED_KEY)));
+    return result;
   }
 
-  // The entries in the set. May contain null or the sentinel value.
-  List<E> _entries;
-
-  // The next valid index in [_entries] or the length of [entries_].
-  // If it is the length of [_entries], calling [hasNext] on the
-  // iterator will return false.
-  int _nextValidIndex;
+  Iterator _keysIterator;
 }