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pkg/compiler/lib/src/util/link_implementation.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.
 
 part of util_implementation;
 
 class LinkIterator<T> implements Iterator<T> {
   T _current;
   Link<T> _link;
 
@@ skipping 151 matching lines @@
   int length = 0;
 
   LinkBuilderImplementation();
 
   Link<T> toLink([Link<T> tail = const Link()]) {
     if (head == null) return tail;
     lastLink.tail = tail;
     Link<T> link = head;
     lastLink = null;
     head = null;
+    length = 0;
     return link;
   }
 
   List<T> toList() {
     if (length == 0) return new List<T>(0);
     List<T> list = new List<T>(length);
     int index = 0;
     Link<T> link = head;
     while (link.isNotEmpty) {
       list[index] = link.head;
       link = link.tail;
       index++;
     }
     lastLink = null;
     head = null;
+    length = 0;
     return list;
   }
 
   Link<T> addLast(T t) {
     length++;
     LinkEntry<T> entry = new LinkEntry<T>(t, null);
     if (head == null) {
       head = entry;
     } else {
       lastLink.tail = entry;
     }
     lastLink = entry;
     return entry;
   }
 
   bool get isEmpty => length == 0;
+
+  T get first {
+    if (head != null) {
+      return head.head;
+    }
+    throw new StateError("no elements");
+  }
+
+  void clear() {
+    head = null;
+    lastLink = null;
+    length = 0;
+  }
 }