Fix DoubleLinkedQueue so that appending to entries also update the queue length.

tests/corelib/queue_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.
 
 library queue.test;
 
 import "package:expect/expect.dart";
 import 'dart:collection';
 
 abstract class QueueTest {
@@ skipping 381 matching lines @@
 class DoubleLinkedQueueTest extends QueueTest {
   Queue newQueue() => new DoubleLinkedQueue();
   Queue newQueueFrom(Iterable elements) => new DoubleLinkedQueue.from(elements);
 
   void testMain() {
     super.testMain();
     testQueueElements();
   }
 
   void testQueueElements() {
-    DoubleLinkedQueue<int> queue1 = new DoubleLinkedQueue<int>.from([1, 2, 4]);
+    DoubleLinkedQueue<int> queue1 = new DoubleLinkedQueue<int>.from([1, 2, 3]);
     DoubleLinkedQueue<int> queue2 = new DoubleLinkedQueue<int>();
     queue2.addAll(queue1);
 
     Expect.equals(queue1.length, queue2.length);
     DoubleLinkedQueueEntry<int> entry1 = queue1.firstEntry();
     DoubleLinkedQueueEntry<int> entry2 = queue2.firstEntry();
     while (entry1 != null) {
       Expect.equals(true, !identical(entry1, entry2));
       entry1 = entry1.nextEntry();
       entry2 = entry2.nextEntry();
     }
     Expect.equals(null, entry2);
+
+    var firstEntry = queue1.firstEntry();
+    var secondEntry = queue1.firstEntry().nextEntry();
+    var thirdEntry = queue1.lastEntry();
+    firstEntry.prepend(4);
+    firstEntry.append(5);
+    secondEntry.prepend(6);
+    secondEntry.append(7);
+    thirdEntry.prepend(8);
+    thirdEntry.append(9);
+    Expect.equals(9, queue1.length);
+    Expect.listEquals(queue1.toList(), [4, 1, 5, 6, 2, 7, 8, 3, 9]);
+    Expect.equals(1, firstEntry.remove());
+    Expect.equals(2, secondEntry.remove());
+    Expect.equals(3, thirdEntry.remove());
+    Expect.equals(6, queue1.length);
+    Expect.listEquals(queue1.toList(), [4, 5, 6, 7, 8, 9]);
   }
 }
 
+void linkEntryTest() {
+  var entry = new DoubleLinkedQueueEntry(42);
+  Expect.equals(null, entry.previousEntry());
+  Expect.equals(null, entry.nextEntry());
+
+  entry.append(37);
+  entry.prepend(87);
+  var prev = entry.previousEntry();
+  var next = entry.nextEntry();
+  Expect.equals(42, entry.element);
+  Expect.equals(37, next.element);
+  Expect.equals(87, prev.element);
+  Expect.identical(entry, prev.nextEntry());
+  Expect.identical(entry, next.previousEntry());
+  Expect.equals(null, next.nextEntry());
+  Expect.equals(null, prev.previousEntry());
+
+  entry.element = 117;
+  Expect.equals(117, entry.element);
+  Expect.identical(next, entry.nextEntry());
+  Expect.identical(prev, entry.previousEntry());
+
+  Expect.equals(117, entry.remove());
+  Expect.identical(next, prev.nextEntry());
+  Expect.identical(prev, next.previousEntry());
+  Expect.equals(null, next.nextEntry());
+  Expect.equals(null, prev.previousEntry());
+  Expect.equals(37, next.element);
+  Expect.equals(87, prev.element);
+
+  Expect.equals(37, next.remove());
+  Expect.equals(87, prev.element);
+  Expect.equals(null, prev.nextEntry());
+  Expect.equals(null, prev.previousEntry());
+
+  Expect.equals(87, prev.remove());
+}
+
 
 main() {
   new DoubleLinkedQueueTest().testMain();
   new ListQueueTest().testMain();
+  linkEntryTest();
 }