pkg/collection: mark fields in wrappers as final

pkg/collection/lib/wrappers.dart

 // Copyright (c) 2013, 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.
 
 /**
  * Delegating wrappers for [Iterable], [List], [Set], [Queue] and [Map].
  *
  * Also adds unmodifiable views for `Set` and `Map`, and a fixed length
  * view for `List`. The unmodifable list view from `dart:collection` is exported
  * as well, just for completeness.
  */
 library dart.pkg.collection.wrappers;
 
 import "dart:collection";
 import "dart:math" show Random;
 
 export "dart:collection" show UnmodifiableListView;
 
 part "src/unmodifiable_wrappers.dart";
 
 /**
  * Creates an [Iterable] that delegates all operations to a base iterable.
  *
  * This class can be used hide non-`Iterable` methods of an iterable object,
  * or it can be extended to add extra functionality on top of an existing
  * iterable object.
  */
 class DelegatingIterable<E> implements Iterable<E> {
-  Iterable<E> _base;
+  final Iterable<E> _base;
 
   /**
    * Create a wrapper that forwards operations to [base].
    */
   DelegatingIterable(Iterable<E> base) : _base = base;
 
   bool any(bool test(E element)) => _base.any(test);
 
   bool contains(Object element) => _base.contains(element);
 
@@ skipping 248 matching lines @@
 }
 
 /**
  * Creates a [Map] that delegates all operations to a base map.
  *
  * This class can be used hide non-`Map` methods of an object that extends
  * `Map`, or it can be extended to add extra functionality on top of an existing
  * map object.
  */
 class DelegatingMap<K, V> implements Map<K, V> {
-  Map<K, V> _base;
+  final Map<K, V> _base;
+
   DelegatingMap(Map<K, V> base) : _base = base;
 
   V operator [](Object key) => _base[key];
 
   void operator []=(K key, V value) {
     _base[key] = value;
   }
 
   void addAll(Map<K, V> other) {
     _base.addAll(other);
@@ skipping 20 matching lines @@
   int get length => _base.length;
 
   V putIfAbsent(K key, V ifAbsent()) => _base.putIfAbsent(key, ifAbsent);
 
   V remove(Object key) => _base.remove(key);
 
   Iterable<V> get values => _base.values;
 
   String toString() => _base.toString();
 }