pkg/collection: define delegating collection constructors as const

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.
@@ skipping 13 matching lines @@
  * 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> {
   final Iterable<E> _base;
 
   /**
    * Create a wrapper that forwards operations to [base].
    */
-  DelegatingIterable(Iterable<E> base) : _base = base;
+  const DelegatingIterable(Iterable<E> base) : _base = base;
 
   bool any(bool test(E element)) => _base.any(test);
 
   bool contains(Object element) => _base.contains(element);
 
   E elementAt(int index) => _base.elementAt(index);
 
   bool every(bool test(E element)) => _base.every(test);
 
   Iterable expand(Iterable f(E element)) => _base.expand(f);
@@ skipping 50 matching lines @@
 
 
 /**
  * Creates a [List] that delegates all operations to a base list.
  *
  * This class can be used hide non-`List` methods of a list object,
  * or it can be extended to add extra functionality on top of an existing
  * list object.
  */
 class DelegatingList<E> extends DelegatingIterable<E> implements List<E> {
-  DelegatingList(List<E> base) : super(base);
+  const DelegatingList(List<E> base) : super(base);
 
   List<E> get _listBase => _base;
 
   E operator [](int index) => _listBase[index];
 
   void operator []=(int index, E value) {
     _listBase[index] = value;
   }
 
   void add(E value) {
@@ skipping 78 matching lines @@
 
 
 /**
  * Creates a [Set] that delegates all operations to a base set.
  *
  * This class can be used hide non-`Set` methods of a set object,
  * or it can be extended to add extra functionality on top of an existing
  * set object.
  */
 class DelegatingSet<E> extends DelegatingIterable<E> implements Set<E> {
-  DelegatingSet(Set<E> base) : super(base);
+  const DelegatingSet(Set<E> base) : super(base);
 
   Set<E> get _setBase => _base;
 
   bool add(E value) => _setBase.add(value);
 
   void addAll(Iterable<E> elements) {
     _setBase.addAll(elements);
   }
 
   void clear() {
@@ skipping 30 matching lines @@
 }
 
 /**
  * Creates a [Queue] that delegates all operations to a base queue.
  *
  * This class can be used hide non-`Queue` methods of a queue object,
  * or it can be extended to add extra functionality on top of an existing
  * queue object.
  */
 class DelegatingQueue<E> extends DelegatingIterable<E> implements Queue<E> {
-  DelegatingQueue(Queue<E> queue) : super(queue);
+  const DelegatingQueue(Queue<E> queue) : super(queue);
 
   Queue<E> get _baseQueue => _base;
 
   void add(E value) {
     _baseQueue.add(value);
   }
 
   void addAll(Iterable<E> iterable) {
     _baseQueue.addAll(iterable);
   }
@@ skipping 24 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> {
   final Map<K, V> _base;
 
-  DelegatingMap(Map<K, V> base) : _base = base;
+  const 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 19 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();
 }