Update {,Linked}Hash{Set,Map} documentation.

sdk/lib/collection/linked_hash_map.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.
 
 part of dart.collection;
 
 /**
  * A hash-table based implementation of [Map].
  *
  * The insertion order of keys is remembered,
@@ skipping 25 matching lines @@
    * key's own [Object.hashCode] is used.
    *
    * If using methods like [operator[]], [remove] and [containsKey] together
    * with a custom equality and hashcode, an extra `isValidKey` function
    * can be supplied. This function is called before calling [equals] or
    * [hashCode] with an argument that may not be a [K] instance, and if the
    * call returns false, the key is assumed to not be in the set.
    * The [isValidKey] function defaults to just testing if the object is a
    * [K] instance.
    *
+   * Example:
+   *
+   *     new LinkedHashMap<int,int>(equals: (int a, int b) => (b - a) % 5 == 0,
+   *                                hashCode: (int e) => e % 5)
+   *
+   * This example map does not need an `isValidKey` function to be passed.
+   * The default function accepts only `int` values, which can safely be
+   * passed to both the `equals` and `hashCode` functions.
+   *
+   * If neither `equals`, `hashCode`, nor `isValidKey` is provided,
+   * the default `isValidKey` instead accepts all keys.
+   * The default equality and hashcode operations are assumed to work on all
+   * objects.
+   *
+   * Likewise, if `equals` is [identical], `hashCode` is [identityHashCode]
+   * and `isValidKey` is omitted, the resulting map is identity based,
+   * and the `isValidKey` defaults to accepting all keys.
+   * Such a map can be created directly using [LinkedHashMap.identity].
+   *
    * The used `equals` and `hashCode` method should always be consistent,
    * so that if `equals(a, b)` then `hashCode(a) == hashCode(b)`. The hash
    * of an object, or what it compares equal to, should not change while the
    * object is in the table. If it does change, the result is unpredictable.
    *
    * If you supply one of [equals] and [hashCode],
    * you should generally also to supply the other.
-   * An example would be using [identical] and [identityHashCode],
-   * which is equivalent to using the shorthand [LinkedHashMap.identity]).
    */
-  external factory LinkedHashMap({ bool equals(K key1, K key2),
-                                   int hashCode(K key),
-                                   bool isValidKey(potentialKey) });
+  external factory LinkedHashMap({bool equals(K key1, K key2),
+                                  int hashCode(K key),
+                                  bool isValidKey(potentialKey)});
 
   /**
    * Creates an insertion-ordered identity-based map.
    *
    * Effectively a shorthand for:
    *
-   *     new LinkedHashMap(equals: identical, hashCode: identityHashCodeOf)
+   *     new LinkedHashMap(equals: identical,
+   *                       hashCode: identityHashCodeOf)
    */
   external factory LinkedHashMap.identity();
 
   /**
    * Creates a [LinkedHashMap] that contains all key value pairs of [other].
    */
   factory LinkedHashMap.from(Map other) {
     LinkedHashMap<K, V> result = new LinkedHashMap<K, V>();
     other.forEach((k, v) { result[k] = v; });
     return result;
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    * overwrites the previous value.
    *
    * It is an error if the two [Iterable]s don't have the same length.
    */
   factory LinkedHashMap.fromIterables(Iterable<K> keys, Iterable<V> values) {
     LinkedHashMap<K, V> map = new LinkedHashMap<K, V>();
     Maps._fillMapWithIterables(map, keys, values);
     return map;
   }
 }