Change List/Set/Map/Queue.from constructrs to accept any iterable.

sdk/lib/collection/linked_hash_set.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 [LinkedHashSet] is a hash-table based [Set] implementation.
  *
  * The `LinkedHashSet` also keep track of the order that elements were inserted
@@ skipping 47 matching lines @@
 
   /**
    * Creates an insertion-ordered identity-based set.
    *
    * Effectively a shorthand for:
    *
    *     new LinkedHashSet(equals: identical, hashCode: identityHashCodeOf)
    */
   external factory LinkedHashSet.identity();
 
-  factory LinkedHashSet.from(Iterable<E> iterable) {
-    return new LinkedHashSet<E>()..addAll(iterable);
+  /**
+   * Create a linked hash set containing all of [elements].
+   *
+   * Creates a linked hash set as by `new LinkedHashSet<E>()` and adds each
+   * element of`elements` to this set in the order they are iterated.
+   *
+   * All the [elements] should be assignable to [E].
+   * The `elements` iterable itself may have any element type,
+   * so this constructor can be used to down-cast a `Set`, for example as:
+   *
+   *     Set<SuperType> superSet = ...;
+   *     Iterable<SuperType> tmp = superSet.where((e) => e is SubType);
+   *     Set<SubType> subSet = new LinkedHashSet<SubType>.from(tmp);
+   */
+  factory LinkedHashSet.from(Iterable<E> elements) {
+    LinkedHashSet<E> result = new LinkedHashSet<E>();
+    for (final E element in elements) {

[Søren Gjesse, 2015/01/05 15:35:15]

Any particular reason for using final here?

[Lasse Reichstein Nielsen, 2015/01/06 10:14:45]

No. Copied it from somewhere else that had a final.
No reason not to make it final either.

+      result.add(element);
+    }
+    return result;
   }
 
   /**
    * Executes a function on each element of the set.
    *
    * The elements are iterated in insertion order.
    */
   void forEach(void action(E element));
 
   /**
    * Provides an iterator that iterates over the elements in insertion order.
    */
   Iterator<E> get iterator;
 }