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

sdk/lib/collection/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;
 
 /** Default function for equality comparison in customized HashMaps */
 bool _defaultEquals(a, b) => a == b;
 /** Default function for hash-code computation in customized HashMaps */
 int _defaultHashCode(a) => a.hashCode;
@@ skipping 62 matching lines @@
   /**
    * Creates an unordered identity-based map.
    *
    * Effectively a shorthand for:
    *
    *     new HashMap(equals: identical, hashCode: identityHashCodeOf)
    */
   external factory HashMap.identity();
 
   /**
-   * Creates a [HashMap] that contains all key value pairs of [other].
+   * Creates a [HashMap] that contains all key/value pairs of [other].
    */
-  factory HashMap.from(Map<K, V> other) {
-    return new HashMap<K, V>()..addAll(other);
+  factory HashMap.from(Map other) {
+    HashMap<K, V> result = new HashMap<K, V>();
+    other.forEach((k, v) { result[k] = v; });

[Søren Gjesse, 2015/01/05 15:35:15]

Add types K and V?

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

The forEach method has type (K',V')->void where other:Map<K',V'>.
A (K,V)->void function might not be assignable to (K',V')->void, even if all the
keys and values of `other` happens to be K/V.

Example:
 class C {}
 class I {}
 class D extends C implements I {}
 Map<C,C> foo = ...;
 if (c.keys.every((v) => v is I) && c.values.every((v) => v is I)) {
   new Map<I,I>.from(foo);
 }

But it's tempting, so I'll add a test to catch it if someone decides to add K
and V later.

[Søren Gjesse, 2015/01/06 12:09:05]

Of cause.

+    return result;
   }
 
   /**
    * Creates a [HashMap] where the keys and values are computed from the
    * [iterable].
    *
    * For each element of the [iterable] this constructor computes a key/value
    * pair, by applying [key] and [value] respectively.
    *
    * The keys of the key/value pairs do not need to be unique. The last
@@ skipping 19 matching lines @@
    * overwrites the previous value.
    *
    * It is an error if the two [Iterable]s don't have the same length.
    */
   factory HashMap.fromIterables(Iterable<K> keys, Iterable<V> values) {
     HashMap<K, V> map = new HashMap<K, V>();
     Maps._fillMapWithIterables(map, keys, values);
     return map;
   }
 }