Add List.asMap().

sdk/lib/_collection_dev/list.dart

Index: sdk/lib/_collection_dev/list.dart
diff --git a/sdk/lib/_collection_dev/list.dart b/sdk/lib/_collection_dev/list.dart
index 9384627d9b97c62565b3dca4adfc9ab6ec1b8f95..9d845e08293e004a248a3cd4e447b6f3c005b764 100644
--- a/sdk/lib/_collection_dev/list.dart
+++ b/sdk/lib/_collection_dev/list.dart
@@ -24,6 +24,10 @@ abstract class ListBase<E> extends ListIterable<E> implements List<E> {
   E elementAt(int index) {
     return this[index];
   }
+
+  Map<int, E> asMap() {
+    return new ListMapView(this);
+  }
 }
 
 /**
@@ -244,3 +248,57 @@ class CodeUnits extends UnmodifiableListBase<int> {
   int get length => _string.length;
   int operator[](int i) => _string.codeUnitAt(i);
 }
+
+class _ListIndexIterable extends ListIterable<int> {
+  List _backedList;
+
+  _ListIndexIterable(this._backedList);
+
+  int get length => _backedList.length;
+  int elementAt(int index) {
+    if (index < 0 || index >= length) throw new RangeError(index);
+    return index;
+  }
+}
+
+class ListMapView<E> implements Map<int, E> {
+  List<E> _values;
+
+  ListMapView(this._values);
+
+  E operator[] (int key) => containsKey(key) ? _values[key] : null;
+  int get length => _values.length;
+
+  Iterable<E> get values => new SubListIterable<E>(_values, 0, null);
+  Iterable<int> get keys => new _ListIndexIterable(_values);

[Lasse Reichstein Nielsen, 2013/03/04 08:28:37]

_ListIndicesIterable?

[floitsch, 2013/03/04 16:50:20]

Done.

+
+  bool get isEmpty => _values.isEmpty;
+  bool containsValue(E value) => _values.contains(value);
+  bool containsKey(int key) => key is int && key >= 0 && key < length;

[Lasse Reichstein Nielsen, 2013/03/04 08:28:37]

Drop the "key is int".

[floitsch, 2013/03/04 16:50:20]

The key is int is crucial. Otherwise it will return true for things that aren't
in it.
Since we decide to move towards accepting any Object (removing the type in the
signature) I will keep it.

+
+  void forEach(void f(int key, E value)) {
+    int length = _values.length;
+    for (int i = 0; i < length; i++) {
+      f(i, _values[i]);
+      if (length != _values.length) {
+        throw new ConcurrentModificationError(_values);
+      }
+    }
+  }
+
+  void operator[]= (int key, E value) {
+    throw new UnsupportedError("Cannot modify an unmodifiable map");
+  }
+
+  E putIfAbsent(int key, E ifAbsent()) {
+    throw new UnsupportedError("Cannot modify an unmodifiable map");
+  }
+
+  E remove(int key) {
+    throw new UnsupportedError("Cannot modify an unmodifiable map");
+  }
+
+  void clear() {
+    throw new UnsupportedError("Cannot modify an unmodifiable map");
+  }
+}