Fix typo in ListMixin.insertAll.

sdk/lib/collection/list.dart

Index: sdk/lib/collection/list.dart
diff --git a/sdk/lib/collection/list.dart b/sdk/lib/collection/list.dart
index e7d902ece79cc6220c7f998359313b214eed8b1b..9b6b753a815db1dd3f729e54e021322f743bfc58 100644
--- a/sdk/lib/collection/list.dart
+++ b/sdk/lib/collection/list.dart
@@ -476,7 +476,7 @@ abstract class ListMixin<E> implements List<E> {
 
   void insertAll(int index, Iterable<E> iterable) {
     RangeError.checkValueInInterval(index, 0, length, "index");
-    if (iterable is EfficientLength) {
+    if (iterable is! EfficientLength || identical(iterable, this)) {

[Søren Gjesse, 2015/06/01 11:37:57]

Are these cased covered by tests? I guess that we only have tests where
"identical" is hit which also has EfficientLength.

[Lasse Reichstein Nielsen, 2015/06/01 13:13:10]

Probably not. It's hard to test because it only affects performance, not
behavior. There should still be coverage for the code, but it wouldn't have
caught the inverted is-test here.
Since this object is a List which always has EfficientLength, identical implies
"is EfficientLength".

       iterable = iterable.toList();
     }
     int insertionLength = iterable.length;
@@ -484,6 +484,12 @@ abstract class ListMixin<E> implements List<E> {
     // will end up being modified but the operation not complete. Unless we
     // always go through a "toList" we can't really avoid that.
     this.length += insertionLength;
+    if (iterable.length != insertionLength) {
+      // If the iterable's length is linked to this list's length somehow,
+      // we can't insert one in the other.
+      this.length -= insertionLength;
+      throw new ConcurrentModificationError(iterable);
+    }
     setRange(index + insertionLength, this.length, this, index);
     setAll(index, iterable);
   }