Better casting of for-in loops.

pkg/analyzer/test/src/context/mock_sdk.dart

Index: pkg/analyzer/test/src/context/mock_sdk.dart
diff --git a/pkg/analyzer/test/src/context/mock_sdk.dart b/pkg/analyzer/test/src/context/mock_sdk.dart
index 715ad1cc0c38d1109df9090973e514de116eac77..8103e12219ef70126ee5f65c3446d7aad9854d47 100644
--- a/pkg/analyzer/test/src/context/mock_sdk.dart
+++ b/pkg/analyzer/test/src/context/mock_sdk.dart
@@ -158,6 +158,15 @@ class List<E> implements Iterable<E> {
   void operator []=(int index, E value) {}
   Iterator<E> get iterator => null;
   void clear() {}
+
+  bool get isEmpty => false;
+  E get first => null;
+
+  Iterable/*<R>*/ map/*<R>*/(/*=R*/ f(E e)) => null;
+
+  /*=R*/ fold/*<R>*/(/*=R*/ initialValue,
+      /*=R*/ combine(/*=R*/ previousValue, E element)) => null;
+
 }
 
 class Map<K, V> extends Object {