Fixes #378

test/codegen/extensions.dart

Index: test/codegen/extensions.dart
diff --git a/test/codegen/language/issue_23914_test.dart b/test/codegen/extensions.dart
similarity index 65%
copy from test/codegen/language/issue_23914_test.dart
copy to test/codegen/extensions.dart
index 072f912b74cff3b0bbde89667b3ba30ea84ac71d..d31cf91ebb40db511abf732d14badecd9f256fe7 100644
--- a/test/codegen/language/issue_23914_test.dart
+++ b/test/codegen/extensions.dart
@@ -4,6 +4,8 @@
 
 import 'dart:collection';
 
-main() {
-  var a = new List.unmodifiable(new LinkedList());
+class StringIterable extends IterableBase<String> {
+  final Iterator<String> iterator = null;
 }
+
+main() => new StringIterable();