Add test for complex in expressions in polymer_expressions

pkg/polymer_expressions/test/eval_test.dart

Index: pkg/polymer_expressions/test/eval_test.dart
diff --git a/pkg/polymer_expressions/test/eval_test.dart b/pkg/polymer_expressions/test/eval_test.dart
index 9445d8e0aac180fd7a58c0415d6326ab5c1214ae..9f623ce70cd2c0005137e417c119f841d26c815c 100644
--- a/pkg/polymer_expressions/test/eval_test.dart
+++ b/pkg/polymer_expressions/test/eval_test.dart
@@ -216,6 +216,13 @@ main() {
       expect(comprehension.iterable, orderedEquals([1, 2, 3]));
     });
 
+    test('should evaluate complex "in" expressions', () {
+      var holder = new ListHolder([1, 2, 3]);
+      var scope = new Scope(variables: {'holder': holder});
+      var comprehension = eval(parse('item in holder.items'), scope);
+      expect(comprehension.iterable, orderedEquals([1, 2, 3]));
+    });
+
     test('should handle null iterators in "in" expressions', () {
       var scope = new Scope(variables: {'items': null});
       var comprehension = eval(parse('item in items'), scope);
@@ -361,6 +368,12 @@ class Foo extends ChangeNotifier {
   int x() => age * age;
 }
 
+@reflectable
+class ListHolder {
+  List items;
+  ListHolder(this.items);
+}
+
 parseInt([int radix = 10]) => new IntToString(radix: radix);
 
 class IntToString extends Transformer<int, String> {