Split out Index AST node from Invoke

pkg/polymer_expressions/lib/visitor.dart

Index: pkg/polymer_expressions/lib/visitor.dart
diff --git a/pkg/polymer_expressions/lib/visitor.dart b/pkg/polymer_expressions/lib/visitor.dart
index 03341c275710330d552ac117aa90a437501f1066..2a63936af5a8daeacc769184e09f2da5a948718c 100644
--- a/pkg/polymer_expressions/lib/visitor.dart
+++ b/pkg/polymer_expressions/lib/visitor.dart
@@ -10,6 +10,8 @@ abstract class Visitor {
   visit(Expression s) => s.accept(this);
   visitEmptyExpression(EmptyExpression e);
   visitParenthesizedExpression(ParenthesizedExpression e);
+  visitGetter(Getter i);
+  visitIndex(Index i);
   visitInvoke(Invoke i);
   visitLiteral(Literal l);
   visitMapLiteral(MapLiteral l);
@@ -30,6 +32,17 @@ abstract class RecursiveVisitor extends Visitor {
     visitExpression(e);
   }
 
+  visitGetter(Getter i) {
+    visit(i.receiver);
+    visitExpression(i);
+  }
+
+  visitIndex(Index i) {
+    visit(i.receiver);
+    visit(i.argument);
+    visitExpression(i);
+  }
+
   visitInvoke(Invoke i) {
     visit(i.receiver);
     if (i.arguments != null) {