Changes in polymer-expressions to prepare for codegen in polymer:

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 08a6a022aac7498305e659c6daf013dedf6ceadd..8c4118df150aa432128a079f8e874285fb7829c8 100644
--- a/pkg/polymer_expressions/lib/visitor.dart
+++ b/pkg/polymer_expressions/lib/visitor.dart
@@ -24,28 +24,36 @@ abstract class Visitor {
   visitInExpression(InExpression c);
 }
 
-abstract class RecursiveVisitor extends Visitor {
-  visitExpression(Expression e);
+class RecursiveVisitor extends Visitor {
+  preVisitExpression(Expression e) {}
+  visitExpression(Expression e) {}
 
-  visitEmptyExpression(EmptyExpression e) => visitExpression(e);
+  visitEmptyExpression(EmptyExpression e) {
+    preVisitExpression(e);
+    visitExpression(e);
+  }
 
   visitParenthesizedExpression(ParenthesizedExpression e) {
+    preVisitExpression(e);
     visit(e.child);
     visitExpression(e);
   }
 
   visitGetter(Getter i) {
+    preVisitExpression(i);
     visit(i.receiver);
     visitExpression(i);
   }
 
   visitIndex(Index i) {
+    preVisitExpression(i);
     visit(i.receiver);
     visit(i.argument);
     visitExpression(i);
   }
 
   visitInvoke(Invoke i) {
+    preVisitExpression(i);
     visit(i.receiver);
     if (i.arguments != null) {
       for (var a in i.arguments) {
@@ -55,9 +63,13 @@ abstract class RecursiveVisitor extends Visitor {
     visitExpression(i);
   }
 
-  visitLiteral(Literal l) => visitExpression(l);
+  visitLiteral(Literal l) {
+    preVisitExpression(l);
+    visitExpression(l);
+  }
 
   visitListLiteral(ListLiteral l) {
+    preVisitExpression(l);
     for (var i in l.items) {
       visit(i);
     }
@@ -65,6 +77,7 @@ abstract class RecursiveVisitor extends Visitor {
   }
 
   visitMapLiteral(MapLiteral l) {
+    preVisitExpression(l);
     for (var e in l.entries) {
       visit(e);
     }
@@ -72,25 +85,32 @@ abstract class RecursiveVisitor extends Visitor {
   }
 
   visitMapLiteralEntry(MapLiteralEntry e) {
+    preVisitExpression(e);
     visit(e.key);
     visit(e.entryValue);
     visitExpression(e);
   }
 
-  visitIdentifier(Identifier i) => visitExpression(i);
+  visitIdentifier(Identifier i) {
+    preVisitExpression(i);
+    visitExpression(i);
+  }
 
   visitBinaryOperator(BinaryOperator o) {
+    preVisitExpression(o);
     visit(o.left);
     visit(o.right);
     visitExpression(o);
   }
 
   visitUnaryOperator(UnaryOperator o) {
+    preVisitExpression(o);
     visit(o.child);
     visitExpression(o);
   }
 
   visitTernaryOperator(TernaryOperator o) {
+    preVisitExpression(o);
     visit(o.condition);
     visit(o.trueExpr);
     visit(o.falseExpr);
@@ -98,8 +118,9 @@ abstract class RecursiveVisitor extends Visitor {
   }
 
   visitInExpression(InExpression c) {
+    preVisitExpression(c);
     visit(c.left);
     visit(c.right);
     visitExpression(c);
   }
-}
+}