move fancy_syntax into Dart SVN

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
new file mode 100644
index 0000000000000000000000000000000000000000..a11a0d4c0933395273543d84e71fe6758f88631a
--- /dev/null
+++ b/pkg/polymer_expressions/lib/visitor.dart
@@ -0,0 +1,76 @@
+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library polymer_expressions.visitor;
+
+import 'expression.dart';
+
+abstract class Visitor<E extends Expression> {
+  visit(E s) => s.accept(this);
+  visitEmptyExpression(EmptyExpression e);
+  visitParenthesizedExpression(ParenthesizedExpression e);
+  visitInvoke(Invoke i);
+  visitLiteral(Literal l);
+  visitMapLiteral(MapLiteral l);
+  visitMapLiteralEntry(MapLiteralEntry l);
+  visitIdentifier(Identifier i);
+  visitBinaryOperator(BinaryOperator o);
+  visitUnaryOperator(UnaryOperator o);
+  visitInExpression(InExpression c);
+}
+
+abstract class RecursiveVisitor<E> extends Visitor<E> {
+  visitExpression(E e);
+
+  visitEmptyExpression(EmptyExpression e) => visitExpression(e);
+
+  visitParenthesizedExpression(ParenthesizedExpression e) {
+    visit(e);
+    visitExpression(e);
+  }
+
+  visitInvoke(Invoke i) {
+    visit(i.receiver);
+    if (i.arguments != null) {
+      for (var a in i.arguments) {
+        visit(a);
+      }
+    }
+    visitExpression(i);
+  }
+
+  visitLiteral(Literal l) => visitExpression(l);
+
+  visitMapLiteral(MapLiteral l) {
+    for (var e in l.entries) {
+      visit(e);
+    }
+    visitExpression(l);
+  }
+
+  visitMapLiteralEntry(MapLiteralEntry e) {
+    visit(e.key);
+    visit(e.entryValue);
+    visitExpression(e);
+  }
+
+  visitIdentifier(Identifier i) => visitExpression(i);
+
+  visitBinaryOperator(BinaryOperator o) {
+    visit(o.left);
+    visit(o.right);
+    visitExpression(o);
+  }
+
+  visitUnaryOperator(UnaryOperator o) {
+    visit(o.child);
+    visitExpression(o);
+  }
+
+  visitInExpression(InExpression c) {
+    visit(c.left);
+    visit(c.right);
+    visitExpression(c);
+  }
+}