diff --git a/util/walk.js b/util/walk.js
new file mode 100644
index 0000000000..18f9af5e56
--- /dev/null
+++ b/util/walk.js
@@ -0,0 +1,183 @@
+(function(exports) {
+  "use strict";
+
+  exports.simple = function(node, visitors, base, state) {
+    if (!base) base = exports;
+    function c(node, st, override) {
+      var type = override || node.type, found = visitors[type];
+      if (found) found(node, st);
+      base[type](node, st, c);
+    }
+    c(node, state);
+  };
+  exports.recursive = function(node, state, funcs, base) {
+    var visitor = exports.make(funcs, base);
+    function c(node, st, override) {
+      visitor[override || node.type](node, st, c);
+    }
+    c(node, state);
+  };
+  exports.make = function(funcs, base) {
+    if (!base) base = exports;
+    var visitor = {};
+    for (var type in base)
+      visitor[type] = funcs.hasOwnProperty(type) ? funcs[type] : base[type];
+    return visitor;
+  };
+
+  function skipThrough(node, st, c) { c(node, st); }
+  function ignore(node, st, c) {}
+
+  exports.Program = exports.BlockStatement = function(node, st, c) {
+    for (var i = 0; i < node.body.length; ++i)
+      c(node.body[i], st, "Statement");
+  };
+  exports.Statement = skipThrough;
+  exports.EmptyStatement = ignore;
+  exports.ExpressionStatement = function(node, st, c) {
+    c(node.expression, st, "Expression");
+  };
+  exports.IfStatement = function(node, st, c) {
+    c(node.test, st, "Expression");
+    c(node.consequent, st, "Statement");
+    if (node.alternate) c(node.alternate, st, "Statement");
+  };
+  exports.LabeledStatement = function(node, st, c) {
+    c(node.body, st, "Statement");
+  };
+  exports.BreakStatement = exports.ContinueStatement = ignore;
+  exports.WithStatement = function(node, st, c) {
+    c(node.object, st, "Expression");
+    c(node.body, st, "Statement");
+  };
+  exports.SwitchStatement = function(node, st, c) {
+    c(node.discriminant, st, "Expression");
+    for (var i = 0; i < node.cases.length; ++i) {
+      var cs = node.cases[i];
+      if (cs.test) c(cs.test, st, "Expression");
+      for (var j = 0; j < cs.consequent.length; ++j)
+        c(cs.consequent[j], st, "Statement");
+    }
+  };
+  exports.ReturnStatement = function(node, st, c) {
+    if (node.argument) c(node.argument, st, "Expression");
+  };
+  exports.ThrowStatement = function(node, st, c) {
+    c(node.argument, st, "Expression");
+  };
+  exports.TryStatement = function(node, st, c) {
+    c(node.block, st, "Statement");
+    for (var i = 0; i < node.handlers.length; ++i)
+      c(node.handlers[i].body, st, "ScopeBody");
+    if (node.finalizer) c(node.finalizer, st, "Statement");
+  };
+  exports.WhileStatement = function(node, st, c) {
+    c(node.test, st, "Expression");
+    c(node.body, st, "Statement");
+  };
+  exports.DoWhileStatement = exports.WhileStatement;
+  exports.ForStatement = function(node, st, c) {
+    if (node.init) c(node.init, st, "ForInit");
+    if (node.test) c(node.test, st, "Expression");
+    if (node.update) c(node.update, st, "Expression");
+    c(node.body, st, "Statement");
+  };
+  exports.ForInStatement = function(node, st, c) {
+    c(node.left, st, "ForInit");
+    c(node.right, st, "Expression");
+    c(node.body, st, "Statement");
+  };
+  exports.ForInit = function(node, st, c) {
+    if (node.type == "VariableDeclaration") c(node, st);
+    else c(node, st, "Expression");
+  };
+  exports.DebuggerStatement = ignore;
+
+  exports.FunctionDeclaration = function(node, st, c) {
+    c(node, st, "Function");
+  };
+  exports.VariableDeclaration = function(node, st, c) {
+    for (var i = 0; i < node.declarations.length; ++i) {
+      var decl = node.declarations[i];
+      if (decl.init) c(decl.init, st, "Expression");
+    }
+  };
+
+  exports.Function = function(node, st, c) {
+    c(node.body, st, "ScopeBody");
+  };
+  exports.ScopeBody = skipThrough;
+
+  exports.Expression = skipThrough;
+  exports.ThisExpression = ignore;
+  exports.ArrayExpression = function(node, st, c) {
+    for (var i = 0; i < node.elements.length; ++i) {
+      var elt = node.elements[i];
+      if (elt) c(elt, st, "Expression");
+    }
+  };
+  exports.ObjectExpression = function(node, st, c) {
+    for (var i = 0; i < node.properties.length; ++i)
+      c(node.properties[i].value, st, "Expression");
+  };
+  exports.FunctionExpression = exports.FunctionDeclaration;
+  exports.SequenceExpression = function(node, st, c) {
+    for (var i = 0; i < node.expressions.length; ++i)
+      c(node.expressions[i], st, "Expression");
+  };
+  exports.UnaryExpression = exports.UpdateExpression = function(node, st, c) {
+    c(node.argument, st, "Expression");
+  };
+  exports.BinaryExpression = exports.AssignmentExpression = exports.LogicalExpression = function(node, st, c) {
+    c(node.left, st, "Expression");
+    c(node.right, st, "Expression");
+  };
+  exports.ConditionalExpression = function(node, st, c) {
+    c(node.test, st, "Expression");
+    c(node.consequent, st, "Expression");
+    c(node.alternate, st, "Expression");
+  };
+  exports.NewExpression = exports.CallExpression = function(node, st, c) {
+    c(node.callee, st, "Expression");
+    if (node.arguments) for (var i = 0; i < node.arguments.length; ++i)
+      c(node.arguments[i], st, "Expression");
+  };
+  exports.MemberExpression = function(node, st, c) {
+    c(node.object, st, "Expression");
+    if (node.computed) c(node.property, st, "Expression");
+  };
+  exports.Identifier = exports.Literal = ignore;
+
+  function makeScope(prev) {
+    return {vars: Object.create(null), prev: prev};
+  }
+  exports.scopeVisitor = exports.make({
+    Function: function(node, scope, c) {
+      var inner = makeScope(scope);
+      for (var i = 0; i < node.params.length; ++i)
+        inner.vars[node.params[i].name] = "argument";
+      if (node.type == "FunctionDeclaration")
+        scope.vars[node.id.name] = "function";
+      else if (node.id)
+        inner.vars[node.id.name] = "function'";
+      c(node.body, inner, "ScopeBody");
+    },
+    TryStatement: function(node, scope, c) {
+      c(node.block, scope, "Statement");
+      for (var i = 0; i < node.handlers.length; ++i) {
+        var handler = node.handlers[i], inner = makeScope(scope);
+        inner.vars[handler.param.name] = "catch";
+        c(handler.body, inner, "ScopeBody");
+      }
+      if (node.finalizer) c(node.finalizer, scope, "Statement");
+    },
+    VariableDeclaration: function(node, scope, c) {
+      for (var i = 0; i < node.declarations.length; ++i) {
+        var decl = node.declarations[i];
+        scope.vars[decl.id.name] = "var";
+        if (decl.init) c(decl.init, scope, "Expression");
+      }
+    }
+  });
+
+})(typeof exports == "undefined" ? acorn.walk = {} : exports);