Avoid closures when traversing

2015-01-17 00:10:57 +03:00
parent 8dc4996547
commit f9480b5280
36 changed files with 257 additions and 215 deletions
--- a/lib/6to5/transformation/helpers/name-method.js
+++ b/lib/6to5/transformation/helpers/name-method.js
@@ -9,28 +9,31 @@ module.exports = function (node, file, scope) {
  var id = t.toIdentifier(key.value);
  key = t.identifier(id);

-  var selfReference = false;
-  var outerDeclar = scope.get(id, true);
+  var state = {
+    id: id,
+    selfReference: false,
+    outerDeclar: scope.get(id, true),
+  };

  traverse(node, {
-    enter: function (node, parent, scope) {
+    enter: function (node, parent, scope, context, state) {
      // check if this node is an identifier that matches the same as our function id
-      if (!t.isIdentifier(node, { name: id })) return;
+      if (!t.isIdentifier(node, { name: state.id })) return;

      // check if this node is the one referenced
      if (!t.isReferenced(node, parent)) return;

      // check that we don't have a local variable declared as that removes the need
      // for the wrapper
-      var localDeclar = scope.get(id, true);
-      if (localDeclar !== outerDeclar) return;
+      var localDeclar = scope.get(state.id, true);
+      if (localDeclar !== state.outerDeclar) return;

-      selfReference = true;
-      this.stop();
+      state.selfReference = true;
+      context.stop();
    }
-  }, scope);
+  }, scope, state);

-  if (selfReference) {
+  if (state.selfReference) {
    node.value = util.template("property-method-assignment-wrapper", {
      FUNCTION: node.value,
      FUNCTION_ID: key,
--- a/lib/6to5/transformation/helpers/remap-async-to-generator.js
+++ b/lib/6to5/transformation/helpers/remap-async-to-generator.js
@@ -6,8 +6,8 @@ module.exports = function (node, callId) {
  node.generator = true;

  traverse(node, {
-    enter: function (node) {
-      if (t.isFunction(node)) this.skip();
+    enter: function (node, parent, scope, context) {
+      if (t.isFunction(node)) context.skip();

      if (t.isAwaitExpression(node)) {
        node.type = "YieldExpression";
--- a/lib/6to5/transformation/modules/_default.js
+++ b/lib/6to5/transformation/modules/_default.js
@@ -20,13 +20,13 @@ DefaultFormatter.prototype.getLocalExports = function () {
  var localExports = {};

  traverse(this.file.ast, {
-    enter: function (node) {
+    enter: function (node, parent, scope, context, localExports) {
      var declar = node && node.declaration;
      if (t.isExportDeclaration(node) && declar && t.isStatement(declar)) {
        _.extend(localExports, t.getIds(declar, true));
      }
    }
-  });
+  }, null, localExports);

  return localExports;
 };
@@ -35,12 +35,12 @@ DefaultFormatter.prototype.getLocalImports = function () {
  var localImports = {};

  traverse(this.file.ast, {
-    enter: function (node) {
+    enter: function (node, parent, scope, context, localImports) {
      if (t.isImportDeclaration(node)) {
        _.extend(localImports, t.getIds(node, true));
      }
    }
-  });
+  }, null, localImports);

  return localImports;
 };
@@ -62,7 +62,7 @@ DefaultFormatter.prototype.checkCollisions = function () {
  };

  traverse(file.ast, {
-    enter: function (node) {
+    enter: function (node, parent, scope, context, check) {
      if (t.isAssignmentExpression(node)) {

        var left = node.left;
@@ -75,7 +75,7 @@ DefaultFormatter.prototype.checkCollisions = function () {
        _.each(t.getIds(node, true), check);
      }
    }
-  });
+  }, null, check);
 };

 DefaultFormatter.prototype.remapExportAssignment = function (node) {
@@ -100,9 +100,9 @@ DefaultFormatter.prototype.remapAssignments = function () {
  };

  traverse(this.file.ast, {
-    enter: function (node, parent, scope) {
+    enter: function (node, parent, scope, context, isLocalReference) {
      if (t.isUpdateExpression(node) && isLocalReference(node.argument, scope)) {
-        this.skip();
+        context.skip();

        // expand to long file assignment expression
        var assign = t.assignmentExpression(node.operator[0] + "=", node.argument, t.literal(1));
@@ -130,11 +130,11 @@ DefaultFormatter.prototype.remapAssignments = function () {
      }

      if (t.isAssignmentExpression(node) && isLocalReference(node.left, scope)) {
-        this.skip();
+        context.skip();
        return self.remapExportAssignment(node);
      }
    }
-  });
+  }, null, isLocalReference);
 };

 DefaultFormatter.prototype.getModuleName = function () {
--- a/lib/6to5/transformation/modules/system.js
+++ b/lib/6to5/transformation/modules/system.js
@@ -63,28 +63,31 @@ SystemFormatter.prototype.importSpecifier = function (specifier, node, nodes) {

 SystemFormatter.prototype.buildRunnerSetters = function (block, hoistDeclarators) {
  return t.arrayExpression(_.map(this.ids, function (uid, source) {
-    var nodes = [];
+    var state = {
+      nodes: [],
+      hoistDeclarators: hoistDeclarators
+    };

    traverse(block, {
-      enter: function (node) {
+      enter: function (node, parent, scope, context, state) {
        if (node._importSource === source) {
          if (t.isVariableDeclaration(node)) {
            _.each(node.declarations, function (declar) {
-              hoistDeclarators.push(t.variableDeclarator(declar.id));
-              nodes.push(t.expressionStatement(
+              state.hoistDeclarators.push(t.variableDeclarator(declar.id));
+              state.nodes.push(t.expressionStatement(
                t.assignmentExpression("=", declar.id, declar.init)
              ));
            });
          } else {
-            nodes.push(node);
+            state.nodes.push(node);
          }

-          this.remove();
+          context.remove();
        }
      }
-    });
+    }, null, state);

-    return t.functionExpression(null, [uid], t.blockStatement(nodes));
+    return t.functionExpression(null, [uid], t.blockStatement(state.nodes));
  }));
 };

@@ -112,10 +115,10 @@ SystemFormatter.prototype.transform = function (ast) {

  // hoist up all variable declarations
  traverse(block, {
-    enter: function (node, parent, scope) {
+    enter: function (node, parent, scope, context, hoistDeclarators) {
      if (t.isFunction(node)) {
        // nothing inside is accessible
-        return this.skip();
+        return context.skip();
      }

      if (t.isVariableDeclaration(node)) {
@@ -150,7 +153,8 @@ SystemFormatter.prototype.transform = function (ast) {
        return nodes;
      }
    }
-  });
+  }, null, hoistDeclarators);
+
  if (hoistDeclarators.length) {
    var hoistDeclar = t.variableDeclaration("var", hoistDeclarators);
    hoistDeclar._blockHoist = true;
@@ -159,15 +163,15 @@ SystemFormatter.prototype.transform = function (ast) {

  // hoist up function declarations for circular references
  traverse(block, {
-    enter: function (node) {
-      if (t.isFunction(node)) this.skip();
+    enter: function (node, parent, scope, context, handlerBody) {
+      if (t.isFunction(node)) context.skip();

      if (t.isFunctionDeclaration(node) || node._blockHoist) {
        handlerBody.push(node);
-        this.remove();
+        context.remove();
      }
    }
-  });
+  }, null, handlerBody);

  handlerBody.push(returnStatement);

--- a/lib/6to5/transformation/transformer.js
+++ b/lib/6to5/transformation/transformer.js
@@ -4,6 +4,25 @@ var traverse = require("../traverse");
 var t        = require("../types");
 var _        = require("lodash");

+function noop() { }
+
+function enter(node, parent, scope, context, args) {
+  var fns = args[1][node.type];
+  if (!fns) return;
+  return fns.enter(node, parent, scope, context, args[0]);
+}
+
+function exit(node, parent, scope, context, args) {
+  var fns = args[1][node.type];
+  if (!fns) return;
+  return fns.exit(node, parent, scope, context, args[0]);
+}
+
+var traverseOpts = {
+  enter: enter,
+  exit: exit
+};
+
 function Transformer(key, transformer, opts) {
  this.manipulateOptions = transformer.manipulateOptions;
  this.experimental      = !!transformer.experimental;
@@ -32,6 +51,9 @@ Transformer.prototype.normalise = function (transformer) {

    if (!_.isObject(fns)) return;

+    if (!fns.enter) fns.enter = noop;
+    if (!fns.exit) fns.exit = noop;
+
    transformer[type] = fns;

    var aliases = t.FLIPPED_ALIAS_KEYS[type];
@@ -54,28 +76,8 @@ Transformer.prototype.astRun = function (file, key) {
 };

 Transformer.prototype.transform = function (file) {
-  var transformer = this.transformer;
-
-  var build = function (exit) {
-    return function (node, parent, scope) {
-      var fns = transformer[node.type];
-      if (!fns) return;
-
-      var fn = fns.enter;
-      if (exit) fn = fns.exit;
-      if (!fn) return;
-
-      return fn.call(this, node, parent, file, scope);
-    };
-  };
-
  this.astRun(file, "before");
-
-  traverse(file.ast, {
-    enter: build(),
-    exit:  build(true)
-  });
-
+  traverse(file.ast, traverseOpts, null, [file, this.transformer]);
  this.astRun(file, "after");
 };

--- a/lib/6to5/transformation/transformers/_alias-functions.js
+++ b/lib/6to5/transformation/transformers/_alias-functions.js
@@ -5,22 +5,23 @@ var go = function (getBody, node, file, scope) {
  var argumentsId;
  var thisId;

-  var getArgumentsId = function () {
-    return argumentsId = argumentsId || file.generateUidIdentifier("arguments", scope);
-  };
-
-  var getThisId = function () {
-    return thisId = thisId || file.generateUidIdentifier("this", scope);
+  var state = {
+    getArgumentsId: function () {
+      return argumentsId = argumentsId || file.generateUidIdentifier("arguments", scope);
+    },
+    getThisId: function () {
+      return thisId = thisId || file.generateUidIdentifier("this", scope);
+    }
  };

  // traverse the function and find all alias functions so we can alias
  // `arguments` and `this` if necessary
  traverse(node, {
-    enter: function (node) {
+    enter: function (node, parent, scope, context, state) {
      if (!node._aliasFunction) {
        if (t.isFunction(node)) {
          // stop traversal of this node as it'll be hit again by this transformer
-          return this.skip();
+          return context.skip();
        } else {
          return;
        }
@@ -28,30 +29,30 @@ var go = function (getBody, node, file, scope) {

      // traverse all child nodes of this function and find `arguments` and `this`
      traverse(node, {
-        enter: function (node, parent) {
+        enter: function (node, parent, scope, context, state) {
          if (t.isFunction(node) && !node._aliasFunction) {
-            return this.skip();
+            return context.skip();
          }

-          if (node._ignoreAliasFunctions) return this.skip();
+          if (node._ignoreAliasFunctions) return context.skip();

          var getId;

          if (t.isIdentifier(node) && node.name === "arguments") {
-            getId = getArgumentsId;
+            getId = state.getArgumentsId;
          } else if (t.isThisExpression(node)) {
-            getId = getThisId;
+            getId = state.getThisId;
          } else {
            return;
          }

          if (t.isReferenced(node, parent)) return getId();
        }
-      });
+      }, null, state);

-      return this.skip();
+      return context.skip();
    }
-  });
+  }, null, state);

  var body;

@@ -71,14 +72,14 @@ var go = function (getBody, node, file, scope) {
  }
 };

-exports.Program = function (node, parent, file, scope) {
+exports.Program = function (node, parent, scope, context, file) {
  go(function () {
    return node.body;
  }, node, file, scope);
 };

 exports.FunctionDeclaration =
-exports.FunctionExpression = function (node, parent, file, scope) {
+exports.FunctionExpression = function (node, parent, scope, context, file) {
  go(function () {
    t.ensureBlock(node);
    return node.body.body;
--- a/lib/6to5/transformation/transformers/es6-classes.js
+++ b/lib/6to5/transformation/transformers/es6-classes.js
@@ -3,11 +3,11 @@ var traverse   = require("../../traverse");
 var util       = require("../../util");
 var t          = require("../../types");

-exports.ClassDeclaration = function (node, parent, file, scope) {
+exports.ClassDeclaration = function (node, parent, scope, context, file) {
  return new Class(node, file, scope, true).run();
 };

-exports.ClassExpression = function (node, parent, file, scope) {
+exports.ClassExpression = function (node, parent, scope, context, file) {
  if (!node.id) {
    if (t.isProperty(parent) && parent.value === node && !parent.computed && t.isIdentifier(parent.key)) {
      // var o = { foo: class {} };
@@ -316,16 +316,16 @@ Class.prototype.replaceSuperReferences = function (methodNode) {

  function traverseLevel(node, topLevel) {
    traverse(node, {
-      enter: function (node, parent) {
+      enter: function (node, parent, scope, context) {
        if (t.isFunction(node) && !t.isArrowFunctionExpression(node)) {
          // we need to call traverseLevel again so we're context aware
          traverseLevel(node, false);
-          return this.skip();
+          return context.skip();
        }

        if (t.isProperty(node, { method: true }) || t.isMethodDefinition(node)) {
          // break on object methods
-          return this.skip();
+          return context.skip();
        }

        var getThisReference = function () {
--- a/lib/6to5/transformation/transformers/es6-computed-property-names.js
+++ b/lib/6to5/transformation/transformers/es6-computed-property-names.js
@@ -1,6 +1,6 @@
 var t = require("../../types");

-exports.ObjectExpression = function (node, parent, file, scope) {
+exports.ObjectExpression = function (node, parent, scope, context, file) {
  var hasComputed = false;

  for (var i = 0; i < node.properties.length; i++) {
--- a/lib/6to5/transformation/transformers/es6-constants.js
+++ b/lib/6to5/transformation/transformers/es6-constants.js
@@ -6,7 +6,7 @@ exports.Program =
 exports.BlockStatement =
 exports.ForInStatement =
 exports.ForOfStatement =
-exports.ForStatement = function (node, parent, file) {
+exports.ForStatement = function (node, parent, scope, context, file) {
  var hasConstants = false;
  var constants = {};

@@ -69,14 +69,19 @@ exports.ForStatement = function (node, parent, file) {

  if (!hasConstants) return;

+  var state = {
+    check: check,
+    getIds: getIds
+  };
+
  traverse(node, {
-    enter: function (child, parent, scope) {
+    enter: function (child, parent, scope, context, state) {
      if (child._ignoreConstant) return;
      if (t.isVariableDeclaration(child)) return;

      if (t.isVariableDeclarator(child) || t.isDeclaration(child) || t.isAssignmentExpression(child)) {
-        check(parent, getIds(child), scope);
+        state.check(parent, state.getIds(child), scope);
      }
    }
-  });
+  }, null, state);
 };
--- a/lib/6to5/transformation/transformers/es6-default-parameters.js
+++ b/lib/6to5/transformation/transformers/es6-default-parameters.js
@@ -2,7 +2,7 @@ var traverse = require("../../traverse");
 var util     = require("../../util");
 var t        = require("../../types");

-exports.Function = function (node, parent, file, scope) {
+exports.Function = function (node, parent, scope, context, file) {
  if (!node.defaults || !node.defaults.length) return;
  t.ensureBlock(node);

--- a/lib/6to5/transformation/transformers/es6-destructuring.js
+++ b/lib/6to5/transformation/transformers/es6-destructuring.js
@@ -148,7 +148,7 @@ var pushPattern = function (opts) {
 };

 exports.ForInStatement =
-exports.ForOfStatement = function (node, parent, file, scope) {
+exports.ForOfStatement = function (node, parent, scope, context, file) {
  var declar = node.left;
  if (!t.isVariableDeclaration(declar)) return;

@@ -174,7 +174,7 @@ exports.ForOfStatement = function (node, parent, file, scope) {
  block.body = nodes.concat(block.body);
 };

-exports.Function = function (node, parent, file, scope) {
+exports.Function = function (node, parent, scope, context, file) {
  var nodes = [];

  var hasDestructuring = false;
@@ -205,7 +205,7 @@ exports.Function = function (node, parent, file, scope) {
  block.body = nodes.concat(block.body);
 };

-exports.CatchClause = function (node, parent, file, scope) {
+exports.CatchClause = function (node, parent, scope, context, file) {
  var pattern = node.param;
  if (!t.isPattern(pattern)) return;

@@ -223,7 +223,7 @@ exports.CatchClause = function (node, parent, file, scope) {
  node.body.body = nodes.concat(node.body.body);
 };

-exports.ExpressionStatement = function (node, parent, file, scope) {
+exports.ExpressionStatement = function (node, parent, scope, context, file) {
  var expr = node.expression;
  if (expr.type !== "AssignmentExpression") return;

@@ -245,7 +245,7 @@ exports.ExpressionStatement = function (node, parent, file, scope) {
  return nodes;
 };

-exports.AssignmentExpression = function (node, parent, file, scope) {
+exports.AssignmentExpression = function (node, parent, scope, context, file) {
  if (parent.type === "ExpressionStatement") return;
  if (!t.isPattern(node.left)) return;

@@ -270,7 +270,7 @@ exports.AssignmentExpression = function (node, parent, file, scope) {
  return t.toSequenceExpression(nodes, scope);
 };

-exports.VariableDeclaration = function (node, parent, file, scope) {
+exports.VariableDeclaration = function (node, parent, scope, context, file) {
  if (t.isForInStatement(parent) || t.isForOfStatement(parent)) return;

  var nodes = [];
--- a/lib/6to5/transformation/transformers/es6-for-of.js
+++ b/lib/6to5/transformation/transformers/es6-for-of.js
@@ -1,11 +1,11 @@
 var util = require("../../util");
 var t    = require("../../types");

-exports.ForOfStatement = function (node, parent, file, scope) {
+exports.ForOfStatement = function (node, parent, scope, context, file) {
  var callback = spec;
  if (file.isLoose("forOf")) callback = loose;

-  var build  = callback(node, parent, file, scope);
+  var build  = callback(node, parent, scope, context, file);
  var declar = build.declar;
  var loop   = build.loop;
  var block  = loop.body;
@@ -31,7 +31,7 @@ exports.ForOfStatement = function (node, parent, file, scope) {
  return loop;
 };

-var loose = function (node, parent, file, scope) {
+var loose = function (node, parent, scope, context, file) {
  var left = node.left;
  var declar, id;

@@ -63,7 +63,7 @@ var loose = function (node, parent, file, scope) {
  };
 };

-var spec = function (node, parent, file, scope) {
+var spec = function (node, parent, scope, context, file) {
  var left = node.left;
  var declar;

--- a/lib/6to5/transformation/transformers/es6-let-scoping.js
+++ b/lib/6to5/transformation/transformers/es6-let-scoping.js
@@ -34,7 +34,7 @@ exports.VariableDeclaration = function (node, parent) {
  isLet(node, parent);
 };

-exports.Loop = function (node, parent, file, scope) {
+exports.Loop = function (node, parent, scope, context, file) {
  var init = node.left || node.init;
  if (isLet(init, node)) {
    t.ensureBlock(node);
@@ -46,7 +46,7 @@ exports.Loop = function (node, parent, file, scope) {
    node.label = parent.label;
  }

-  var letScoping = new LetScoping(node, node.body, parent, file, scope);
+  var letScoping = new LetScoping(node, node.body, parent, scope, file);
  letScoping.run();

  if (node.label && !t.isLabeledStatement(parent)) {
@@ -55,9 +55,9 @@ exports.Loop = function (node, parent, file, scope) {
  }
 };

-exports.BlockStatement = function (block, parent, file, scope) {
+exports.BlockStatement = function (block, parent, scope, context, file) {
  if (!t.isLoop(parent)) {
-    var letScoping = new LetScoping(false, block, parent, file, scope);
+    var letScoping = new LetScoping(false, block, parent, scope, file);
    letScoping.run();
  }
 };
@@ -68,11 +68,11 @@ exports.BlockStatement = function (block, parent, file, scope) {
 * @param {Boolean|Node} loopParent
 * @param {Node} block
 * @param {Node} parent
- * @param {File} file
 * @param {Scope} scope
+ * @param {File} file
 */

-function LetScoping(loopParent, block, parent, file, scope) {
+function LetScoping(loopParent, block, parent, scope, file) {
  this.loopParent = loopParent;
  this.parent     = parent;
  this.scope      = scope;
@@ -167,7 +167,7 @@ LetScoping.prototype.remap = function () {

  if (!this.info.hasDuplicates) return;

-  var replace = function (node, parent, scope) {
+  var replace = function (node, parent, scope, context, replacements) {
    if (!t.isIdentifier(node)) return;
    if (!t.isReferenced(node, parent)) return;
    if (scope && scope.hasOwn(node.name)) return;
@@ -176,7 +176,7 @@ LetScoping.prototype.remap = function () {

  var traverseReplace = function (node, parent) {
    replace(node, parent);
-    traverse(node, { enter: replace });
+    traverse(node, { enter: replace }, null, replacements);
  };

  var loopParent = this.loopParent;
@@ -186,7 +186,7 @@ LetScoping.prototype.remap = function () {
    traverseReplace(loopParent.update, loopParent);
  }

-  traverse(block, { enter: replace });
+  traverse(block, { enter: replace }, null, replacements);
 };

 /**
@@ -277,11 +277,11 @@ LetScoping.prototype.checkLoop = function () {
  };

  traverse(this.block, {
-    enter: function (node, parent) {
+    enter: function (node, parent, scope, context) {
      var replace;

      if (t.isFunction(node) || t.isLoop(node)) {
-        return this.skip();
+        return context.skip();
      }

      if (node && !node.label) {
@@ -305,7 +305,7 @@ LetScoping.prototype.checkLoop = function () {

      if (replace) return t.inherits(replace, node);
    }
-  });
+  }, null, has);

  return has;
 };
@@ -316,9 +316,8 @@ LetScoping.prototype.checkLoop = function () {
 */

 LetScoping.prototype.hoistVarDeclarations = function () {
-  var self = this;
  traverse(this.block, {
-    enter: function (node, parent) {
+    enter: function (node, parent, scope, context, self) {
      if (t.isForStatement(node)) {
        if (isVar(node.init, node)) {
          node.init = t.sequenceExpression(self.pushDeclar(node.init));
@@ -330,10 +329,10 @@ LetScoping.prototype.hoistVarDeclarations = function () {
      } else if (isVar(node, parent)) {
        return self.pushDeclar(node).map(t.expressionStatement);
      } else if (t.isFunction(node)) {
-        return this.skip();
+        return context.skip();
      }
    }
-  });
+  }, null, this);
 };

 /**
@@ -359,13 +358,15 @@ LetScoping.prototype.getParams = function (params) {
 */

 LetScoping.prototype.getLetReferences = function () {
-  var closurify = false;
-  var self = this;
+  var state = {
+    self: this,
+    closurify: false
+  };

  // traverse through this block, stopping on functions and checking if they
  // contain any outside let references
  traverse(this.block, {
-    enter: function (node, parent, scope) {
+    enter: function (node, parent, scope, context, state) {
      if (t.isFunction(node)) {
        traverse(node, {
          enter: function (node, parent) {
@@ -379,22 +380,22 @@ LetScoping.prototype.getLetReferences = function () {
            // to our let scope
            if (scope.hasOwn(node.name, true)) return;

-            closurify = true;
+            state.closurify = true;

            // this key doesn't appear just outside our scope
-            if (!_.contains(self.info.outsideKeys, node.name)) return;
+            if (!_.contains(state.self.info.outsideKeys, node.name)) return;

            // push this badboy
-            self.letReferences[node.name] = node;
+            state.self.letReferences[node.name] = node;
          }
-        });
+        }, null, state);

-        return this.skip();
+        return context.skip();
      }
    }
-  });
+  }, null, state);

-  return closurify;
+  return state.closurify;
 };

 /**
--- a/lib/6to5/transformation/transformers/es6-modules.js
+++ b/lib/6to5/transformation/transformers/es6-modules.js
@@ -6,7 +6,7 @@ exports.ast = {
  }
 };

-exports.ImportDeclaration = function (node, parent, file) {
+exports.ImportDeclaration = function (node, parent, scope, context, file) {
  var nodes = [];

  if (node.specifiers.length) {
@@ -26,7 +26,7 @@ exports.ImportDeclaration = function (node, parent, file) {
  return nodes;
 };

-exports.ExportDeclaration = function (node, parent, file) {
+exports.ExportDeclaration = function (node, parent, scope, context, file) {
  var nodes = [];

  if (node.declaration) {
--- a/lib/6to5/transformation/transformers/es6-property-method-assignment.js
+++ b/lib/6to5/transformation/transformers/es6-property-method-assignment.js
@@ -2,7 +2,7 @@ var nameMethod = require("../helpers/name-method");
 var util       = require("../../util");
 var t          = require("../../types");

-exports.Property = function (node, parent, file, scope) {
+exports.Property = function (node, parent, scope, context, file) {
  if (!node.method) return;

  node.method = false;
--- a/lib/6to5/transformation/transformers/es6-rest-parameters.js
+++ b/lib/6to5/transformation/transformers/es6-rest-parameters.js
@@ -1,7 +1,7 @@
 var util = require("../../util");
 var t    = require("../../types");

-exports.Function = function (node, parent, file) {
+exports.Function = function (node, parent, scope, context, file) {
  if (!node.rest) return;

  var rest = node.rest;
--- a/lib/6to5/transformation/transformers/es6-spread.js
+++ b/lib/6to5/transformation/transformers/es6-spread.js
@@ -40,7 +40,7 @@ var build = function (props, file) {
  return nodes;
 };

-exports.ArrayExpression = function (node, parent, file) {
+exports.ArrayExpression = function (node, parent, scope, context, file) {
  var elements = node.elements;
  if (!hasSpread(elements)) return;

@@ -55,7 +55,7 @@ exports.ArrayExpression = function (node, parent, file) {
  return t.callExpression(t.memberExpression(first, t.identifier("concat")), nodes);
 };

-exports.CallExpression = function (node, parent, file, scope) {
+exports.CallExpression = function (node, parent, scope, context, file) {
  var args = node.arguments;
  if (!hasSpread(args)) return;

@@ -95,7 +95,7 @@ exports.CallExpression = function (node, parent, file, scope) {
  node.arguments.unshift(contextLiteral);
 };

-exports.NewExpression = function (node, parent, file) {
+exports.NewExpression = function (node, parent, scope, context, file) {
  var args = node.arguments;
  if (!hasSpread(args)) return;

--- a/lib/6to5/transformation/transformers/es6-template-literals.js
+++ b/lib/6to5/transformation/transformers/es6-template-literals.js
@@ -4,7 +4,7 @@ var buildBinaryExpression = function (left, right) {
  return t.binaryExpression("+", left, right);
 };

-exports.TaggedTemplateExpression = function (node, parent, file) {
+exports.TaggedTemplateExpression = function (node, parent, scope, context, file) {
  var args = [];
  var quasi = node.quasi;

--- a/lib/6to5/transformation/transformers/es7-abstract-references.js
+++ b/lib/6to5/transformation/transformers/es7-abstract-references.js
@@ -21,7 +21,7 @@ var container = function (parent, call, ret) {
  }
 };

-exports.AssignmentExpression = function (node, parent, file, scope) {
+exports.AssignmentExpression = function (node, parent, scope, context, file) {
  var left = node.left;
  if (!t.isVirtualPropertyExpression(left)) return;

@@ -74,7 +74,7 @@ exports.UnaryExpression = function (node, parent) {
  return container(parent, call, t.literal(true));
 };

-exports.CallExpression = function (node, parent, file, scope) {
+exports.CallExpression = function (node, parent, scope, context, file) {
  var callee = node.callee;
  if (!t.isVirtualPropertyExpression(callee)) return;

--- a/lib/6to5/transformation/transformers/es7-array-comprehension.js
+++ b/lib/6to5/transformation/transformers/es7-array-comprehension.js
@@ -5,7 +5,7 @@ var t                  = require("../../types");

 exports.experimental = true;

-var build = function (node, parent, file, scope) {
+var build = function (node, parent, scope, context, file) {
  var uid = scope.generateUidBasedOnNode(parent, file);

  var container = util.template("array-comprehension-container", {
@@ -34,8 +34,8 @@ var build = function (node, parent, file, scope) {
  return container;
 };

-exports.ComprehensionExpression = function (node, parent, file, scope) {
+exports.ComprehensionExpression = function (node, parent, scope, context, file) {
  if (node.generator) return;

-  return build(node, parent, file, scope);
+  return build(node, parent, scope, context, file);
 };
--- a/lib/6to5/transformation/transformers/es7-object-spread.js
+++ b/lib/6to5/transformation/transformers/es7-object-spread.js
@@ -4,7 +4,7 @@ var t = require("../../types");

 exports.experimental = true;

-exports.ObjectExpression = function (node, parent, file) {
+exports.ObjectExpression = function (node, parent, scope, context, file) {
  var hasSpread = false;
  var i;
  var prop;
--- a/lib/6to5/transformation/transformers/optional-async-to-generator.js
+++ b/lib/6to5/transformation/transformers/optional-async-to-generator.js
@@ -5,7 +5,7 @@ exports.optional = true;

 exports.manipulateOptions = bluebirdCoroutines.manipulateOptions;

-exports.Function = function (node, parent, file) {
+exports.Function = function (node, parent, scope, context, file) {
  if (!node.async || node.generator) return;

  return remapAsyncToGenerator(node, file.addHelper("async-to-generator"));
--- a/lib/6to5/transformation/transformers/optional-bluebird-coroutines.js
+++ b/lib/6to5/transformation/transformers/optional-bluebird-coroutines.js
@@ -9,7 +9,7 @@ exports.manipulateOptions = function (opts) {
 exports.optional = true;


-exports.Function = function (node, parent, file) {
+exports.Function = function (node, parent, scope, context, file) {
  if (!node.async || node.generator) return;

  return remapAsyncToGenerator(
--- a/lib/6to5/transformation/transformers/optional-core-aliasing.js
+++ b/lib/6to5/transformation/transformers/optional-core-aliasing.js
@@ -26,7 +26,7 @@ exports.ast = {

  exit: function (ast, file) {
    traverse(ast, {
-      enter: function (node, parent) {
+      enter: function (node, parent, scope, context) {
        var prop;

        if (t.isMemberExpression(node) && t.isReferenced(node, parent)) {
@@ -37,7 +37,7 @@ exports.ast = {
          if (!t.isReferenced(obj, node)) return;

          if (!node.computed && coreHas(obj) && _.has(core[obj.name], prop.name)) {
-            this.skip();
+            context.skip();
            return t.prependToMemberExpression(node, file._coreId);
          }
        } else if (t.isIdentifier(node) && !t.isMemberExpression(parent) && t.isReferenced(node, parent) && _.contains(ALIASABLE_CONSTRUCTORS, node.name)) {
--- a/lib/6to5/transformation/transformers/optional-proto-to-assign.js
+++ b/lib/6to5/transformation/transformers/optional-proto-to-assign.js
@@ -17,7 +17,7 @@ var buildDefaultsCallExpression = function (expr, ref, file) {
 exports.optional = true;
 exports.secondPass = true;

-exports.AssignmentExpression = function (node, parent, file, scope) {
+exports.AssignmentExpression = function (node, parent, scope, context, file) {
  if (t.isExpressionStatement(parent)) return;
  if (!isProtoAssignmentExpression(node)) return;

@@ -32,7 +32,7 @@ exports.AssignmentExpression = function (node, parent, file, scope) {
  return t.toSequenceExpression(nodes);
 };

-exports.ExpressionStatement = function (node, parent, file) {
+exports.ExpressionStatement = function (node, parent, scope, context, file) {
  var expr = node.expression;
  if (!t.isAssignmentExpression(expr, { operator: "=" })) return;

@@ -41,7 +41,7 @@ exports.ExpressionStatement = function (node, parent, file) {
  }
 };

-exports.ObjectExpression = function (node, parent, file) {
+exports.ObjectExpression = function (node, parent, scope, context, file) {
  var proto;

  for (var i = 0; i < node.properties.length; i++) {
--- a/lib/6to5/transformation/transformers/optional-typeof-symbol.js
+++ b/lib/6to5/transformation/transformers/optional-typeof-symbol.js
@@ -2,8 +2,8 @@ var t = require("../../types");

 exports.optional = true;

-exports.UnaryExpression = function (node, parent, file) {
-  this.skip();
+exports.UnaryExpression = function (node, parent, scope, context, file) {
+  context.skip();

  if (node.operator === "typeof") {
    var call = t.callExpression(file.addHelper("typeof"), [node.argument]);
--- a/lib/6to5/transformation/transformers/playground-memoization-operator.js
+++ b/lib/6to5/transformation/transformers/playground-memoization-operator.js
@@ -48,7 +48,7 @@ var buildAssignment = function (expr, obj, prop) {
  return t.assignmentExpression("=", buildAbsoluteRef(expr.left, obj, prop), expr.right);
 };

-exports.ExpressionStatement = function (node, parent, file, scope) {
+exports.ExpressionStatement = function (node, parent, scope, context, file) {
  var expr = node.expression;
  if (!isMemo(expr)) return;

@@ -66,7 +66,7 @@ exports.ExpressionStatement = function (node, parent, file, scope) {
  return nodes;
 };

-exports.AssignmentExpression = function (node, parent, file, scope) {
+exports.AssignmentExpression = function (node, parent, scope, context, file) {
  if (t.isExpressionStatement(parent)) return;
  if (!isMemo(node)) return;

--- a/lib/6to5/transformation/transformers/playground-method-binding.js
+++ b/lib/6to5/transformation/transformers/playground-method-binding.js
@@ -1,6 +1,6 @@
 var t = require("../../types");

-exports.BindMemberExpression = function (node, parent, file, scope) {
+exports.BindMemberExpression = function (node, parent, scope, context, file) {
  var object = node.object;
  var prop   = node.property;

@@ -22,7 +22,7 @@ exports.BindMemberExpression = function (node, parent, file, scope) {
  }
 };

-exports.BindFunctionExpression = function (node, parent, file, scope) {
+exports.BindFunctionExpression = function (node, parent, scope, context, file) {
  var buildCall = function (args) {
    var param = file.generateUidIdentifier("val", scope);
    return t.functionExpression(null, [param], t.blockStatement([
--- a/lib/6to5/transformation/transformers/playground-object-getter-memoization.js
+++ b/lib/6to5/transformation/transformers/playground-object-getter-memoization.js
@@ -2,7 +2,7 @@ var traverse = require("../../traverse");
 var t        = require("../../types");

 exports.Property =
-exports.MethodDefinition = function (node, parent, file) {
+exports.MethodDefinition = function (node, parent, scope, context, file) {
  if (node.kind !== "memo") return;
  node.kind = "get";

--- a/lib/6to5/transformation/transformers/react.js
+++ b/lib/6to5/transformation/transformers/react.js
@@ -15,7 +15,7 @@ exports.XJSIdentifier = function (node) {
  }
 };

-exports.XJSNamespacedName = function (node, parent, file) {
+exports.XJSNamespacedName = function (node, parent, scope, context, file) {
  throw file.errorWithNode(node, "Namespace tags are not supported. ReactJSX is not XML.");
 };

@@ -42,7 +42,7 @@ var isTag = function(tagName) {
 };

 exports.XJSOpeningElement = {
-  exit: function (node, parent, file) {
+  exit: function (node, parent, scope, context, file) {
    var reactCompat = file.opts.reactCompat;
    var tagExpr = node.name;
    var args = [];
--- a/lib/6to5/transformation/transformers/spec-no-for-in-of-assignment.js
+++ b/lib/6to5/transformation/transformers/spec-no-for-in-of-assignment.js
@@ -1,7 +1,7 @@
 var t = require("../../types");

 exports.ForInStatement =
-exports.ForOfStatement = function (node, parent, file) {
+exports.ForOfStatement = function (node, parent, scope, context, file) {
  var left = node.left;
  if (t.isVariableDeclaration(left)) {
    var declar = left.declarations[0];
--- a/lib/6to5/transformation/transformers/spec-setters.js
+++ b/lib/6to5/transformation/transformers/spec-setters.js
@@ -1,5 +1,5 @@
 exports.MethodDefinition =
-exports.Property = function (node, parent, file) {
+exports.Property = function (node, parent, scope, context, file) {
  if (node.kind === "set" && node.value.params.length !== 1) {
    throw file.errorWithNode(node.value, "Setters must have only one parameter");
  }
--- a/lib/6to5/traverse/index.js
+++ b/lib/6to5/traverse/index.js
@@ -1,9 +1,13 @@
 module.exports = traverse;

+/* jshint maxparams:7 */
+
 var Scope = require("./scope");
 var t     = require("../types");
 var _     = require("lodash");

+function noop() { }
+
 function TraversalContext() {
  this.didSkip = false;
  this.didRemove = false;
@@ -35,7 +39,7 @@ TraversalContext.prototype.reset = function () {
  this.didRemove = false;
 };

-TraversalContext.prototype.maybeReplace = function (result, obj, key, node) {
+function replaceNode(obj, key, node, result) {
  var isArray = Array.isArray(result);

  // inherit comments from original node to the first replacement node
@@ -44,7 +48,7 @@ TraversalContext.prototype.maybeReplace = function (result, obj, key, node) {
  if (inheritTo) t.inheritsComments(inheritTo, node);

  // replace the node
-  node = obj[key] = result;
+  obj[key] = result;

  // we're replacing a statement or block node with an array of statements so we better
  // ensure that it's a block
@@ -53,11 +57,48 @@ TraversalContext.prototype.maybeReplace = function (result, obj, key, node) {
  }

  if (isArray) {
-    this.flatten();
+    return true;
  }
+}
+
+TraversalContext.prototype.enterNode = function (obj, key, node, enter, parent, scope, state) {
+  var result = enter(node, parent, scope, this, state);
+  var flatten = false;
+
+  if (result) {
+    flatten = replaceNode(obj, key, node, result);
+    node = result;
+
+    if (flatten) {
+      this.didFlatten = true;
+    }
+  }
+
+  if (this.didRemove) {
+    obj[key] = null;
+    this.didFlatten = true;
+  }
+
+  return node;
 };

-TraversalContext.prototype.visitNode = function (obj, key, opts, scope, parent) {
+TraversalContext.prototype.exitNode = function (obj, key, node, exit, parent, scope, state) {
+  var result = exit(node, parent, scope, this, state);
+  var flatten = false;
+
+  if (result) {
+    flatten = replaceNode(obj, key, node, result);
+    node = result;
+
+    if (flatten) {
+      this.didFlatten = true;
+    }
+  }
+
+  return node;
+};
+
+TraversalContext.prototype.visitNode = function (obj, key, opts, scope, parent, state) {
  this.reset();

  var node = obj[key];
@@ -70,48 +111,23 @@ TraversalContext.prototype.visitNode = function (obj, key, opts, scope, parent)
  if (t.isScope(node))
    ourScope = new Scope(node, scope);

-  var result;
+  node = this.enterNode(obj, key, node, opts.enter, parent, ourScope, state);

-  // enter
-  if (opts.enter) {
-    result = opts.enter.call(this, node, parent, ourScope);
+  if (this.didSkip)
+    return this.didStop;

-    if (result) {
-      this.maybeReplace(result, obj, key, node);
-      node = obj[key];
-    }
-
-    if (this.didRemove) {
-      node = obj[key] = null;
-      this.flatten();
-    }
-
-    // stop traversal
-    if (this.didSkip)
-      return this.didStop;
-  }
-
-  // traverse node
-  traverseNode(node, opts, ourScope);
-
-  // exit
-  if (opts.exit) {
-    result = opts.exit.call(this, node, parent, ourScope);
-
-    if (result) {
-      this.maybeReplace(result, obj, key, node);
-    }
-  }
+  traverseNode(node, opts, ourScope, state);
+  this.exitNode(obj, key, node, opts.exit, parent, ourScope, state);

  return this.didStop;
 };

-TraversalContext.prototype.visit = function (node, key, opts, scope) {
+TraversalContext.prototype.visit = function (node, key, opts, scope, state) {
  var nodes = node[key];
  if (!nodes) return;

  if (!Array.isArray(nodes)) {
-    return this.visitNode(node, key, opts, scope, node);
+    return this.visitNode(node, key, opts, scope, node, state);
  }

  if (nodes.length === 0) {
@@ -119,7 +135,7 @@ TraversalContext.prototype.visit = function (node, key, opts, scope) {
  }

  for (var k = 0; k < nodes.length; k++) {
-    if (nodes[k] && this.visitNode(nodes, k, opts, scope, node))
+    if (nodes[k] && this.visitNode(nodes, k, opts, scope, node, state))
      return true;
  }

@@ -133,31 +149,33 @@ TraversalContext.prototype.visit = function (node, key, opts, scope) {
  }
 };

-function traverseNode(node, opts, scope) {
+function traverseNode(node, opts, scope, state) {
  var keys = t.VISITOR_KEYS[node.type];
  if (!keys) return;

-  opts = opts || {};
  var context = new TraversalContext();
-
  for (var j = 0; j < keys.length; j++) {
-    if (context.visit(node, keys[j], opts, scope))
+    if (context.visit(node, keys[j], opts, scope, state))
      return;
  }
 }

-function traverse(parent, opts, scope) {
+function traverse(parent, opts, scope, state) {
  // falsy node
  if (!parent) return;

+  if (!opts) opts = {};
+  if (!opts.enter) opts.enter = noop;
+  if (!opts.exit) opts.exit = noop;
+
  // array of nodes
  if (!Array.isArray(parent)) {
-    traverseNode(parent, opts, scope);
+    traverseNode(parent, opts, scope, state);
    return;
  }

  for (var i = 0; i < parent.length; i++) {
-    traverseNode(parent[i], opts, scope);
+    traverseNode(parent[i], opts, scope, state);
  }
 }

@@ -190,23 +208,25 @@ traverse.removeProperties = function (tree) {
 traverse.hasType = function (tree, type, blacklistTypes) {
  blacklistTypes = [].concat(blacklistTypes || []);

-  var has = false;
-
  // the node we're searching in is blacklisted
  if (_.contains(blacklistTypes, tree.type)) return false;

  // the type we're looking for is the same as the passed node
  if (tree.type === type) return true;

+  var state = {
+    has: false
+  };
+
  traverse(tree, {
    blacklist: blacklistTypes,
-    enter: function (node) {
+    enter: function (node, parent, scope, context, state) {
      if (node.type === type) {
-        has = true;
-        this.skip();
+        state.has = true;
+        context.skip();
      }
    }
-  });
+  }, null, state);

-  return has;
+  return state.has;
 };
--- a/lib/6to5/traverse/scope.js
+++ b/lib/6to5/traverse/scope.js
@@ -159,8 +159,13 @@ Scope.prototype.getInfo = function () {
  // Program, Function - var variables

  if (t.isProgram(block) || t.isFunction(block)) {
+    var state = {
+      blockId: block.id,
+      add: add
+    };
+
    traverse(block, {
-      enter: function (node, parent, scope) {
+      enter: function (node, parent, scope, context, state) {
        if (t.isFor(node)) {
          _.each(FOR_KEYS, function (key) {
            var declar = node[key];
@@ -170,22 +175,22 @@ Scope.prototype.getInfo = function () {

        // this block is a function so we'll stop since none of the variables
        // declared within are accessible
-        if (t.isFunction(node)) return this.skip();
+        if (t.isFunction(node)) return context.skip();

        // function identifier doesn't belong to this scope
-        if (block.id && node === block.id) return;
+        if (state.blockId && node === state.blockId) return;

        if (t.isIdentifier(node) && t.isReferenced(node, parent) && !scope.has(node.name)) {
-          add(node, true);
+          state.add(node, true);
        }

        // we've ran into a declaration!
        // we'll let the BlockStatement scope deal with `let` declarations unless
        if (t.isDeclaration(node) && !t.isLet(node)) {
-          add(node);
+          state.add(node);
        }
      }
-    }, this);
+    }, this, state);
  }

  // Function - params, rest
--- a/lib/6to5/types/index.js
+++ b/lib/6to5/types/index.js
@@ -575,4 +575,5 @@ t.isSpecifierDefault = function (specifier) {
  return t.isIdentifier(specifier.id) && specifier.id.name === "default";
 };

-toFastProperties(t);
+toFastProperties(t);
+toFastProperties(t.VISITOR_KEYS);
--- a/lib/6to5/util.js
+++ b/lib/6to5/util.js
@@ -142,12 +142,12 @@ exports.template = function (name, nodes, keepExpression) {

  if (!_.isEmpty(nodes)) {
    traverse(template, {
-      enter: function (node) {
+      enter: function (node, parent, scope, context, nodes) {
        if (t.isIdentifier(node) && _.has(nodes, node.name)) {
          return nodes[node.name];
        }
      }
-    });
+    }, null, nodes);
  }

  var node = template.body[0];