From 6f664ca64e9e76683fa52c97e0148d8e857933ae Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Thu, 7 May 2015 15:53:22 +0100
Subject: [PATCH 01/30] merge internal transformers into single traversal pass

---
 src/babel/transformation/file/index.js        | 76 ++++++++++---------
 ...-binary-assignment-operator-transformer.js |  4 -
 .../helpers/build-react-transformer.js        |  6 --
 src/babel/transformation/index.js             |  7 ++
 src/babel/transformation/transformer-pass.js  | 19 ++---
 src/babel/transformation/transformer.js       | 13 ----
 .../transformers/es5/properties.mutators.js   | 42 +++++-----
 .../transformers/es6/arrow-functions.js       |  2 -
 .../transformers/es6/block-scoping.js         |  4 -
 .../transformers/es6/classes.js               | 10 +--
 .../transformers/es6/constants.js             |  4 -
 .../transformers/es6/destructuring.js         |  5 --
 .../transformation/transformers/es6/for-of.js |  2 -
 .../transformers/es6/modules.js               |  2 -
 .../transformers/es6/object-super.js          |  2 -
 .../transformers/es6/parameters.default.js    |  6 --
 .../transformers/es6/parameters.rest.js       |  4 -
 .../transformers/es6/properties.computed.js   | 70 +++++++++--------
 .../transformers/es6/properties.shorthand.js  |  4 -
 .../transformers/es6/regex.sticky.js          |  4 -
 .../transformers/es6/regex.unicode.js         |  4 -
 .../transformation/transformers/es6/spread.js |  2 -
 .../transformers/es6/template-literals.js     |  4 -
 .../transformers/es7/async-functions.js       |  4 -
 .../transformers/es7/class-properties.js      |  4 -
 .../transformers/es7/decorators.js            |  4 -
 .../transformers/es7/do-expressions.js        |  2 -
 .../transformers/es7/export-extensions.js     |  4 -
 .../es7/trailing-function-commas.js           |  4 -
 .../transformation/transformers/index.js      | 66 +---------------
 .../transformers/internal/hoist-directives.js | 16 ++++
 .../transformers/internal/module-formatter.js |  2 -
 .../transformers/internal/modules.js          |  4 -
 .../transformers/internal/shadow-functions.js | 29 +++----
 .../transformers/internal/strict.js           | 19 -----
 .../transformers/internal/validation.js       | 17 -----
 .../transformers/optimisation/flow.for-of.js  |  1 -
 .../transformation/transformers/other/flow.js |  4 -
 .../transformers/other/regenerator.js         |  8 +-
 .../transformers/other/strict.js              | 35 ++++++---
 .../spec/block-scoped-functions.js            | 15 ----
 .../transformers/validation/react.js          |  8 --
 .../validation/undeclared-variable-check.js   |  3 +-
 src/babel/traversal/index.js                  |  9 ++-
 src/babel/traversal/path/index.js             | 67 +++++++++-------
 src/babel/traversal/visitors.js               | 23 ++++--
 .../es6.arrow-functions/arguments/expected.js | 10 +--
 .../assignment-expression/expected.js         |  6 +-
 48 files changed, 243 insertions(+), 417 deletions(-)
 create mode 100644 src/babel/transformation/transformers/internal/hoist-directives.js
 delete mode 100644 src/babel/transformation/transformers/internal/strict.js

diff --git a/src/babel/transformation/file/index.js b/src/babel/transformation/file/index.js
index bec58c718a..bb2d3697db 100644
--- a/src/babel/transformation/file/index.js
+++ b/src/babel/transformation/file/index.js
@@ -4,6 +4,7 @@ import moduleFormatters from "../modules";
 import PluginManager from "./plugin-manager";
 import shebangRegex from "shebang-regex";
 import TraversalPath from "../../traversal/path";
+import Transformer from "../transformer";
 import isFunction from "lodash/lang/isFunction";
 import isAbsolute from "path-is-absolute";
 import resolveRc from "../../tools/resolve-rc";
@@ -26,19 +27,6 @@ import path from "path";
 import each from "lodash/collection/each";
 import * as t from "../../types";
 
-var checkTransformerVisitor = {
-  exit(node, parent, scope, state) {
-    checkPath(state.stack, this);
-  }
-};
-
-function checkPath(stack, path) {
-  each(stack, function (pass) {
-    if (pass.shouldRun || pass.ran) return;
-    pass.checkPath(path);
-  });
-}
-
 export default class File {
   constructor(opts = {}, pipeline) {
     this.dynamicImportTypes = {};
@@ -234,7 +222,46 @@ export default class File {
     stack = beforePlugins.concat(stack, afterPlugins);
 
     // register
-    this.transformerStack = stack.concat(secondaryStack);
+    this.transformerStack = this.mergeStack(stack.concat(secondaryStack));
+
+
+  }
+
+  mergeStack(_stack) {
+    var stack  = [];
+    var ignore = [];
+
+    for (let pass of (_stack: Array)) {
+      // been merged
+      if (ignore.indexOf(pass) >= 0) continue;
+
+      var category = pass.transformer.metadata.category;
+
+      // can't merge
+      if (!pass.canTransform() || !category) {
+        stack.push(pass);
+        continue;
+      }
+
+      var mergeStack = [];
+      for (let pass of (_stack: Array)) {
+        if (pass.transformer.metadata.category === category) {
+          mergeStack.push(pass);
+          ignore.push(pass);
+        }
+      }
+
+      var visitors = [];
+      for (let pass of (mergeStack: Array)) {
+        visitors.push(pass.handlers);
+      }
+      var visitor = traverse.visitors.merge(visitors);
+      var mergeTransformer = new Transformer(category, visitor);
+      //console.log(mergeTransformer);
+      stack.push(mergeTransformer.buildPass(this));
+    }
+
+    return stack;
   }
 
   set(key: string, val): any {
@@ -357,23 +384,6 @@ export default class File {
     return err;
   }
 
-  checkPath(path) {
-    if (Array.isArray(path)) {
-      for (var i = 0; i < path.length; i++) {
-        this.checkPath(path[i]);
-      }
-      return;
-    }
-
-    var stack = this.transformerStack;
-
-    checkPath(stack, path);
-
-    path.traverse(checkTransformerVisitor, {
-      stack: stack
-    });
-  }
-
   mergeSourceMap(map: Object) {
     var opts = this.opts;
 
@@ -461,10 +471,6 @@ export default class File {
     this._addAst(ast);
     this.log.debug("End set AST");
 
-    this.log.debug("Start prepass");
-    this.checkPath(this.path);
-    this.log.debug("End prepass");
-
     this.log.debug("Start module formatter init");
     var modFormatter = this.moduleFormatter = this.getModuleFormatter(this.opts.modules);
     if (modFormatter.init && this.transformers["es6.modules"].canTransform()) {
diff --git a/src/babel/transformation/helpers/build-binary-assignment-operator-transformer.js b/src/babel/transformation/helpers/build-binary-assignment-operator-transformer.js
index 45a6d812c5..04ffc4c1b3 100644
--- a/src/babel/transformation/helpers/build-binary-assignment-operator-transformer.js
+++ b/src/babel/transformation/helpers/build-binary-assignment-operator-transformer.js
@@ -10,10 +10,6 @@ export default function (exports, opts) {
     return t.assignmentExpression("=", left, right);
   };
 
-  exports.shouldVisit = function (node) {
-    return node.operator && (node.operator === opts.operator || node.operator === opts.operator + "=");
-  };
-
   exports.ExpressionStatement = function (node, parent, scope, file) {
     // hit the `AssignmentExpression` one below
     if (this.isCompletionRecord()) return;
diff --git a/src/babel/transformation/helpers/build-react-transformer.js b/src/babel/transformation/helpers/build-react-transformer.js
index 46a9bdfef7..c63bd60882 100644
--- a/src/babel/transformation/helpers/build-react-transformer.js
+++ b/src/babel/transformation/helpers/build-react-transformer.js
@@ -10,12 +10,6 @@ import * as react from "./react";
 import * as t from "../../types";
 
 export default function (exports, opts) {
-  exports.shouldVisit = function (node) {
-    if (t.isJSX(node)) return true;
-    if (react.isCreateClass(node)) return true;
-    return false;
-  };
-
   exports.JSXIdentifier = function (node, parent) {
     if (node.name === "this" && this.isReferenced()) {
       return t.thisExpression();
diff --git a/src/babel/transformation/index.js b/src/babel/transformation/index.js
index 442ed37849..3f71068bc2 100644
--- a/src/babel/transformation/index.js
+++ b/src/babel/transformation/index.js
@@ -5,6 +5,13 @@ var pipeline = new Pipeline;
 //
 
 import transformers from "./transformers";
+
+for (var key in transformers) {
+  var transformer = transformers[key];
+  var metadata = transformer.metadata = transformer.metadata || {};
+  metadata.category = metadata.category || "builtin";
+}
+
 pipeline.addTransformers(transformers);
 
 //
diff --git a/src/babel/transformation/transformer-pass.js b/src/babel/transformation/transformer-pass.js
index 38c3e8ef8c..715ba6de2e 100644
--- a/src/babel/transformation/transformer-pass.js
+++ b/src/babel/transformation/transformer-pass.js
@@ -8,27 +8,18 @@ import traverse from "../traversal";
 
 export default class TransformerPass {
   constructor(file: File, transformer: Transformer) {
-    this.shouldTransform = !transformer.shouldVisit;
-    this.transformer     = transformer;
-    this.handlers        = transformer.handlers;
-    this.skipKey         = transformer.skipKey;
-    this.file            = file;
-    this.ran             = false;
+    this.transformer = transformer;
+    this.handlers    = transformer.handlers;
+    this.skipKey     = transformer.skipKey;
+    this.file        = file;
+    this.ran         = false;
   }
 
   canTransform(): boolean {
     return this.file.pipeline.canTransform(this.transformer, this.file.opts);
   }
 
-  checkPath(path: TraversalPath): boolean {
-    if (this.shouldTransform || this.ran) return;
-
-    this.shouldTransform = this.transformer.shouldVisit(path.node);
-  }
-
   transform() {
-    if (!this.shouldTransform) return;
-
     var file = this.file;
 
     file.log.debug(`Start transformer ${this.transformer.key}`);
diff --git a/src/babel/transformation/transformer.js b/src/babel/transformation/transformer.js
index 3e12abcf1d..a5fac03bf9 100644
--- a/src/babel/transformation/transformer.js
+++ b/src/babel/transformation/transformer.js
@@ -25,7 +25,6 @@ export default class Transformer {
     };
 
     this.manipulateOptions = take("manipulateOptions");
-    this.shouldVisit       = take("shouldVisit");
     this.metadata          = take("metadata") || {};
     this.parser            = take("parser");
     this.post              = take("post");
@@ -41,18 +40,6 @@ export default class Transformer {
 
     this.handlers = this.normalize(transformer);
     this.key      = transformerKey;
-
-    //
-
-    if (!this.shouldVisit && !this.handlers.enter && !this.handlers.exit) {
-      var types = Object.keys(this.handlers);
-      this.shouldVisit = function (node) {
-        for (var i = 0; i < types.length; i++) {
-          if (node.type === types[i]) return true;
-        }
-        return false;
-      };
-    }
   }
 
   normalize(transformer: Object): Object {
diff --git a/src/babel/transformation/transformers/es5/properties.mutators.js b/src/babel/transformation/transformers/es5/properties.mutators.js
index 9b1deb2870..7fe77c7f41 100644
--- a/src/babel/transformation/transformers/es5/properties.mutators.js
+++ b/src/babel/transformation/transformers/es5/properties.mutators.js
@@ -1,28 +1,26 @@
 import * as defineMap from "../../helpers/define-map";
 import * as t from "../../../types";
 
-export function shouldVisit(node) {
-  return t.isProperty(node) && (node.kind === "get" || node.kind === "set");
-}
+export var ObjectExpression = {
+  exit(node, parent, scope, file) {
+    var mutatorMap = {};
+    var hasAny = false;
 
-export function ObjectExpression(node, parent, scope, file) {
-  var mutatorMap = {};
-  var hasAny = false;
+    node.properties = node.properties.filter(function (prop) {
+      if (prop.kind === "get" || prop.kind === "set") {
+        hasAny = true;
+        defineMap.push(mutatorMap, prop, prop.kind, file);
+        return false;
+      } else {
+        return true;
+      }
+    });
 
-  node.properties = node.properties.filter(function (prop) {
-    if (prop.kind === "get" || prop.kind === "set") {
-      hasAny = true;
-      defineMap.push(mutatorMap, prop, prop.kind, file);
-      return false;
-    } else {
-      return true;
-    }
-  });
+    if (!hasAny) return;
 
-  if (!hasAny) return;
-
-  return t.callExpression(
-    t.memberExpression(t.identifier("Object"), t.identifier("defineProperties")),
-    [node, defineMap.toDefineObject(mutatorMap)]
-  );
-}
+    return t.callExpression(
+      t.memberExpression(t.identifier("Object"), t.identifier("defineProperties")),
+      [node, defineMap.toDefineObject(mutatorMap)]
+    );
+  }
+};
diff --git a/src/babel/transformation/transformers/es6/arrow-functions.js b/src/babel/transformation/transformers/es6/arrow-functions.js
index d40d436727..39d93f829a 100644
--- a/src/babel/transformation/transformers/es6/arrow-functions.js
+++ b/src/babel/transformation/transformers/es6/arrow-functions.js
@@ -1,7 +1,5 @@
 import * as t from "../../../types";
 
-export var shouldVisit = t.isArrowFunctionExpression;
-
 export function ArrowFunctionExpression(node) {
   t.ensureBlock(node);
 
diff --git a/src/babel/transformation/transformers/es6/block-scoping.js b/src/babel/transformation/transformers/es6/block-scoping.js
index 1b81d95232..850dca35f0 100644
--- a/src/babel/transformation/transformers/es6/block-scoping.js
+++ b/src/babel/transformation/transformers/es6/block-scoping.js
@@ -37,10 +37,6 @@ function standardizeLets(declars) {
   }
 }
 
-export function shouldVisit(node) {
-  return t.isVariableDeclaration(node) && (node.kind === "let" || node.kind === "const");
-}
-
 export function VariableDeclaration(node, parent, scope, file) {
   if (!isLet(node, parent)) return;
 
diff --git a/src/babel/transformation/transformers/es6/classes.js b/src/babel/transformation/transformers/es6/classes.js
index 670a18b5fb..e1bb106659 100644
--- a/src/babel/transformation/transformers/es6/classes.js
+++ b/src/babel/transformation/transformers/es6/classes.js
@@ -11,17 +11,17 @@ import * as t from "../../../types";
 
 const PROPERTY_COLLISION_METHOD_NAME = "__initializeProperties";
 
-export var shouldVisit = t.isClass;
-
 export function ClassDeclaration(node, parent, scope, file) {
   return t.variableDeclaration("let", [
     t.variableDeclarator(node.id, t.toExpression(node))
   ]);
 }
 
-export function ClassExpression(node, parent, scope, file) {
-  return new ClassTransformer(this, file).run();
-}
+export var ClassExpression = {
+  exit(node, parent, scope, file) {
+    return new ClassTransformer(this, file).run();
+  }
+};
 
 var collectPropertyReferencesVisitor = {
   Identifier: {
diff --git a/src/babel/transformation/transformers/es6/constants.js b/src/babel/transformation/transformers/es6/constants.js
index b8df344bfb..4125b68d10 100644
--- a/src/babel/transformation/transformers/es6/constants.js
+++ b/src/babel/transformation/transformers/es6/constants.js
@@ -1,10 +1,6 @@
 import * as messages from "../../../messages";
 import * as t from "../../../types";
 
-export function shouldVisit(node) {
-  return t.isVariableDeclaration(node, { kind: "const" }) || t.isImportDeclaration(node);
-}
-
 var visitor = {
   enter(node, parent, scope, state) {
     if (this.isAssignmentExpression() || this.isUpdateExpression()) {
diff --git a/src/babel/transformation/transformers/es6/destructuring.js b/src/babel/transformation/transformers/es6/destructuring.js
index 5dd84da762..5fb2df518b 100644
--- a/src/babel/transformation/transformers/es6/destructuring.js
+++ b/src/babel/transformation/transformers/es6/destructuring.js
@@ -1,8 +1,6 @@
 import * as messages from "../../../messages";
 import * as t from "../../../types";
 
-export var shouldVisit = t.isPattern;
-
 export function ForOfStatement(node, parent, scope, file) {
   var left = node.left;
 
@@ -83,7 +81,6 @@ exports.Function = function (node, parent, scope, file) {
 
   var block = node.body;
   block.body = nodes.concat(block.body);
-  this.checkSelf();
 };
 
 export function CatchClause(node, parent, scope, file) {
@@ -104,8 +101,6 @@ export function CatchClause(node, parent, scope, file) {
   destructuring.init(pattern, ref);
 
   node.body.body = nodes.concat(node.body.body);
-
-  this.checkSelf();
 }
 
 export function ExpressionStatement(node, parent, scope, file) {
diff --git a/src/babel/transformation/transformers/es6/for-of.js b/src/babel/transformation/transformers/es6/for-of.js
index 7d007d6465..b986492da9 100644
--- a/src/babel/transformation/transformers/es6/for-of.js
+++ b/src/babel/transformation/transformers/es6/for-of.js
@@ -2,8 +2,6 @@ import * as messages from "../../../messages";
 import * as util from  "../../../util";
 import * as t from "../../../types";
 
-export var shouldVisit = t.isForOfStatement;
-
 export function ForOfStatement(node, parent, scope, file) {
   if (this.get("right").isArrayExpression()) {
     return _ForOfStatementArray.call(this, node, scope, file);
diff --git a/src/babel/transformation/transformers/es6/modules.js b/src/babel/transformation/transformers/es6/modules.js
index 5abf2b1af4..6141ab9217 100644
--- a/src/babel/transformation/transformers/es6/modules.js
+++ b/src/babel/transformation/transformers/es6/modules.js
@@ -1,7 +1,5 @@
 import * as t from "../../../types";
 
-export { shouldVisit } from "../internal/modules";
-
 function keepBlockHoist(node, nodes) {
   if (node._blockHoist) {
     for (let i = 0; i < nodes.length; i++) {
diff --git a/src/babel/transformation/transformers/es6/object-super.js b/src/babel/transformation/transformers/es6/object-super.js
index b261520da2..10d01e09f8 100644
--- a/src/babel/transformation/transformers/es6/object-super.js
+++ b/src/babel/transformation/transformers/es6/object-super.js
@@ -1,8 +1,6 @@
 import ReplaceSupers from "../../helpers/replace-supers";
 import * as t from "../../../types";
 
-export var shouldVisit = t.isSuper;
-
 function Property(path, node, scope, getObjectRef, file) {
   if (!node.method) return;
 
diff --git a/src/babel/transformation/transformers/es6/parameters.default.js b/src/babel/transformation/transformers/es6/parameters.default.js
index 56345ee839..165c177844 100644
--- a/src/babel/transformation/transformers/es6/parameters.default.js
+++ b/src/babel/transformation/transformers/es6/parameters.default.js
@@ -3,10 +3,6 @@ import * as util from  "../../../util";
 import traverse from  "../../../traversal";
 import * as t from "../../../types";
 
-export function shouldVisit(node) {
-  return t.isFunction(node) && hasDefaults(node);
-}
-
 var hasDefaults = function (node) {
   for (var i = 0; i < node.params.length; i++) {
     if (!t.isIdentifier(node.params[i])) return true;
@@ -96,6 +92,4 @@ exports.Function = function (node, parent, scope, file) {
   } else {
     node.body.body = body.concat(node.body.body);
   }
-
-  this.checkSelf();
 };
diff --git a/src/babel/transformation/transformers/es6/parameters.rest.js b/src/babel/transformation/transformers/es6/parameters.rest.js
index 631701a766..6b57c156a3 100644
--- a/src/babel/transformation/transformers/es6/parameters.rest.js
+++ b/src/babel/transformation/transformers/es6/parameters.rest.js
@@ -2,8 +2,6 @@ import isNumber from "lodash/lang/isNumber";
 import * as util from  "../../../util";
 import * as t from "../../../types";
 
-export var shouldVisit = t.isRestElement;
-
 var memberExpressionOptimisationVisitor = {
   enter(node, parent, scope, state) {
     // check if this scope has a local binding that will shadow the rest parameter
@@ -96,7 +94,6 @@ exports.Function = function (node, parent, scope, file) {
       candidate.replaceWith(argsId);
       optimizeMemberExpression(candidate.parent, node.params.length);
     }
-    this.checkSelf();
     return;
   }
 
@@ -138,5 +135,4 @@ exports.Function = function (node, parent, scope, file) {
   });
   loop._blockHoist = node.params.length + 1;
   node.body.body.unshift(loop);
-  this.checkSelf();
 };
diff --git a/src/babel/transformation/transformers/es6/properties.computed.js b/src/babel/transformation/transformers/es6/properties.computed.js
index e846e4d2a6..d944844ca0 100644
--- a/src/babel/transformation/transformers/es6/properties.computed.js
+++ b/src/babel/transformation/transformers/es6/properties.computed.js
@@ -63,42 +63,40 @@ function spec(node, body, objId, initProps, file) {
   }
 }
 
-export function shouldVisit(node) {
-  return t.isProperty(node) && node.computed;
-}
+export var ObjectExpression = {
+  exit(node, parent, scope, file) {
+    var hasComputed = false;
 
-export function ObjectExpression(node, parent, scope, file) {
-  var hasComputed = false;
+    for (var i = 0; i < node.properties.length; i++) {
+      hasComputed = t.isProperty(node.properties[i], { computed: true, kind: "init" });
+      if (hasComputed) break;
+    }
 
-  for (var i = 0; i < node.properties.length; i++) {
-    hasComputed = t.isProperty(node.properties[i], { computed: true, kind: "init" });
-    if (hasComputed) break;
+    if (!hasComputed) return;
+
+    var initProps = [];
+    var objId = scope.generateUidBasedOnNode(parent);
+
+    //
+
+    var body = [];
+
+    //
+
+    var callback = spec;
+    if (file.isLoose("es6.properties.computed")) callback = loose;
+
+    var result = callback(node, body, objId, initProps, file);
+    if (result) return result;
+
+    //
+
+    body.unshift(t.variableDeclaration("var", [
+      t.variableDeclarator(objId, t.objectExpression(initProps))
+    ]));
+
+    body.push(t.expressionStatement(objId));
+
+    return body;
   }
-
-  if (!hasComputed) return;
-
-  var initProps = [];
-  var objId = scope.generateUidBasedOnNode(parent);
-
-  //
-
-  var body = [];
-
-  //
-
-  var callback = spec;
-  if (file.isLoose("es6.properties.computed")) callback = loose;
-
-  var result = callback(node, body, objId, initProps, file);
-  if (result) return result;
-
-  //
-
-  body.unshift(t.variableDeclaration("var", [
-    t.variableDeclarator(objId, t.objectExpression(initProps))
-  ]));
-
-  body.push(t.expressionStatement(objId));
-
-  return body;
-}
+};
diff --git a/src/babel/transformation/transformers/es6/properties.shorthand.js b/src/babel/transformation/transformers/es6/properties.shorthand.js
index 5f6830cfb7..b5140ac364 100644
--- a/src/babel/transformation/transformers/es6/properties.shorthand.js
+++ b/src/babel/transformation/transformers/es6/properties.shorthand.js
@@ -1,9 +1,5 @@
 import * as t from "../../../types";
 
-export function shouldVisit(node) {
-  return t.isProperty(node) && (node.method || node.shorthand);
-}
-
 export function Property(node) {
   if (node.method) {
     node.method = false;
diff --git a/src/babel/transformation/transformers/es6/regex.sticky.js b/src/babel/transformation/transformers/es6/regex.sticky.js
index 3227c59635..e298e0501b 100644
--- a/src/babel/transformation/transformers/es6/regex.sticky.js
+++ b/src/babel/transformation/transformers/es6/regex.sticky.js
@@ -1,10 +1,6 @@
 import * as regex from "../../helpers/regex";
 import * as t from "../../../types";
 
-export function shouldVisit(node) {
-  return regex.is(node, "y");
-}
-
 export function Literal(node) {
   if (!regex.is(node, "y")) return;
   return t.newExpression(t.identifier("RegExp"), [
diff --git a/src/babel/transformation/transformers/es6/regex.unicode.js b/src/babel/transformation/transformers/es6/regex.unicode.js
index 58471da84a..a914f2b529 100644
--- a/src/babel/transformation/transformers/es6/regex.unicode.js
+++ b/src/babel/transformation/transformers/es6/regex.unicode.js
@@ -1,10 +1,6 @@
 import rewritePattern from "regexpu/rewrite-pattern";
 import * as regex from "../../helpers/regex";
 
-export function shouldVisit(node) {
-  return regex.is(node, "u");
-}
-
 export function Literal(node) {
   if (!regex.is(node, "u")) return;
   node.regex.pattern = rewritePattern(node.regex.pattern, node.regex.flags);
diff --git a/src/babel/transformation/transformers/es6/spread.js b/src/babel/transformation/transformers/es6/spread.js
index a856453ed0..e7c403588a 100644
--- a/src/babel/transformation/transformers/es6/spread.js
+++ b/src/babel/transformation/transformers/es6/spread.js
@@ -44,8 +44,6 @@ function build(props, scope) {
   return nodes;
 }
 
-export var shouldVisit = t.isSpreadElement;
-
 export function ArrayExpression(node, parent, scope) {
   var elements = node.elements;
   if (!hasSpread(elements)) return;
diff --git a/src/babel/transformation/transformers/es6/template-literals.js b/src/babel/transformation/transformers/es6/template-literals.js
index 10128abaf7..912fcdbbdf 100644
--- a/src/babel/transformation/transformers/es6/template-literals.js
+++ b/src/babel/transformation/transformers/es6/template-literals.js
@@ -4,10 +4,6 @@ var buildBinaryExpression = function (left, right) {
   return t.binaryExpression("+", left, right);
 };
 
-export function shouldVisit(node) {
-  return t.isTemplateLiteral(node) || t.isTaggedTemplateExpression(node);
-}
-
 export function TaggedTemplateExpression(node, parent, scope, file) {
   var quasi = node.quasi;
   var args  = [];
diff --git a/src/babel/transformation/transformers/es7/async-functions.js b/src/babel/transformation/transformers/es7/async-functions.js
index df6bc46bd4..5059fdd666 100644
--- a/src/babel/transformation/transformers/es7/async-functions.js
+++ b/src/babel/transformation/transformers/es7/async-functions.js
@@ -1,7 +1,3 @@
 export var metadata = {
   stage: 1
 };
-
-export function shouldVisit() {
-  return false;
-}
diff --git a/src/babel/transformation/transformers/es7/class-properties.js b/src/babel/transformation/transformers/es7/class-properties.js
index 9c08f42ae1..871398b386 100644
--- a/src/babel/transformation/transformers/es7/class-properties.js
+++ b/src/babel/transformation/transformers/es7/class-properties.js
@@ -1,7 +1,3 @@
 export var metadata = {
   stage: 0
 };
-
-export function shouldVisit() {
-  return false;
-}
diff --git a/src/babel/transformation/transformers/es7/decorators.js b/src/babel/transformation/transformers/es7/decorators.js
index a67843cf3d..af98294cf8 100644
--- a/src/babel/transformation/transformers/es7/decorators.js
+++ b/src/babel/transformation/transformers/es7/decorators.js
@@ -7,10 +7,6 @@ export var metadata = {
   stage: 1
 };
 
-export function shouldVisit(node) {
-  return !!node.decorators;
-}
-
 export function ObjectExpression(node, parent, scope, file) {
   var hasDecorators = false;
   for (var i = 0; i < node.properties.length; i++) {
diff --git a/src/babel/transformation/transformers/es7/do-expressions.js b/src/babel/transformation/transformers/es7/do-expressions.js
index 8f1e18875f..efefe06ba2 100644
--- a/src/babel/transformation/transformers/es7/do-expressions.js
+++ b/src/babel/transformation/transformers/es7/do-expressions.js
@@ -5,8 +5,6 @@ export var metadata = {
   stage: 0
 };
 
-export var shouldVisit = t.isDoExpression;
-
 export function DoExpression(node) {
   var body = node.body.body;
   if (body.length) {
diff --git a/src/babel/transformation/transformers/es7/export-extensions.js b/src/babel/transformation/transformers/es7/export-extensions.js
index 80a11c34ab..77880f3a10 100644
--- a/src/babel/transformation/transformers/es7/export-extensions.js
+++ b/src/babel/transformation/transformers/es7/export-extensions.js
@@ -6,10 +6,6 @@ export var metadata = {
   stage: 1
 };
 
-export function shouldVisit(node) {
-  return t.isExportDefaultSpecifier(node) || t.isExportNamespaceSpecifier(node);
-}
-
 function build(node, nodes, scope) {
   var first = node.specifiers[0];
   if (!t.isExportNamespaceSpecifier(first) && !t.isExportDefaultSpecifier(first)) return;
diff --git a/src/babel/transformation/transformers/es7/trailing-function-commas.js b/src/babel/transformation/transformers/es7/trailing-function-commas.js
index df6bc46bd4..5059fdd666 100644
--- a/src/babel/transformation/transformers/es7/trailing-function-commas.js
+++ b/src/babel/transformation/transformers/es7/trailing-function-commas.js
@@ -1,7 +1,3 @@
 export var metadata = {
   stage: 1
 };
-
-export function shouldVisit() {
-  return false;
-}
diff --git a/src/babel/transformation/transformers/index.js b/src/babel/transformation/transformers/index.js
index 05f7c47c41..0c3ea89b1d 100644
--- a/src/babel/transformation/transformers/index.js
+++ b/src/babel/transformation/transformers/index.js
@@ -1,124 +1,66 @@
 export default {
   "utility.removeDebugger":                require("./utility/remove-debugger"),
   "utility.removeConsole":                 require("./utility/remove-console"),
-
   "utility.inlineEnvironmentVariables":    require("./utility/inline-environment-variables"),
   "utility.inlineExpressions":             require("./utility/inline-expressions"),
-
   "minification.deadCodeElimination":      require("./minification/dead-code-elimination"),
-
   _modules:                                require("./internal/modules"),
-
   "es7.classProperties":                   require("./es7/class-properties"),
   "es7.trailingFunctionCommas":            require("./es7/trailing-function-commas"),
   "es7.asyncFunctions":                    require("./es7/async-functions"),
   "es7.decorators":                        require("./es7/decorators"),
-
   strict:                                  require("./other/strict"),
-
   _validation:                             require("./internal/validation"),
-
   "validation.undeclaredVariableCheck":    require("./validation/undeclared-variable-check"),
   "validation.react":                      require("./validation/react"),
-
-  // this goes at the start so we only transform the original user code
   "spec.functionName":                     require("./spec/function-name"),
-
-  // needs to be before `_shadowFunctions`
   "es6.arrowFunctions":                    require("./es6/arrow-functions"),
-
   "spec.blockScopedFunctions":             require("./spec/block-scoped-functions"),
-
   "optimisation.react.constantElements":   require("./optimisation/react.constant-elements"),
   "optimisation.react.inlineElements":     require("./optimisation/react.inline-elements"),
   reactCompat:                             require("./other/react-compat"),
   react:                                   require("./other/react"),
-
-  // needs to be before `regenerator` due to generator comprehensions
-  // needs to be before `_shadowFunctions`
   "es7.comprehensions":                    require("./es7/comprehensions"),
-
   "es6.classes":                           require("./es6/classes"),
-
   asyncToGenerator:                        require("./other/async-to-generator"),
   bluebirdCoroutines:                      require("./other/bluebird-coroutines"),
-
   "es6.objectSuper":                       require("./es6/object-super"),
   "es7.objectRestSpread":                  require("./es7/object-rest-spread"),
   "es7.exponentiationOperator":            require("./es7/exponentiation-operator"),
-
   "es6.spec.templateLiterals":             require("./es6/spec.template-literals"),
   "es6.templateLiterals":                  require("./es6/template-literals"),
-
   "es5.properties.mutators":               require("./es5/properties.mutators"),
   "es6.properties.shorthand":              require("./es6/properties.shorthand"),
-
-  // needs to be before `_shadowFunctions` due to define property closure
   "es6.properties.computed":               require("./es6/properties.computed"),
-
   "optimisation.flow.forOf":               require("./optimisation/flow.for-of"),
   "es6.forOf":                             require("./es6/for-of"),
-
   "es6.regex.sticky":                      require("./es6/regex.sticky"),
   "es6.regex.unicode":                     require("./es6/regex.unicode"),
-
   "es6.constants":                         require("./es6/constants"),
-
-  // needs to be before `es6.parameters.default` as default parameters will destroy the rest param
   "es6.parameters.rest":                   require("./es6/parameters.rest"),
-
-  // needs to be after `es6.parameters.rest` as we use `toArray` and avoid turning an already known array into one
   "es6.spread":                            require("./es6/spread"),
-
-  // needs to be before `es6.blockScoping` as default parameters have a TDZ
   "es6.parameters.default":                require("./es6/parameters.default"),
-
-  // needs to be before `es6.blockScoping` as let variables may be produced
   "es6.destructuring":                     require("./es6/destructuring"),
-
-  // needs to be before `_shadowFunctions` due to block scopes sometimes being wrapped in a
-  // closure
   "es6.blockScoping":                      require("./es6/block-scoping"),
-
-  // needs to be after `es6.blockScoping` due to needing `letReferences` set on blocks
   "es6.spec.blockScoping":                 require("./es6/spec.block-scoping"),
-
-  // needs to be after `es6.parameters.*` and `es6.blockScoping` due to needing pure
-  // identifiers in parameters and variable declarators
   "es6.tailCall":                          require("./es6/tail-call"),
-
   regenerator:                             require("./other/regenerator"),
-
-  // needs to be after `regenerator` due to needing `regeneratorRuntime` references
-  // needs to be after `es6.forOf` due to needing `Symbol.iterator` references
-  // needs to be before `es6.modules` due to dynamic imports
-  runtime:                                require("./other/runtime"),
-
-  // needs to be before `_blockHoist` due to function hoisting etc
+  runtime:                                 require("./other/runtime"),
   "es7.exportExtensions":                  require("./es7/export-extensions"),
   "es6.modules":                           require("./es6/modules"),
-
-  _blockHoist:                             require("./internal/block-hoist"),
-
   "spec.protoToAssign":                    require("./spec/proto-to-assign"),
-
   _shadowFunctions:                        require("./internal/shadow-functions"),
-
   "es7.doExpressions":                     require("./es7/do-expressions"),
-
   "es6.spec.symbols":                      require("./es6/spec.symbols"),
   ludicrous:                               require("./other/ludicrous"),
   "spec.undefinedToVoid":                  require("./spec/undefined-to-void"),
-
-  _strict:                                 require("./internal/strict"),
   _moduleFormatter:                        require("./internal/module-formatter"),
-
   "es3.propertyLiterals":                  require("./es3/property-literals"),
   "es3.memberExpressionLiterals":          require("./es3/member-expression-literals"),
-
   "minification.memberExpressionLiterals": require("./minification/member-expression-literals"),
   "minification.propertyLiterals":         require("./minification/property-literals"),
-
   jscript:                                 require("./other/jscript"),
-  flow:                                    require("./other/flow")
+  flow:                                    require("./other/flow"),
+  _hoistDirectives:                        require("./internal/hoist-directives"),
+  _blockHoist:                             require("./internal/block-hoist")
 };
diff --git a/src/babel/transformation/transformers/internal/hoist-directives.js b/src/babel/transformation/transformers/internal/hoist-directives.js
new file mode 100644
index 0000000000..8c0c1280cf
--- /dev/null
+++ b/src/babel/transformation/transformers/internal/hoist-directives.js
@@ -0,0 +1,16 @@
+import * as t from "../../../types";
+
+export var BlockStatement = {
+  exit(node) {
+    for (var i = 0; i < node.body.length; i++) {
+      var bodyNode = node.body[i];
+      if (t.isExpressionStatement(bodyNode) && t.isLiteral(bodyNode.expression)) {
+        bodyNode._blockHoist = Infinity;
+      } else {
+        return;
+      }
+    }
+  }
+};
+
+export { BlockStatement as Program };
diff --git a/src/babel/transformation/transformers/internal/module-formatter.js b/src/babel/transformation/transformers/internal/module-formatter.js
index 92ef7baab2..400f27e28a 100644
--- a/src/babel/transformation/transformers/internal/module-formatter.js
+++ b/src/babel/transformation/transformers/internal/module-formatter.js
@@ -1,8 +1,6 @@
 import * as strict from "../../helpers/strict";
 
 export function Program(program, parent, scope, file) {
-  this.stop();
-
   strict.wrap(program, function () {
     program.body = file.dynamicImports.concat(program.body);
   });
diff --git a/src/babel/transformation/transformers/internal/modules.js b/src/babel/transformation/transformers/internal/modules.js
index 5953072c27..6d3dfe83c8 100644
--- a/src/babel/transformation/transformers/internal/modules.js
+++ b/src/babel/transformation/transformers/internal/modules.js
@@ -6,10 +6,6 @@
 
 import * as t from "../../../types";
 
-export function shouldVisit(node) {
-  return t.isImportDeclaration(node) || t.isExportDeclaration(node);
-}
-
 export function ImportDeclaration(node, parent, scope, file) {
   if (node.source) {
     node.source.value = file.resolveModuleSource(node.source.value);
diff --git a/src/babel/transformation/transformers/internal/shadow-functions.js b/src/babel/transformation/transformers/internal/shadow-functions.js
index 4eb4e5e375..30925d8a8f 100644
--- a/src/babel/transformation/transformers/internal/shadow-functions.js
+++ b/src/babel/transformation/transformers/internal/shadow-functions.js
@@ -82,21 +82,24 @@ function aliasFunction(getBody, path, scope) {
   }
 };
 
-export function shouldVisit(node) {
-  return true;
-}
+// todo: on all `this` and `arguments`, walk UP the tree instead of
+// crawling the entire function tree
 
-export function Program(node, parent, scope) {
-  aliasFunction(function () {
-    return node.body;
-  }, this, scope);
+export var Program = {
+  exit(node, parent, scope) {
+    aliasFunction(function () {
+      return node.body;
+    }, this, scope);
+  }
 };
 
-export function FunctionDeclaration(node, parent, scope) {
-  aliasFunction(function () {
-    t.ensureBlock(node);
-    return node.body.body;
-  }, this, scope);
-}
+export var FunctionDeclaration = {
+  exit(node, parent, scope) {
+    aliasFunction(function () {
+      t.ensureBlock(node);
+      return node.body.body;
+    }, this, scope);
+  }
+};
 
 export { FunctionDeclaration as FunctionExpression };
diff --git a/src/babel/transformation/transformers/internal/strict.js b/src/babel/transformation/transformers/internal/strict.js
deleted file mode 100644
index afc820c665..0000000000
--- a/src/babel/transformation/transformers/internal/strict.js
+++ /dev/null
@@ -1,19 +0,0 @@
-import * as t from "../../../types";
-
-export function Program(program, parent, scope, file) {
-  if (file.transformers.strict.canTransform()) {
-    var directive = file.get("existingStrictDirective");
-
-    if (!directive) {
-      directive = t.expressionStatement(t.literal("use strict"));
-      var first = program.body[0];
-      if (first) {
-        directive.leadingComments = first.leadingComments;
-        first.leadingComments = [];
-      }
-    }
-
-    this.unshiftContainer("body", [directive]);
-  }
-  this.stop();
-}
diff --git a/src/babel/transformation/transformers/internal/validation.js b/src/babel/transformation/transformers/internal/validation.js
index 8fab413fdd..da830eabef 100644
--- a/src/babel/transformation/transformers/internal/validation.js
+++ b/src/babel/transformation/transformers/internal/validation.js
@@ -1,10 +1,6 @@
 import * as messages from "../../../messages";
 import * as t from "../../../types";
 
-export var metadata = {
-  readOnly: true
-};
-
 export function ForOfStatement(node, parent, scope, file) {
   var left = node.left;
   if (t.isVariableDeclaration(left)) {
@@ -43,16 +39,3 @@ export function Property(node, parent, scope, file) {
     }
   }
 }
-
-export function BlockStatement(node) {
-  for (var i = 0; i < node.body.length; i++) {
-    var bodyNode = node.body[i];
-    if (t.isExpressionStatement(bodyNode) && t.isLiteral(bodyNode.expression)) {
-      bodyNode._blockHoist = Infinity;
-    } else {
-      return;
-    }
-  }
-}
-
-export { BlockStatement as Program };
diff --git a/src/babel/transformation/transformers/optimisation/flow.for-of.js b/src/babel/transformation/transformers/optimisation/flow.for-of.js
index f69525e307..0f031a9b51 100644
--- a/src/babel/transformation/transformers/optimisation/flow.for-of.js
+++ b/src/babel/transformation/transformers/optimisation/flow.for-of.js
@@ -1,7 +1,6 @@
 import { _ForOfStatementArray } from "../es6/for-of";
 import * as t from "../../../types";
 
-export var shouldVisit = t.isForOfStatement;
 export var metadata = {
   optional: true
 };
diff --git a/src/babel/transformation/transformers/other/flow.js b/src/babel/transformation/transformers/other/flow.js
index b3a963e3cc..bb6bf4c393 100644
--- a/src/babel/transformation/transformers/other/flow.js
+++ b/src/babel/transformation/transformers/other/flow.js
@@ -1,9 +1,5 @@
 import * as t from "../../../types";
 
-export function shouldVisit(node) {
-  return node.isType || node.optional || node.implements || node.typeAnnotation || t.isFlow(node);
-}
-
 export function Flow(node) {
   this.remove();
 }
diff --git a/src/babel/transformation/transformers/other/regenerator.js b/src/babel/transformation/transformers/other/regenerator.js
index 7c109a92a5..2897527cd1 100644
--- a/src/babel/transformation/transformers/other/regenerator.js
+++ b/src/babel/transformation/transformers/other/regenerator.js
@@ -1,14 +1,8 @@
 import regenerator from "regenerator";
 import * as t from "../../../types";
 
-export function shouldVisit(node) {
-  return t.isFunction(node) && (node.async || node.generator);
-}
-
 export var Program = {
-  enter(ast) {
+  exit(ast) {
     regenerator.transform(ast);
-    this.stop();
-    this.checkSelf();
   }
 };
diff --git a/src/babel/transformation/transformers/other/strict.js b/src/babel/transformation/transformers/other/strict.js
index 1c8acc2651..1889800b11 100644
--- a/src/babel/transformation/transformers/other/strict.js
+++ b/src/babel/transformation/transformers/other/strict.js
@@ -1,22 +1,33 @@
 import * as messages from "../../../messages";
 import * as t from "../../../types";
 
-export function Program(program, parent, scope, file) {
-  var first = program.body[0];
-  if (t.isExpressionStatement(first) && t.isLiteral(first.expression, { value: "use strict" })) {
-    file.set("existingStrictDirective", program.body.shift());
+const THIS_BREAK_KEYS = ["FunctionExpression", "FunctionDeclaration", "ClassExpression", "ClassDeclaration"];
+
+export var Program = {
+  enter(program, parent, scope, file) {
+    var first = program.body[0];
+
+    var directive;
+    if (t.isExpressionStatement(first) && t.isLiteral(first.expression, { value: "use strict" })) {
+      directive = first;
+    } else {
+      directive = t.expressionStatement(t.literal("use strict"));
+      this.unshiftContainer("body", directive);
+      if (first) {
+        directive.leadingComments = first.leadingComments;
+        first.leadingComments = [];
+      }
+    }
+    directive._blockHoist = Infinity;
   }
 }
 
-export function FunctionExpression() {
-  this.skip();
-}
-
-export { FunctionExpression as FunctionDeclaration };
-export { FunctionExpression as Class };
-
 export function ThisExpression() {
-  return t.identifier("undefined");
+  if (!this.findParent(function (node) {
+    return !node.shadow && THIS_BREAK_KEYS.indexOf(node.type) >= 0;
+  })) {
+    return t.identifier("undefined");
+  }
 }
 
 export function CallExpression(node, parent, scope, file) {
diff --git a/src/babel/transformation/transformers/spec/block-scoped-functions.js b/src/babel/transformation/transformers/spec/block-scoped-functions.js
index b5327d8c0f..ae16f05fcb 100644
--- a/src/babel/transformation/transformers/spec/block-scoped-functions.js
+++ b/src/babel/transformation/transformers/spec/block-scoped-functions.js
@@ -23,21 +23,6 @@ function statementList(key, path, file) {
   }
 }
 
-export function shouldVisit(node) {
-  var body;
-  if (node.type === "SwitchCase") {
-    body = node.consequent;
-  } else if (node.type === "BlockStatement") {
-    body = node.body;
-  }
-  if (body) {
-    for (var i = 0; i < body.length; i++) {
-      if (body[i].type === "FunctionDeclaration") return true;
-    }
-  }
-  return false;
-}
-
 export function BlockStatement(node, parent, scope, file) {
   if ((t.isFunction(parent) && parent.body === node) || t.isExportDeclaration(parent)) {
     return;
diff --git a/src/babel/transformation/transformers/validation/react.js b/src/babel/transformation/transformers/validation/react.js
index 5666f8c299..536aff1768 100644
--- a/src/babel/transformation/transformers/validation/react.js
+++ b/src/babel/transformation/transformers/validation/react.js
@@ -1,14 +1,6 @@
 import * as messages from "../../../messages";
 import * as t from "../../../types";
 
-export var metadata = {
-  readOnly: true
-};
-
-export function shouldVisit(node) {
-  return t.isModuleDeclaration(node) || (t.isCallExpression(node) && t.isIdentifier(node.callee, { name: "require" }));
-}
-
 // check if the input Literal `source` is an alternate casing of "react"
 function check(source, file) {
   if (t.isLiteral(source)) {
diff --git a/src/babel/transformation/transformers/validation/undeclared-variable-check.js b/src/babel/transformation/transformers/validation/undeclared-variable-check.js
index 01f1f4a86c..f8d3b25a78 100644
--- a/src/babel/transformation/transformers/validation/undeclared-variable-check.js
+++ b/src/babel/transformation/transformers/validation/undeclared-variable-check.js
@@ -2,8 +2,7 @@ import levenshtein from "leven";
 import * as messages from "../../../messages";
 
 export var metadata = {
-  optional: true,
-  readOnly: true
+  optional: true
 };
 
 export function Identifier(node, parent, scope, file) {
diff --git a/src/babel/traversal/index.js b/src/babel/traversal/index.js
index 1f2ccccf12..80cb1f0c93 100644
--- a/src/babel/traversal/index.js
+++ b/src/babel/traversal/index.js
@@ -1,5 +1,5 @@
 import TraversalContext from "./context";
-import { explode, verify } from "./visitors";
+import * as visitors from "./visitors";
 import * as messages from "../messages";
 import includes from "lodash/collection/includes";
 import * as t from "../types";
@@ -14,7 +14,7 @@ export default function traverse(parent, opts, scope, state, parentPath) {
   }
 
   if (!opts) opts = {};
-  verify(opts);
+  visitors.verify(opts);
 
   // array of nodes
   if (Array.isArray(parent)) {
@@ -26,8 +26,9 @@ export default function traverse(parent, opts, scope, state, parentPath) {
   }
 }
 
-traverse.verify = verify;
-traverse.explode = explode;
+traverse.visitors = visitors;
+traverse.verify = visitors.verify;
+traverse.explode = visitors.explode;
 
 traverse.node = function (node, opts, scope, state, parentPath) {
   var keys = t.VISITOR_KEYS[node.type];
diff --git a/src/babel/traversal/path/index.js b/src/babel/traversal/path/index.js
index 14b801de53..23b971a900 100644
--- a/src/babel/traversal/path/index.js
+++ b/src/babel/traversal/path/index.js
@@ -107,12 +107,43 @@ export default class TraversalPath {
     return ancestry;
   }
 
+  /**
+   * Description
+   */
+
+  inType(types) {
+    if (!Array.isArray(types)) types = [types];
+
+    var path = this;
+    while (path) {
+      for (var type of (types: Array)) {
+        if (path.node.type === type) return true;
+      }
+      path = path.parentPath;
+    }
+
+    return false;
+  }
+
+  /**
+   * Description
+   */
+
+  findParent(callback) {
+    var path = this;
+    while (path) {
+      if (callback(path.node)) return path.node;
+      path = path.parentPath;
+    }
+    return null;
+  }
+
   /**
    * Description
    */
 
   queueNode(path) {
-    if (this.context) {
+    if (this.context && this.context.queue) {
       this.context.queue.push(path);
     }
   }
@@ -136,7 +167,6 @@ export default class TraversalPath {
       } else if (this.isStatementOrBlock()) {
         if (this.node) nodes.push(this.node);
         this.container[this.key] = t.blockStatement(nodes);
-        this.checkSelf();
       } else {
         throw new Error("We don't know what to do with this node type. We were previously a Statement but we can't fit in here?");
       }
@@ -163,8 +193,6 @@ export default class TraversalPath {
         paths.push(TraversalPath.get(this, null, node, this.container, to));
       }
     }
-
-    this.checkPaths(paths);
   }
 
   _containerInsertBefore(nodes) {
@@ -234,7 +262,6 @@ export default class TraversalPath {
       } else if (this.isStatementOrBlock()) {
         if (this.node) nodes.unshift(this.node);
         this.container[this.key] = t.blockStatement(nodes);
-        this.checkSelf();
       } else {
         throw new Error("We don't know what to do with this node type. We were previously a Statement but we can't fit in here?");
       }
@@ -528,7 +555,7 @@ export default class TraversalPath {
     }
 
     if (this.node === replacement) {
-      return this.checkSelf();
+      return;
     }
 
     // normalise inserting an entire AST
@@ -572,26 +599,6 @@ export default class TraversalPath {
 
     // potentially create new scope
     this.setScope();
-
-    this.checkSelf();
-  }
-
-  /**
-   * Description
-   */
-
-  checkSelf() {
-    this.checkPaths(this);
-  }
-
-  /**
-   * Description
-   */
-
-  checkPaths(paths) {
-    var scope = this.scope;
-    var file  = scope && scope.file;
-    if (file) file.checkPath(paths);
   }
 
   /**
@@ -691,9 +698,13 @@ export default class TraversalPath {
 
       // call the function with the params (node, parent, scope, state)
       var replacement = fn.call(this, node, this.parent, this.scope, this.state);
-      if (replacement) this.replaceWith(replacement, true);
+      if (replacement) {
+        this.replaceWith(replacement, true);
+        this.queueNode(this);
+        break;
+      }
 
-      if (this.shouldStop) break;
+      if (this.shouldStop || this.removed) break;
     }
   }
 
diff --git a/src/babel/traversal/visitors.js b/src/babel/traversal/visitors.js
index 8e994c1ccb..f922351d1f 100644
--- a/src/babel/traversal/visitors.js
+++ b/src/babel/traversal/visitors.js
@@ -36,12 +36,12 @@ export function explode(visitor, mergeConflicts) {
     if (wrapper.type) {
       // merge the visitor if necessary or just put it back in
       if (visitor[wrapper.type]) {
-        merge(visitor[wrapper.type], fns);
+        mergePair(visitor[wrapper.type], fns);
       } else {
         visitor[wrapper.type] = fns;
       }
     } else {
-      merge(visitor, fns);
+      mergePair(visitor, fns);
     }
   }
 
@@ -61,7 +61,7 @@ export function explode(visitor, mergeConflicts) {
       var existing = visitor[alias];
       if (existing) {
         if (mergeConflicts) {
-          merge(existing, fns);
+          mergePair(existing, fns);
         }
       } else {
         visitor[alias] = fns;
@@ -105,6 +105,19 @@ export function verify(visitor) {
   visitor._verified = true;
 }
 
+export function merge(visitors) {
+  var rootVisitor = {};
+
+  for (var visitor of (visitors: Array)) {
+    for (var type in visitor) {
+      var nodeVisitor = rootVisitor[type] = rootVisitor[type] || {};
+      mergePair(nodeVisitor, visitor[type]);
+    }
+  }
+
+  return rootVisitor;
+}
+
 function ensureEntranceObjects(obj) {
   for (let key in obj) {
     if (shouldIgnoreKey(key)) continue;
@@ -135,7 +148,7 @@ function addSelector(visitor, selector, fns) {
     };
   }
 
-  merge(visitor, fns);
+  mergePair(visitor, fns);
 }
 
 function wrapCheck(wrapper, fn) {
@@ -159,7 +172,7 @@ function shouldIgnoreKey(key) {
   return false;
 }
 
-function merge(dest, src) {
+function mergePair(dest, src) {
   for (var key in src) {
     dest[key] = (dest[key] || []).concat(src[key]);
   }
diff --git a/test/core/fixtures/transformation/es6.arrow-functions/arguments/expected.js b/test/core/fixtures/transformation/es6.arrow-functions/arguments/expected.js
index b8104fab4d..2972f6b9b1 100644
--- a/test/core/fixtures/transformation/es6.arrow-functions/arguments/expected.js
+++ b/test/core/fixtures/transformation/es6.arrow-functions/arguments/expected.js
@@ -11,17 +11,17 @@ function one() {
 one(1, 2);
 
 function two() {
-  var _arguments2 = arguments;
+  var _arguments3 = arguments;
 
   var inner = function inner() {
-    return _arguments2;
+    return _arguments3;
   };
 
   var another = function another() {
-    var _arguments3 = arguments;
+    var _arguments2 = arguments;
 
     var inner2 = function inner2() {
-      return _arguments3;
+      return _arguments2;
     };
   };
 
@@ -66,4 +66,4 @@ function six(obj) {
   };
   return fn();
 }
-six();
\ No newline at end of file
+six();
diff --git a/test/core/fixtures/transformation/spec.proto-to-assign/assignment-expression/expected.js b/test/core/fixtures/transformation/spec.proto-to-assign/assignment-expression/expected.js
index 1a55265b4c..0980420528 100644
--- a/test/core/fixtures/transformation/spec.proto-to-assign/assignment-expression/expected.js
+++ b/test/core/fixtures/transformation/spec.proto-to-assign/assignment-expression/expected.js
@@ -1,11 +1,11 @@
 "use strict";
 
-function _defaults(obj, defaults) { var keys = Object.getOwnPropertyNames(defaults); for (var i = 0; i < keys.length; i++) { var key = keys[i]; var value = Object.getOwnPropertyDescriptor(defaults, key); if (value && value.configurable && obj[key] === undefined) { Object.defineProperty(obj, key, value); } } return obj; }
-
 var _foo, _foo$bar, _foo$bar2;
 
+function _defaults(obj, defaults) { var keys = Object.getOwnPropertyNames(defaults); for (var i = 0; i < keys.length; i++) { var key = keys[i]; var value = Object.getOwnPropertyDescriptor(defaults, key); if (value && value.configurable && obj[key] === undefined) { Object.defineProperty(obj, key, value); } } return obj; }
+
 console.log((_foo = foo, _defaults(_foo, bar), _foo));
 
 console.log((_foo$bar = foo[bar], _defaults(_foo$bar, bar), _foo$bar));
 
-console.log((_foo$bar2 = foo[bar()], _defaults(_foo$bar2, bar), _foo$bar2));
\ No newline at end of file
+console.log((_foo$bar2 = foo[bar()], _defaults(_foo$bar2, bar), _foo$bar2));

From 9ffc265beaa1ec17ac6ce972abf73ac50e190747 Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Thu, 7 May 2015 16:01:00 +0100
Subject: [PATCH 02/30] don't requeue node unless the `type` has changed

---
 src/babel/traversal/path/index.js | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/babel/traversal/path/index.js b/src/babel/traversal/path/index.js
index 23b971a900..408726f235 100644
--- a/src/babel/traversal/path/index.js
+++ b/src/babel/traversal/path/index.js
@@ -699,9 +699,12 @@ export default class TraversalPath {
       // call the function with the params (node, parent, scope, state)
       var replacement = fn.call(this, node, this.parent, this.scope, this.state);
       if (replacement) {
+        var previousType = this.type;
         this.replaceWith(replacement, true);
-        this.queueNode(this);
-        break;
+        if (this.type !== previousType) {
+          this.queueNode(this);
+          break;
+        }
       }
 
       if (this.shouldStop || this.removed) break;

From f17b268a71d20751ee425fd08a0b33f63af67618 Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Thu, 7 May 2015 16:23:33 +0100
Subject: [PATCH 03/30] do member expression and property literal conversion to
 computed on exit rather than on entrance

---
 .../es3/member-expression-literals.js            | 16 +++++++++-------
 .../transformers/es3/property-literals.js        | 14 ++++++++------
 .../minification/member-expression-literals.js   | 16 +++++++++-------
 .../minification/property-literals.js            | 16 +++++++++-------
 4 files changed, 35 insertions(+), 27 deletions(-)

diff --git a/src/babel/transformation/transformers/es3/member-expression-literals.js b/src/babel/transformation/transformers/es3/member-expression-literals.js
index 9b6b30bff7..1665d20b25 100644
--- a/src/babel/transformation/transformers/es3/member-expression-literals.js
+++ b/src/babel/transformation/transformers/es3/member-expression-literals.js
@@ -1,10 +1,12 @@
 import * as t from "../../../types";
 
-export function MemberExpression(node) {
-  var prop = node.property;
-  if (!node.computed && t.isIdentifier(prop) && !t.isValidIdentifier(prop.name)) {
-    // foo.default -> foo["default"]
-    node.property = t.literal(prop.name);
-    node.computed = true;
+export var MemberExpression = {
+  exit(node) {
+    var prop = node.property;
+    if (!node.computed && t.isIdentifier(prop) && !t.isValidIdentifier(prop.name)) {
+      // foo.default -> foo["default"]
+      node.property = t.literal(prop.name);
+      node.computed = true;
+    }
   }
-}
+};
diff --git a/src/babel/transformation/transformers/es3/property-literals.js b/src/babel/transformation/transformers/es3/property-literals.js
index 0c9b26a9cd..f70a81661b 100644
--- a/src/babel/transformation/transformers/es3/property-literals.js
+++ b/src/babel/transformation/transformers/es3/property-literals.js
@@ -1,9 +1,11 @@
 import * as t from "../../../types";
 
-export function Property(node) {
-  var key = node.key;
-  if (!node.computed && t.isIdentifier(key) && !t.isValidIdentifier(key.name)) {
-    // default: "bar" -> "default": "bar"
-    node.key = t.literal(key.name);
+export var Property = {
+  exit(node) {
+    var key = node.key;
+    if (!node.computed && t.isIdentifier(key) && !t.isValidIdentifier(key.name)) {
+      // default: "bar" -> "default": "bar"
+      node.key = t.literal(key.name);
+    }
   }
-}
+};
diff --git a/src/babel/transformation/transformers/minification/member-expression-literals.js b/src/babel/transformation/transformers/minification/member-expression-literals.js
index 2038c70d4b..fe8862dc8c 100644
--- a/src/babel/transformation/transformers/minification/member-expression-literals.js
+++ b/src/babel/transformation/transformers/minification/member-expression-literals.js
@@ -4,11 +4,13 @@ export var metadata = {
   optional: true
 };
 
-export function MemberExpression(node) {
-  var prop = node.property;
-  if (node.computed && t.isLiteral(prop) && t.isValidIdentifier(prop.value)) {
-    // foo["bar"] => foo.bar
-    node.property = t.identifier(prop.value);
-    node.computed = false;
+export var MemberExpression = {
+  exit(node) {
+    var prop = node.property;
+    if (node.computed && t.isLiteral(prop) && t.isValidIdentifier(prop.value)) {
+      // foo["bar"] => foo.bar
+      node.property = t.identifier(prop.value);
+      node.computed = false;
+    }
   }
-}
+};
diff --git a/src/babel/transformation/transformers/minification/property-literals.js b/src/babel/transformation/transformers/minification/property-literals.js
index 84902d2b94..c85769a4e8 100644
--- a/src/babel/transformation/transformers/minification/property-literals.js
+++ b/src/babel/transformation/transformers/minification/property-literals.js
@@ -4,11 +4,13 @@ export var metadata = {
   optional: true
 };
 
-export function Property(node) {
-  var key = node.key;
-  if (t.isLiteral(key) && t.isValidIdentifier(key.value)) {
-    // "foo": "bar" -> foo: "bar"
-    node.key = t.identifier(key.value);
-    node.computed = false;
+export var Property = {
+  exit(node) {
+    var key = node.key;
+    if (t.isLiteral(key) && t.isValidIdentifier(key.value)) {
+      // "foo": "bar" -> foo: "bar"
+      node.key = t.identifier(key.value);
+      node.computed = false;
+    }
   }
-}
+};

From 0bbfd427af7037437afa4700b114bbc5c2e0ce4d Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Thu, 7 May 2015 16:23:47 +0100
Subject: [PATCH 04/30] do module formatter on program exit rather than
 entrance

---
 .../transformers/internal/module-formatter.js  | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/src/babel/transformation/transformers/internal/module-formatter.js b/src/babel/transformation/transformers/internal/module-formatter.js
index 400f27e28a..00cd641998 100644
--- a/src/babel/transformation/transformers/internal/module-formatter.js
+++ b/src/babel/transformation/transformers/internal/module-formatter.js
@@ -1,13 +1,15 @@
 import * as strict from "../../helpers/strict";
 
-export function Program(program, parent, scope, file) {
-  strict.wrap(program, function () {
-    program.body = file.dynamicImports.concat(program.body);
-  });
+export var Program = {
+  exit(program, parent, scope, file) {
+    strict.wrap(program, function () {
+      program.body = file.dynamicImports.concat(program.body);
+    });
 
-  if (!file.transformers["es6.modules"].canTransform()) return;
+    if (!file.transformers["es6.modules"].canTransform()) return;
 
-  if (file.moduleFormatter.transform) {
-    file.moduleFormatter.transform(program);
+    if (file.moduleFormatter.transform) {
+      file.moduleFormatter.transform(program);
+    }
   }
-}
+};

From a1bc0704abd2f5e1de89c09879037b5cc297641a Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Thu, 7 May 2015 20:11:02 +0100
Subject: [PATCH 05/30] attach auxiliary comment to function declaration
 helpers - fixes #1476

---
 src/babel/transformation/file/index.js |  1 +
 test/core/api.js                       | 10 ++++++++++
 2 files changed, 11 insertions(+)

diff --git a/src/babel/transformation/file/index.js b/src/babel/transformation/file/index.js
index bb2d3697db..c31196bf09 100644
--- a/src/babel/transformation/file/index.js
+++ b/src/babel/transformation/file/index.js
@@ -364,6 +364,7 @@ export default class File {
       ref._generated = true;
       ref.id = uid;
       ref.type = "FunctionDeclaration";
+      this.attachAuxiliaryComment(ref);
       this.path.unshiftContainer("body", ref);
     } else {
       ref._compact = true;
diff --git a/test/core/api.js b/test/core/api.js
index 2fb0330ff3..4464600e3e 100644
--- a/test/core/api.js
+++ b/test/core/api.js
@@ -18,6 +18,16 @@ suite("api", function () {
     assert.ok(!result.ast);
   });
 
+  test("{ auxiliaryComment }", function () {
+    assert.ok(transform("class Foo {}", {
+      auxiliaryComment: "foobar"
+    }).code.indexOf("foobar") >= 0);
+
+    assert.ok(transform("for (let i in bar) { foo(function () { i; }); break; continue; }", {
+      auxiliaryComment: "foobar"
+    }).code.indexOf("foobar") >= 0);
+  });
+
   suite("getModuleId() {} option", function () {
     // As of this commit, `getModuleId` is the only option that isn't JSON
     // compatible which is why it's not inside /test/core/fixtures/transformation

From 23ac2319afabb7bf10a7a043dd339bad4685d02b Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Thu, 7 May 2015 20:11:14 +0100
Subject: [PATCH 06/30] add Super node type to ast-types patch

---
 src/babel/patch.js | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/babel/patch.js b/src/babel/patch.js
index 09afdbd301..f8f5dcf95e 100644
--- a/src/babel/patch.js
+++ b/src/babel/patch.js
@@ -33,6 +33,9 @@ def("DoExpression")
   .build("body")
   .field("body", [def("Statement")]);
 
+def("Super")
+  .bases("Expression");
+
 def("ExportDefaultDeclaration")
   .bases("Declaration")
   .build("declaration")

From 380293d030327d4ad4c7cf18fb3b6d61e25d91d6 Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Thu, 7 May 2015 21:35:12 +0100
Subject: [PATCH 07/30] add transformer dependencies - fixes #1477

---
 src/babel/transformation/file/index.js           | 16 +++++++++++++---
 src/babel/transformation/transformer-pass.js     |  9 +++++----
 src/babel/transformation/transformer.js          |  1 +
 .../transformers/es7/class-properties.js         |  3 ++-
 .../transformers/es7/decorators.js               |  1 +
 .../transformers/es7/object-rest-spread.js       |  7 ++-----
 .../transformers/other/async-to-generator.js     |  3 ++-
 .../transformers/other/bluebird-coroutines.js    |  4 ++--
 8 files changed, 28 insertions(+), 16 deletions(-)

diff --git a/src/babel/transformation/file/index.js b/src/babel/transformation/file/index.js
index c31196bf09..e3757ac860 100644
--- a/src/babel/transformation/file/index.js
+++ b/src/babel/transformation/file/index.js
@@ -29,6 +29,8 @@ import * as t from "../../types";
 
 export default class File {
   constructor(opts = {}, pipeline) {
+    this.transformerDependencies = {};
+
     this.dynamicImportTypes = {};
     this.dynamicImportIds   = {};
     this.dynamicImports     = [];
@@ -221,13 +223,21 @@ export default class File {
     }
     stack = beforePlugins.concat(stack, afterPlugins);
 
-    // register
-    this.transformerStack = this.mergeStack(stack.concat(secondaryStack));
+    // build transformer stack
+    stack = stack.concat(secondaryStack);
 
+    // build dependency graph
+    for (var pass of (stack: Array)) {
+      for (var dep of (pass.transformer.dependencies: Array)) {
+        this.transformerDependencies[dep] = pass.key;
+      }
+    }
 
+    // collapse stack categories
+    this.transformerStack = this.collapseStack(stack);
   }
 
-  mergeStack(_stack) {
+  collapseStack(_stack) {
     var stack  = [];
     var ignore = [];
 
diff --git a/src/babel/transformation/transformer-pass.js b/src/babel/transformation/transformer-pass.js
index 715ba6de2e..62e91cd7ca 100644
--- a/src/babel/transformation/transformer-pass.js
+++ b/src/babel/transformation/transformer-pass.js
@@ -10,23 +10,24 @@ export default class TransformerPass {
   constructor(file: File, transformer: Transformer) {
     this.transformer = transformer;
     this.handlers    = transformer.handlers;
-    this.skipKey     = transformer.skipKey;
     this.file        = file;
     this.ran         = false;
+    this.key         = transformer.key;
   }
 
   canTransform(): boolean {
-    return this.file.pipeline.canTransform(this.transformer, this.file.opts);
+    return this.file.transformerDependencies[this.key] ||
+           this.file.pipeline.canTransform(this.transformer, this.file.opts);
   }
 
   transform() {
     var file = this.file;
 
-    file.log.debug(`Start transformer ${this.transformer.key}`);
+    file.log.debug(`Start transformer ${this.key}`);
 
     traverse(file.ast, this.handlers, file.scope, file);
 
-    file.log.debug(`Finish transformer ${this.transformer.key}`);
+    file.log.debug(`Finish transformer ${this.key}`);
 
     this.ran = true;
   }
diff --git a/src/babel/transformation/transformer.js b/src/babel/transformation/transformer.js
index a5fac03bf9..3f700974d9 100644
--- a/src/babel/transformation/transformer.js
+++ b/src/babel/transformation/transformer.js
@@ -26,6 +26,7 @@ export default class Transformer {
 
     this.manipulateOptions = take("manipulateOptions");
     this.metadata          = take("metadata") || {};
+    this.dependencies      = this.metadata.dependencies || [];
     this.parser            = take("parser");
     this.post              = take("post");
     this.pre               = take("pre");
diff --git a/src/babel/transformation/transformers/es7/class-properties.js b/src/babel/transformation/transformers/es7/class-properties.js
index 871398b386..ca95104fab 100644
--- a/src/babel/transformation/transformers/es7/class-properties.js
+++ b/src/babel/transformation/transformers/es7/class-properties.js
@@ -1,3 +1,4 @@
 export var metadata = {
-  stage: 0
+  stage: 0,
+  dependencies: ["es6.classes"]
 };
diff --git a/src/babel/transformation/transformers/es7/decorators.js b/src/babel/transformation/transformers/es7/decorators.js
index af98294cf8..aaa54b0ee2 100644
--- a/src/babel/transformation/transformers/es7/decorators.js
+++ b/src/babel/transformation/transformers/es7/decorators.js
@@ -3,6 +3,7 @@ import * as defineMap from "../../helpers/define-map";
 import * as t from "../../../types";
 
 export var metadata = {
+  dependencies: ["es6.classes"],
   optional: true,
   stage: 1
 };
diff --git a/src/babel/transformation/transformers/es7/object-rest-spread.js b/src/babel/transformation/transformers/es7/object-rest-spread.js
index e6fe46b993..7b9f448f9c 100644
--- a/src/babel/transformation/transformers/es7/object-rest-spread.js
+++ b/src/babel/transformation/transformers/es7/object-rest-spread.js
@@ -3,13 +3,10 @@
 import * as t from "../../../types";
 
 export var metadata = {
-  stage: 1
+  stage: 1,
+  dependencies: ["es6.destructuring"]
 };
 
-export function manipulateOptions(opts) {
-  if (opts.whitelist) opts.whitelist.push("es6.destructuring");
-}
-
 var hasSpread = function (node) {
   for (var i = 0; i < node.properties.length; i++) {
     if (t.isSpreadProperty(node.properties[i])) {
diff --git a/src/babel/transformation/transformers/other/async-to-generator.js b/src/babel/transformation/transformers/other/async-to-generator.js
index 7789fd2506..b5a54b478d 100644
--- a/src/babel/transformation/transformers/other/async-to-generator.js
+++ b/src/babel/transformation/transformers/other/async-to-generator.js
@@ -3,7 +3,8 @@ import remapAsyncToGenerator from "../../helpers/remap-async-to-generator";
 export { manipulateOptions } from "./bluebird-coroutines";
 
 export var metadata = {
-  optional: true
+  optional: true,
+  dependencies: ["es7.asyncFunctions", "es6.classes"]
 };
 
 exports.Function = function (node, parent, scope, file) {
diff --git a/src/babel/transformation/transformers/other/bluebird-coroutines.js b/src/babel/transformation/transformers/other/bluebird-coroutines.js
index cb4f99e09a..2d1c467edd 100644
--- a/src/babel/transformation/transformers/other/bluebird-coroutines.js
+++ b/src/babel/transformation/transformers/other/bluebird-coroutines.js
@@ -2,12 +2,12 @@ import remapAsyncToGenerator from "../../helpers/remap-async-to-generator";
 import * as t from "../../../types";
 
 export function manipulateOptions(opts) {
-  opts.optional.push("es7.asyncFunctions");
   opts.blacklist.push("regenerator");
 }
 
 export var metadata = {
-  optional: true
+  optional: true,
+  dependencies: ["es7.asyncFunctions", "es6.classes"]
 };
 
 exports.Function = function (node, parent, scope, file) {

From 13a6c696681de0eac6eb1945f41907aceb94887c Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Thu, 7 May 2015 23:02:40 +0100
Subject: [PATCH 08/30] add node existence check to each visitor call

---
 src/babel/traversal/path/index.js | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/babel/traversal/path/index.js b/src/babel/traversal/path/index.js
index 408726f235..6ac9cc1819 100644
--- a/src/babel/traversal/path/index.js
+++ b/src/babel/traversal/path/index.js
@@ -696,6 +696,9 @@ export default class TraversalPath {
     for (var fn of (fns: Array)) {
       if (!fn) continue;
 
+      var node = this.node;
+      if (!node) return;
+
       // call the function with the params (node, parent, scope, state)
       var replacement = fn.call(this, node, this.parent, this.scope, this.state);
       if (replacement) {
@@ -703,11 +706,11 @@ export default class TraversalPath {
         this.replaceWith(replacement, true);
         if (this.type !== previousType) {
           this.queueNode(this);
-          break;
+          return;
         }
       }
 
-      if (this.shouldStop || this.removed) break;
+      if (this.shouldStop || this.removed) return;
     }
   }
 

From 6e8ab16b25e96486b9f41f9e7965ae1927ee1807 Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Fri, 8 May 2015 00:22:23 +0100
Subject: [PATCH 09/30] run es6.spec.blockScoping transformer on exit rather
 than enter

---
 .../transformers/es6/spec.block-scoping.js     | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/src/babel/transformation/transformers/es6/spec.block-scoping.js b/src/babel/transformation/transformers/es6/spec.block-scoping.js
index 43699b2b1b..0ca41863a9 100644
--- a/src/babel/transformation/transformers/es6/spec.block-scoping.js
+++ b/src/babel/transformation/transformers/es6/spec.block-scoping.js
@@ -31,14 +31,16 @@ export var metadata = {
   optional: true
 };
 
-export function BlockStatement(node, parent, scope, file) {
-  var letRefs = node._letReferences;
-  if (!letRefs) return;
+export var BlockStatement = {
+  exit(node, parent, scope, file) {
+    var letRefs = node._letReferences;
+    if (!letRefs) return;
 
-  this.traverse(visitor, {
-    letRefs: letRefs,
-    file:    file
-  });
-}
+    this.traverse(visitor, {
+      letRefs: letRefs,
+      file:    file
+    });
+  }
+};
 
 export { BlockStatement as Program, BlockStatement as Loop };

From 8daf95bf5911f52ddeefeac3176741ab8b4b424c Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Fri, 8 May 2015 00:22:43 +0100
Subject: [PATCH 10/30] name additional methods that are now covered since the
 naming is done in tandem

---
 src/babel/transformation/transformers/spec/function-name.js | 5 ++++-
 .../es7.decorators/class-getter-and-setter/expected.js      | 6 +++---
 .../transformation/es7.decorators/class-getter/expected.js  | 4 ++--
 .../es7.decorators/class-init-instance-props/expected.js    | 4 ++--
 .../es7.decorators/class-init-static-props/expected.js      | 4 ++--
 .../transformation/es7.decorators/class-setter/expected.js  | 4 ++--
 .../transformation/es7.decorators/object/expected.js        | 2 +-
 7 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/src/babel/transformation/transformers/spec/function-name.js b/src/babel/transformation/transformers/spec/function-name.js
index bf31ee407a..928036e0be 100644
--- a/src/babel/transformation/transformers/spec/function-name.js
+++ b/src/babel/transformation/transformers/spec/function-name.js
@@ -1 +1,4 @@
-export { bare as FunctionExpression, bare as ArrowFunctionExpression } from "../../helpers/name-method";
+export {
+  bare as FunctionExpression,
+  bare as ArrowFunctionExpression
+} from "../../helpers/name-method";
diff --git a/test/core/fixtures/transformation/es7.decorators/class-getter-and-setter/expected.js b/test/core/fixtures/transformation/es7.decorators/class-getter-and-setter/expected.js
index 73f0d1d146..8e9b70a100 100644
--- a/test/core/fixtures/transformation/es7.decorators/class-getter-and-setter/expected.js
+++ b/test/core/fixtures/transformation/es7.decorators/class-getter-and-setter/expected.js
@@ -8,8 +8,8 @@ var Foo = (function () {
   babelHelpers.createDecoratedClass(Foo, [{
     key: "foo",
     decorators: [bar, foo],
-    get: function () {},
-    set: function (bar) {}
+    get: function get() {},
+    set: function set(bar) {}
   }]);
   return Foo;
-})();
\ No newline at end of file
+})();
diff --git a/test/core/fixtures/transformation/es7.decorators/class-getter/expected.js b/test/core/fixtures/transformation/es7.decorators/class-getter/expected.js
index 3beba2e582..06b1d2294e 100644
--- a/test/core/fixtures/transformation/es7.decorators/class-getter/expected.js
+++ b/test/core/fixtures/transformation/es7.decorators/class-getter/expected.js
@@ -8,7 +8,7 @@ var Foo = (function () {
   babelHelpers.createDecoratedClass(Foo, [{
     key: "foo",
     decorators: [bar],
-    get: function () {}
+    get: function get() {}
   }]);
   return Foo;
-})();
\ No newline at end of file
+})();
diff --git a/test/core/fixtures/transformation/es7.decorators/class-init-instance-props/expected.js b/test/core/fixtures/transformation/es7.decorators/class-init-instance-props/expected.js
index 6753403675..e564a5f47e 100644
--- a/test/core/fixtures/transformation/es7.decorators/class-init-instance-props/expected.js
+++ b/test/core/fixtures/transformation/es7.decorators/class-init-instance-props/expected.js
@@ -11,10 +11,10 @@ var Foo = (function () {
   babelHelpers.createDecoratedClass(Foo, [{
     key: "foo",
     decorators: [bar],
-    initializer: function () {
+    initializer: function initializer() {
       return "Bar";
     },
     enumerable: true
   }], null, _instanceInitializers);
   return Foo;
-})();
\ No newline at end of file
+})();
diff --git a/test/core/fixtures/transformation/es7.decorators/class-init-static-props/expected.js b/test/core/fixtures/transformation/es7.decorators/class-init-static-props/expected.js
index c365832ed7..8bdff77924 100644
--- a/test/core/fixtures/transformation/es7.decorators/class-init-static-props/expected.js
+++ b/test/core/fixtures/transformation/es7.decorators/class-init-static-props/expected.js
@@ -10,11 +10,11 @@ var Foo = (function () {
   babelHelpers.createDecoratedClass(Foo, null, [{
     key: "foo",
     decorators: [bar],
-    initializer: function () {
+    initializer: function initializer() {
       return "Bar";
     },
     enumerable: true
   }], null, _staticInitializers);
   babelHelpers.defineDecoratedPropertyDescriptor(Foo, "foo", _staticInitializers);
   return Foo;
-})();
\ No newline at end of file
+})();
diff --git a/test/core/fixtures/transformation/es7.decorators/class-setter/expected.js b/test/core/fixtures/transformation/es7.decorators/class-setter/expected.js
index ece61ab6e1..57426dd80c 100644
--- a/test/core/fixtures/transformation/es7.decorators/class-setter/expected.js
+++ b/test/core/fixtures/transformation/es7.decorators/class-setter/expected.js
@@ -8,7 +8,7 @@ var Foo = (function () {
   babelHelpers.createDecoratedClass(Foo, [{
     key: "foo",
     decorators: [bar],
-    set: function (arg) {}
+    set: function set(arg) {}
   }]);
   return Foo;
-})();
\ No newline at end of file
+})();
diff --git a/test/core/fixtures/transformation/es7.decorators/object/expected.js b/test/core/fixtures/transformation/es7.decorators/object/expected.js
index b6259d0cdc..efe805cf25 100644
--- a/test/core/fixtures/transformation/es7.decorators/object/expected.js
+++ b/test/core/fixtures/transformation/es7.decorators/object/expected.js
@@ -17,4 +17,4 @@ var obj = babelHelpers.createDecoratedObject([{
   initializer: function initializer() {
     return "wow";
   }
-}]);
\ No newline at end of file
+}]);

From 2621081a13ad7720e8c28a9dc8aa3a4b1086748a Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Fri, 8 May 2015 00:23:00 +0100
Subject: [PATCH 11/30] merge in astVisitor in runtime transformer - unsure why
 this was separate in the first place

---
 .../transformers/other/runtime/index.js       | 176 +++++++++---------
 1 file changed, 85 insertions(+), 91 deletions(-)

diff --git a/src/babel/transformation/transformers/other/runtime/index.js b/src/babel/transformation/transformers/other/runtime/index.js
index 972701e099..dbb3632d56 100644
--- a/src/babel/transformation/transformers/other/runtime/index.js
+++ b/src/babel/transformation/transformers/other/runtime/index.js
@@ -9,98 +9,11 @@ var isSymbolIterator = t.buildMatchMemberExpression("Symbol.iterator");
 
 const RUNTIME_MODULE_NAME = "babel-runtime";
 
-var astVisitor = traverse.explode({
-  Identifier(node, parent, scope, file) {
-    if (!this.isReferenced()) return;
-    if (t.isMemberExpression(parent)) return;
-    if (!has(definitions.builtins, node.name)) return;
-    if (scope.getBindingIdentifier(node.name)) return;
-
-    // Symbol() -> _core.Symbol(); new Promise -> new _core.Promise
-    var modulePath = definitions.builtins[node.name];
-    return file.addImport(`${RUNTIME_MODULE_NAME}/core-js/${modulePath}`, node.name, "absoluteDefault");
-  },
-
-  CallExpression(node, parent, scope, file) {
-    // arr[Symbol.iterator]() -> _core.$for.getIterator(arr)
-
-    var callee = node.callee;
-    if (node.arguments.length) return;
-
-    if (!t.isMemberExpression(callee)) return;
-    if (!callee.computed) return;
-
-    var prop = callee.property;
-    if (!isSymbolIterator(prop)) return;
-
-    return t.callExpression(file.addImport(`${RUNTIME_MODULE_NAME}/core-js/get-iterator`, "getIterator", "absoluteDefault"), [callee.object]);
-  },
-
-  BinaryExpression(node, parent, scope, file) {
-    // Symbol.iterator in arr -> core.$for.isIterable(arr)
-
-    if (node.operator !== "in") return;
-
-    var left = node.left;
-    if (!isSymbolIterator(left)) return;
-
-    return t.callExpression(
-      file.addImport(`${RUNTIME_MODULE_NAME}/core-js/is-iterable`, "isIterable", "absoluteDefault"),
-      [node.right]
-    );
-  },
-
-  MemberExpression: {
-    enter(node, parent, scope, file) {
-      // Array.from -> _core.Array.from
-
-      if (!this.isReferenced()) return;
-
-      var obj = node.object;
-      var prop = node.property;
-
-      if (!t.isReferenced(obj, node)) return;
-
-      if (node.computed) return;
-
-      if (!has(definitions.methods, obj.name)) return;
-
-      var methods = definitions.methods[obj.name];
-      if (!has(methods, prop.name)) return;
-
-      if (scope.getBindingIdentifier(obj.name)) return;
-
-      var modulePath = methods[prop.name];
-      return file.addImport(`${RUNTIME_MODULE_NAME}/core-js/${modulePath}`, `${obj.name}$${prop.name}`, "absoluteDefault");
-    },
-
-    exit(node, parent, scope, file) {
-      if (!this.isReferenced()) return;
-
-      var prop = node.property;
-      var obj  = node.object;
-
-      if (!has(definitions.builtins, obj.name)) return;
-      if (scope.getBindingIdentifier(obj.name)) return;
-
-      var modulePath = definitions.builtins[obj.name];
-      return t.memberExpression(
-        file.addImport(`${RUNTIME_MODULE_NAME}/core-js/${modulePath}`, `${obj.name}`, "absoluteDefault"),
-        prop
-      );
-    }
-  }
-});
-
-exports.metadata = {
+export var metadata = {
   optional: true
 };
 
-exports.Program = function (node, parent, scope, file) {
-  this.traverse(astVisitor, file);
-};
-
-exports.pre = function (file) {
+export function pre(file) {
   file.set("helperGenerator", function (name) {
     return file.addImport(`${RUNTIME_MODULE_NAME}/helpers/${name}`, name, "absoluteDefault");
   });
@@ -108,10 +21,91 @@ exports.pre = function (file) {
   file.setDynamic("regeneratorIdentifier", function () {
     return file.addImport(`${RUNTIME_MODULE_NAME}/regenerator`, "regeneratorRuntime", "absoluteDefault");
   });
+}
+
+export function Identifier(node, parent, scope, file) {
+  if (!this.isReferenced()) return;
+  if (t.isMemberExpression(parent)) return;
+  if (!has(definitions.builtins, node.name)) return;
+  if (scope.getBindingIdentifier(node.name)) return;
+
+  // Symbol() -> _core.Symbol(); new Promise -> new _core.Promise
+  var modulePath = definitions.builtins[node.name];
+  return file.addImport(`${RUNTIME_MODULE_NAME}/core-js/${modulePath}`, node.name, "absoluteDefault");
+}
+
+export function CallExpression(node, parent, scope, file) {
+  // arr[Symbol.iterator]() -> _core.$for.getIterator(arr)
+
+  var callee = node.callee;
+  if (node.arguments.length) return;
+
+  if (!t.isMemberExpression(callee)) return;
+  if (!callee.computed) return;
+
+  var prop = callee.property;
+  if (!isSymbolIterator(prop)) return;
+
+  return t.callExpression(file.addImport(`${RUNTIME_MODULE_NAME}/core-js/get-iterator`, "getIterator", "absoluteDefault"), [callee.object]);
+}
+
+export function BinaryExpression(node, parent, scope, file) {
+  // Symbol.iterator in arr -> core.$for.isIterable(arr)
+
+  if (node.operator !== "in") return;
+
+  var left = node.left;
+  if (!isSymbolIterator(left)) return;
+
+  return t.callExpression(
+    file.addImport(`${RUNTIME_MODULE_NAME}/core-js/is-iterable`, "isIterable", "absoluteDefault"),
+    [node.right]
+  );
+}
+
+export var MemberExpression = {
+  enter(node, parent, scope, file) {
+    // Array.from -> _core.Array.from
+
+    if (!this.isReferenced()) return;
+
+    var obj = node.object;
+    var prop = node.property;
+
+    if (!t.isReferenced(obj, node)) return;
+
+    if (node.computed) return;
+
+    if (!has(definitions.methods, obj.name)) return;
+
+    var methods = definitions.methods[obj.name];
+    if (!has(methods, prop.name)) return;
+
+    if (scope.getBindingIdentifier(obj.name)) return;
+
+    var modulePath = methods[prop.name];
+    return file.addImport(`${RUNTIME_MODULE_NAME}/core-js/${modulePath}`, `${obj.name}$${prop.name}`, "absoluteDefault");
+  },
+
+  exit(node, parent, scope, file) {
+    if (!this.isReferenced()) return;
+
+    var prop = node.property;
+    var obj  = node.object;
+
+    if (!has(definitions.builtins, obj.name)) return;
+    if (scope.getBindingIdentifier(obj.name)) return;
+
+    var modulePath = definitions.builtins[obj.name];
+    return t.memberExpression(
+      file.addImport(`${RUNTIME_MODULE_NAME}/core-js/${modulePath}`, `${obj.name}`, "absoluteDefault"),
+      prop
+    );
+  }
 };
 
-exports.Identifier = function (node, parent, scope, file) {
+export function Identifier(node, parent, scope, file) {
   if (this.isReferencedIdentifier({ name: "regeneratorRuntime" })) {
     return file.get("regeneratorIdentifier");
   }
-};
+}

From 2fbb3cad9f67a5bb5e9f9f768d69cd10141c0035 Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Fri, 8 May 2015 00:23:28 +0100
Subject: [PATCH 12/30] add isUser and isGenerated path methods

---
 src/babel/traversal/path/index.js | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/src/babel/traversal/path/index.js b/src/babel/traversal/path/index.js
index 6ac9cc1819..68735963d8 100644
--- a/src/babel/traversal/path/index.js
+++ b/src/babel/traversal/path/index.js
@@ -125,6 +125,22 @@ export default class TraversalPath {
     return false;
   }
 
+  /**
+   * Check whether this node was a part of the original AST.
+   */
+
+  isUser() {
+    return this.node && !!this.node.loc;
+  }
+
+  /**
+   * Check whether this node was generated by us and not a part of the original AST.
+   */
+
+  isGenerated() {
+    return !this.isUser();
+  }
+
   /**
    * Description
    */

From 78b72512cbbf620f58de318f44c1da853ab3bafa Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Fri, 8 May 2015 00:24:04 +0100
Subject: [PATCH 13/30] better verify the type of the new node before
 requeueing it and also stop current node traversal on skip

---
 src/babel/traversal/path/index.js | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/babel/traversal/path/index.js b/src/babel/traversal/path/index.js
index 68735963d8..1988f661ff 100644
--- a/src/babel/traversal/path/index.js
+++ b/src/babel/traversal/path/index.js
@@ -717,16 +717,19 @@ export default class TraversalPath {
 
       // call the function with the params (node, parent, scope, state)
       var replacement = fn.call(this, node, this.parent, this.scope, this.state);
+
       if (replacement) {
         var previousType = this.type;
+
         this.replaceWith(replacement, true);
-        if (this.type !== previousType) {
+
+        if (previousType !== this.type) {
           this.queueNode(this);
           return;
         }
       }
 
-      if (this.shouldStop || this.removed) return;
+      if (this.shouldStop || this.shouldSkip || this.removed) return;
     }
   }
 

From 5b793f88824f23285f360657836184adb3a52f69 Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Fri, 8 May 2015 15:25:34 +0100
Subject: [PATCH 14/30] fix TraversalPath#_getPattern incorrectly iterating
 over the parts

---
 src/babel/traversal/path/index.js | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/babel/traversal/path/index.js b/src/babel/traversal/path/index.js
index 1988f661ff..1cbe84ce59 100644
--- a/src/babel/traversal/path/index.js
+++ b/src/babel/traversal/path/index.js
@@ -820,8 +820,7 @@ export default class TraversalPath {
 
   _getPattern(parts) {
     var path = this;
-    for (var i = 0; i > parts.length; i++) {
-      var part = parts[i];
+    for (var part of (parts: Array)) {
       if (part === ".") {
         path = path.parentPath;
       } else {

From 8f52229a868d278c930f5336e6be6373d9f3fa01 Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Fri, 8 May 2015 15:25:50 +0100
Subject: [PATCH 15/30] add get function name to source map classes test

---
 test/core/fixtures/transformation/source-maps/class/expected.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/core/fixtures/transformation/source-maps/class/expected.js b/test/core/fixtures/transformation/source-maps/class/expected.js
index 25517b3e99..c9b2c12183 100644
--- a/test/core/fixtures/transformation/source-maps/class/expected.js
+++ b/test/core/fixtures/transformation/source-maps/class/expected.js
@@ -7,7 +7,7 @@ var Test = (function () {
 
   babelHelpers.createClass(Test, [{
     key: "bar",
-    get: function () {
+    get: function get() {
       throw new Error("wow");
     }
   }]);

From ba516901aff678563a0c39a29a944af46956788b Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Fri, 8 May 2015 15:26:00 +0100
Subject: [PATCH 16/30] restructure transformers into multiple categories

---
 src/babel/transformation/index.js             |  2 +-
 .../es3/member-expression-literals.js         |  4 +++
 .../transformers/es3/property-literals.js     |  4 +++
 .../transformers/es6/block-scoping.js         |  4 +++
 .../transformers/es6/modules.js               |  4 +++
 .../transformers/es6/spec.block-scoping.js    |  3 +-
 .../transformation/transformers/index.js      | 25 +++++++++++------
 .../transformers/internal/block-hoist.js      |  4 +++
 .../transformers/internal/module-formatter.js |  4 +++
 .../member-expression-literals.js             |  3 +-
 .../minification/property-literals.js         |  3 +-
 .../transformation/transformers/other/flow.js |  1 -
 .../transformers/other/regenerator.js         |  4 +++
 .../transformers/other/runtime/index.js       | 28 ++++++++-----------
 14 files changed, 62 insertions(+), 31 deletions(-)

diff --git a/src/babel/transformation/index.js b/src/babel/transformation/index.js
index 3f71068bc2..5a523a4ea2 100644
--- a/src/babel/transformation/index.js
+++ b/src/babel/transformation/index.js
@@ -9,7 +9,7 @@ import transformers from "./transformers";
 for (var key in transformers) {
   var transformer = transformers[key];
   var metadata = transformer.metadata = transformer.metadata || {};
-  metadata.category = metadata.category || "builtin";
+  metadata.category = metadata.category || "builtin-basic";
 }
 
 pipeline.addTransformers(transformers);
diff --git a/src/babel/transformation/transformers/es3/member-expression-literals.js b/src/babel/transformation/transformers/es3/member-expression-literals.js
index 1665d20b25..d4465fde70 100644
--- a/src/babel/transformation/transformers/es3/member-expression-literals.js
+++ b/src/babel/transformation/transformers/es3/member-expression-literals.js
@@ -1,5 +1,9 @@
 import * as t from "../../../types";
 
+export var metadata = {
+  category: "builtin-cleanup"
+};
+
 export var MemberExpression = {
   exit(node) {
     var prop = node.property;
diff --git a/src/babel/transformation/transformers/es3/property-literals.js b/src/babel/transformation/transformers/es3/property-literals.js
index f70a81661b..ecfd63c8dd 100644
--- a/src/babel/transformation/transformers/es3/property-literals.js
+++ b/src/babel/transformation/transformers/es3/property-literals.js
@@ -1,5 +1,9 @@
 import * as t from "../../../types";
 
+export var metadata = {
+  category: "builtin-cleanup"
+};
+
 export var Property = {
   exit(node) {
     var key = node.key;
diff --git a/src/babel/transformation/transformers/es6/block-scoping.js b/src/babel/transformation/transformers/es6/block-scoping.js
index 850dca35f0..515c0711e9 100644
--- a/src/babel/transformation/transformers/es6/block-scoping.js
+++ b/src/babel/transformation/transformers/es6/block-scoping.js
@@ -37,6 +37,10 @@ function standardizeLets(declars) {
   }
 }
 
+export var metadata = {
+  category: "builtin-advanced"
+};
+
 export function VariableDeclaration(node, parent, scope, file) {
   if (!isLet(node, parent)) return;
 
diff --git a/src/babel/transformation/transformers/es6/modules.js b/src/babel/transformation/transformers/es6/modules.js
index 6141ab9217..80772e3163 100644
--- a/src/babel/transformation/transformers/es6/modules.js
+++ b/src/babel/transformation/transformers/es6/modules.js
@@ -8,6 +8,10 @@ function keepBlockHoist(node, nodes) {
   }
 }
 
+export var metadata = {
+  category: "builtin-modules"
+};
+
 export function ImportDeclaration(node, parent, scope, file) {
   // flow type
   if (node.isType) return;
diff --git a/src/babel/transformation/transformers/es6/spec.block-scoping.js b/src/babel/transformation/transformers/es6/spec.block-scoping.js
index 0ca41863a9..6906b1d7c1 100644
--- a/src/babel/transformation/transformers/es6/spec.block-scoping.js
+++ b/src/babel/transformation/transformers/es6/spec.block-scoping.js
@@ -28,7 +28,8 @@ var visitor = traverse.explode({
 });
 
 export var metadata = {
-  optional: true
+  optional: true,
+  category: "builtin-advanced"
 };
 
 export var BlockStatement = {
diff --git a/src/babel/transformation/transformers/index.js b/src/babel/transformation/transformers/index.js
index 0c3ea89b1d..a4e0317b84 100644
--- a/src/babel/transformation/transformers/index.js
+++ b/src/babel/transformation/transformers/index.js
@@ -1,4 +1,5 @@
 export default {
+  // builtin-basic
   "utility.removeDebugger":                require("./utility/remove-debugger"),
   "utility.removeConsole":                 require("./utility/remove-console"),
   "utility.inlineEnvironmentVariables":    require("./utility/inline-environment-variables"),
@@ -41,26 +42,32 @@ export default {
   "es6.spread":                            require("./es6/spread"),
   "es6.parameters.default":                require("./es6/parameters.default"),
   "es6.destructuring":                     require("./es6/destructuring"),
-  "es6.blockScoping":                      require("./es6/block-scoping"),
-  "es6.spec.blockScoping":                 require("./es6/spec.block-scoping"),
   "es6.tailCall":                          require("./es6/tail-call"),
-  regenerator:                             require("./other/regenerator"),
-  runtime:                                 require("./other/runtime"),
   "es7.exportExtensions":                  require("./es7/export-extensions"),
-  "es6.modules":                           require("./es6/modules"),
   "spec.protoToAssign":                    require("./spec/proto-to-assign"),
   _shadowFunctions:                        require("./internal/shadow-functions"),
   "es7.doExpressions":                     require("./es7/do-expressions"),
   "es6.spec.symbols":                      require("./es6/spec.symbols"),
   ludicrous:                               require("./other/ludicrous"),
   "spec.undefinedToVoid":                  require("./spec/undefined-to-void"),
+  jscript:                                 require("./other/jscript"),
+  flow:                                    require("./other/flow"),
+  _hoistDirectives:                        require("./internal/hoist-directives"),
+
+  // builtin-modules
+  "es6.modules":                           require("./es6/modules"),
+  regenerator:                             require("./other/regenerator"),
+  runtime:                                 require("./other/runtime"),
   _moduleFormatter:                        require("./internal/module-formatter"),
+
+  // builtin-advanced
+  "es6.blockScoping":                      require("./es6/block-scoping"),
+  "es6.spec.blockScoping":                 require("./es6/spec.block-scoping"),
+
+  // builtin-cleanup
   "es3.propertyLiterals":                  require("./es3/property-literals"),
   "es3.memberExpressionLiterals":          require("./es3/member-expression-literals"),
   "minification.memberExpressionLiterals": require("./minification/member-expression-literals"),
   "minification.propertyLiterals":         require("./minification/property-literals"),
-  jscript:                                 require("./other/jscript"),
-  flow:                                    require("./other/flow"),
-  _hoistDirectives:                        require("./internal/hoist-directives"),
-  _blockHoist:                             require("./internal/block-hoist")
+  _blockHoist:                             require("./internal/block-hoist"),
 };
diff --git a/src/babel/transformation/transformers/internal/block-hoist.js b/src/babel/transformation/transformers/internal/block-hoist.js
index b732e2b2f3..700d91b2a9 100644
--- a/src/babel/transformation/transformers/internal/block-hoist.js
+++ b/src/babel/transformation/transformers/internal/block-hoist.js
@@ -1,5 +1,9 @@
 import sortBy from "lodash/collection/sortBy";
 
+export var metadata = {
+  category: "builtin-cleanup"
+};
+
 // Priority:
 //
 //  - 0 We want this to be at the **very** bottom
diff --git a/src/babel/transformation/transformers/internal/module-formatter.js b/src/babel/transformation/transformers/internal/module-formatter.js
index 00cd641998..da48d94c6d 100644
--- a/src/babel/transformation/transformers/internal/module-formatter.js
+++ b/src/babel/transformation/transformers/internal/module-formatter.js
@@ -1,5 +1,9 @@
 import * as strict from "../../helpers/strict";
 
+export var metadata = {
+  category: "builtin-modules"
+};
+
 export var Program = {
   exit(program, parent, scope, file) {
     strict.wrap(program, function () {
diff --git a/src/babel/transformation/transformers/minification/member-expression-literals.js b/src/babel/transformation/transformers/minification/member-expression-literals.js
index fe8862dc8c..a7d9823535 100644
--- a/src/babel/transformation/transformers/minification/member-expression-literals.js
+++ b/src/babel/transformation/transformers/minification/member-expression-literals.js
@@ -1,7 +1,8 @@
 import * as t from "../../../types";
 
 export var metadata = {
-  optional: true
+  optional: true,
+  category: "builtin-cleanup"
 };
 
 export var MemberExpression = {
diff --git a/src/babel/transformation/transformers/minification/property-literals.js b/src/babel/transformation/transformers/minification/property-literals.js
index c85769a4e8..d1d682fbdb 100644
--- a/src/babel/transformation/transformers/minification/property-literals.js
+++ b/src/babel/transformation/transformers/minification/property-literals.js
@@ -1,7 +1,8 @@
 import * as t from "../../../types";
 
 export var metadata = {
-  optional: true
+  optional: true,
+  category: "builtin-cleanup"
 };
 
 export var Property = {
diff --git a/src/babel/transformation/transformers/other/flow.js b/src/babel/transformation/transformers/other/flow.js
index bb6bf4c393..14fc5bcbc4 100644
--- a/src/babel/transformation/transformers/other/flow.js
+++ b/src/babel/transformation/transformers/other/flow.js
@@ -6,7 +6,6 @@ export function Flow(node) {
 
 export function ClassProperty(node) {
   node.typeAnnotation = null;
-  if (!node.value) this.remove();
 }
 
 export function Class(node) {
diff --git a/src/babel/transformation/transformers/other/regenerator.js b/src/babel/transformation/transformers/other/regenerator.js
index 2897527cd1..9d1b17e675 100644
--- a/src/babel/transformation/transformers/other/regenerator.js
+++ b/src/babel/transformation/transformers/other/regenerator.js
@@ -1,6 +1,10 @@
 import regenerator from "regenerator";
 import * as t from "../../../types";
 
+export var metadata = {
+  category: "builtin-modules"
+};
+
 export var Program = {
   exit(ast) {
     regenerator.transform(ast);
diff --git a/src/babel/transformation/transformers/other/runtime/index.js b/src/babel/transformation/transformers/other/runtime/index.js
index dbb3632d56..3fa283268d 100644
--- a/src/babel/transformation/transformers/other/runtime/index.js
+++ b/src/babel/transformation/transformers/other/runtime/index.js
@@ -10,10 +10,11 @@ var isSymbolIterator = t.buildMatchMemberExpression("Symbol.iterator");
 const RUNTIME_MODULE_NAME = "babel-runtime";
 
 export var metadata = {
-  optional: true
+  optional: true,
+  category: "builtin-modules"
 };
 
-export function pre(file) {
+export function Program(node, parent, scope, file) {
   file.set("helperGenerator", function (name) {
     return file.addImport(`${RUNTIME_MODULE_NAME}/helpers/${name}`, name, "absoluteDefault");
   });
@@ -23,8 +24,11 @@ export function pre(file) {
   });
 }
 
-export function Identifier(node, parent, scope, file) {
-  if (!this.isReferenced()) return;
+export function ReferencedIdentifier(node, parent, scope, file) {
+  if (node.name === "regeneratorRuntime") {
+    return file.get("regeneratorIdentifier");
+  }
+
   if (t.isMemberExpression(parent)) return;
   if (!has(definitions.builtins, node.name)) return;
   if (scope.getBindingIdentifier(node.name)) return;
@@ -37,14 +41,12 @@ export function Identifier(node, parent, scope, file) {
 export function CallExpression(node, parent, scope, file) {
   // arr[Symbol.iterator]() -> _core.$for.getIterator(arr)
 
-  var callee = node.callee;
   if (node.arguments.length) return;
 
+  var callee = node.callee;
   if (!t.isMemberExpression(callee)) return;
   if (!callee.computed) return;
-
-  var prop = callee.property;
-  if (!isSymbolIterator(prop)) return;
+  if (!this.get("callee.property").matchesPattern("Symbol.iterator")) return;
 
   return t.callExpression(file.addImport(`${RUNTIME_MODULE_NAME}/core-js/get-iterator`, "getIterator", "absoluteDefault"), [callee.object]);
 }
@@ -53,9 +55,7 @@ export function BinaryExpression(node, parent, scope, file) {
   // Symbol.iterator in arr -> core.$for.isIterable(arr)
 
   if (node.operator !== "in") return;
-
-  var left = node.left;
-  if (!isSymbolIterator(left)) return;
+  if (!this.get("left").matchesPattern("Symbol.iterator")) return;
 
   return t.callExpression(
     file.addImport(`${RUNTIME_MODULE_NAME}/core-js/is-iterable`, "isIterable", "absoluteDefault"),
@@ -103,9 +103,3 @@ export var MemberExpression = {
     );
   }
 };
-
-export function Identifier(node, parent, scope, file) {
-  if (this.isReferencedIdentifier({ name: "regeneratorRuntime" })) {
-    return file.get("regeneratorIdentifier");
-  }
-}

From c526a3eb0424e9b24479ca2e2d8237d28512a53c Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Fri, 8 May 2015 15:51:56 +0100
Subject: [PATCH 17/30] move shadow-functions internal transformer to
 builtin-cleanup category

---
 .../transformation/transformers/internal/shadow-functions.js  | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/babel/transformation/transformers/internal/shadow-functions.js b/src/babel/transformation/transformers/internal/shadow-functions.js
index 30925d8a8f..decec95409 100644
--- a/src/babel/transformation/transformers/internal/shadow-functions.js
+++ b/src/babel/transformation/transformers/internal/shadow-functions.js
@@ -85,6 +85,10 @@ function aliasFunction(getBody, path, scope) {
 // todo: on all `this` and `arguments`, walk UP the tree instead of
 // crawling the entire function tree
 
+export var metadata = {
+  category: "builtin-cleanup"
+};
+
 export var Program = {
   exit(node, parent, scope) {
     aliasFunction(function () {

From 4a439d8c8e04cc4d8ef78d568abc754868e7958d Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Fri, 8 May 2015 15:52:08 +0100
Subject: [PATCH 18/30] update flow strip type annotations test

---
 .../flow/strip-type-annotations/expected.js            | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/test/core/fixtures/transformation/flow/strip-type-annotations/expected.js b/test/core/fixtures/transformation/flow/strip-type-annotations/expected.js
index 6a52c762fc..277f1ad2f0 100644
--- a/test/core/fixtures/transformation/flow/strip-type-annotations/expected.js
+++ b/test/core/fixtures/transformation/flow/strip-type-annotations/expected.js
@@ -64,8 +64,14 @@ class Foo8 {
   "bar"() {}
 }
 function foo(requiredParam, optParam) {}
-class Foo9 {}
-class Foo10 {}
+class Foo9 {
+  prop1;
+  prop2;
+}
+class Foo10 {
+  static prop1;
+  prop2;
+}
 var x = 4;
 class Array {
   concat(items) {}

From abf4a5495a08938f5d2feffbcf0f3dd17b4112c0 Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Fri, 8 May 2015 22:51:47 +0100
Subject: [PATCH 19/30] don't pretty print variable declarators in concise mode

---
 src/babel/generation/generators/statements.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/babel/generation/generators/statements.js b/src/babel/generation/generators/statements.js
index 5a9b0067d6..81ba6f2c83 100644
--- a/src/babel/generation/generators/statements.js
+++ b/src/babel/generation/generators/statements.js
@@ -191,7 +191,7 @@ export function VariableDeclaration(node, print, parent) {
   }
 
   var sep = ",";
-  if (!this.format.compact && hasInits && !this.format.retainLines) {
+  if (!this.format.compact && !this.format.concise && hasInits && !this.format.retainLines) {
     sep += `\n${repeating(" ", node.kind.length + 1)}`;
   } else {
     sep += " ";

From 2a9a59f7842402e7308d9ba74bdb83eab5e4d476 Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Fri, 8 May 2015 22:52:02 +0100
Subject: [PATCH 20/30] remove incomplete ludicrous transformer

---
 .../templates/helper-ludicrous-in.js          |  1 -
 .../helper-ludicrous-proxy-create.js          |  4 --
 .../helper-ludicrous-proxy-directory.js       |  1 -
 .../transformers/other/ludicrous.js           | 66 -------------------
 4 files changed, 72 deletions(-)
 delete mode 100644 src/babel/transformation/templates/helper-ludicrous-in.js
 delete mode 100644 src/babel/transformation/templates/helper-ludicrous-proxy-create.js
 delete mode 100644 src/babel/transformation/templates/helper-ludicrous-proxy-directory.js
 delete mode 100644 src/babel/transformation/transformers/other/ludicrous.js

diff --git a/src/babel/transformation/templates/helper-ludicrous-in.js b/src/babel/transformation/templates/helper-ludicrous-in.js
deleted file mode 100644
index 80348f0da7..0000000000
--- a/src/babel/transformation/templates/helper-ludicrous-in.js
+++ /dev/null
@@ -1 +0,0 @@
-Object(RIGHT)[LEFT] !== undefined;
diff --git a/src/babel/transformation/templates/helper-ludicrous-proxy-create.js b/src/babel/transformation/templates/helper-ludicrous-proxy-create.js
deleted file mode 100644
index 8ecc6af771..0000000000
--- a/src/babel/transformation/templates/helper-ludicrous-proxy-create.js
+++ /dev/null
@@ -1,4 +0,0 @@
-(function (proxy, directory) {
-  directory.push(proxy);
-  return proxy;
-})
diff --git a/src/babel/transformation/templates/helper-ludicrous-proxy-directory.js b/src/babel/transformation/templates/helper-ludicrous-proxy-directory.js
deleted file mode 100644
index 5e1ab7855e..0000000000
--- a/src/babel/transformation/templates/helper-ludicrous-proxy-directory.js
+++ /dev/null
@@ -1 +0,0 @@
-[];
diff --git a/src/babel/transformation/transformers/other/ludicrous.js b/src/babel/transformation/transformers/other/ludicrous.js
deleted file mode 100644
index d2c56bb118..0000000000
--- a/src/babel/transformation/transformers/other/ludicrous.js
+++ /dev/null
@@ -1,66 +0,0 @@
-import * as t from "../../../types";
-import * as util from "../../../util";
-
-export var metadata = {
-  optional: true
-};
-
-// foo in bar
-export function BinaryExpression(node) {
-  if (node.operator === "in") {
-    return util.template("ludicrous-in", {
-      LEFT: node.left,
-      RIGHT: node.right
-    });
-  }
-}
-
-// { 1: "foo" }
-export function Property(node) {
-  var key = node.key;
-  if (t.isLiteral(key) && typeof key.value === "number") {
-    key.value = "" + key.value;
-  }
-}
-
-// /foobar/g
-export function Literal(node) {
-  if (node.regex) {
-    node.regex.pattern = "foobar";
-    node.regex.flags = "";
-  }
-}
-
-// foo.bar
-export function MemberExpression(node) {
-
-}
-
-// Object.setPrototypeOf
-// Object.preventExtensions
-// Object.keys
-// Object.isExtensible
-// Object.getOwnPropertyDescriptor
-// Object.defineProperty
-export function CallExpression(node) {
-
-}
-
-// delete foo.bar
-export function UnaryExpression(node) {
-
-}
-
-// foo.bar = bar;
-export function AssignmentExpression(node) {
-
-}
-
-// new Proxy
-export function NewExpression(node, parent, scope, file) {
-  if (this.get("callee").isIdentifier({ name: "Proxy" })) {
-    return t.callExpression(file.addHelper("proxy-create"), [node.arguments[0], file.addHelper("proxy-directory")]);
-  } else {
-    // possible proxy constructor
-  }
-}

From d6a5c390791a738a57fe973f925ca158c765ab17 Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Fri, 8 May 2015 22:52:19 +0100
Subject: [PATCH 21/30] update classes to reflect new transformer precedence

---
 .../exports-default/expected.js               |  6 ++---
 .../exports-from/expected.js                  |  8 +++----
 .../exports-named/expected.js                 |  6 ++---
 .../exports-variable/expected.js              |  6 ++---
 .../get-module-name-option/expected.js        |  8 +++----
 .../hoist-function-exports/expected.js        |  6 ++---
 .../imports-default/expected.js               |  8 +++----
 .../imports-glob/expected.js                  |  8 +++----
 .../imports-mixing/expected.js                |  8 +++----
 .../imports-named/expected.js                 |  8 +++----
 .../es6.modules-system/imports/expected.js    |  8 +++----
 .../es6.modules-system/overview/expected.js   |  6 ++---
 .../es6.modules-system/remap/expected.js      |  6 ++---
 .../class-getter-and-setter/expected.js       |  4 ++--
 .../es7.decorators/class-getter/expected.js   |  2 +-
 .../class-init-instance-props/expected.js     |  2 +-
 .../class-init-static-props/expected.js       |  2 +-
 .../es7.decorators/class-setter/expected.js   |  2 +-
 .../object-getter-and-setter/actual.js        |  2 +-
 .../object-getter-and-setter/expected.js      |  4 ++--
 .../es7.decorators/object-getter/expected.js  |  2 +-
 .../es7.decorators/object-setter/actual.js    |  2 +-
 .../es7.decorators/object-setter/expected.js  |  2 +-
 .../es7.decorators/object/expected.js         |  8 +++----
 .../transformation/runtime/full/expected.js   | 23 ++++++++++---------
 .../source-maps/class/expected.js             |  2 +-
 26 files changed, 75 insertions(+), 74 deletions(-)

diff --git a/test/core/fixtures/transformation/es6.modules-system/exports-default/expected.js b/test/core/fixtures/transformation/es6.modules-system/exports-default/expected.js
index 453baf6142..7854fc3ce8 100644
--- a/test/core/fixtures/transformation/es6.modules-system/exports-default/expected.js
+++ b/test/core/fixtures/transformation/es6.modules-system/exports-default/expected.js
@@ -1,4 +1,6 @@
 System.register([], function (_export) {
+  "use strict";
+
   var _default, Foo;
 
   _export("default", foo);
@@ -10,8 +12,6 @@ System.register([], function (_export) {
   return {
     setters: [],
     execute: function () {
-      "use strict";
-
       _export("default", 42);
 
       _export("default", {});
@@ -39,4 +39,4 @@ System.register([], function (_export) {
       _export("default", Foo);
     }
   };
-});
\ No newline at end of file
+});
diff --git a/test/core/fixtures/transformation/es6.modules-system/exports-from/expected.js b/test/core/fixtures/transformation/es6.modules-system/exports-from/expected.js
index c1eaca763d..b7b8242360 100644
--- a/test/core/fixtures/transformation/es6.modules-system/exports-from/expected.js
+++ b/test/core/fixtures/transformation/es6.modules-system/exports-from/expected.js
@@ -1,4 +1,6 @@
 System.register(["foo"], function (_export) {
+  "use strict";
+
   return {
     setters: [function (_foo) {
       for (var _key in _foo) {
@@ -19,8 +21,6 @@ System.register(["foo"], function (_export) {
 
       _export("bar", _foo.bar);
     }],
-    execute: function () {
-      "use strict";
-    }
+    execute: function () {}
   };
-});
\ No newline at end of file
+});
diff --git a/test/core/fixtures/transformation/es6.modules-system/exports-named/expected.js b/test/core/fixtures/transformation/es6.modules-system/exports-named/expected.js
index 410345bcfa..86487ee2f5 100644
--- a/test/core/fixtures/transformation/es6.modules-system/exports-named/expected.js
+++ b/test/core/fixtures/transformation/es6.modules-system/exports-named/expected.js
@@ -1,9 +1,9 @@
 System.register([], function (_export) {
+  "use strict";
+
   return {
     setters: [],
     execute: function () {
-      "use strict";
-
       _export("foo", foo);
 
       _export("foo", foo);
@@ -19,4 +19,4 @@ System.register([], function (_export) {
       _export("bar", bar);
     }
   };
-});
\ No newline at end of file
+});
diff --git a/test/core/fixtures/transformation/es6.modules-system/exports-variable/expected.js b/test/core/fixtures/transformation/es6.modules-system/exports-variable/expected.js
index c5ab473b75..bc93dd73b5 100644
--- a/test/core/fixtures/transformation/es6.modules-system/exports-variable/expected.js
+++ b/test/core/fixtures/transformation/es6.modules-system/exports-variable/expected.js
@@ -1,4 +1,6 @@
 System.register([], function (_export) {
+  "use strict";
+
   var foo, foo2, foo3, foo4, foo5, foo6, foo8;
 
   _export("foo7", foo7);
@@ -10,8 +12,6 @@ System.register([], function (_export) {
   return {
     setters: [],
     execute: function () {
-      "use strict";
-
       foo = 1;
 
       _export("foo", foo);
@@ -43,4 +43,4 @@ System.register([], function (_export) {
       _export("foo3", foo3 = 5);
     }
   };
-});
\ No newline at end of file
+});
diff --git a/test/core/fixtures/transformation/es6.modules-system/get-module-name-option/expected.js b/test/core/fixtures/transformation/es6.modules-system/get-module-name-option/expected.js
index 0f7fc369ae..0def1f9524 100644
--- a/test/core/fixtures/transformation/es6.modules-system/get-module-name-option/expected.js
+++ b/test/core/fixtures/transformation/es6.modules-system/get-module-name-option/expected.js
@@ -1,8 +1,8 @@
 System.register("my custom module name", [], function (_export) {
+  "use strict";
+
   return {
     setters: [],
-    execute: function () {
-      "use strict";
-    }
+    execute: function () {}
   };
-});
\ No newline at end of file
+});
diff --git a/test/core/fixtures/transformation/es6.modules-system/hoist-function-exports/expected.js b/test/core/fixtures/transformation/es6.modules-system/hoist-function-exports/expected.js
index 4056aa7a5e..ad3421dd2e 100644
--- a/test/core/fixtures/transformation/es6.modules-system/hoist-function-exports/expected.js
+++ b/test/core/fixtures/transformation/es6.modules-system/hoist-function-exports/expected.js
@@ -1,4 +1,6 @@
 System.register(["./evens"], function (_export) {
+  "use strict";
+
   var isEven, p, isOdd;
 
   _export("nextOdd", nextOdd);
@@ -12,8 +14,6 @@ System.register(["./evens"], function (_export) {
       isEven = _evens.isEven;
     }],
     execute: function () {
-      "use strict";
-
       p = 5;
 
       _export("p", p);
@@ -27,4 +27,4 @@ System.register(["./evens"], function (_export) {
       _export("isOdd", isOdd);
     }
   };
-});
\ No newline at end of file
+});
diff --git a/test/core/fixtures/transformation/es6.modules-system/imports-default/expected.js b/test/core/fixtures/transformation/es6.modules-system/imports-default/expected.js
index 2cb90409c2..16a71b2ed4 100644
--- a/test/core/fixtures/transformation/es6.modules-system/imports-default/expected.js
+++ b/test/core/fixtures/transformation/es6.modules-system/imports-default/expected.js
@@ -1,12 +1,12 @@
 System.register(["foo"], function (_export) {
+  "use strict";
+
   var foo, foo2;
   return {
     setters: [function (_foo) {
       foo = _foo["default"];
       foo2 = _foo["default"];
     }],
-    execute: function () {
-      "use strict";
-    }
+    execute: function () {}
   };
-});
\ No newline at end of file
+});
diff --git a/test/core/fixtures/transformation/es6.modules-system/imports-glob/expected.js b/test/core/fixtures/transformation/es6.modules-system/imports-glob/expected.js
index 67e60e45ca..5df9008d7c 100644
--- a/test/core/fixtures/transformation/es6.modules-system/imports-glob/expected.js
+++ b/test/core/fixtures/transformation/es6.modules-system/imports-glob/expected.js
@@ -1,11 +1,11 @@
 System.register(["foo"], function (_export) {
+  "use strict";
+
   var foo;
   return {
     setters: [function (_foo) {
       foo = _foo;
     }],
-    execute: function () {
-      "use strict";
-    }
+    execute: function () {}
   };
-});
\ No newline at end of file
+});
diff --git a/test/core/fixtures/transformation/es6.modules-system/imports-mixing/expected.js b/test/core/fixtures/transformation/es6.modules-system/imports-mixing/expected.js
index 9ac0cd5ce2..786d2e6869 100644
--- a/test/core/fixtures/transformation/es6.modules-system/imports-mixing/expected.js
+++ b/test/core/fixtures/transformation/es6.modules-system/imports-mixing/expected.js
@@ -1,12 +1,12 @@
 System.register(["foo"], function (_export) {
+  "use strict";
+
   var foo, xyz;
   return {
     setters: [function (_foo) {
       foo = _foo["default"];
       xyz = _foo.baz;
     }],
-    execute: function () {
-      "use strict";
-    }
+    execute: function () {}
   };
-});
\ No newline at end of file
+});
diff --git a/test/core/fixtures/transformation/es6.modules-system/imports-named/expected.js b/test/core/fixtures/transformation/es6.modules-system/imports-named/expected.js
index b66550bded..e6704667be 100644
--- a/test/core/fixtures/transformation/es6.modules-system/imports-named/expected.js
+++ b/test/core/fixtures/transformation/es6.modules-system/imports-named/expected.js
@@ -1,4 +1,6 @@
 System.register(["foo"], function (_export) {
+  "use strict";
+
   var bar, bar2, baz, baz2, baz3, xyz;
   return {
     setters: [function (_foo) {
@@ -9,8 +11,6 @@ System.register(["foo"], function (_export) {
       baz3 = _foo.bar;
       xyz = _foo.xyz;
     }],
-    execute: function () {
-      "use strict";
-    }
+    execute: function () {}
   };
-});
\ No newline at end of file
+});
diff --git a/test/core/fixtures/transformation/es6.modules-system/imports/expected.js b/test/core/fixtures/transformation/es6.modules-system/imports/expected.js
index 2b02e610fc..005c4b922f 100644
--- a/test/core/fixtures/transformation/es6.modules-system/imports/expected.js
+++ b/test/core/fixtures/transformation/es6.modules-system/imports/expected.js
@@ -1,8 +1,8 @@
 System.register(["foo", "foo-bar", "./directory/foo-bar"], function (_export) {
+  "use strict";
+
   return {
     setters: [function (_foo) {}, function (_fooBar) {}, function (_directoryFooBar) {}],
-    execute: function () {
-      "use strict";
-    }
+    execute: function () {}
   };
-});
\ No newline at end of file
+});
diff --git a/test/core/fixtures/transformation/es6.modules-system/overview/expected.js b/test/core/fixtures/transformation/es6.modules-system/overview/expected.js
index b4b80d7d38..c818618f83 100644
--- a/test/core/fixtures/transformation/es6.modules-system/overview/expected.js
+++ b/test/core/fixtures/transformation/es6.modules-system/overview/expected.js
@@ -1,4 +1,6 @@
 System.register(["foo", "foo-bar", "./directory/foo-bar"], function (_export) {
+  "use strict";
+
   var foo, foo2, bar, bar2, test2;
   return {
     setters: [function (_foo) {
@@ -8,8 +10,6 @@ System.register(["foo", "foo-bar", "./directory/foo-bar"], function (_export) {
       bar2 = _foo.foo;
     }, function (_fooBar) {}, function (_directoryFooBar) {}],
     execute: function () {
-      "use strict";
-
       _export("test", test);
 
       test2 = 5;
@@ -19,4 +19,4 @@ System.register(["foo", "foo-bar", "./directory/foo-bar"], function (_export) {
       _export("default", test);
     }
   };
-});
\ No newline at end of file
+});
diff --git a/test/core/fixtures/transformation/es6.modules-system/remap/expected.js b/test/core/fixtures/transformation/es6.modules-system/remap/expected.js
index c0922ff2b4..7bedb706ab 100644
--- a/test/core/fixtures/transformation/es6.modules-system/remap/expected.js
+++ b/test/core/fixtures/transformation/es6.modules-system/remap/expected.js
@@ -1,10 +1,10 @@
 System.register([], function (_export) {
+  "use strict";
+
   var test, a, b, d;
   return {
     setters: [],
     execute: function () {
-      "use strict";
-
       test = 2;
 
       _export("test", test);
@@ -39,4 +39,4 @@ System.register([], function (_export) {
       _export("f", _export("e", d = 4));
     }
   };
-});
\ No newline at end of file
+});
diff --git a/test/core/fixtures/transformation/es7.decorators/class-getter-and-setter/expected.js b/test/core/fixtures/transformation/es7.decorators/class-getter-and-setter/expected.js
index 8e9b70a100..8aa07f0846 100644
--- a/test/core/fixtures/transformation/es7.decorators/class-getter-and-setter/expected.js
+++ b/test/core/fixtures/transformation/es7.decorators/class-getter-and-setter/expected.js
@@ -8,8 +8,8 @@ var Foo = (function () {
   babelHelpers.createDecoratedClass(Foo, [{
     key: "foo",
     decorators: [bar, foo],
-    get: function get() {},
-    set: function set(bar) {}
+    get: function () {},
+    set: function (bar) {}
   }]);
   return Foo;
 })();
diff --git a/test/core/fixtures/transformation/es7.decorators/class-getter/expected.js b/test/core/fixtures/transformation/es7.decorators/class-getter/expected.js
index 06b1d2294e..8c7d3a793d 100644
--- a/test/core/fixtures/transformation/es7.decorators/class-getter/expected.js
+++ b/test/core/fixtures/transformation/es7.decorators/class-getter/expected.js
@@ -8,7 +8,7 @@ var Foo = (function () {
   babelHelpers.createDecoratedClass(Foo, [{
     key: "foo",
     decorators: [bar],
-    get: function get() {}
+    get: function () {}
   }]);
   return Foo;
 })();
diff --git a/test/core/fixtures/transformation/es7.decorators/class-init-instance-props/expected.js b/test/core/fixtures/transformation/es7.decorators/class-init-instance-props/expected.js
index e564a5f47e..db03a7b153 100644
--- a/test/core/fixtures/transformation/es7.decorators/class-init-instance-props/expected.js
+++ b/test/core/fixtures/transformation/es7.decorators/class-init-instance-props/expected.js
@@ -11,7 +11,7 @@ var Foo = (function () {
   babelHelpers.createDecoratedClass(Foo, [{
     key: "foo",
     decorators: [bar],
-    initializer: function initializer() {
+    initializer: function () {
       return "Bar";
     },
     enumerable: true
diff --git a/test/core/fixtures/transformation/es7.decorators/class-init-static-props/expected.js b/test/core/fixtures/transformation/es7.decorators/class-init-static-props/expected.js
index 8bdff77924..6c0c573906 100644
--- a/test/core/fixtures/transformation/es7.decorators/class-init-static-props/expected.js
+++ b/test/core/fixtures/transformation/es7.decorators/class-init-static-props/expected.js
@@ -10,7 +10,7 @@ var Foo = (function () {
   babelHelpers.createDecoratedClass(Foo, null, [{
     key: "foo",
     decorators: [bar],
-    initializer: function initializer() {
+    initializer: function () {
       return "Bar";
     },
     enumerable: true
diff --git a/test/core/fixtures/transformation/es7.decorators/class-setter/expected.js b/test/core/fixtures/transformation/es7.decorators/class-setter/expected.js
index 57426dd80c..7b9537b539 100644
--- a/test/core/fixtures/transformation/es7.decorators/class-setter/expected.js
+++ b/test/core/fixtures/transformation/es7.decorators/class-setter/expected.js
@@ -8,7 +8,7 @@ var Foo = (function () {
   babelHelpers.createDecoratedClass(Foo, [{
     key: "foo",
     decorators: [bar],
-    set: function set(arg) {}
+    set: function (arg) {}
   }]);
   return Foo;
 })();
diff --git a/test/core/fixtures/transformation/es7.decorators/object-getter-and-setter/actual.js b/test/core/fixtures/transformation/es7.decorators/object-getter-and-setter/actual.js
index 772c63c875..37a0b6a98f 100644
--- a/test/core/fixtures/transformation/es7.decorators/object-getter-and-setter/actual.js
+++ b/test/core/fixtures/transformation/es7.decorators/object-getter-and-setter/actual.js
@@ -5,7 +5,7 @@ var obj = {
   },
 
   @foo
-  set foo() {
+  set foo(bar) {
 
   }
 };
diff --git a/test/core/fixtures/transformation/es7.decorators/object-getter-and-setter/expected.js b/test/core/fixtures/transformation/es7.decorators/object-getter-and-setter/expected.js
index 117515628e..68c9af550f 100644
--- a/test/core/fixtures/transformation/es7.decorators/object-getter-and-setter/expected.js
+++ b/test/core/fixtures/transformation/es7.decorators/object-getter-and-setter/expected.js
@@ -3,6 +3,6 @@
 var obj = babelHelpers.createDecoratedObject([{
   key: "foo",
   decorators: [foo, foo],
-  get: function get() {},
-  set: function set() {}
+  get: function () {},
+  set: function (bar) {}
 }]);
diff --git a/test/core/fixtures/transformation/es7.decorators/object-getter/expected.js b/test/core/fixtures/transformation/es7.decorators/object-getter/expected.js
index bb651cf283..e0aa727de6 100644
--- a/test/core/fixtures/transformation/es7.decorators/object-getter/expected.js
+++ b/test/core/fixtures/transformation/es7.decorators/object-getter/expected.js
@@ -3,5 +3,5 @@
 var obj = babelHelpers.createDecoratedObject([{
   key: "foo",
   decorators: [foo],
-  get: function get() {}
+  get: function () {}
 }]);
diff --git a/test/core/fixtures/transformation/es7.decorators/object-setter/actual.js b/test/core/fixtures/transformation/es7.decorators/object-setter/actual.js
index ec760bb339..52eb95db88 100644
--- a/test/core/fixtures/transformation/es7.decorators/object-setter/actual.js
+++ b/test/core/fixtures/transformation/es7.decorators/object-setter/actual.js
@@ -1,6 +1,6 @@
 var obj = {
   @foo
-  set foo() {
+  set foo(bar) {
 
   }
 };
diff --git a/test/core/fixtures/transformation/es7.decorators/object-setter/expected.js b/test/core/fixtures/transformation/es7.decorators/object-setter/expected.js
index 6b16d5c65c..ee3dc12281 100644
--- a/test/core/fixtures/transformation/es7.decorators/object-setter/expected.js
+++ b/test/core/fixtures/transformation/es7.decorators/object-setter/expected.js
@@ -3,5 +3,5 @@
 var obj = babelHelpers.createDecoratedObject([{
   key: "foo",
   decorators: [foo],
-  set: function set() {}
+  set: function (bar) {}
 }]);
diff --git a/test/core/fixtures/transformation/es7.decorators/object/expected.js b/test/core/fixtures/transformation/es7.decorators/object/expected.js
index efe805cf25..7a7cc30560 100644
--- a/test/core/fixtures/transformation/es7.decorators/object/expected.js
+++ b/test/core/fixtures/transformation/es7.decorators/object/expected.js
@@ -3,18 +3,18 @@
 var obj = babelHelpers.createDecoratedObject([{
   key: "bar",
   decorators: [foo],
-  initializer: function initializer() {
-    return function () {};
+  initializer: function () {
+    return function bar() {};
   }
 }, {
   key: "foo",
   decorators: [bar],
-  initializer: function initializer() {
+  initializer: function () {
     return "lol";
   }
 }, {
   key: "yes",
-  initializer: function initializer() {
+  initializer: function () {
     return "wow";
   }
 }]);
diff --git a/test/core/fixtures/transformation/runtime/full/expected.js b/test/core/fixtures/transformation/runtime/full/expected.js
index 2f08b10a1c..3f3795a497 100644
--- a/test/core/fixtures/transformation/runtime/full/expected.js
+++ b/test/core/fixtures/transformation/runtime/full/expected.js
@@ -1,20 +1,21 @@
 "use strict";
 
-var _Object$defineProperty = require("babel-runtime/core-js/object/define-property")["default"];
-
-var _Symbol = require("babel-runtime/core-js/symbol")["default"];
-
-var _regeneratorRuntime = require("babel-runtime/regenerator")["default"];
-
-var _interopRequireDefault = require("babel-runtime/helpers/interop-require-default")["default"];
-
-var _interopRequireWildcard = require("babel-runtime/helpers/interop-require-wildcard")["default"];
-
 _Object$defineProperty(exports, "__esModule", {
   value: true
 });
 
 exports.giveWord = giveWord;
+
+var _regeneratorRuntime = require("babel-runtime/regenerator")["default"];
+
+var _Object$defineProperty = require("babel-runtime/core-js/object/define-property")["default"];
+
+var _Symbol = require("babel-runtime/core-js/symbol")["default"];
+
+var _interopRequireDefault = require("babel-runtime/helpers/interop-require-default")["default"];
+
+var _interopRequireWildcard = require("babel-runtime/helpers/interop-require-wildcard")["default"];
+
 var marked0$0 = [giveWord].map(_regeneratorRuntime.mark);
 
 var _someModule = require("someModule");
@@ -41,4 +42,4 @@ function giveWord() {
 }
 
 _someModule2["default"];
-bar;
\ No newline at end of file
+bar;
diff --git a/test/core/fixtures/transformation/source-maps/class/expected.js b/test/core/fixtures/transformation/source-maps/class/expected.js
index c9b2c12183..25517b3e99 100644
--- a/test/core/fixtures/transformation/source-maps/class/expected.js
+++ b/test/core/fixtures/transformation/source-maps/class/expected.js
@@ -7,7 +7,7 @@ var Test = (function () {
 
   babelHelpers.createClass(Test, [{
     key: "bar",
-    get: function get() {
+    get: function () {
       throw new Error("wow");
     }
   }]);

From 8292d6d8ad8319c550f9338fafac7d409a8b3b7f Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Fri, 8 May 2015 22:52:38 +0100
Subject: [PATCH 22/30] fix replacement requeue exiting too early

---
 src/babel/traversal/path/index.js | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/src/babel/traversal/path/index.js b/src/babel/traversal/path/index.js
index 1cbe84ce59..bf9dd5688f 100644
--- a/src/babel/traversal/path/index.js
+++ b/src/babel/traversal/path/index.js
@@ -717,19 +717,18 @@ export default class TraversalPath {
 
       // call the function with the params (node, parent, scope, state)
       var replacement = fn.call(this, node, this.parent, this.scope, this.state);
+      var previousType = this.type;
 
       if (replacement) {
-        var previousType = this.type;
-
         this.replaceWith(replacement, true);
-
-        if (previousType !== this.type) {
-          this.queueNode(this);
-          return;
-        }
       }
 
       if (this.shouldStop || this.shouldSkip || this.removed) return;
+
+      if (replacement && previousType !== this.type) {
+        this.queueNode(this);
+        return;
+      }
     }
   }
 

From b376b6b33bc55421c9c98c8899ebce95cff33640 Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Fri, 8 May 2015 22:53:03 +0100
Subject: [PATCH 23/30] store uncollapsed transformer pass stack so we have
 access to it when calling pre and post methods

---
 src/babel/transformation/file/index.js | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/src/babel/transformation/file/index.js b/src/babel/transformation/file/index.js
index e3757ac860..7b2a8f1e10 100644
--- a/src/babel/transformation/file/index.js
+++ b/src/babel/transformation/file/index.js
@@ -86,10 +86,7 @@ export default class File {
     "interop-require",
   ];
 
-  static soloHelpers = [
-    "ludicrous-proxy-create",
-    "ludicrous-proxy-directory"
-  ];
+  static soloHelpers = [];
 
   static options = require("./options");
 
@@ -224,7 +221,7 @@ export default class File {
     stack = beforePlugins.concat(stack, afterPlugins);
 
     // build transformer stack
-    stack = stack.concat(secondaryStack);
+    this.uncollapsedTransformerStack = stack = stack.concat(secondaryStack);
 
     // build dependency graph
     for (var pass of (stack: Array)) {
@@ -557,10 +554,8 @@ export default class File {
   }
 
   call(key: string) {
-    var stack = this.transformerStack;
-    for (var i = 0; i < stack.length; i++) {
-      var transformer = stack[i].transformer;
-      var fn = transformer[key];
+    for (var pass of (this.uncollapsedTransformerStack: Array)) {
+      var fn = pass.transformer[key];
       if (fn) fn(this);
     }
   }

From 8f9d02d6891dd9f8a829b91ec362476e650944dc Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Fri, 8 May 2015 22:53:31 +0100
Subject: [PATCH 24/30] further work splitting up transformers into their own
 "category" in order of what they need and what they actually do

---
 .../es3/member-expression-literals.js         |  2 +-
 .../transformers/es3/property-literals.js     |  2 +-
 .../transformers/es5/properties.mutators.js   | 38 ++++++++---------
 .../transformers/es6/destructuring.js         |  4 ++
 .../transformers/es6/properties.computed.js   |  4 +-
 .../transformers/es6/tail-call.js             |  4 ++
 .../transformation/transformers/index.js      | 41 ++++++++++++-------
 .../transformers/internal/block-hoist.js      |  2 +-
 .../transformers/internal/modules.js          |  4 ++
 .../transformers/internal/shadow-functions.js |  2 +-
 .../transformers/internal/validation.js       |  4 ++
 .../minification/dead-code-elimination.js     |  3 +-
 .../member-expression-literals.js             |  2 +-
 .../minification/property-literals.js         |  2 +-
 .../transformers/other/regenerator.js         | 10 ++---
 .../transformers/other/runtime/index.js       |  4 +-
 .../transformers/spec/function-name.js        |  4 ++
 .../utility/inline-environment-variables.js   |  3 +-
 .../utility/inline-expressions.js             |  3 +-
 .../transformers/utility/remove-console.js    |  3 +-
 .../transformers/utility/remove-debugger.js   |  3 +-
 21 files changed, 88 insertions(+), 56 deletions(-)

diff --git a/src/babel/transformation/transformers/es3/member-expression-literals.js b/src/babel/transformation/transformers/es3/member-expression-literals.js
index d4465fde70..e80f5c62d1 100644
--- a/src/babel/transformation/transformers/es3/member-expression-literals.js
+++ b/src/babel/transformation/transformers/es3/member-expression-literals.js
@@ -1,7 +1,7 @@
 import * as t from "../../../types";
 
 export var metadata = {
-  category: "builtin-cleanup"
+  category: "builtin-trailing"
 };
 
 export var MemberExpression = {
diff --git a/src/babel/transformation/transformers/es3/property-literals.js b/src/babel/transformation/transformers/es3/property-literals.js
index ecfd63c8dd..9fa015e82b 100644
--- a/src/babel/transformation/transformers/es3/property-literals.js
+++ b/src/babel/transformation/transformers/es3/property-literals.js
@@ -1,7 +1,7 @@
 import * as t from "../../../types";
 
 export var metadata = {
-  category: "builtin-cleanup"
+  category: "builtin-trailing"
 };
 
 export var Property = {
diff --git a/src/babel/transformation/transformers/es5/properties.mutators.js b/src/babel/transformation/transformers/es5/properties.mutators.js
index 7fe77c7f41..a3161efae8 100644
--- a/src/babel/transformation/transformers/es5/properties.mutators.js
+++ b/src/babel/transformation/transformers/es5/properties.mutators.js
@@ -1,26 +1,24 @@
 import * as defineMap from "../../helpers/define-map";
 import * as t from "../../../types";
 
-export var ObjectExpression = {
-  exit(node, parent, scope, file) {
-    var mutatorMap = {};
-    var hasAny = false;
+export function ObjectExpression(node, parent, scope, file) {
+  var mutatorMap = {};
+  var hasAny = false;
 
-    node.properties = node.properties.filter(function (prop) {
-      if (prop.kind === "get" || prop.kind === "set") {
-        hasAny = true;
-        defineMap.push(mutatorMap, prop, prop.kind, file);
-        return false;
-      } else {
-        return true;
-      }
-    });
+  node.properties = node.properties.filter(function (prop) {
+    if (prop.kind === "get" || prop.kind === "set") {
+      hasAny = true;
+      defineMap.push(mutatorMap, prop, prop.kind, file);
+      return false;
+    } else {
+      return true;
+    }
+  });
 
-    if (!hasAny) return;
+  if (!hasAny) return;
 
-    return t.callExpression(
-      t.memberExpression(t.identifier("Object"), t.identifier("defineProperties")),
-      [node, defineMap.toDefineObject(mutatorMap)]
-    );
-  }
-};
+  return t.callExpression(
+    t.memberExpression(t.identifier("Object"), t.identifier("defineProperties")),
+    [node, defineMap.toDefineObject(mutatorMap)]
+  );
+}
diff --git a/src/babel/transformation/transformers/es6/destructuring.js b/src/babel/transformation/transformers/es6/destructuring.js
index 5fb2df518b..53e7b2d22b 100644
--- a/src/babel/transformation/transformers/es6/destructuring.js
+++ b/src/babel/transformation/transformers/es6/destructuring.js
@@ -1,6 +1,10 @@
 import * as messages from "../../../messages";
 import * as t from "../../../types";
 
+export var metadata = {
+  category: "builtin-advanced"
+};
+
 export function ForOfStatement(node, parent, scope, file) {
   var left = node.left;
 
diff --git a/src/babel/transformation/transformers/es6/properties.computed.js b/src/babel/transformation/transformers/es6/properties.computed.js
index d944844ca0..9c477f8348 100644
--- a/src/babel/transformation/transformers/es6/properties.computed.js
+++ b/src/babel/transformation/transformers/es6/properties.computed.js
@@ -67,8 +67,8 @@ export var ObjectExpression = {
   exit(node, parent, scope, file) {
     var hasComputed = false;
 
-    for (var i = 0; i < node.properties.length; i++) {
-      hasComputed = t.isProperty(node.properties[i], { computed: true, kind: "init" });
+    for (var prop of (node.properties: Array)) {
+      hasComputed = t.isProperty(prop, { computed: true, kind: "init" });
       if (hasComputed) break;
     }
 
diff --git a/src/babel/transformation/transformers/es6/tail-call.js b/src/babel/transformation/transformers/es6/tail-call.js
index 12fb5a8a8d..e3a9482067 100644
--- a/src/babel/transformation/transformers/es6/tail-call.js
+++ b/src/babel/transformation/transformers/es6/tail-call.js
@@ -6,6 +6,10 @@ import * as util from  "../../../util";
 import map from "lodash/collection/map";
 import * as t from "../../../types";
 
+export var metadata = {
+  category: "builtin-trailing"
+};
+
 exports.Function = function (node, parent, scope, file) {
   if (node.generator || node.async) return;
   var tailCall = new TailCallTransformer(this, scope, file);
diff --git a/src/babel/transformation/transformers/index.js b/src/babel/transformation/transformers/index.js
index a4e0317b84..7977ee9e9f 100644
--- a/src/babel/transformation/transformers/index.js
+++ b/src/babel/transformation/transformers/index.js
@@ -1,20 +1,24 @@
 export default {
-  // builtin-basic
+  //- builtin-setup
+  _validation:                             require("./internal/validation"),
   "utility.removeDebugger":                require("./utility/remove-debugger"),
   "utility.removeConsole":                 require("./utility/remove-console"),
   "utility.inlineEnvironmentVariables":    require("./utility/inline-environment-variables"),
   "utility.inlineExpressions":             require("./utility/inline-expressions"),
   "minification.deadCodeElimination":      require("./minification/dead-code-elimination"),
   _modules:                                require("./internal/modules"),
+  "spec.functionName":                     require("./spec/function-name"),
+
+  //- builtin-basic
+  // this is where the bulk of the ES6 transformations take place, none of them require traversal state
+  // so they can all be concatenated together for performance
   "es7.classProperties":                   require("./es7/class-properties"),
   "es7.trailingFunctionCommas":            require("./es7/trailing-function-commas"),
   "es7.asyncFunctions":                    require("./es7/async-functions"),
   "es7.decorators":                        require("./es7/decorators"),
   strict:                                  require("./other/strict"),
-  _validation:                             require("./internal/validation"),
   "validation.undeclaredVariableCheck":    require("./validation/undeclared-variable-check"),
   "validation.react":                      require("./validation/react"),
-  "spec.functionName":                     require("./spec/function-name"),
   "es6.arrowFunctions":                    require("./es6/arrow-functions"),
   "spec.blockScopedFunctions":             require("./spec/block-scoped-functions"),
   "optimisation.react.constantElements":   require("./optimisation/react.constant-elements"),
@@ -41,30 +45,37 @@ export default {
   "es6.parameters.rest":                   require("./es6/parameters.rest"),
   "es6.spread":                            require("./es6/spread"),
   "es6.parameters.default":                require("./es6/parameters.default"),
-  "es6.destructuring":                     require("./es6/destructuring"),
-  "es6.tailCall":                          require("./es6/tail-call"),
   "es7.exportExtensions":                  require("./es7/export-extensions"),
   "spec.protoToAssign":                    require("./spec/proto-to-assign"),
-  _shadowFunctions:                        require("./internal/shadow-functions"),
   "es7.doExpressions":                     require("./es7/do-expressions"),
   "es6.spec.symbols":                      require("./es6/spec.symbols"),
-  ludicrous:                               require("./other/ludicrous"),
   "spec.undefinedToVoid":                  require("./spec/undefined-to-void"),
   jscript:                                 require("./other/jscript"),
   flow:                                    require("./other/flow"),
   _hoistDirectives:                        require("./internal/hoist-directives"),
 
-  // builtin-modules
-  "es6.modules":                           require("./es6/modules"),
-  regenerator:                             require("./other/regenerator"),
-  runtime:                                 require("./other/runtime"),
-  _moduleFormatter:                        require("./internal/module-formatter"),
-
-  // builtin-advanced
+  //- builtin-advanced
+  "es6.destructuring":                     require("./es6/destructuring"),
   "es6.blockScoping":                      require("./es6/block-scoping"),
   "es6.spec.blockScoping":                 require("./es6/spec.block-scoping"),
 
-  // builtin-cleanup
+  // es6 syntax transformation is **forbidden** past this point since regenerator will chuck a massive
+  // hissy fit
+
+  //- regenerator
+  regenerator:                             require("./other/regenerator"),
+
+  //- builtin-modules
+  runtime:                                 require("./other/runtime"),
+  "es6.modules":                           require("./es6/modules"),
+  _moduleFormatter:                        require("./internal/module-formatter"),
+
+  //- builtin-trailing
+  // these clean up the output and do finishing up transformations, it's important to note that by this
+  // stage you can't import any new modules or insert new ES6 as all those transformers have already
+  // been ran
+  "es6.tailCall":                          require("./es6/tail-call"),
+  _shadowFunctions:                        require("./internal/shadow-functions"),
   "es3.propertyLiterals":                  require("./es3/property-literals"),
   "es3.memberExpressionLiterals":          require("./es3/member-expression-literals"),
   "minification.memberExpressionLiterals": require("./minification/member-expression-literals"),
diff --git a/src/babel/transformation/transformers/internal/block-hoist.js b/src/babel/transformation/transformers/internal/block-hoist.js
index 700d91b2a9..2ab60a0755 100644
--- a/src/babel/transformation/transformers/internal/block-hoist.js
+++ b/src/babel/transformation/transformers/internal/block-hoist.js
@@ -1,7 +1,7 @@
 import sortBy from "lodash/collection/sortBy";
 
 export var metadata = {
-  category: "builtin-cleanup"
+  category: "builtin-trailing"
 };
 
 // Priority:
diff --git a/src/babel/transformation/transformers/internal/modules.js b/src/babel/transformation/transformers/internal/modules.js
index 6d3dfe83c8..71d51e7a25 100644
--- a/src/babel/transformation/transformers/internal/modules.js
+++ b/src/babel/transformation/transformers/internal/modules.js
@@ -6,6 +6,10 @@
 
 import * as t from "../../../types";
 
+export var metadata = {
+  category: "builtin-setup"
+};
+
 export function ImportDeclaration(node, parent, scope, file) {
   if (node.source) {
     node.source.value = file.resolveModuleSource(node.source.value);
diff --git a/src/babel/transformation/transformers/internal/shadow-functions.js b/src/babel/transformation/transformers/internal/shadow-functions.js
index decec95409..d082fd1ba8 100644
--- a/src/babel/transformation/transformers/internal/shadow-functions.js
+++ b/src/babel/transformation/transformers/internal/shadow-functions.js
@@ -86,7 +86,7 @@ function aliasFunction(getBody, path, scope) {
 // crawling the entire function tree
 
 export var metadata = {
-  category: "builtin-cleanup"
+  category: "builtin-trailing"
 };
 
 export var Program = {
diff --git a/src/babel/transformation/transformers/internal/validation.js b/src/babel/transformation/transformers/internal/validation.js
index da830eabef..31dfabc78e 100644
--- a/src/babel/transformation/transformers/internal/validation.js
+++ b/src/babel/transformation/transformers/internal/validation.js
@@ -1,6 +1,10 @@
 import * as messages from "../../../messages";
 import * as t from "../../../types";
 
+export var metadata = {
+  category: "builtin-setup"
+};
+
 export function ForOfStatement(node, parent, scope, file) {
   var left = node.left;
   if (t.isVariableDeclaration(left)) {
diff --git a/src/babel/transformation/transformers/minification/dead-code-elimination.js b/src/babel/transformation/transformers/minification/dead-code-elimination.js
index 2d840f991e..58524530bb 100644
--- a/src/babel/transformation/transformers/minification/dead-code-elimination.js
+++ b/src/babel/transformation/transformers/minification/dead-code-elimination.js
@@ -18,7 +18,8 @@ function toStatements(node) {
 }
 
 export var metadata = {
-  optional: true
+  optional: true,
+  category: "builtin-setup"
 };
 
 export function Identifier(node, parent, scope) {
diff --git a/src/babel/transformation/transformers/minification/member-expression-literals.js b/src/babel/transformation/transformers/minification/member-expression-literals.js
index a7d9823535..333bd02201 100644
--- a/src/babel/transformation/transformers/minification/member-expression-literals.js
+++ b/src/babel/transformation/transformers/minification/member-expression-literals.js
@@ -2,7 +2,7 @@ import * as t from "../../../types";
 
 export var metadata = {
   optional: true,
-  category: "builtin-cleanup"
+  category: "builtin-trailing"
 };
 
 export var MemberExpression = {
diff --git a/src/babel/transformation/transformers/minification/property-literals.js b/src/babel/transformation/transformers/minification/property-literals.js
index d1d682fbdb..4bdc31ae59 100644
--- a/src/babel/transformation/transformers/minification/property-literals.js
+++ b/src/babel/transformation/transformers/minification/property-literals.js
@@ -2,7 +2,7 @@ import * as t from "../../../types";
 
 export var metadata = {
   optional: true,
-  category: "builtin-cleanup"
+  category: "builtin-trailing"
 };
 
 export var Property = {
diff --git a/src/babel/transformation/transformers/other/regenerator.js b/src/babel/transformation/transformers/other/regenerator.js
index 9d1b17e675..d276ec9908 100644
--- a/src/babel/transformation/transformers/other/regenerator.js
+++ b/src/babel/transformation/transformers/other/regenerator.js
@@ -2,11 +2,9 @@ import regenerator from "regenerator";
 import * as t from "../../../types";
 
 export var metadata = {
-  category: "builtin-modules"
+  category: "regenerator"
 };
 
-export var Program = {
-  exit(ast) {
-    regenerator.transform(ast);
-  }
-};
+export function Program(ast) {
+  regenerator.transform(ast);
+}
diff --git a/src/babel/transformation/transformers/other/runtime/index.js b/src/babel/transformation/transformers/other/runtime/index.js
index 3fa283268d..5d9a0dbc44 100644
--- a/src/babel/transformation/transformers/other/runtime/index.js
+++ b/src/babel/transformation/transformers/other/runtime/index.js
@@ -11,10 +11,10 @@ const RUNTIME_MODULE_NAME = "babel-runtime";
 
 export var metadata = {
   optional: true,
-  category: "builtin-modules"
+  category: "builtin-post-modules"
 };
 
-export function Program(node, parent, scope, file) {
+export function pre(file) {
   file.set("helperGenerator", function (name) {
     return file.addImport(`${RUNTIME_MODULE_NAME}/helpers/${name}`, name, "absoluteDefault");
   });
diff --git a/src/babel/transformation/transformers/spec/function-name.js b/src/babel/transformation/transformers/spec/function-name.js
index 928036e0be..d45d2a4165 100644
--- a/src/babel/transformation/transformers/spec/function-name.js
+++ b/src/babel/transformation/transformers/spec/function-name.js
@@ -1,3 +1,7 @@
+export var metadata = {
+  category: "builtin-setup"
+};
+
 export {
   bare as FunctionExpression,
   bare as ArrowFunctionExpression
diff --git a/src/babel/transformation/transformers/utility/inline-environment-variables.js b/src/babel/transformation/transformers/utility/inline-environment-variables.js
index 97725fbc51..5c00d13ccc 100644
--- a/src/babel/transformation/transformers/utility/inline-environment-variables.js
+++ b/src/babel/transformation/transformers/utility/inline-environment-variables.js
@@ -1,7 +1,8 @@
 import * as t from "../../../types";
 
 export var metadata = {
-  optional: true
+  optional: true,
+  category: "builtin-setup"
 };
 
 var match = t.buildMatchMemberExpression("process.env");
diff --git a/src/babel/transformation/transformers/utility/inline-expressions.js b/src/babel/transformation/transformers/utility/inline-expressions.js
index 437cce640d..5fbb8de75c 100644
--- a/src/babel/transformation/transformers/utility/inline-expressions.js
+++ b/src/babel/transformation/transformers/utility/inline-expressions.js
@@ -1,7 +1,8 @@
 import * as t from "../../../types";
 
 export var metadata = {
-  optional: true
+  optional: true,
+  category: "builtin-setup"
 };
 
 export function Expression(node, parent, scope) {
diff --git a/src/babel/transformation/transformers/utility/remove-console.js b/src/babel/transformation/transformers/utility/remove-console.js
index 317840ce3e..88106ee69a 100644
--- a/src/babel/transformation/transformers/utility/remove-console.js
+++ b/src/babel/transformation/transformers/utility/remove-console.js
@@ -1,7 +1,8 @@
 import * as t from "../../../types";
 
 export var metadata = {
-  optional: true
+  optional: true,
+  category: "builtin-setup"
 };
 
 export function CallExpression(node, parent) {
diff --git a/src/babel/transformation/transformers/utility/remove-debugger.js b/src/babel/transformation/transformers/utility/remove-debugger.js
index f7d84d0e81..b797c700cc 100644
--- a/src/babel/transformation/transformers/utility/remove-debugger.js
+++ b/src/babel/transformation/transformers/utility/remove-debugger.js
@@ -1,7 +1,8 @@
 import * as t from "../../../types";
 
 export var metadata = {
-  optional: true
+  optional: true,
+  category: "builtin-setup"
 };
 
 export function ExpressionStatement(node) {

From 2fd1b2a484fd888591ff4ea7a5f10006a73b1682 Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Fri, 8 May 2015 22:54:15 +0100
Subject: [PATCH 25/30] rename category metadata option to group

---
 src/babel/transformation/file/index.js                    | 8 ++++----
 src/babel/transformation/index.js                         | 2 +-
 .../transformers/es3/member-expression-literals.js        | 2 +-
 .../transformation/transformers/es3/property-literals.js  | 2 +-
 .../transformation/transformers/es6/block-scoping.js      | 2 +-
 .../transformation/transformers/es6/destructuring.js      | 2 +-
 src/babel/transformation/transformers/es6/modules.js      | 2 +-
 .../transformation/transformers/es6/spec.block-scoping.js | 2 +-
 src/babel/transformation/transformers/es6/tail-call.js    | 2 +-
 .../transformation/transformers/internal/block-hoist.js   | 2 +-
 .../transformers/internal/module-formatter.js             | 2 +-
 src/babel/transformation/transformers/internal/modules.js | 2 +-
 .../transformers/internal/shadow-functions.js             | 2 +-
 .../transformation/transformers/internal/validation.js    | 2 +-
 .../transformers/minification/dead-code-elimination.js    | 2 +-
 .../minification/member-expression-literals.js            | 2 +-
 .../transformers/minification/property-literals.js        | 2 +-
 .../transformation/transformers/other/regenerator.js      | 2 +-
 .../transformation/transformers/other/runtime/index.js    | 2 +-
 .../transformation/transformers/spec/function-name.js     | 2 +-
 .../transformers/utility/inline-environment-variables.js  | 2 +-
 .../transformers/utility/inline-expressions.js            | 2 +-
 .../transformation/transformers/utility/remove-console.js | 2 +-
 .../transformers/utility/remove-debugger.js               | 2 +-
 24 files changed, 27 insertions(+), 27 deletions(-)

diff --git a/src/babel/transformation/file/index.js b/src/babel/transformation/file/index.js
index 7b2a8f1e10..27f0453ed8 100644
--- a/src/babel/transformation/file/index.js
+++ b/src/babel/transformation/file/index.js
@@ -242,17 +242,17 @@ export default class File {
       // been merged
       if (ignore.indexOf(pass) >= 0) continue;
 
-      var category = pass.transformer.metadata.category;
+      var group = pass.transformer.metadata.group;
 
       // can't merge
-      if (!pass.canTransform() || !category) {
+      if (!pass.canTransform() || !group) {
         stack.push(pass);
         continue;
       }
 
       var mergeStack = [];
       for (let pass of (_stack: Array)) {
-        if (pass.transformer.metadata.category === category) {
+        if (pass.transformer.metadata.group === group) {
           mergeStack.push(pass);
           ignore.push(pass);
         }
@@ -263,7 +263,7 @@ export default class File {
         visitors.push(pass.handlers);
       }
       var visitor = traverse.visitors.merge(visitors);
-      var mergeTransformer = new Transformer(category, visitor);
+      var mergeTransformer = new Transformer(group, visitor);
       //console.log(mergeTransformer);
       stack.push(mergeTransformer.buildPass(this));
     }
diff --git a/src/babel/transformation/index.js b/src/babel/transformation/index.js
index 5a523a4ea2..11b0780fd1 100644
--- a/src/babel/transformation/index.js
+++ b/src/babel/transformation/index.js
@@ -9,7 +9,7 @@ import transformers from "./transformers";
 for (var key in transformers) {
   var transformer = transformers[key];
   var metadata = transformer.metadata = transformer.metadata || {};
-  metadata.category = metadata.category || "builtin-basic";
+  metadata.group = metadata.group || "builtin-basic";
 }
 
 pipeline.addTransformers(transformers);
diff --git a/src/babel/transformation/transformers/es3/member-expression-literals.js b/src/babel/transformation/transformers/es3/member-expression-literals.js
index e80f5c62d1..af026a5171 100644
--- a/src/babel/transformation/transformers/es3/member-expression-literals.js
+++ b/src/babel/transformation/transformers/es3/member-expression-literals.js
@@ -1,7 +1,7 @@
 import * as t from "../../../types";
 
 export var metadata = {
-  category: "builtin-trailing"
+  group: "builtin-trailing"
 };
 
 export var MemberExpression = {
diff --git a/src/babel/transformation/transformers/es3/property-literals.js b/src/babel/transformation/transformers/es3/property-literals.js
index 9fa015e82b..ffb13ddc64 100644
--- a/src/babel/transformation/transformers/es3/property-literals.js
+++ b/src/babel/transformation/transformers/es3/property-literals.js
@@ -1,7 +1,7 @@
 import * as t from "../../../types";
 
 export var metadata = {
-  category: "builtin-trailing"
+  group: "builtin-trailing"
 };
 
 export var Property = {
diff --git a/src/babel/transformation/transformers/es6/block-scoping.js b/src/babel/transformation/transformers/es6/block-scoping.js
index 515c0711e9..8d8f8a8f88 100644
--- a/src/babel/transformation/transformers/es6/block-scoping.js
+++ b/src/babel/transformation/transformers/es6/block-scoping.js
@@ -38,7 +38,7 @@ function standardizeLets(declars) {
 }
 
 export var metadata = {
-  category: "builtin-advanced"
+  group: "builtin-advanced"
 };
 
 export function VariableDeclaration(node, parent, scope, file) {
diff --git a/src/babel/transformation/transformers/es6/destructuring.js b/src/babel/transformation/transformers/es6/destructuring.js
index 53e7b2d22b..5c779cac21 100644
--- a/src/babel/transformation/transformers/es6/destructuring.js
+++ b/src/babel/transformation/transformers/es6/destructuring.js
@@ -2,7 +2,7 @@ import * as messages from "../../../messages";
 import * as t from "../../../types";
 
 export var metadata = {
-  category: "builtin-advanced"
+  group: "builtin-advanced"
 };
 
 export function ForOfStatement(node, parent, scope, file) {
diff --git a/src/babel/transformation/transformers/es6/modules.js b/src/babel/transformation/transformers/es6/modules.js
index 80772e3163..688fcf2baa 100644
--- a/src/babel/transformation/transformers/es6/modules.js
+++ b/src/babel/transformation/transformers/es6/modules.js
@@ -9,7 +9,7 @@ function keepBlockHoist(node, nodes) {
 }
 
 export var metadata = {
-  category: "builtin-modules"
+  group: "builtin-modules"
 };
 
 export function ImportDeclaration(node, parent, scope, file) {
diff --git a/src/babel/transformation/transformers/es6/spec.block-scoping.js b/src/babel/transformation/transformers/es6/spec.block-scoping.js
index 6906b1d7c1..f7fc4ff0ab 100644
--- a/src/babel/transformation/transformers/es6/spec.block-scoping.js
+++ b/src/babel/transformation/transformers/es6/spec.block-scoping.js
@@ -29,7 +29,7 @@ var visitor = traverse.explode({
 
 export var metadata = {
   optional: true,
-  category: "builtin-advanced"
+  group: "builtin-advanced"
 };
 
 export var BlockStatement = {
diff --git a/src/babel/transformation/transformers/es6/tail-call.js b/src/babel/transformation/transformers/es6/tail-call.js
index e3a9482067..4da3e46365 100644
--- a/src/babel/transformation/transformers/es6/tail-call.js
+++ b/src/babel/transformation/transformers/es6/tail-call.js
@@ -7,7 +7,7 @@ import map from "lodash/collection/map";
 import * as t from "../../../types";
 
 export var metadata = {
-  category: "builtin-trailing"
+  group: "builtin-trailing"
 };
 
 exports.Function = function (node, parent, scope, file) {
diff --git a/src/babel/transformation/transformers/internal/block-hoist.js b/src/babel/transformation/transformers/internal/block-hoist.js
index 2ab60a0755..934d21b1e2 100644
--- a/src/babel/transformation/transformers/internal/block-hoist.js
+++ b/src/babel/transformation/transformers/internal/block-hoist.js
@@ -1,7 +1,7 @@
 import sortBy from "lodash/collection/sortBy";
 
 export var metadata = {
-  category: "builtin-trailing"
+  group: "builtin-trailing"
 };
 
 // Priority:
diff --git a/src/babel/transformation/transformers/internal/module-formatter.js b/src/babel/transformation/transformers/internal/module-formatter.js
index da48d94c6d..4235eeb4fb 100644
--- a/src/babel/transformation/transformers/internal/module-formatter.js
+++ b/src/babel/transformation/transformers/internal/module-formatter.js
@@ -1,7 +1,7 @@
 import * as strict from "../../helpers/strict";
 
 export var metadata = {
-  category: "builtin-modules"
+  group: "builtin-modules"
 };
 
 export var Program = {
diff --git a/src/babel/transformation/transformers/internal/modules.js b/src/babel/transformation/transformers/internal/modules.js
index 71d51e7a25..ac64b0e455 100644
--- a/src/babel/transformation/transformers/internal/modules.js
+++ b/src/babel/transformation/transformers/internal/modules.js
@@ -7,7 +7,7 @@
 import * as t from "../../../types";
 
 export var metadata = {
-  category: "builtin-setup"
+  group: "builtin-setup"
 };
 
 export function ImportDeclaration(node, parent, scope, file) {
diff --git a/src/babel/transformation/transformers/internal/shadow-functions.js b/src/babel/transformation/transformers/internal/shadow-functions.js
index d082fd1ba8..04d11f7811 100644
--- a/src/babel/transformation/transformers/internal/shadow-functions.js
+++ b/src/babel/transformation/transformers/internal/shadow-functions.js
@@ -86,7 +86,7 @@ function aliasFunction(getBody, path, scope) {
 // crawling the entire function tree
 
 export var metadata = {
-  category: "builtin-trailing"
+  group: "builtin-trailing"
 };
 
 export var Program = {
diff --git a/src/babel/transformation/transformers/internal/validation.js b/src/babel/transformation/transformers/internal/validation.js
index 31dfabc78e..626c236fee 100644
--- a/src/babel/transformation/transformers/internal/validation.js
+++ b/src/babel/transformation/transformers/internal/validation.js
@@ -2,7 +2,7 @@ import * as messages from "../../../messages";
 import * as t from "../../../types";
 
 export var metadata = {
-  category: "builtin-setup"
+  group: "builtin-setup"
 };
 
 export function ForOfStatement(node, parent, scope, file) {
diff --git a/src/babel/transformation/transformers/minification/dead-code-elimination.js b/src/babel/transformation/transformers/minification/dead-code-elimination.js
index 58524530bb..8f17b338df 100644
--- a/src/babel/transformation/transformers/minification/dead-code-elimination.js
+++ b/src/babel/transformation/transformers/minification/dead-code-elimination.js
@@ -19,7 +19,7 @@ function toStatements(node) {
 
 export var metadata = {
   optional: true,
-  category: "builtin-setup"
+  group: "builtin-setup"
 };
 
 export function Identifier(node, parent, scope) {
diff --git a/src/babel/transformation/transformers/minification/member-expression-literals.js b/src/babel/transformation/transformers/minification/member-expression-literals.js
index 333bd02201..877a924b11 100644
--- a/src/babel/transformation/transformers/minification/member-expression-literals.js
+++ b/src/babel/transformation/transformers/minification/member-expression-literals.js
@@ -2,7 +2,7 @@ import * as t from "../../../types";
 
 export var metadata = {
   optional: true,
-  category: "builtin-trailing"
+  group: "builtin-trailing"
 };
 
 export var MemberExpression = {
diff --git a/src/babel/transformation/transformers/minification/property-literals.js b/src/babel/transformation/transformers/minification/property-literals.js
index 4bdc31ae59..c6cf4e7538 100644
--- a/src/babel/transformation/transformers/minification/property-literals.js
+++ b/src/babel/transformation/transformers/minification/property-literals.js
@@ -2,7 +2,7 @@ import * as t from "../../../types";
 
 export var metadata = {
   optional: true,
-  category: "builtin-trailing"
+  group: "builtin-trailing"
 };
 
 export var Property = {
diff --git a/src/babel/transformation/transformers/other/regenerator.js b/src/babel/transformation/transformers/other/regenerator.js
index d276ec9908..957fc6af94 100644
--- a/src/babel/transformation/transformers/other/regenerator.js
+++ b/src/babel/transformation/transformers/other/regenerator.js
@@ -2,7 +2,7 @@ import regenerator from "regenerator";
 import * as t from "../../../types";
 
 export var metadata = {
-  category: "regenerator"
+  group: "regenerator"
 };
 
 export function Program(ast) {
diff --git a/src/babel/transformation/transformers/other/runtime/index.js b/src/babel/transformation/transformers/other/runtime/index.js
index 5d9a0dbc44..27dd6c7a15 100644
--- a/src/babel/transformation/transformers/other/runtime/index.js
+++ b/src/babel/transformation/transformers/other/runtime/index.js
@@ -11,7 +11,7 @@ const RUNTIME_MODULE_NAME = "babel-runtime";
 
 export var metadata = {
   optional: true,
-  category: "builtin-post-modules"
+  group: "builtin-post-modules"
 };
 
 export function pre(file) {
diff --git a/src/babel/transformation/transformers/spec/function-name.js b/src/babel/transformation/transformers/spec/function-name.js
index d45d2a4165..2b384fcddb 100644
--- a/src/babel/transformation/transformers/spec/function-name.js
+++ b/src/babel/transformation/transformers/spec/function-name.js
@@ -1,5 +1,5 @@
 export var metadata = {
-  category: "builtin-setup"
+  group: "builtin-setup"
 };
 
 export {
diff --git a/src/babel/transformation/transformers/utility/inline-environment-variables.js b/src/babel/transformation/transformers/utility/inline-environment-variables.js
index 5c00d13ccc..e40ed44d17 100644
--- a/src/babel/transformation/transformers/utility/inline-environment-variables.js
+++ b/src/babel/transformation/transformers/utility/inline-environment-variables.js
@@ -2,7 +2,7 @@ import * as t from "../../../types";
 
 export var metadata = {
   optional: true,
-  category: "builtin-setup"
+  group: "builtin-setup"
 };
 
 var match = t.buildMatchMemberExpression("process.env");
diff --git a/src/babel/transformation/transformers/utility/inline-expressions.js b/src/babel/transformation/transformers/utility/inline-expressions.js
index 5fbb8de75c..858a696a90 100644
--- a/src/babel/transformation/transformers/utility/inline-expressions.js
+++ b/src/babel/transformation/transformers/utility/inline-expressions.js
@@ -2,7 +2,7 @@ import * as t from "../../../types";
 
 export var metadata = {
   optional: true,
-  category: "builtin-setup"
+  group: "builtin-setup"
 };
 
 export function Expression(node, parent, scope) {
diff --git a/src/babel/transformation/transformers/utility/remove-console.js b/src/babel/transformation/transformers/utility/remove-console.js
index 88106ee69a..cdbeb53a38 100644
--- a/src/babel/transformation/transformers/utility/remove-console.js
+++ b/src/babel/transformation/transformers/utility/remove-console.js
@@ -2,7 +2,7 @@ import * as t from "../../../types";
 
 export var metadata = {
   optional: true,
-  category: "builtin-setup"
+  group: "builtin-setup"
 };
 
 export function CallExpression(node, parent) {
diff --git a/src/babel/transformation/transformers/utility/remove-debugger.js b/src/babel/transformation/transformers/utility/remove-debugger.js
index b797c700cc..e2d8c7dbe1 100644
--- a/src/babel/transformation/transformers/utility/remove-debugger.js
+++ b/src/babel/transformation/transformers/utility/remove-debugger.js
@@ -2,7 +2,7 @@ import * as t from "../../../types";
 
 export var metadata = {
   optional: true,
-  category: "builtin-setup"
+  group: "builtin-setup"
 };
 
 export function ExpressionStatement(node) {

From 590a165776bcc754be1705c98c994fe4d3bc59bd Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Fri, 8 May 2015 23:09:45 +0100
Subject: [PATCH 26/30] move hoistDirectives transformer to builtin-setup

---
 src/babel/transformation/transformers/index.js                | 2 +-
 .../transformation/transformers/internal/hoist-directives.js  | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/babel/transformation/transformers/index.js b/src/babel/transformation/transformers/index.js
index 7977ee9e9f..93551c5181 100644
--- a/src/babel/transformation/transformers/index.js
+++ b/src/babel/transformation/transformers/index.js
@@ -1,6 +1,7 @@
 export default {
   //- builtin-setup
   _validation:                             require("./internal/validation"),
+  _hoistDirectives:                        require("./internal/hoist-directives"),
   "utility.removeDebugger":                require("./utility/remove-debugger"),
   "utility.removeConsole":                 require("./utility/remove-console"),
   "utility.inlineEnvironmentVariables":    require("./utility/inline-environment-variables"),
@@ -52,7 +53,6 @@ export default {
   "spec.undefinedToVoid":                  require("./spec/undefined-to-void"),
   jscript:                                 require("./other/jscript"),
   flow:                                    require("./other/flow"),
-  _hoistDirectives:                        require("./internal/hoist-directives"),
 
   //- builtin-advanced
   "es6.destructuring":                     require("./es6/destructuring"),
diff --git a/src/babel/transformation/transformers/internal/hoist-directives.js b/src/babel/transformation/transformers/internal/hoist-directives.js
index 8c0c1280cf..a3dbe27811 100644
--- a/src/babel/transformation/transformers/internal/hoist-directives.js
+++ b/src/babel/transformation/transformers/internal/hoist-directives.js
@@ -1,5 +1,9 @@
 import * as t from "../../../types";
 
+export var metadata = {
+  group: "builtin-setup"
+};
+
 export var BlockStatement = {
   exit(node) {
     for (var i = 0; i < node.body.length; i++) {

From b02a1112bcbfee975c88e2b58e61711579a313bc Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Fri, 8 May 2015 23:10:02 +0100
Subject: [PATCH 27/30] change ClassExpression visitor to enter instead of
 exist in the es6.classes transformer

---
 src/babel/transformation/transformers/es6/classes.js | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/src/babel/transformation/transformers/es6/classes.js b/src/babel/transformation/transformers/es6/classes.js
index e1bb106659..90ca984e7f 100644
--- a/src/babel/transformation/transformers/es6/classes.js
+++ b/src/babel/transformation/transformers/es6/classes.js
@@ -17,11 +17,9 @@ export function ClassDeclaration(node, parent, scope, file) {
   ]);
 }
 
-export var ClassExpression = {
-  exit(node, parent, scope, file) {
-    return new ClassTransformer(this, file).run();
-  }
-};
+export function ClassExpression(node, parent, scope, file) {
+  return new ClassTransformer(this, file).run();
+}
 
 var collectPropertyReferencesVisitor = {
   Identifier: {

From f0bfdfb699b68c8456ad5f7b1bf289843d125f8e Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Fri, 8 May 2015 23:13:27 +0100
Subject: [PATCH 28/30] skip traversing back into ReturnStatement replacement
 when rewriting loops in the es6.blockScoping transformer

---
 src/babel/transformation/transformers/es6/block-scoping.js | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/babel/transformation/transformers/es6/block-scoping.js b/src/babel/transformation/transformers/es6/block-scoping.js
index 8d8f8a8f88..8d1a5948a3 100644
--- a/src/babel/transformation/transformers/es6/block-scoping.js
+++ b/src/babel/transformation/transformers/es6/block-scoping.js
@@ -233,6 +233,7 @@ var loopVisitor = {
 
     if (replace) {
       replace = t.returnStatement(replace);
+      this.skip();
       return t.inherits(replace, node);
     }
   }

From 920c84a1f226462fc502620f7095596e99529cd3 Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Fri, 8 May 2015 23:33:20 +0100
Subject: [PATCH 29/30] move shadow function visitors to entrance instead of
 exit

---
 .../transformers/internal/shadow-functions.js | 26 ++++++++-----------
 .../es6.arrow-functions/arguments/expected.js |  8 +++---
 2 files changed, 15 insertions(+), 19 deletions(-)

diff --git a/src/babel/transformation/transformers/internal/shadow-functions.js b/src/babel/transformation/transformers/internal/shadow-functions.js
index 04d11f7811..92ab2f9687 100644
--- a/src/babel/transformation/transformers/internal/shadow-functions.js
+++ b/src/babel/transformation/transformers/internal/shadow-functions.js
@@ -89,21 +89,17 @@ export var metadata = {
   group: "builtin-trailing"
 };
 
-export var Program = {
-  exit(node, parent, scope) {
-    aliasFunction(function () {
-      return node.body;
-    }, this, scope);
-  }
-};
+export function Program(node, parent, scope) {
+  aliasFunction(function () {
+    return node.body;
+  }, this, scope);
+}
 
-export var FunctionDeclaration = {
-  exit(node, parent, scope) {
-    aliasFunction(function () {
-      t.ensureBlock(node);
-      return node.body.body;
-    }, this, scope);
-  }
-};
+export function FunctionDeclaration(node, parent, scope) {
+  aliasFunction(function () {
+    t.ensureBlock(node);
+    return node.body.body;
+  }, this, scope);
+}
 
 export { FunctionDeclaration as FunctionExpression };
diff --git a/test/core/fixtures/transformation/es6.arrow-functions/arguments/expected.js b/test/core/fixtures/transformation/es6.arrow-functions/arguments/expected.js
index 2972f6b9b1..3ddd69015f 100644
--- a/test/core/fixtures/transformation/es6.arrow-functions/arguments/expected.js
+++ b/test/core/fixtures/transformation/es6.arrow-functions/arguments/expected.js
@@ -11,17 +11,17 @@ function one() {
 one(1, 2);
 
 function two() {
-  var _arguments3 = arguments;
+  var _arguments2 = arguments;
 
   var inner = function inner() {
-    return _arguments3;
+    return _arguments2;
   };
 
   var another = function another() {
-    var _arguments2 = arguments;
+    var _arguments3 = arguments;
 
     var inner2 = function inner2() {
-      return _arguments2;
+      return _arguments3;
     };
   };
 

From 89e31085d2ee6cd4c135f9f6be90faf3c6522d48 Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Fri, 8 May 2015 23:33:30 +0100
Subject: [PATCH 30/30] ensure dynamic imports are hoisted

---
 .../transformers/internal/module-formatter.js         |  5 +++++
 .../fixtures/transformation/runtime/full/expected.js  | 11 +++++------
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/src/babel/transformation/transformers/internal/module-formatter.js b/src/babel/transformation/transformers/internal/module-formatter.js
index 4235eeb4fb..36f6206d72 100644
--- a/src/babel/transformation/transformers/internal/module-formatter.js
+++ b/src/babel/transformation/transformers/internal/module-formatter.js
@@ -7,6 +7,11 @@ export var metadata = {
 export var Program = {
   exit(program, parent, scope, file) {
     strict.wrap(program, function () {
+      // ensure that these are at the top, just like normal imports
+      for (var node of (file.dynamicImports: Array)) {
+        node._blockHoist = 3;
+      }
+
       program.body = file.dynamicImports.concat(program.body);
     });
 
diff --git a/test/core/fixtures/transformation/runtime/full/expected.js b/test/core/fixtures/transformation/runtime/full/expected.js
index 3f3795a497..d83975b0db 100644
--- a/test/core/fixtures/transformation/runtime/full/expected.js
+++ b/test/core/fixtures/transformation/runtime/full/expected.js
@@ -1,11 +1,5 @@
 "use strict";
 
-_Object$defineProperty(exports, "__esModule", {
-  value: true
-});
-
-exports.giveWord = giveWord;
-
 var _regeneratorRuntime = require("babel-runtime/regenerator")["default"];
 
 var _Object$defineProperty = require("babel-runtime/core-js/object/define-property")["default"];
@@ -16,6 +10,11 @@ var _interopRequireDefault = require("babel-runtime/helpers/interop-require-defa
 
 var _interopRequireWildcard = require("babel-runtime/helpers/interop-require-wildcard")["default"];
 
+_Object$defineProperty(exports, "__esModule", {
+  value: true
+});
+
+exports.giveWord = giveWord;
 var marked0$0 = [giveWord].map(_regeneratorRuntime.mark);
 
 var _someModule = require("someModule");