v2.6.0

Add .es to register extensions

.gitmodules

@@ -0,0 +1,6 @@
+[submodule "vendor/traceur"]
+	path = vendor/traceur
+	url = https://github.com/google/traceur-compiler
+[submodule "vendor/regenerator"]
+	path = vendor/regenerator
+	url = https://github.com/facebook/regenerator

CHANGELOG.md

@@ -1,6 +1,74 @@
 # Changelog
 
-Gaps between patch versions are faulty/broken releases.
+> **Tags:**
+> - [New Feature]
+> - [Bug Fix]
+> - [Spec Compliancy]
+> - [Breaking Change]
+> - [Documentation]
+> - [Internal]
+> - [Misc]
+
+_Note: Gaps between patch versions are faulty/broken releases._
+
+## 2.6.0
+
+ * [Internal] Fix incorrect AST node `identifier("this")`.
+ * [Spec Compliancy] Add `interopRequireWildcard` around wildcard imports and exports to handle non-object exports.
+ * [Internal] Upgrade `acorn-6to5`.
+ * [New Feature] Basic destructuring defaults
+ * [New Feature] Add `.es` to list of supported extensions.
+ * [New Feature] Add optional `typeofSymbol` transformer.
+ * [Bug Fix] Better handling of number literal property keys.
+ * [Bug Fix] [Internal] Better `toIdentifier` method that handles reserved words.
+ * [Internal] Upgrade to `core-js` 4.0.0.
+ * [Internal] Upgrade to `regenerator` 0.8.3.
+ * [Bug Fix] Handle `NewExpression` paren insertion edegcases better.
+ * [Spec Compliancy] Class inheritance now has a `function` or `null` type check.
+ * [Misc] Move `"use strict";` to inside module bodies instead of at the top of the file.
+
+## 2.5.0
+
+ * Remove `noDuplicateProperties` transformer.
+ * Better generated UIDs based on nodes.
+ * Default parameters now use `arguments[i]`, conditionals and variable declarations instead of using long-form if statements.
+
+## 2.4.10
+
+ * Upgrade `acorn-6to5`.
+
+## 2.4.9
+
+ * Upgrade `acorn-6to5`.
+ * Add optional `protoToAssign` transformer.
+ * Fix missing properties from computed property keys.
+ * Make ES7 comprehensions `let` variables.
+
+## 2.4.8
+
+ * Make `require("6to5/register")` work with browserify - [#370](https://github.com/6to5/6to5/pull/370). Thanks [@hughsk](https://github.com/hughsk)!
+
+## 2.4.7
+
+ * Upgrade `acorn-6to5`.
+
+## 2.4.6
+
+ * Move `coreAliasing` and `undefinedToVoid` transformers down to catch `moduleFormatter` transforms.
+
+## 2.4.5
+
+ * Avoid printing comments if they've already been output.
+
+## 2.4.4
+
+ * Add `module` type to browser build `<script>` handler.
+ * Fix some `MemberExpression` modifying incorrectly setting `property` to a `MemberExpression`.
+
+## 2.4.3
+
+ * Upgrade `acorn-6to5`.
+ * Add support for `FunctionDeclaration`s in `bluebirdCoroutines` and `asyncToGenerators` transformers.
 
 ## 2.4.2
 

CODE_OF_CONDUCT.md

@@ -0,0 +1,13 @@
+# Contributor Code of Conduct
+
+As contributors and maintainers of this project, we pledge to respect all people who contribute through reporting issues, posting feature requests, updating documentation, submitting pull requests or patches, and other activities.
+
+We are committed to making participation in this project a harassment-free experience for everyone, regardless of level of experience, gender, gender identity and expression, sexual orientation, disability, personal appearance, body size, race, age, or religion.
+
+Examples of unacceptable behavior by participants include the use of sexual language or imagery, derogatory comments or personal attacks, trolling, public or private harassment, insults, or other unprofessional conduct.
+
+Project maintainers have the right and responsibility to remove, edit, or reject comments, commits, code, wiki edits, issues, and other contributions that are not aligned to this Code of Conduct. Project maintainers who do not follow the Code of Conduct may be removed from the project team.
+
+Instances of abusive, harassing, or otherwise unacceptable behavior may be reported by opening an issue or contacting one or more of the project maintainers.
+
+This Code of Conduct is adapted from the [Contributor Covenant](http://contributor-covenant.org), version 1.0.0, available at [http://contributor-covenant.org/version/1/0/0/](http://contributor-covenant.org/version/1/0/0/)

CONTRIBUTING.md

@@ -1,5 +1,7 @@
 # Contributing
 
+Before contributing, please read the [code of conduct](https://github.com/6to5/6to5/blob/master/CODE_OF_CONDUCT.md).
+
  * **General**
    * No ES6 syntax features or methods, exclusively ES5.
    * Max of five arguments for functions

Makefile

@@ -6,7 +6,23 @@ MOCHA_CMD = node_modules/mocha/bin/_mocha
 
 export NODE_ENV = test
 
-.PHONY: clean test test-cov test-clean lint test-travis test-spec test-browser publish bench build
+.PHONY: clean test test-cov test-clean lint test-travis test-spec test-browser publish bench build bootstrap
+
+build:
+	mkdir -p dist
+
+	node bin/cache-templates
+
+	node $(BROWSERIFY_CMD) -e lib/6to5/polyfill.js >dist/polyfill.js
+	node $(UGLIFY_CMD) dist/polyfill.js >dist/polyfill.min.js
+
+	node $(BROWSERIFY_CMD) lib/6to5/browser.js -s to5 >dist/6to5.js
+	node $(UGLIFY_CMD) dist/6to5.js >dist/6to5.min.js
+
+	node bin/6to5-runtime >dist/runtime.js
+	node $(UGLIFY_CMD) dist/runtime.js >dist/runtime.min.js
+
+	rm -rf templates.json
 
 clean:
 	rm -rf coverage templates.json test/tmp dist
@@ -45,22 +61,6 @@ test-browser:
 
 	test -n "`which open`" && open test/browser.html
 
-build:
-	mkdir -p dist
-
-	node bin/cache-templates
-
-	node $(BROWSERIFY_CMD) -e lib/6to5/polyfill.js >dist/polyfill.js
-	node $(UGLIFY_CMD) dist/polyfill.js >dist/polyfill.min.js
-
-	node $(BROWSERIFY_CMD) lib/6to5/browser.js -s to5 >dist/6to5.js
-	node $(UGLIFY_CMD) dist/6to5.js >dist/6to5.min.js
-
-	node bin/6to5-runtime >dist/runtime.js
-	node $(UGLIFY_CMD) dist/runtime.js >dist/runtime.min.js
-
-	rm -rf templates.json
-
 publish:
 	git pull --rebase
 
@@ -81,3 +81,8 @@ publish:
 	git push --follow-tags
 
 	rm -rf templates.json browser.js runtime.js browser-polyfill.js
+
+bootstrap:
+	npm install
+	git submodule update --init
+	cd vendor/regenerator; npm install

NOTES.md

@@ -0,0 +1,3 @@
+# Notes
+
+ * Wildcard exports/imports wont normalise if `export default` is a non-object.

doc/caveats.md

@@ -9,12 +9,15 @@ You may alternatively selectively include what you need:
 | Feature                     | Requirements                                                                                                           |
 | --------------------------- | ---------------------------------------------------------------------------------------------------------------------- |
 | Abstract References         | [experimental](experimental.md), `Symbol`                                                                              |
-| Array destructuring         | `Array.isArray`, `Array.from`                                                                                          |
+| Array destructuring         | `Array.from`                                                                                                           |
 | Async functions, Generators | [experimental](experimental.md), [regenerator runtime](https://github.com/facebook/regenerator/blob/master/runtime.js) |
-| Comprehensions              | [experimental](experimental.md), `Array.isArray`, `Array.from`                                                         |
+| Comprehensions              | [experimental](experimental.md), `Array.from`                                                                          |
 | For Of                      | `Symbol`, `prototype[Symbol.iterator]`                                                                                 |
+| Modules                     | `Object.assign`*                                                                                                       |
 | Object spread/rest          | [experimental](experimental.md), `Object.assign`                                                                       |
-| Spread                      | `Array.isArray`, `Array.from`                                                                                          |
+| Spread                      | `Array.from`                                                                                                           |
+
+*Only required for exporting a non-function `default` with additional `export`s.
 
 ## ES5
 
@@ -26,13 +29,13 @@ ES5 such as lower versions of IE then using the
 
 ## Internet Explorer
 
-### Classes (9 and below)
+### Classes (10 and below)
 
 If you're inheriting from a class then static properties are inherited from it
 via [\_\_proto\_\_](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/proto),
 this is widely supported but you may run into problems with much older browsers.
 
-**NOTE:** `__proto__` is not supported on IE <= 9 so static properties
+**NOTE:** `__proto__` is not supported in IE <= 10 so static properties
 **will not** be inherited. A possible workaround is to use `super();`:
 
 ```javascript
@@ -56,4 +59,4 @@ unfortunate as it's required to set getters and setters. Due to this if
 you plan on supporting IE8 or below then the user of getters and setters
 isn't recommended.
 
-Reference: [MDN](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty#Internet_Explorer_8_specific_notes).
+**Reference**: [MDN](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty#Internet_Explorer_8_specific_notes).

doc/differences.md

@@ -49,13 +49,12 @@ var seattlers = (function() {
 }());
 ```
 
-As you can tell, it's not very pretty, unreadable even. Instead of mapping
-directly to a runtime, like other transpilers, 6to5 maps directly to the
-equivalent ES5.
+As you can tell, it's not very pretty. Instead of mapping directly to a
+runtime, like other transpilers, 6to5 maps directly to the equivalent ES5.
 
 Sometimes there are little inline functions that 6to5 needs. These are
 placed at the top of your file much like coffee-script does. If these
-are bother you then you can use the [optional runtime](optional-runtime.md).
+bother you then you can use the [optional runtime](optional-runtime.md).
 We promise that these inline functions will never be significant and will
 always be used as little as possible.
 
@@ -79,43 +78,43 @@ that when you turn it off and use your code in a full ES6 environment
 
 ### Features
 
-|                              | 6to5 | Traceur | es6-transpiler | esnext | es6now | jstransform |
-| ---------------------------- | ---- | ------- | -------------- | ------ | ------ | ----------- |
-| Source maps                  | ✓    | ✓       | ✓              | ✓      |        | ✓           |
-| No compiler global pollution | ✓    |         | ✓              | ✓      |        | ✓           |
-| Optional runtime             | ✓    |         | ✓              |        |        | ✓           |
-| Browser compiler             | ✓    | ✓       |                | ✓      |        |             |
+|                              | 6to5 | Traceur | es6-transpiler | es6now | jstransform |
+| ---------------------------- | ---- | ------- | -------------- | ------ | ----------- |
+| Source maps                  | ✓    | ✓       | ✓              |        | ✓           |
+| No compiler global pollution | ✓    |         | ✓              |        | ✓           |
+| Optional runtime             | ✓    |         | ✓              |        | ✓           |
+| Browser compiler             | ✓    | ✓       |                |        |             |
 
 ### Language Support
 
-|                              | 6to5 | Traceur | es6-transpiler | esnext | es6now | jstransform |
-| ---------------------------- | ---- | ------- | -------------- | ------ | ------ | ----------- |
-| Abstract references          | ✓    |         |                |        |        |             |
-| Array comprehension          | ✓    | ✓       | ✓              |        |        |             |
-| Arrow functions              | ✓    | ✓       | ✓              | ✓      | ✓      | ✓           |
-| Async functions              | ✓    | ✓       |                | ✓      |        |             |
-| Async generator functions    | ✓    | ✓       |                |        |        |             |
-| Classes                      | ✓    | ✓       | ✓              | ✓      | ✓      | ✓           |
-| Computed property names      | ✓    | ✓       | ✓              | ✓      | ✓      |             |
-| Constants                    | ✓    | ✓       | ✓              |        |        |             |
-| Default parameters           | ✓    | ✓       | ✓              | ✓      | ✓      |             |
-| Destructuring                | ✓    | ✓       | ✓              | ✓      | ✓      | ✓           |
-| Exponentiation operator      | ✓    | ✓       |                |        |        |             |
-| Flow types                   | ✓    |         |                |        |        | ✓           |
-| For-of                       | ✓    | ✓       | ✓              | ✓      | ✓      |             |
-| Generators                   | ✓    | ✓       |                | ✓      |        |             |
-| Generator comprehension      | ✓    | ✓       |                |        |        |             |
-| JSX                          | ✓    |         |                |        |        |             |
-| Let scoping                  | ✓    | ✓       | ✓              |        |        |             |
-| Modules                      | ✓    | ✓       |                |        | ✓      |             |
-| Object rest/spread           | ✓    |         |                |        |        | ✓           |
-| Property method assignment   | ✓    | ✓       | ✓              | ✓      | ✓      | ✓           |
-| Property name shorthand      | ✓    | ✓       | ✓              | ✓      | ✓      | ✓           |
-| Rest parameters              | ✓    | ✓       | ✓              | ✓      | ✓      | ✓           |
-| React                        | ✓    |         |                |        |        |             |
-| Spread                       | ✓    | ✓       | ✓              | ✓      | ✓      |             |
-| Template literals            | ✓    | ✓       | ✓              | ✓      | ✓      | ✓           |
-| Unicode regex                | ✓    | ✓       | ✓              |        |        |             |
+|                              | 6to5 | Traceur | es6-transpiler | es6now | jstransform |
+| ---------------------------- | ---- | ------- | -------------- | ------ | ----------- |
+| Abstract references          | ✓    |         |                |        |             |
+| Array comprehension          | ✓    | ✓       | ✓              |        |             |
+| Arrow functions              | ✓    | ✓       | ✓              | ✓      | ✓           |
+| Async functions              | ✓    | ✓       |                |        |             |
+| Async generator functions    | ✓    | ✓       |                |        |             |
+| Classes                      | ✓    | ✓       | ✓              | ✓      | ✓           |
+| Computed property names      | ✓    | ✓       | ✓              | ✓      |             |
+| Constants                    | ✓    | ✓       | ✓              |        |             |
+| Default parameters           | ✓    | ✓       | ✓              | ✓      |             |
+| Destructuring                | ✓    | ✓       | ✓              | ✓      | ✓           |
+| Exponentiation operator      | ✓    | ✓       |                |        |             |
+| Flow types                   | ✓    |         |                |        | ✓           |
+| For-of                       | ✓    | ✓       | ✓              | ✓      |             |
+| Generators                   | ✓    | ✓       |                |        |             |
+| Generator comprehension      | ✓    | ✓       |                |        |             |
+| JSX                          | ✓    |         |                |        |             |
+| Let scoping                  | ✓    | ✓       | ✓              |        |             |
+| Modules                      | ✓    | ✓       |                | ✓      |             |
+| Object rest/spread           | ✓    |         |                |        | ✓           |
+| Property method assignment   | ✓    | ✓       | ✓              | ✓      | ✓           |
+| Property name shorthand      | ✓    | ✓       | ✓              | ✓      | ✓           |
+| Rest parameters              | ✓    | ✓       | ✓              | ✓      | ✓           |
+| React                        | ✓    |         |                |        |             |
+| Spread                       | ✓    | ✓       | ✓              | ✓      |             |
+| Template literals            | ✓    | ✓       | ✓              | ✓      | ✓           |
+| Unicode regex                | ✓    | ✓       | ✓              |        |             |
 
 ### [Traceur](https://github.com/google/traceur-compiler)
 

doc/index.md

@@ -52,7 +52,7 @@ And it doesn't end here! To see all the ways you can use 6to5, check out the
  - [Let scoping](features.md#let-scoping)
  - [Modules](features.md#modules)
  - [Numeric literals](features.md#numeric-literals)
- - [Object Rest/Spread](features.md#object-rest-spread) ([experimental](experimental.md))
+ - [Object rest/spread](features.md#object-rest-spread) ([experimental](experimental.md))
  - [Property method assignment](features.md#property-method-assignment)
  - [Property name shorthand](features.md#property-name-shorthand)
  - [React/JSX](react.md)

doc/playground.md

@@ -18,11 +18,19 @@ to5.transform("code", { playground: true });
 
  * [Memoization operator](#memoization-operator)
  * [Method binding](#method-binding)
+ * [Method binding function shorthand](#method-binding-function-shorthand)
  * [Object getter memoization](#object-getter-memoization)
  * [This shorthand](#this-shorthand)
 
 ### Memoization assignment operator
 
+The memoization assignment operator allows you to lazily set an object property.
+It checks whether there's a property defined on the object and if there isn't then
+the right hand value is set.
+
+This means that `obj.x` in the following `var x = { x: undefined }; obj.x ?= 2;`
+will still be `undefined` because it's already been defined on the object.
+
 ```javascript
 var obj = {};
 obj.x ?= 2;
@@ -42,7 +50,7 @@ var obj = {};
 obj.x ?= 2;
 ```
 
-equivalent to:
+equivalent to
 
 ```javascript
 var obj = {};
@@ -54,17 +62,25 @@ if (!Object.prototype.hasOwnProperty.call(obj, "x")) obj.x = 2;
 ```javascript
 var fn = obj#method;
 var fn = obj#method("foob");
-
-["foo", "bar"].map(#toUpperCase); // ["FOO", "BAR"]
-[1.1234, 23.53245, 3].map(#toFixed(2)); // ["1.12", "23.53", "3.00"]
 ```
 
-equivalent to:
+equivalent to
 
 ```javascript
 var fn = obj.method.bind(obj);
 var fn = obj.method.bind(obj, "foob");
+```
 
+### Method binding function shorthand
+
+```javascript
+["foo", "bar"].map(#toUpperCase); // ["FOO", "BAR"]
+[1.1234, 23.53245, 3].map(#toFixed(2)); // ["1.12", "23.53", "3.00"]
+```
+
+equivalent to
+
+```javascript
 ["foo", "bar"].map(function (val) { return val.toUpperCase(); });
 [1.1234, 23.53245, 3].map(function (val) { return val.toFixed(2); });
 ```

doc/usage.md

@@ -208,7 +208,7 @@ result.ast;
 
 ### Require hook
 
-All subsequent files required by node with the extensions `.es6` and `.js` will
+All subsequent files required by node with the extensions `.es6`, `.es` and `.js` will
 be transformed by 6to5. The polyfill specified in [Polyfill](polyfill.md) is
 also required; but this is automatically loaded when using:
 

lib/6to5/browser.js

@@ -34,7 +34,7 @@ transform.load = function (url, callback, opts, hold) {
 
 var runScripts = function () {
   var scripts = [];
-  var types   = ["text/ecmascript-6", "text/6to5"];
+  var types   = ["text/ecmascript-6", "text/6to5", "module"];
   var index   = 0;
 
   var exec = function () {
@@ -60,8 +60,9 @@ var runScripts = function () {
     }
   };
 
-  var _scripts = global.document.getElementsByTagName("script");
-  for (var i in _scripts) {
+  var _scripts = global.document .getElementsByTagName("script");
+
+  for (var i = 0; i < _scripts.length; ++i) {
     var _script = _scripts[i];
     if (types.indexOf(_script.type) >= 0) scripts.push(_script);
   }

lib/6to5/file.js

@@ -10,14 +10,17 @@ var t         = require("./types");
 var _         = require("lodash");
 
 function File(opts) {
-  this.opts         = File.normaliseOptions(opts);
-  this.transformers = this.getTransformers();
-  this.uids         = {};
-  this.ast          = {};
+  this.dynamicImports   = [];
+  this.dynamicImportIds = {};
+  this.opts             = File.normaliseOptions(opts);
+  this.transformers     = this.getTransformers();
+  this.uids             = {};
+  this.ast              = {};
 }
 
-File.declarations = [
+File.helpers = [
   "inherits",
+  "defaults",
   "prototype-properties",
   "apply-constructor",
   "tagged-template-literal",
@@ -27,12 +30,17 @@ File.declarations = [
   "object-without-properties",
   "has-own",
   "slice",
+  "bind",
   "define-property",
-  "async-to-generator"
+  "async-to-generator",
+  "interop-require-wildcard",
+  "typeof",
+  "exports-wildcard"
 ];
 
-File.excludeDeclarationsFromRuntime = [
-  "async-to-generator"
+File.excludeHelpersFromRuntime = [
+  "async-to-generator",
+  "typeof"
 ];
 
 File.normaliseOptions = function (opts) {
@@ -96,25 +104,30 @@ File.normaliseOptions = function (opts) {
 File.prototype.getTransformers = function () {
   var file = this;
   var transformers = [];
+  var secondPassTransformers = [];
 
   _.each(transform.transformers, function (transformer) {
     if (transformer.canRun(file)) {
       transformers.push(transformer);
 
+      if (transformer.secondPass) {
+        secondPassTransformers.push(transformer);
+      }
+
       if (transformer.manipulateOptions) {
         transformer.manipulateOptions(file.opts, file);
       }
     }
   });
 
-  return transformers;
+  return transformers.concat(secondPassTransformers);
 };
 
 File.prototype.toArray = function (node, i) {
   if (t.isArrayExpression(node)) {
     return node;
   } else if (t.isIdentifier(node) && node.name === "arguments") {
-    return t.callExpression(t.memberExpression(this.addDeclaration("slice"), t.identifier("call")), [node]);
+    return t.callExpression(t.memberExpression(this.addHelper("slice"), t.identifier("call")), [node]);
   } else {
     var declarationName = "to-array";
     var args = [node];
@@ -122,7 +135,7 @@ File.prototype.toArray = function (node, i) {
       args.push(t.literal(i));
       declarationName = "sliced-to-array";
     }
-    return t.callExpression(this.addDeclaration(declarationName), args);
+    return t.callExpression(this.addHelper(declarationName), args);
   }
 };
 
@@ -153,14 +166,24 @@ File.prototype.parseShebang = function (code) {
   return code;
 };
 
-File.prototype.addImport = function (id, source) {
-  var specifiers = [t.importSpecifier(t.identifier("default"), id)];
-  var declar = t.importDeclaration(specifiers, t.literal(source));
-  this.ast.program.body.unshift(declar);
+File.prototype.addImport = function (source, name) {
+  name = name || source;
+  var id = this.dynamicImportIds[name];
+
+  if (!id) {
+    id = this.dynamicImportIds[name] = this.generateUidIdentifier(name);
+
+    var specifiers = [t.importSpecifier(t.identifier("default"), id)];
+    var declar = t.importDeclaration(specifiers, t.literal(source));
+    declar._blockHoist = 3;
+    this.dynamicImports.push(declar);
+  }
+
+  return id;
 };
 
-File.prototype.addDeclaration = function (name) {
-  if (!_.contains(File.declarations, name)) {
+File.prototype.addHelper = function (name) {
+  if (!_.contains(File.helpers, name)) {
     throw new ReferenceError("unknown declaration " + name);
   }
 
@@ -171,7 +194,7 @@ File.prototype.addDeclaration = function (name) {
 
   var ref;
   var runtimeNamespace = this.opts.runtime;
-  if (runtimeNamespace && !_.contains(File.excludeDeclarationsFromRuntime, name)) {
+  if (runtimeNamespace && !_.contains(File.excludeHelpersFromRuntime, name)) {
     name = t.identifier(t.toIdentifier(name));
     return t.memberExpression(t.identifier(runtimeNamespace), name);
   } else {
@@ -265,7 +288,7 @@ File.prototype.generate = function () {
 };
 
 File.prototype.generateUid = function (name, scope) {
-  name = t.toIdentifier(name);
+  name = t.toIdentifier(name).replace(/^_+/, "");
 
   scope = scope || this.scope;
 

lib/6to5/generation/generator.js

@@ -148,11 +148,11 @@ CodeGenerator.prototype.print = function (node, parent, opts) {
   };
 
   if (this[node.type]) {
-    var needsCommentParens = t.isExpression(node) && node.leadingComments && node.leadingComments.length;
-    var needsParens        = needsCommentParens || n.needsParens(node, parent);
+    var needsNoLineTermParens = n.needsParensNoLineTerminator(node, parent);
+    var needsParens           = needsNoLineTermParens || n.needsParens(node, parent);
 
     if (needsParens) this.push("(");
-    if (needsCommentParens) this.indent();
+    if (needsNoLineTermParens) this.indent();
 
     this.printLeadingComments(node, parent);
 
@@ -163,7 +163,7 @@ CodeGenerator.prototype.print = function (node, parent, opts) {
 
     this[node.type](node, this.buildPrint(node), parent);
 
-    if (needsCommentParens) {
+    if (needsNoLineTermParens) {
       this.newline();
       this.dedent();
     }
@@ -274,14 +274,21 @@ CodeGenerator.prototype._printComments = function (comments) {
   var self = this;
 
   _.each(comments, function (comment) {
+    var skip = false;
+
     // find the original comment in the ast and set it as displayed
     _.each(self.ast.comments, function (origComment) {
       if (origComment.start === comment.start) {
+        // comment has already been output
+        if (origComment._displayed) skip = true;
+
         origComment._displayed = true;
         return false;
       }
     });
 
+    if (skip) return;
+
     // whitespace before
     self.newline(self.whitespace.getNewlinesBefore(comment));
 

lib/6to5/generation/generators/expressions.js

@@ -1,5 +1,6 @@
 var util = require("../../util");
 var t    = require("../../types");
+var _    = require("lodash");
 
 exports.UnaryExpression = function (node, print) {
   var hasSpace = /[a-z]$/.test(node.operator);
@@ -86,6 +87,7 @@ exports.ExpressionStatement = function (node, print) {
 
 exports.BinaryExpression =
 exports.LogicalExpression =
+exports.AssignmentPattern =
 exports.AssignmentExpression = function (node, print) {
   print(node.left);
   this.push(" " + node.operator + " ");
@@ -98,7 +100,16 @@ exports.MemberExpression = function (node, print) {
   var obj = node.object;
   print(obj);
 
-  if (node.computed) {
+  if (!node.computed && t.isMemberExpression(node.property)) {
+    throw new TypeError("Got a MemberExpression for MemberExpression property");
+  }
+
+  var computed = node.computed;
+  if (t.isLiteral(node.property) && _.isNumber(node.property.value)) {
+    computed = true;
+  }
+
+  if (computed) {
     this.push("[");
     print(node.property);
     this.push("]");

lib/6to5/generation/node/index.js

@@ -61,14 +61,40 @@ Node.prototype.needsParens = function () {
   if (!parent) return false;
 
   if (t.isNewExpression(parent) && parent.callee === node) {
-    return t.isCallExpression(node) || _.some(node, function (val) {
+    if (t.isCallExpression(node)) return true;
+
+    var hasCall = _.some(node, function (val) {
       return t.isCallExpression(val);
     });
+    if (hasCall) return true;
   }
 
   return find(parens, node, parent);
 };
 
+Node.prototype.needsParensNoLineTerminator = function () {
+  var parent = this.parent;
+  var node   = this.node;
+
+  if (!parent) return false;
+
+  // no comments
+  if (!node.leadingComments || !node.leadingComments.length) {
+    return false;
+  }
+
+  if (t.isYieldExpression(parent) || t.isAwaitExpression(parent)) {
+    return true;
+  }
+
+  if (t.isContinueStatement(parent) || t.isBreakStatement(parent) ||
+      t.isReturnStatement(parent) || t.isThrowStatement(parent)) {
+    return true;
+  }
+
+  return false;
+};
+
 _.each(Node.prototype, function (fn, key) {
   Node[key] = function (node, parent) {
     var n = new Node(node, parent);

lib/6to5/generation/node/parentheses.js

@@ -13,15 +13,30 @@ _.each([
   ["<", ">", "<=", ">=", "in", "instanceof"],
   [">>", "<<", ">>>"],
   ["+", "-"],
-  ["*", "/", "%"]
+  ["*", "/", "%"],
+  ["**"]
 ], function (tier, i) {
   _.each(tier, function (op) {
     PRECEDENCE[op] = i;
   });
 });
 
+exports.ObjectExpression = function (node, parent) {
+  if (t.isExpressionStatement(parent)) {
+    // ({ foo: "bar" });
+    return true;
+  }
+
+  if (t.isMemberExpression(parent) && parent.object === node) {
+    // ({ foo: "bar" }).foo
+    return true;
+  }
+
+  return false;
+};
+
 exports.Binary = function (node, parent) {
-  if (t.isCallExpression(parent) && parent.callee === node) {
+  if ((t.isCallExpression(parent) || t.isNewExpression(parent)) && parent.callee === node) {
     return true;
   }
 

lib/6to5/patch.js

@@ -12,6 +12,12 @@ var types = require("ast-types");
 var def   = types.Type.def;
 var or    = types.Type.or;
 
+def("AssignmentPattern")
+    .bases("Pattern")
+    .build("left", "right")
+    .field("left", def("Pattern"))
+    .field("right", def("Expression"));
+
 // Acorn - Same as ImportNamespaceSpecifier but `id` is `name`
 def("ImportBatchSpecifier")
   .bases("Specifier")

lib/6to5/register-browser.js

@@ -0,0 +1,4 @@
+// Required to safely use 6to5/register within a browserify codebase.
+module.exports = function () {};
+
+require("./polyfill");

lib/6to5/register.js

@@ -123,7 +123,7 @@ var hookExtensions = function (_exts) {
   });
 };
 
-hookExtensions([".es6", ".js"]);
+hookExtensions([".es6", ".es", ".js"]);
 
 module.exports = function (opts) {
   // normalise options

lib/6to5/runtime-generator.js

@@ -18,8 +18,8 @@ module.exports = function (namespace) {
     )
   ]));
 
-  _.each(File.declarations, function (name) {
-    if (_.contains(File.excludeDeclarationsFromRuntime, name)) {
+  _.each(File.helpers, function (name) {
+    if (_.contains(File.excludeHelpersFromRuntime, name)) {
       return false;
     }
 

lib/6to5/transformation/modules/_default.js

@@ -51,7 +51,7 @@ DefaultFormatter.prototype.remapAssignments = function () {
   traverse(this.file.ast, {
     enter: function (node, parent, scope) {
       if (t.isUpdateExpression(node) && isLocalReference(node.argument, scope)) {
-        this.stop();
+        this.skip();
 
         // expand to long file assignment expression
         var assign = t.assignmentExpression(node.operator[0] + "=", node.argument, t.literal(1));
@@ -79,7 +79,7 @@ DefaultFormatter.prototype.remapAssignments = function () {
       }
 
       if (t.isAssignmentExpression(node) && isLocalReference(node.left, scope)) {
-        this.stop();
+        this.skip();
         return self.remapExportAssignment(node);
       }
     }
@@ -141,10 +141,17 @@ DefaultFormatter.prototype._exportSpecifier = function (getRef, specifier, node,
       // export * from "foo";
       nodes.push(this._exportsWildcard(getRef(), node));
     } else {
+      var ref;
+      if (t.isSpecifierDefault(specifier.id) || this.noInteropRequire) {
+        ref = t.memberExpression(getRef(), specifier.id);
+      } else {
+        ref = t.callExpression(this.file.addHelper("interop-require"), [getRef()]);
+      }
+
       // export { foo } from "test";
       nodes.push(this._exportsAssign(
         t.getSpecifierName(specifier),
-        t.memberExpression(getRef(), specifier.id),
+        ref,
         node
       ));
     }
@@ -155,9 +162,9 @@ DefaultFormatter.prototype._exportSpecifier = function (getRef, specifier, node,
 };
 
 DefaultFormatter.prototype._exportsWildcard = function (objectIdentifier) {
-  return util.template("exports-wildcard", {
-    OBJECT: objectIdentifier
-  }, true);
+  return t.expressionStatement(t.callExpression(this.file.addHelper("exports-wildcard"), [
+    t.callExpression(this.file.addHelper("interop-require-wildcard"), [objectIdentifier])
+  ]));
 };
 
 DefaultFormatter.prototype._exportsAssign = function (id, init) {

lib/6to5/transformation/modules/amd.js

@@ -85,7 +85,7 @@ AMDFormatter.prototype.importSpecifier = function (specifier, node, nodes) {
     // import * as bar from "foo";
   } else if (t.isSpecifierDefault(specifier) && !this.noInteropRequire) {
     // import foo from "foo";
-    ref = t.callExpression(this.file.addDeclaration("interop-require"), [ref]);
+    ref = t.callExpression(this.file.addHelper("interop-require"), [ref]);
   } else {
     // import {foo} from "foo";
     ref = t.memberExpression(ref, specifier.id, false);

lib/6to5/transformation/modules/common.js

@@ -26,24 +26,30 @@ CommonJSFormatter.prototype.importSpecifier = function (specifier, node, nodes)
   if (t.isSpecifierDefault(specifier)) {
     nodes.push(t.variableDeclaration("var", [
       t.variableDeclarator(variableName,
-        t.callExpression(this.file.addDeclaration("interop-require"), [util.template("require", {
+        t.callExpression(this.file.addHelper("interop-require"), [util.template("require", {
           MODULE_NAME: node.source
         })])
       )
     ]));
   } else {
-    // import foo from "foo";
-
-    var templateName = "require-assign";
-
-    // import * as bar from "foo";
-    if (specifier.type !== "ImportBatchSpecifier") templateName += "-key";
-
-    nodes.push(util.template(templateName, {
-      VARIABLE_NAME: variableName,
-      MODULE_NAME:   node.source,
-      KEY:           specifier.id
-    }));
+    if (specifier.type === "ImportBatchSpecifier") {
+      // import * as bar from "foo";
+      nodes.push(t.variableDeclaration("var", [
+        t.variableDeclarator(
+          variableName,
+          t.callExpression(this.file.addHelper("interop-require-wildcard"), [
+            t.callExpression(t.identifier("require"), [node.source])
+          ])
+        )
+      ]));
+    } else {
+      // import foo from "foo";
+      nodes.push(util.template("require-assign-key", {
+        VARIABLE_NAME: variableName,
+        MODULE_NAME:   node.source,
+        KEY:           specifier.id
+      }));
+    }
   }
 };
 
@@ -65,7 +71,7 @@ CommonJSFormatter.prototype.exportDeclaration = function (node, nodes) {
     // exports = module.exports = VALUE;
     if (this.hasNonDefaultExports) templateName = "exports-default-module-override";
 
-    if (t.isFunction(declar) || !this.hasNonDefaultExports) {
+    if (t.isFunctionDeclaration(declar) || !this.hasNonDefaultExports) {
       assign = util.template(templateName, {
         VALUE: this._pushStatement(declar, nodes)
       }, true);

lib/6to5/transformation/modules/system.js

@@ -1,6 +1,7 @@
 module.exports = SystemFormatter;
 
 var AMDFormatter = require("./amd");
+var useStrict    = require("../transformers/use-strict");
 var traverse     = require("../../traverse");
 var util         = require("../../util");
 var t            = require("../../types");
@@ -31,7 +32,7 @@ SystemFormatter.prototype._exportsWildcard = function (objectIdentifier, node) {
   var right = objectIdentifier;
 
   var block = t.blockStatement([
-    this.buildExportCall(leftIdentifier, valIdentifier)
+    t.expressionStatement(this.buildExportCall(leftIdentifier, valIdentifier))
   ]);
 
   return this._addImportSource(t.forInStatement(left, right, block), node);
@@ -114,7 +115,7 @@ SystemFormatter.prototype.transform = function (ast) {
     enter: function (node, parent, scope) {
       if (t.isFunction(node)) {
         // nothing inside is accessible
-        return this.stop();
+        return this.skip();
       }
 
       if (t.isVariableDeclaration(node)) {
@@ -159,7 +160,7 @@ SystemFormatter.prototype.transform = function (ast) {
   // hoist up function declarations for circular references
   traverse(block, {
     enter: function (node) {
-      if (t.isFunction(node)) this.stop();
+      if (t.isFunction(node)) this.skip();
 
       if (t.isFunctionDeclaration(node) || node._blockHoist) {
         handlerBody.push(node);
@@ -170,5 +171,9 @@ SystemFormatter.prototype.transform = function (ast) {
 
   handlerBody.push(returnStatement);
 
+  if (useStrict._has(block)) {
+    handlerBody.unshift(block.body.shift());
+  }
+
   program.body = [runner];
 };

lib/6to5/transformation/templates/bind.js

@@ -0,0 +1 @@
+Function.prototype.bind

lib/6to5/transformation/templates/class-super-constructor-call.js

@@ -1,3 +1,3 @@
-if (SUPER_NAME) {
+if (SUPER_NAME !== null) {
   SUPER_NAME.apply(this, arguments);
 }

lib/6to5/transformation/templates/default-parameter.js

@@ -0,0 +1 @@
+var VARIABLE_NAME = ARGUMENTS[ARGUMENT_KEY] === undefined ? DEFAULT_VALUE : ARGUMENTS[ARGUMENT_KEY];

lib/6to5/transformation/templates/defaults.js

@@ -0,0 +1,8 @@
+(function (obj, defaults) {
+  for (var key in defaults) {
+    if (obj[key] === undefined) {
+      obj[key] = defaults[key];
+    }
+  }
+  return obj;
+})

lib/6to5/transformation/templates/exports-wildcard.js

@@ -1,5 +1,7 @@
 (function (obj) {
   for (var i in obj) {
-    exports[i] = obj[i];
+    if (exports[i] !== undefined) {
+      exports[i] = obj[i];
+    }
   }
-})(OBJECT);
+})

lib/6to5/transformation/templates/if-undefined-set-to.js

@@ -1 +0,0 @@
-if (VARIABLE === undefined) VARIABLE = DEFAULT;

lib/6to5/transformation/templates/inherits.js

@@ -1,4 +1,7 @@
 (function (child, parent) {
+  if (typeof parent !== "function" && parent !== null) {
+    throw new TypeError("Super expression must either be null or a function, not " + typeof parent);
+  }
   child.prototype = Object.create(parent && parent.prototype, {
     constructor: {
       value: child,

lib/6to5/transformation/templates/interop-require-wildcard.js

@@ -0,0 +1,3 @@
+(function (obj) {
+  return obj && obj.constructor === Object ? obj : { default: obj };
+})

lib/6to5/transformation/templates/object-define-properties-closure.js

@@ -0,0 +1,5 @@
+
+(function (KEY) {
+  CONTENT;
+  return KEY;
+})(OBJECT);

lib/6to5/transformation/templates/property-method-assignment-wrapper.js

@@ -0,0 +1,11 @@
+(function (FUNCTION_KEY) {
+  var WRAPPER_KEY = function FUNCTION_ID() {
+    return FUNCTION_KEY.apply(this, arguments);
+  };
+
+  WRAPPER_KEY.toString = function () {
+    return FUNCTION_KEY.toString();
+  };
+
+  return WRAPPER_KEY;
+})(FUNCTION)

lib/6to5/transformation/templates/require-assign.js

@@ -1 +0,0 @@
-var VARIABLE_NAME = require(MODULE_NAME);

lib/6to5/transformation/templates/rest.js

@@ -0,0 +1,3 @@
+for (var KEY = START; KEY < ARGUMENTS.length; KEY++) {
+  ARRAY[$__0] = ARGUMENTS[KEY];
+}

lib/6to5/transformation/templates/typeof.js

@@ -0,0 +1,3 @@
+(function (obj) {
+  return obj && obj.constructor === Symbol ? "symbol" : typeof obj;
+});

lib/6to5/transformation/transform.js

@@ -42,7 +42,6 @@ _.each({
   // spec
   specBlockHoistFunctions:   require("./transformers/spec-block-hoist-functions"),
   specNoForInOfAssignment:   require("./transformers/spec-no-for-in-of-assignment"),
-  specNoDuplicateProperties: require("./transformers/spec-no-duplicate-properties"),
 
   // playground
   methodBinding:             require("./transformers/playground-method-binding"),
@@ -66,7 +65,7 @@ _.each({
   exponentiationOperator:    require("./transformers/es7-exponentiation-operator"),
   spread:                    require("./transformers/es6-spread"),
   templateLiterals:          require("./transformers/es6-template-literals"),
-  propertyMethodAssignment:  require("./transformers/es5-property-method-assignment"),
+  propertyMethodAssignment:  require("./transformers/es6-property-method-assignment"),
   destructuring:             require("./transformers/es6-destructuring"),
   defaultParameters:         require("./transformers/es6-default-parameters"),
   forOf:                     require("./transformers/es6-for-of"),
@@ -81,15 +80,18 @@ _.each({
   generators:                require("./transformers/es6-generators"),
   restParameters:            require("./transformers/es6-rest-parameters"),
 
+  protoToAssign:             require("./transformers/optional-proto-to-assign"),
+
   _declarations:             require("./transformers/_declarations"),
 
-  coreAliasing:              require("./transformers/optional-core-aliasing"),
-  undefinedToVoid:           require("./transformers/optional-undefined-to-void"),
-
   // wrap up
+  useStrict:                 require("./transformers/use-strict"),
   _aliasFunctions:           require("./transformers/_alias-functions"),
   _moduleFormatter:          require("./transformers/_module-formatter"),
-  useStrict:                 require("./transformers/use-strict"),
+
+  typeofSymbol:              require("./transformers/optional-typeof-symbol"),
+  coreAliasing:              require("./transformers/optional-core-aliasing"),
+  undefinedToVoid:           require("./transformers/optional-undefined-to-void"),
 
   // spec
   specPropertyLiterals:         require("./transformers/spec-property-literals"),

lib/6to5/transformation/transformer.js

@@ -7,20 +7,26 @@ var _        = require("lodash");
 function Transformer(key, transformer, opts) {
   this.manipulateOptions = transformer.manipulateOptions;
   this.experimental      = !!transformer.experimental;
-  this.transformer       = Transformer.normalise(transformer);
+  this.secondPass        = !!transformer.secondPass;
+  this.transformer       = this.normalise(transformer);
   this.optional          = !!transformer.optional;
   this.opts              = opts || {};
   this.key               = key;
 }
 
-Transformer.normalise = function (transformer) {
+Transformer.prototype.normalise = function (transformer) {
+  var self = this;
+
   if (_.isFunction(transformer)) {
     transformer = { ast: transformer };
   }
 
   _.each(transformer, function (fns, type) {
     // hidden property
-    if (type[0] === "_") return;
+    if (type[0] === "_") {
+      self[type] = fns;
+      return;
+    }
 
     if (_.isFunction(fns)) fns = { enter: fns };
 
@@ -41,16 +47,14 @@ Transformer.normalise = function (transformer) {
 
 Transformer.prototype.astRun = function (file, key) {
   var transformer = this.transformer;
-  var ast         = file.ast;
 
   if (transformer.ast && transformer.ast[key]) {
-    transformer.ast[key](ast, file);
+    transformer.ast[key](file.ast, file);
   }
 };
 
 Transformer.prototype.transform = function (file) {
   var transformer = this.transformer;
-  var ast         = file.ast;
 
   var build = function (exit) {
     return function (node, parent, scope) {
@@ -67,7 +71,7 @@ Transformer.prototype.transform = function (file) {
 
   this.astRun(file, "before");
 
-  traverse(ast, {
+  traverse(file.ast, {
     enter: build(),
     exit:  build(true)
   });

lib/6to5/transformation/transformers/_alias-functions.js

@@ -20,7 +20,7 @@ var go = function (getBody, node, file, scope) {
       if (!node._aliasFunction) {
         if (t.isFunction(node)) {
           // stop traversal of this node as it'll be hit again by this transformer
-          return this.stop();
+          return this.skip();
         } else {
           return;
         }
@@ -30,10 +30,10 @@ var go = function (getBody, node, file, scope) {
       traverse(node, {
         enter: function (node, parent) {
           if (t.isFunction(node) && !node._aliasFunction) {
-            return this.stop();
+            return this.skip();
           }
 
-          if (node._ignoreAliasFunctions) return this.stop();
+          if (node._ignoreAliasFunctions) return this.skip();
 
           var getId;
 
@@ -49,7 +49,7 @@ var go = function (getBody, node, file, scope) {
         }
       });
 
-      return this.stop();
+      return this.skip();
     }
   });
 
@@ -67,7 +67,7 @@ var go = function (getBody, node, file, scope) {
   }
 
   if (thisId) {
-    pushDeclaration(thisId, t.identifier("this"));
+    pushDeclaration(thisId, t.thisExpression());
   }
 };
 

lib/6to5/transformation/transformers/_block-hoist.js

@@ -1,4 +1,5 @@
-var _ = require("lodash");
+var useStrict = require("./use-strict");
+var _         = require("lodash");
 
 // Priority:
 //
@@ -17,13 +18,15 @@ exports.Program = {
     }
     if (!hasChange) return;
 
-    var nodePriorities = _.groupBy(node.body, function (bodyNode) {
-      var priority = bodyNode._blockHoist;
-      if (priority == null) priority = 1;
-      if (priority === true) priority = 2;
-      return priority;
-    });
+    useStrict._wrap(node, function () {
+      var nodePriorities = _.groupBy(node.body, function (bodyNode) {
+        var priority = bodyNode._blockHoist;
+        if (priority == null) priority = 1;
+        if (priority === true) priority = 2;
+        return priority;
+      });
 
-    node.body = _.flatten(_.values(nodePriorities).reverse());
+      node.body = _.flatten(_.values(nodePriorities).reverse());
+    });
   }
 };

lib/6to5/transformation/transformers/_declarations.js

@@ -1,25 +1,32 @@
-var t = require("../../types");
+var useStrict = require("./use-strict");
+var t         = require("../../types");
+
+exports.secondPass = true;
 
 exports.BlockStatement =
 exports.Program = function (node) {
   var kinds = {};
   var kind;
 
-  for (var i in node._declarations) {
-    var declar = node._declarations[i];
+  useStrict._wrap(node, function () {
+    for (var i in node._declarations) {
+      var declar = node._declarations[i];
 
-    kind = declar.kind || "var";
-    var declarNode = t.variableDeclarator(declar.id, declar.init);
+      kind = declar.kind || "var";
+      var declarNode = t.variableDeclarator(declar.id, declar.init);
 
-    if (!declar.init) {
-      kinds[kind] = kinds[kind] || [];
-      kinds[kind].push(declarNode);
-    } else {
-      node.body.unshift(t.variableDeclaration(kind, [declarNode]));
+      if (!declar.init) {
+        kinds[kind] = kinds[kind] || [];
+        kinds[kind].push(declarNode);
+      } else {
+        node.body.unshift(t.variableDeclaration(kind, [declarNode]));
+      }
     }
-  }
 
-  for (kind in kinds) {
-    node.body.unshift(t.variableDeclaration(kind, kinds[kind]));
-  }
+    for (kind in kinds) {
+      node.body.unshift(t.variableDeclaration(kind, kinds[kind]));
+    }
+  });
+
+  node._declarations = null;
 };

lib/6to5/transformation/transformers/es5-property-method-assignment.js

@@ -1,41 +0,0 @@
-var util = require("../../util");
-var t    = require("../../types");
-
-exports.Property = function (node) {
-  if (node.method) node.method = false;
-};
-
-exports.ObjectExpression = function (node, parent, file) {
-  var mutatorMap = {};
-  var hasAny = false;
-
-  node.properties = node.properties.filter(function (prop) {
-    if (prop.kind === "get" || prop.kind === "set") {
-      hasAny = true;
-      util.pushMutatorMap(mutatorMap, prop.key, prop.kind, prop.value);
-      return false;
-    } else {
-      return true;
-    }
-  });
-
-  if (!hasAny) return;
-
-  if (node.properties.length) {
-    var objId = t.getUid(parent, file);
-
-    return util.template("object-define-properties-closure", {
-      KEY: objId,
-      OBJECT: node,
-      CONTENT: util.template("object-define-properties", {
-        OBJECT: objId,
-        PROPS:  util.buildDefineProperties(mutatorMap)
-      })
-    });
-  } else {
-    return util.template("object-define-properties", {
-      OBJECT: node,
-      PROPS:  util.buildDefineProperties(mutatorMap)
-    });
-  }
-};

lib/6to5/transformation/transformers/es6-classes.js

@@ -89,14 +89,14 @@ Class.prototype.run = function () {
     this.closure = true;
 
     // so we're only evaluating it once
-    var superRef = t.getUid(superName, this.file);
+    var superRef = this.scope.generateUidBasedOnNode(superName, this.file);
     body.unshift(t.variableDeclaration("var", [
       t.variableDeclarator(superRef, superName)
     ]));
     superName = superRef;
 
     this.superName = superName;
-    body.push(t.expressionStatement(t.callExpression(file.addDeclaration("inherits"), [className, superName])));
+    body.push(t.expressionStatement(t.callExpression(file.addHelper("inherits"), [className, superName])));
   }
 
   this.buildBody();
@@ -175,7 +175,7 @@ Class.prototype.buildBody = function () {
     if (instanceProps) args.push(instanceProps);
 
     body.push(t.expressionStatement(
-      t.callExpression(this.file.addDeclaration("prototype-properties"), args)
+      t.callExpression(this.file.addHelper("prototype-properties"), args)
     ));
   }
 };
@@ -276,7 +276,7 @@ Class.prototype.replaceInstanceSuperReferences = function (methodNode) {
         if (callee.object.name !== "super") return;
 
         // super.test(); -> ClassName.prototype.MethodName.call(this);
-        callee.property = t.memberExpression(callee.property, t.identifier("call"));
+        t.appendToMemberExpression(callee, t.identifier("call"));
         node.arguments.unshift(t.thisExpression());
       }
     }

lib/6to5/transformation/transformers/es6-computed-property-names.js

@@ -1,6 +1,6 @@
 var t = require("../../types");
 
-exports.ObjectExpression = function (node, parent, file) {
+exports.ObjectExpression = function (node, parent, file, scope) {
   var hasComputed = false;
   var prop;
   var key;
@@ -13,7 +13,7 @@ exports.ObjectExpression = function (node, parent, file) {
 
   if (!hasComputed) return;
 
-  var objId = t.getUid(parent, file);
+  var objId = scope.generateUidBasedOnNode(parent, file);
 
   var body = [];
   var container = t.functionExpression(null, [], t.blockStatement(body));
@@ -44,7 +44,7 @@ exports.ObjectExpression = function (node, parent, file) {
       broken = true;
     }
 
-    if (!broken || t.isLiteral(prop.key, { value: "__proto__" })) {
+    if (!broken || t.isLiteral(t.toComputedKey(prop, prop.key), { value: "__proto__" })) {
       initProps.push(prop);
       props[i] = null;
     }
@@ -61,13 +61,14 @@ exports.ObjectExpression = function (node, parent, file) {
     var bodyNode;
 
     if (prop.computed && t.isMemberExpression(key) && t.isIdentifier(key.object, { name: "Symbol" })) {
+      // { [Symbol.iterator]: "foo" }
       bodyNode = t.assignmentExpression(
         "=",
         t.memberExpression(objId, key, true),
         prop.value
       );
     } else {
-      bodyNode = t.callExpression(file.addDeclaration("define-property"), [objId, key, prop.value]);
+      bodyNode = t.callExpression(file.addHelper("define-property"), [objId, key, prop.value]);
     }
 
     body.push(t.expressionStatement(bodyNode));
@@ -79,7 +80,7 @@ exports.ObjectExpression = function (node, parent, file) {
     var first = body[0].expression;
 
     if (t.isCallExpression(first)) {
-      first.arguments[0] = t.objectExpression([]);
+      first.arguments[0] = t.objectExpression(initProps);
       return first;
     }
   }

lib/6to5/transformation/transformers/es6-default-parameters.js

@@ -49,16 +49,29 @@ exports.Function = function (node, parent, file, scope) {
 
   var body = [];
 
+  var argsIdentifier = t.identifier("arguments");
+  argsIdentifier._ignoreAliasFunctions = true;
+
+  var lastNonDefaultParam = 0;
+
   for (i in node.defaults) {
     def = node.defaults[i];
-    if (!def) continue;
+    if (!def) {
+      lastNonDefaultParam = +i + 1;
+      continue;
+    }
 
-    body.push(util.template("if-undefined-set-to", {
-      VARIABLE: node.params[i],
-      DEFAULT:  def
+    body.push(util.template("default-parameter", {
+      VARIABLE_NAME: node.params[i],
+      DEFAULT_VALUE: def,
+      ARGUMENT_KEY:  t.literal(+i),
+      ARGUMENTS:     argsIdentifier
     }, true));
   }
 
+  // we need to cut off all trailing default parameters
+  node.params = node.params.slice(0, lastNonDefaultParam);
+
   if (iife) {
     var container = t.functionExpression(null, [], node.body, node.generator);
     container._aliasFunction = true;

lib/6to5/transformation/transformers/es6-destructuring.js

@@ -20,11 +20,31 @@ var push = function (opts, nodes, elem, parentId) {
     pushObjectPattern(opts, nodes, elem, parentId);
   } else if (t.isArrayPattern(elem)) {
     pushArrayPattern(opts, nodes, elem, parentId);
+  } else if (t.isAssignmentPattern(elem)) {
+    pushAssignmentPattern(opts, nodes, elem, parentId);
   } else {
     nodes.push(buildVariableAssign(opts, elem, parentId));
   }
 };
 
+var pushAssignmentPattern = function (opts, nodes, pattern, parentId) {
+  var tempParentId = opts.scope.generateUidBasedOnNode(parentId, opts.file);
+
+  nodes.push(t.variableDeclaration("var", [
+    t.variableDeclarator(tempParentId, parentId)
+  ]));
+
+  nodes.push(buildVariableAssign(
+    opts,
+    pattern.left,
+    t.conditionalExpression(
+      t.binaryExpression("===", tempParentId, t.identifier("undefined")),
+      pattern.right,
+      tempParentId
+    )
+  ));
+};
+
 var pushObjectPattern = function (opts, nodes, pattern, parentId) {
   for (var i in pattern.properties) {
     var prop = pattern.properties[i];
@@ -45,9 +65,11 @@ var pushObjectPattern = function (opts, nodes, pattern, parentId) {
         }
         keys = t.arrayExpression(keys);
 
-        var value = t.callExpression(opts.file.addDeclaration("object-without-properties"), [parentId, keys]);
+        var value = t.callExpression(opts.file.addHelper("object-without-properties"), [parentId, keys]);
         nodes.push(buildVariableAssign(opts, prop.argument, value));
     } else {
+      if (t.isLiteral(prop.key)) prop.computed = true;
+
       var pattern2   = prop.value;
       var patternId2 = t.memberExpression(parentId, prop.key, prop.computed);
 
@@ -75,7 +97,7 @@ var pushArrayPattern = function (opts, nodes, pattern, parentId) {
 
   var toArray = opts.file.toArray(parentId, !hasSpreadElement && pattern.elements.length);
 
-  var _parentId = t.getUid(parentId, opts.file, opts.scope);
+  var _parentId = opts.scope.generateUidBasedOnNode(parentId, opts.file);
   nodes.push(t.variableDeclaration("var", [
     t.variableDeclarator(_parentId, toArray)
   ]));
@@ -113,7 +135,7 @@ var pushPattern = function (opts) {
   var scope = opts.scope;
 
   if (!t.isMemberExpression(parentId) && !t.isIdentifier(parentId)) {
-    var key = t.getUid(parentId, file, scope);
+    var key = scope.generateUidBasedOnNode(parentId, file);
 
     nodes.push(t.variableDeclaration("var", [
       t.variableDeclarator(key, parentId)
@@ -183,6 +205,24 @@ exports.Function = function (node, parent, file, scope) {
   block.body = nodes.concat(block.body);
 };
 
+exports.CatchClause = function (node, parent, file, scope) {
+  var pattern = node.param;
+  if (!t.isPattern(pattern)) return;
+
+  var ref = file.generateUidIdentifier("ref", scope);
+  node.param = ref;
+
+  var nodes = [];
+
+  push({
+    kind: "var",
+    file: file,
+    scope: scope
+  }, nodes, pattern, ref);
+
+  node.body.body = nodes.concat(node.body.body);
+};
+
 exports.ExpressionStatement = function (node, parent, file, scope) {
   var expr = node.expression;
   if (expr.type !== "AssignmentExpression") return;

lib/6to5/transformation/transformers/es6-let-scoping.js

@@ -280,7 +280,7 @@ LetScoping.prototype.checkLoop = function () {
       var replace;
 
       if (t.isFunction(node) || t.isLoop(node)) {
-        return this.stop();
+        return this.skip();
       }
 
       if (node && !node.label) {
@@ -329,7 +329,7 @@ LetScoping.prototype.hoistVarDeclarations = function () {
       } else if (isVar(node, parent)) {
         return self.pushDeclar(node).map(t.expressionStatement);
       } else if (t.isFunction(node)) {
-        return this.stop();
+        return this.skip();
       }
     }
   });
@@ -376,7 +376,7 @@ LetScoping.prototype.getLetReferences = function () {
 
             // this scope has a variable with the same name so it couldn't belong
             // to our let scope
-            if (scope.hasOwn(node.name)) return;
+            if (scope.hasOwn(node.name, true)) return;
 
             closurify = true;
 
@@ -388,9 +388,7 @@ LetScoping.prototype.getLetReferences = function () {
           }
         });
 
-        return this.stop();
-      } else if (t.isLoop(node)) {
-        return this.stop();
+        return this.skip();
       }
     }
   });

lib/6to5/transformation/transformers/es6-modules.js

@@ -1,5 +1,11 @@
 var t = require("../../types");
 
+exports.ast = {
+  before: function (ast, file) {
+    ast.program.body = file.dynamicImports.concat(ast.program.body);
+  }
+};
+
 exports.ImportDeclaration = function (node, parent, file) {
   var nodes = [];
 
@@ -11,6 +17,12 @@ exports.ImportDeclaration = function (node, parent, file) {
     file.moduleFormatter.importDeclaration(node, nodes, parent);
   }
 
+  if (nodes.length === 1) {
+    // inherit `_blockHoist`
+    // this for `_blockHoist` in File.prototype.addImport
+    nodes[0]._blockHoist = node._blockHoist;
+  }
+
   return nodes;
 };
 

lib/6to5/transformation/transformers/es6-property-method-assignment.js

@@ -0,0 +1,82 @@
+var traverse = require("../../traverse");
+var util     = require("../../util");
+var t        = require("../../types");
+
+exports.Property = function (node, parent, file, scope) {
+  if (!node.method) return;
+
+  node.method = false;
+
+  var key = t.toComputedKey(node, node.key);
+  if (!t.isLiteral(key)) return; // we can't set a function id with this
+
+  var id = t.toIdentifier(key.value);
+  key = t.identifier(id);
+
+  var selfReference = false;
+  var outerDeclar = scope.get(id, true);
+
+  traverse(node, {
+    enter: function (node, parent, scope) {
+      // check if this node is an identifier that matches the same as our function id
+      if (!t.isIdentifier(node, { name: id })) return;
+
+      // check if this node is the one referenced
+      if (!t.isReferenced(node, parent)) return;
+
+      // check that we don't have a local variable declared as that removes the need
+      // for the wrapper
+      var localDeclar = scope.get(id, true);
+      if (localDeclar !== outerDeclar) return;
+
+      selfReference = true;
+      this.stop();
+    }
+  }, scope);
+
+  if (selfReference) {
+    node.value = util.template("property-method-assignment-wrapper", {
+      FUNCTION: node.value,
+      FUNCTION_ID: key,
+      FUNCTION_KEY: file.generateUidIdentifier(id, scope),
+      WRAPPER_KEY: file.generateUidIdentifier(id + "Wrapper", scope)
+    });
+  } else {
+    node.value.id = key;
+  }
+};
+
+exports.ObjectExpression = function (node, parent, file, scope) {
+  var mutatorMap = {};
+  var hasAny = false;
+
+  node.properties = node.properties.filter(function (prop) {
+    if (prop.kind === "get" || prop.kind === "set") {
+      hasAny = true;
+      util.pushMutatorMap(mutatorMap, prop.key, prop.kind, prop.value);
+      return false;
+    } else {
+      return true;
+    }
+  });
+
+  if (!hasAny) return;
+
+  if (node.properties.length) {
+    var objId = scope.generateUidBasedOnNode(parent, file);
+
+    return util.template("object-define-properties-closure", {
+      KEY: objId,
+      OBJECT: node,
+      CONTENT: util.template("object-define-properties", {
+        OBJECT: objId,
+        PROPS:  util.buildDefineProperties(mutatorMap)
+      })
+    });
+  } else {
+    return util.template("object-define-properties", {
+      OBJECT: node,
+      PROPS:  util.buildDefineProperties(mutatorMap)
+    });
+  }
+};

lib/6to5/transformation/transformers/es6-rest-parameters.js

@@ -1,4 +1,5 @@
-var t = require("../../types");
+var util = require("../../util");
+var t    = require("../../types");
 
 exports.Function = function (node, parent, file) {
   if (!node.rest) return;
@@ -8,15 +9,19 @@ exports.Function = function (node, parent, file) {
 
   t.ensureBlock(node);
 
-  var call = file.toArray(t.identifier("arguments"));
+  var argsId = t.identifier("arguments");
+  argsId._ignoreAliasFunctions = true;
 
-  if (node.params.length) {
-    call.arguments.push(t.literal(node.params.length));
-  }
+  node.body.body.unshift(
+    t.variableDeclaration("var", [
+      t.variableDeclarator(rest, t.arrayExpression([]))
+    ]),
 
-  call._ignoreAliasFunctions = true;
-
-  node.body.body.unshift(t.variableDeclaration("var", [
-    t.variableDeclarator(rest, call)
-  ]));
+    util.template("rest", {
+      ARGUMENTS: argsId,
+      START: t.literal(node.params.length),
+      ARRAY: rest,
+      KEY: file.generateUidIdentifier("key")
+    })
+  );
 };

lib/6to5/transformation/transformers/es6-spread.js

@@ -1,4 +1,5 @@
 var t = require("../../types");
+var _ = require("lodash");
 
 var getSpreadLiteral = function (spread, file) {
   return file.toArray(spread.argument);
@@ -58,7 +59,7 @@ exports.CallExpression = function (node, parent, file, scope) {
   var args = node.arguments;
   if (!hasSpread(args)) return;
 
-  var contextLiteral = t.literal(null);
+  var contextLiteral = t.identifier("undefined");
 
   node.arguments = [];
 
@@ -77,23 +78,16 @@ exports.CallExpression = function (node, parent, file, scope) {
   }
 
   var callee = node.callee;
-  var temp;
 
   if (t.isMemberExpression(callee)) {
-    contextLiteral = callee.object;
-
-    if (t.isDynamic(contextLiteral)) {
-      temp = contextLiteral = scope.generateTemp(file);
+    var temp = scope.generateTempBasedOnNode(callee.object, file);
+    if (temp) {
       callee.object = t.assignmentExpression("=", temp, callee.object);
-    }
-
-    if (callee.computed) {
-      callee.object = t.memberExpression(callee.object, callee.property, true);
-      callee.property = t.identifier("apply");
-      callee.computed = false;
+      contextLiteral = temp;
     } else {
-      callee.property = t.memberExpression(callee.property, t.identifier("apply"));
+      contextLiteral = callee.object;
     }
+    t.appendToMemberExpression(callee, t.identifier("apply"));
   } else {
     node.callee = t.memberExpression(node.callee, t.identifier("apply"));
   }
@@ -105,7 +99,14 @@ exports.NewExpression = function (node, parent, file) {
   var args = node.arguments;
   if (!hasSpread(args)) return;
 
+  var nativeType = t.isIdentifier(node.callee) && _.contains(t.NATIVE_TYPE_NAMES, node.callee.name);
+
   var nodes = build(args, file);
+
+  if (nativeType) {
+    nodes.unshift(t.arrayExpression([t.literal(null)]));
+  }
+
   var first = nodes.shift();
 
   if (nodes.length) {
@@ -114,5 +115,15 @@ exports.NewExpression = function (node, parent, file) {
     args = first;
   }
 
-  return t.callExpression(file.addDeclaration("apply-constructor"), [node.callee, args]);
+  if (nativeType) {
+    return t.newExpression(
+      t.callExpression(
+        t.memberExpression(file.addHelper("bind"), t.identifier("apply")),
+        [node.callee, args]
+      ),
+      []
+    );
+  } else {
+    return t.callExpression(file.addHelper("apply-constructor"), [node.callee, args]);
+  }
 };

lib/6to5/transformation/transformers/es6-template-literals.js

@@ -17,7 +17,7 @@ exports.TaggedTemplateExpression = function (node, parent, file) {
     raw.push(t.literal(elem.value.raw));
   }
 
-  args.push(t.callExpression(file.addDeclaration("tagged-template-literal"), [
+  args.push(t.callExpression(file.addHelper("tagged-template-literal"), [
     t.arrayExpression(strings),
     t.arrayExpression(raw)
   ]));

lib/6to5/transformation/transformers/es7-abstract-references.js

@@ -30,10 +30,8 @@ exports.AssignmentExpression = function (node, parent, file, scope) {
 
   // we need to return `node.right`
   if (!t.isExpressionStatement(parent)) {
-    // `node.right` isn't a simple identifier so we need to reference it
-    if (t.isDynamic(value)) {
-      temp = value = scope.generateTemp(file);
-    }
+    temp = scope.generateTempBasedOnNode(node.right, file);
+    if (temp) value = temp;
   }
 
   if (node.operator !== "=") {
@@ -80,11 +78,7 @@ exports.CallExpression = function (node, parent, file, scope) {
   var callee = node.callee;
   if (!t.isVirtualPropertyExpression(callee)) return;
 
-  var temp;
-  if (t.isDynamic(callee.object)) {
-    // we need to save `callee.object` so we can call it again
-    temp = scope.generateTemp(file);
-  }
+  var temp = scope.generateTempBasedOnNode(callee.object, file);
 
   var call = util.template("abstract-expression-call", {
     PROPERTY: callee.property,

lib/6to5/transformation/transformers/es7-array-comprehension.js

@@ -5,7 +5,7 @@ var t        = require("../../types");
 exports.experimental = true;
 
 var build = function (node, parent, file, scope) {
-  var uid = t.getUid(parent, file, scope);
+  var uid = scope.generateUidBasedOnNode(parent, file);
 
   var container = util.template("array-comprehension-container", {
     KEY: uid
@@ -49,7 +49,7 @@ exports._build = function (node, buildBody) {
   }
 
   return t.forOfStatement(
-    t.variableDeclaration("var", [t.variableDeclarator(self.left)]),
+    t.variableDeclaration("let", [t.variableDeclarator(self.left)]),
     self.right,
     t.blockStatement([child])
   );

lib/6to5/transformation/transformers/optional-async-to-generator.js

@@ -1,5 +1,4 @@
 var bluebirdCoroutines = require("./optional-bluebird-coroutines");
-var t                  = require("../../types");
 
 exports.optional = true;
 
@@ -8,7 +7,5 @@ exports.manipulateOptions = bluebirdCoroutines.manipulateOptions;
 exports.Function = function (node, parent, file) {
   if (!node.async || node.generator) return;
 
-  bluebirdCoroutines._Function(node);
-
-  return t.callExpression(file.addDeclaration("async-to-generator"), [node]);
+  return bluebirdCoroutines._Function(node, file.addHelper("async-to-generator"));
 };

lib/6to5/transformation/transformers/optional-bluebird-coroutines.js

@@ -8,27 +8,36 @@ exports.manipulateOptions = function (opts) {
 
 exports.optional = true;
 
-exports._Function = function (node) {
+exports._Function = function (node, callId) {
   node.async = false;
   node.generator = true;
 
   traverse(node, {
     enter: function (node) {
-      if (t.isFunction(node)) this.stop();
+      if (t.isFunction(node)) this.skip();
 
       if (t.isAwaitExpression(node)) {
         node.type = "YieldExpression";
       }
     }
   });
+
+  var call = t.callExpression(callId, [node]);
+
+  if (t.isFunctionDeclaration(node)) {
+    var declar = t.variableDeclaration("var", [
+      t.variableDeclarator(node.id, call)
+    ]);
+    declar._blockHoist = true;
+    return declar;
+  } else {
+    return call;
+  }
 };
 
 exports.Function = function (node, parent, file) {
   if (!node.async || node.generator) return;
 
-  exports._Function(node);
-
-  var id = t.identifier("Bluebird");
-  file.addImport(id, "bluebird");
-  return t.callExpression(t.memberExpression(id, t.identifier("coroutine")), [node]);
+  var id = file.addImport("bluebird");
+  return exports._Function(node, t.memberExpression(id, t.identifier("coroutine")));
 };

lib/6to5/transformation/transformers/optional-core-aliasing.js

@@ -12,8 +12,7 @@ exports.optional = true;
 
 exports.ast = {
   enter: function (ast, file) {
-    file._coreId = file.generateUidIdentifier("core");
-    file.addImport(file._coreId, "core-js/library");
+    file._coreId = file.addImport("core-js/library", "core");
   },
 
   exit: function (ast, file) {
@@ -28,9 +27,9 @@ exports.ast = {
 
           if (!t.isReferenced(obj, node)) return;
 
-          if (coreHas(obj) && _.has(core[obj.name], prop.name)) {
-            this.stop();
-            return t.memberExpression(file._coreId, node);
+          if (!node.computed && coreHas(obj) && _.has(core[obj.name], prop.name)) {
+            this.skip();
+            return t.prependToMemberExpression(node, file._coreId);
           }
         } else if (t.isIdentifier(node) && !t.isMemberExpression(parent) && t.isReferenced(node, parent) && coreHas(node)) {
           // new Promise -> new _core.Promise

lib/6to5/transformation/transformers/optional-proto-to-assign.js

@@ -0,0 +1,63 @@
+var t = require("../../types");
+var _ = require("lodash");
+
+var OBJECT_ASSIGN_MEMBER = t.memberExpression(t.identifier("Object"), t.identifier("assign"));
+
+var isProtoKey = function (node) {
+  return t.isLiteral(t.toComputedKey(node, node.key), { value: "__proto__" });
+};
+
+var isProtoAssignmentExpression = function (node) {
+  var left = node.left;
+  return t.isMemberExpression(left) && t.isLiteral(t.toComputedKey(left, left.property), { value: "__proto__" });
+};
+
+var buildDefaultsCallExpression = function (expr, ref, file) {
+  return t.expressionStatement(t.callExpression(file.addHelper("defaults"), [ref, expr.right]));
+};
+
+exports.optional = true;
+exports.secondPass = true;
+
+exports.AssignmentExpression = function (node, parent, file, scope) {
+  if (t.isExpressionStatement(parent)) return;
+  if (!isProtoAssignmentExpression(node)) return;
+
+  var nodes = [];
+  var left  = node.left.object;
+  var temp  = scope.generateTempBasedOnNode(node.left.object, file);
+
+  nodes.push(t.expressionStatement(t.assignmentExpression("=", temp, left)));
+  nodes.push(buildDefaultsCallExpression(node, temp, file));
+  if (temp) nodes.push(temp);
+
+  return t.toSequenceExpression(nodes);
+};
+
+exports.ExpressionStatement = function (node, parent, file) {
+  var expr = node.expression;
+  if (!t.isAssignmentExpression(expr, { operator: "=" })) return;
+
+  if (isProtoAssignmentExpression(expr)) {
+    return buildDefaultsCallExpression(expr, expr.left.object, file);
+  }
+};
+
+exports.ObjectExpression = function (node) {
+  var proto;
+
+  for (var i in node.properties) {
+    var prop = node.properties[i];
+
+    if (isProtoKey(prop)) {
+      proto = prop.value;
+      _.pull(node.properties, prop);
+    }
+  }
+
+  if (proto) {
+    var args = [t.objectExpression([]), proto];
+    if (node.properties.length) args.push(node);
+    return t.callExpression(OBJECT_ASSIGN_MEMBER, args);
+  }
+};

lib/6to5/transformation/transformers/optional-typeof-symbol.js

@@ -0,0 +1,9 @@
+var t = require("../../types");
+
+exports.optional = true;
+
+exports.UnaryExpression = function (node, parent, file) {
+  if (node.operator === "typeof") {
+    return t.callExpression(file.addHelper("typeof"), [node.argument]);
+  }
+};

lib/6to5/transformation/transformers/playground-memoization-operator.js

@@ -10,7 +10,7 @@ var getPropRef = function (nodes, prop, file, scope) {
   if (t.isIdentifier(prop)) {
     return t.literal(prop.name);
   } else {
-    var temp = t.getUid(prop, file, scope);
+    var temp = scope.generateUidBasedOnNode(prop, file);
     nodes.push(t.variableDeclaration("var", [
       t.variableDeclarator(temp, prop)
     ]));
@@ -19,22 +19,18 @@ var getPropRef = function (nodes, prop, file, scope) {
 };
 
 var getObjRef = function (nodes, obj, file, scope) {
-  if (t.isDynamic(obj)) {
-    var temp = t.getUid(obj, file, scope);
-    nodes.push(t.variableDeclaration("var", [
-      t.variableDeclarator(temp, obj)
-    ]));
-    return temp;
-  } else {
-    return obj;
-  }
+  var temp = scope.generateUidBasedOnNode(obj, file);
+  nodes.push(t.variableDeclaration("var", [
+    t.variableDeclarator(temp, obj)
+  ]));
+  return temp;
 };
 
 var buildHasOwn = function (obj, prop, file) {
   return t.unaryExpression(
     "!",
     t.callExpression(
-      t.memberExpression(file.addDeclaration("has-own"), t.identifier("call")),
+      t.memberExpression(file.addHelper("has-own"), t.identifier("call")),
       [obj, prop]
     ),
     true

lib/6to5/transformation/transformers/playground-method-binding.js

@@ -1,14 +1,11 @@
 var t = require("../../types");
-var _ = require("lodash");
 
 exports.BindMemberExpression = function (node, parent, file, scope) {
   var object = node.object;
   var prop   = node.property;
 
-  var temp;
-  if (t.isDynamic(object)) {
-    temp = object = scope.generateTemp(file);
-  }
+  var temp = scope.generateTempBasedOnNode(node.object, file);
+  if (temp) object = temp;
 
   var call = t.callExpression(
     t.memberExpression(t.memberExpression(object, prop), t.identifier("bind")),
@@ -33,16 +30,12 @@ exports.BindFunctionExpression = function (node, parent, file, scope) {
     ]));
   };
 
-  if (_.find(node.arguments, t.isDynamic)) {
-    var temp = scope.generateTemp(file, "args");
+  var temp = scope.generateTemp(file, "args");
 
-    return t.sequenceExpression([
-      t.assignmentExpression("=", temp, t.arrayExpression(node.arguments)),
-      buildCall(node.arguments.map(function (node, i) {
-        return t.memberExpression(temp, t.literal(i), true);
-      }))
-    ]);
-  } else {
-    return buildCall(node.arguments);
-  }
+  return t.sequenceExpression([
+    t.assignmentExpression("=", temp, t.arrayExpression(node.arguments)),
+    buildCall(node.arguments.map(function (node, i) {
+      return t.memberExpression(temp, t.literal(i), true);
+    }))
+  ]);
 };

lib/6to5/transformation/transformers/playground-object-getter-memoization.js

@@ -20,7 +20,7 @@ exports.MethodDefinition = function (node, parent, file) {
       if (t.isFunction(node)) return;
 
       if (t.isReturnStatement(node) && node.argument) {
-        node.argument = t.memberExpression(t.callExpression(file.addDeclaration("define-property"), [
+        node.argument = t.memberExpression(t.callExpression(file.addHelper("define-property"), [
           t.thisExpression(),
           key,
           node.argument

lib/6to5/transformation/transformers/spec-no-duplicate-properties.js

@@ -1,25 +0,0 @@
-var t = require("../../types");
-
-exports.ObjectExpression = function (node, parent, file) {
-  var keys = [];
-
-  for (var i in node.properties) {
-    var prop = node.properties[i];
-    if (prop.computed || prop.kind !== "init") continue;
-
-    var key = prop.key;
-    if (t.isIdentifier(key)) {
-      key = key.name;
-    } else if (t.isLiteral(key)) {
-      key = key.value;
-    } else {
-      continue;
-    }
-
-    if (keys.indexOf(key) >= 0) {
-      throw file.errorWithNode(prop.key, "Duplicate property key");
-    } else {
-      keys.push(key);
-    }
-  }
-};

lib/6to5/transformation/transformers/use-strict.js

@@ -1,14 +1,27 @@
 var t = require("../../types");
 
+exports._has = function (node) {
+  var first = node.body[0];
+  return t.isExpressionStatement(first) && t.isLiteral(first.expression, { value: "use strict" });
+};
+
+exports._wrap = function (node, callback) {
+  var useStrictNode;
+  if (exports._has(node)) {
+    useStrictNode = node.body.shift();
+  }
+
+  callback();
+
+  if (useStrictNode) {
+    node.body.unshift(useStrictNode);
+  }
+};
+
 exports.ast = {
   exit: function (ast) {
-    var body = ast.program.body;
-    var first = body[0];
-
-    var noStrict = !first || !t.isExpressionStatement(first) || !t.isLiteral(first.expression) || first.expression.value !== "use strict";
-
-    if (noStrict) {
-      body.unshift(t.expressionStatement(t.literal("use strict")));
+    if (!exports._has(ast.program)) {
+      ast.program.body.unshift(t.expressionStatement(t.literal("use strict")));
     }
   }
 };

lib/6to5/traverse/index.js

@@ -22,12 +22,14 @@ function traverse(parent, opts, scope) {
 
   opts = opts || {};
 
+  var stopped = false;
+
   for (var i in keys) {
     var key = keys[i];
     var nodes = parent[key];
     if (!nodes) continue;
 
-    var updated = false;
+    var flatten = false;
 
     var handle = function (obj, key) {
       var node = obj[key];
@@ -50,7 +52,8 @@ function traverse(parent, opts, scope) {
 
         // replace the node
         node = obj[key] = result;
-        updated = true;
+
+        if (isArray) flatten = true;
 
         // we're replacing a statement or block node with an array of statements so we better
         // ensure that it's a block
@@ -59,16 +62,20 @@ function traverse(parent, opts, scope) {
         }
       };
 
-      var stopped = false;
+      var skipped = false;
       var removed = false;
 
       var context = {
         stop: function () {
-          stopped = true;
+          skipped = stopped = true;
+        },
+
+        skip: function () {
+          skipped = true;
         },
 
         remove: function () {
-          this.stop();
+          this.skip();
           removed = true;
         }
       };
@@ -84,11 +91,11 @@ function traverse(parent, opts, scope) {
 
         if (removed) {
           obj[key] = null;
-          updated = true;
+          flatten = true;
         }
 
         // stop iteration
-        if (stopped) return;
+        if (skipped) return;
       }
 
       // traverse node
@@ -103,9 +110,10 @@ function traverse(parent, opts, scope) {
     if (_.isArray(nodes)) {
       for (i in nodes) {
         handle(nodes, i);
+        if (stopped) return;
       }
 
-      if (updated) {
+      if (flatten) {
         parent[key] = _.flatten(parent[key]);
 
         if (key === "body") {
@@ -115,6 +123,7 @@ function traverse(parent, opts, scope) {
       }
     } else {
       handle(parent, key);
+      if (stopped) return;
     }
   }
 }
@@ -161,7 +170,7 @@ traverse.hasType = function (tree, type, blacklistTypes) {
     enter: function (node) {
       if (node.type === type) {
         has = true;
-        this.stop();
+        this.skip();
       }
     }
   });

lib/6to5/traverse/scope.js

@@ -31,6 +31,13 @@ Scope.add = function (node, references) {
   _.defaults(references, t.getIds(node, true));
 };
 
+/**
+ * Description
+ *
+ * @param {File} file
+ * @param {String} [name="temp"]
+ */
+
 Scope.prototype.generateTemp = function (file, name) {
   var id = file.generateUidIdentifier(name || "temp", this);
   this.push({
@@ -40,6 +47,70 @@ Scope.prototype.generateTemp = function (file, name) {
   return id;
 };
 
+/*
+ * Description
+ *
+ * @param {Object} parent
+ * @param {File} file
+ * @param {Scope} scope
+ * @returns {Object}
+ */
+
+Scope.prototype.generateUidBasedOnNode = function (parent, file) {
+  var node = parent;
+
+  if (t.isAssignmentExpression(parent)) {
+    node = parent.left;
+  } else if (t.isVariableDeclarator(parent)) {
+    node = parent.id;
+  } else if (t.isProperty(node)) {
+    node = node.key;
+  }
+
+  var parts = [];
+
+  var add = function (node) {
+    if (t.isMemberExpression(node)) {
+      add(node.object);
+      add(node.property);
+    } else if (t.isIdentifier(node)) {
+      parts.push(node.name);
+    } else if (t.isLiteral(node)) {
+      parts.push(node.value);
+    } else if (t.isCallExpression(node)) {
+      add(node.callee);
+    }
+  };
+
+  add(node);
+
+  var id = parts.join("$");
+  id = id.replace(/^_/, "") || "ref";
+
+  return file.generateUidIdentifier(id, this);
+};
+
+/**
+ * Description
+ *
+ * @param {Object} node
+ * @param {File} file
+ * @returns {Object}
+ */
+
+Scope.prototype.generateTempBasedOnNode = function (node, file) {
+  if (t.isIdentifier(node) && this.has(node.name, true)) {
+    return null;
+  }
+
+  var id = this.generateUidBasedOnNode(node, file);
+  this.push({
+    key: id.name,
+    id: id
+  });
+  return id;
+};
+
 Scope.prototype.getInfo = function () {
   var block = this.block;
   if (block._scopeInfo) return block._scopeInfo;
@@ -93,7 +164,7 @@ Scope.prototype.getInfo = function () {
 
         // this block is a function so we'll stop since none of the variables
         // declared within are accessible
-        if (t.isFunction(node)) return this.stop();
+        if (t.isFunction(node)) return this.skip();
 
         // function identifier doesn't belong to this scope
         if (block.id && node === block.id) return;
@@ -123,6 +194,12 @@ Scope.prototype.getInfo = function () {
   return info;
 };
 
+/**
+ * Description
+ *
+ * @param {Object} opts
+ */
+
 Scope.prototype.push = function (opts) {
   var block = this.block;
 
@@ -143,33 +220,84 @@ Scope.prototype.push = function (opts) {
   }
 };
 
+/**
+ * Description
+ *
+ * @param {Object} node
+ */
+
 Scope.prototype.add = function (node) {
   Scope.add(node, this.references);
 };
 
+/**
+ * Description
+ *
+ * @param {String} [id]
+ * @param {Boolean} [decl]
+ */
+
 Scope.prototype.get = function (id, decl) {
   return id && (this.getOwn(id, decl) || this.parentGet(id, decl));
 };
 
+/**
+ * Description
+ *
+ * @param {String} [id]
+ * @param {Boolean} [decl]
+ */
+
 Scope.prototype.getOwn = function (id, decl) {
   var refs = this.references;
   if (decl) refs = this.declarations;
   return _.has(refs, id) && refs[id];
 };
 
+/**
+ * Description
+ *
+ * @param {String} [id]
+ * @param {Boolean} [decl]
+ */
+
 Scope.prototype.parentGet = function (id, decl) {
   return this.parent && this.parent.get(id, decl);
 };
 
+/**
+ * Description
+ *
+ * @param {String} [id]
+ * @param {Boolean} [decl]
+ * @returns {Boolean}
+ */
+
 Scope.prototype.has = function (id, decl) {
   return (id && (this.hasOwn(id, decl) || this.parentHas(id, decl))) ||
          _.contains(Scope.defaultDeclarations, id);
 };
 
+/**
+ * Description
+ *
+ * @param {String} [id]
+ * @param {Boolean} [decl]
+ * @returns {Boolean}
+ */
+
 Scope.prototype.hasOwn = function (id, decl) {
   return !!this.getOwn(id, decl);
 };
 
+/**
+ * Description
+ *
+ * @param {String} [id]
+ * @param {Boolean} [decl]
+ * @returns {Boolean}
+ */
+
 Scope.prototype.parentHas = function (id, decl) {
   return this.parent && this.parent.has(id, decl);
 };

lib/6to5/types/alias-keys.json

@@ -39,8 +39,9 @@
   "ForInStatement": ["Statement", "For", "Scope", "Loop"],
   "ForStatement":   ["Statement", "For", "Scope", "Loop"],
 
-  "ObjectPattern": ["Pattern"],
-  "ArrayPattern":  ["Pattern"],
+  "ObjectPattern":     ["Pattern"],
+  "ArrayPattern":      ["Pattern"],
+  "AssignmentPattern": ["Pattern"],
 
   "Property": ["UserWhitespacable"],
   "XJSElement": ["UserWhitespacable", "Expression"],

lib/6to5/types/index.js

@@ -3,6 +3,10 @@ var _       = require("lodash");
 
 var t = exports;
 
+t.NATIVE_TYPE_NAMES = ["Array", "Object", "Number", "Boolean", "Date", "Array", "String"];
+
+//
+
 var addAssert = function (type, is) {
   t["assert" + type] = function (node, opts) {
     opts = opts || {};
@@ -64,7 +68,28 @@ _.each(t.FLIPPED_ALIAS_KEYS, function (types, type) {
   addAssert(type, is);
 });
 
-//
+/**
+ * Description
+ *
+ * @param {Object} node
+ * @returns {Object}
+ */
+
+t.toComputedKey = function (node, key) {
+  if (!node.computed) {
+    if (t.isIdentifier(key)) key = t.literal(key.name);
+  }
+  return key;
+};
+
+/*
+ * Shallowly checks to see if the passed `node` will evaluate to a
+ * falsy. This is if `node` is a `Literal` and `value` is falsy or
+ * `node` is an `Identifier` with a name of `undefiend`.
+ *
+ * @param {Object} node
+ * @returns {Boolean}
+ */
 
 t.isFalsyExpression = function (node) {
   if (t.isLiteral(node)) {
@@ -75,7 +100,14 @@ t.isFalsyExpression = function (node) {
   return false;
 };
 
-//
+/**
+ * Turn an array of statement `nodes` into a `SequenceExpression`.
+ *
+ * Variable declarations are turned into simple assignments and their
+ * declarations hoisted to the top of the current scope.
+ *
+ * Expression statements are just resolved to their standard expression.
+ */
 
 t.toSequenceExpression = function (nodes, scope) {
   var exprs = [];
@@ -97,7 +129,11 @@ t.toSequenceExpression = function (nodes, scope) {
     }
   });
 
-  return t.sequenceExpression(exprs);
+  if (exprs.length === 1) {
+    return exprs[0];
+  } else {
+    return t.sequenceExpression(exprs);
+  }
 };
 
 //
@@ -116,21 +152,43 @@ t.shallowEqual = function (actual, expected) {
   return same;
 };
 
-//
+/**
+ * Description
+ *
+ * @param {Object} member
+ * @param {Object} append
+ * @param {Boolean} [computed]
+ * @returns {Object} member
+ */
 
-t.isDynamic = function (node) {
-  if (t.isExpressionStatement(node)) {
-    return t.isDynamic(node.expression);
-  } else if (t.isIdentifier(node) || t.isLiteral(node) || t.isThisExpression(node)) {
-    return false;
-  } else if (t.isMemberExpression(node)) {
-    return t.isDynamic(node.object) || t.isDynamic(node.property);
-  } else {
-    return true;
-  }
+t.appendToMemberExpression = function (member, append, computed) {
+  member.object   = t.memberExpression(member.object, member.property, member.computed);
+  member.property = append;
+  member.computed = !!computed;
+  return member;
 };
 
-// todo: https://github.com/eventualbuddha/ast-util/blob/9bf91c5ce8/lib/index.js#L454-L507
+/**
+ * Description
+ *
+ * @param {Object} member
+ * @param {Object} append
+ * @returns {Object} member
+ */
+
+t.prependToMemberExpression = function (member, append) {
+  member.object = t.memberExpression(append, member.object);
+  return member;
+};
+
+/**
+ * Description
+ *
+ * @param {Object} node
+ * @param {Object} parent
+ * @returns {Boolean}
+ */
+
 t.isReferenced = function (node, parent) {
   // we're a property key and we aren't computed so we aren't referenced
   if (t.isProperty(parent) && parent.key === node && !parent.computed) return false;
@@ -152,9 +210,29 @@ t.isReferenced = function (node, parent) {
   return false;
 };
 
+/**
+ * Description
+ *
+ * @param {String} name
+ * @returns {Boolean}
+ */
+
+t.isValidIdentifier = function (name) {
+  return _.isString(name) && esutils.keyword.isIdentifierName(name) && !esutils.keyword.isReservedWordES6(name, true);
+};
+
+/*
+ * Description
+ *
+ * @param {String} name
+ * @returns {String}
+ */
+
 t.toIdentifier = function (name) {
   if (t.isIdentifier(name)) return name.name;
 
+  name = name + "";
+
   // replace all non-valid identifiers with dashes
   name = name.replace(/[^a-zA-Z0-9$_]/g, "-");
 
@@ -169,18 +247,33 @@ t.toIdentifier = function (name) {
   // remove underscores from start of name
   name = name.replace(/^\_/, "");
 
+  if (!t.isValidIdentifier(name)) {
+    name = "_" + name;
+  }
+
   return name || '_';
 };
 
-t.isValidIdentifier = function (name) {
-  return _.isString(name) && esutils.keyword.isIdentifierName(name) && !esutils.keyword.isKeywordES6(name, true);
-};
+/**
+ * Description
+ *
+ * @param {Object} node
+ * @param {String} key
+ */
 
 t.ensureBlock = function (node, key) {
   key = key || "body";
   node[key] = t.toBlock(node[key], node);
 };
 
+/**
+ * Description
+ *
+ * @param {Object} node
+ * @param {Boolean} [ignore]
+ * @returns {Object|Boolean}
+ */
+
 t.toStatement = function (node, ignore) {
   if (t.isStatement(node)) {
     return node;
@@ -214,6 +307,14 @@ t.toStatement = function (node, ignore) {
   return node;
 };
 
+/**
+ * Description
+ *
+ * @param {Object} node
+ * @param {Object} parent
+ * @returns {Object}
+ */
+
 t.toBlock = function (node, parent) {
   if (t.isBlockStatement(node)) {
     return node;
@@ -234,48 +335,14 @@ t.toBlock = function (node, parent) {
   return t.blockStatement(node);
 };
 
-t.getUid = function (parent, file, scope) {
-  var node = parent;
-
-  if (t.isAssignmentExpression(parent)) {
-    node = parent.left;
-  } else if (t.isVariableDeclarator(parent)) {
-    node = parent.id;
-  }
-
-  var id = "ref";
-
-  if (t.isProperty(node)) {
-    node = node.key;
-  }
-
-  if (t.isIdentifier(node)) {
-    id = node.name;
-  } else if (t.isLiteral(node)) {
-    id = node.value;
-  } else if (t.isMemberExpression(node)) {
-    var parts = [];
-
-    var add = function (node) {
-      if (t.isMemberExpression(node)) {
-        add(node.object);
-        add(node.property);
-      } else if (t.isIdentifier(node)) {
-        parts.push(node.name);
-      } else if (t.isLiteral(node)) {
-        parts.push(node.value);
-      }
-    };
-
-    add(node);
-
-    id = parts.join("$");
-  }
-
-  id = id.replace(/^_/, "");
-
-  return file.generateUidIdentifier(id, scope);
-};
+/**
+ * Description
+ *
+ * @param {Object} node
+ * @param {Boolean} [map]
+ * @param {Array} [ignoreTypes]
+ * @returns {Array|Object}
+ */
 
 t.getIds = function (node, map, ignoreTypes) {
   ignoreTypes = ignoreTypes || [];
@@ -327,10 +394,24 @@ t.getIds.arrays = {
   ObjectPattern: ["properties"]
 };
 
+/**
+ * Description
+ *
+ * @param {Object} node
+ * @returns {Boolean}
+ */
+
 t.isLet = function (node) {
   return t.isVariableDeclaration(node) && (node.kind !== "var" || node._let);
 };
 
+/**
+ * Description
+ *
+ * @param {Object} node
+ * @returns {Boolean}
+ */
+
 t.isVar = function (node) {
   return t.isVariableDeclaration(node, { kind: "var" }) && !node._let;
 };
@@ -339,6 +420,13 @@ t.isVar = function (node) {
 
 t.COMMENT_KEYS = ["leadingComments", "trailingComments"];
 
+/**
+ * Description
+ *
+ * @param {Object} child
+ * @returns {Object} child
+ */
+
 t.removeComments = function (child) {
   _.each(t.COMMENT_KEYS, function (key) {
     delete child[key];
@@ -346,6 +434,14 @@ t.removeComments = function (child) {
   return child;
 };
 
+/**
+ * Description
+ *
+ * @param {Object} child
+ * @param {Object} parent
+ * @returns {Object} child
+ */
+
 t.inheritsComments = function (child, parent) {
   _.each(t.COMMENT_KEYS, function (key) {
     child[key]  = _.uniq(_.compact([].concat(child[key], parent[key])));
@@ -353,7 +449,13 @@ t.inheritsComments = function (child, parent) {
   return child;
 };
 
-//
+/**
+ * Description
+ *
+ * @param {Object} child
+ * @param {Object} parent
+ * @returns {Object} child
+ */
 
 t.inherits = function (child, parent) {
   child.loc   = parent.loc;
@@ -364,10 +466,24 @@ t.inherits = function (child, parent) {
   return child;
 };
 
+/**
+ * Description
+ *
+ * @param {Object} specifier
+ * @returns {String}
+ */
+
 t.getSpecifierName = function (specifier) {
   return specifier.name || specifier.id;
 };
 
+/**
+ * Description
+ *
+ * @param {Object} specifier
+ * @returns {Boolean}
+ */
+
 t.isSpecifierDefault = function (specifier) {
   return t.isIdentifier(specifier.id) && specifier.id.name === "default";
 };

lib/6to5/types/visitor-keys.json

@@ -3,6 +3,7 @@
   "ArrayPattern":              ["elements"],
   "ArrowFunctionExpression":   ["params", "defaults", "rest", "body"],
   "AssignmentExpression":      ["left", "right"],
+  "AssignmentPattern":         ["left", "right"],
   "AwaitExpression":           ["argument"],
   "BinaryExpression":          ["left", "right"],
   "BindFunctionExpression":    ["callee", "arguments"],

lib/6to5/util.js

@@ -12,7 +12,7 @@ var _          = require("lodash");
 exports.inherits = util.inherits;
 
 exports.canCompile = function (filename, altExts) {
-  var exts = altExts || [".js", ".jsx", ".es6"];
+  var exts = altExts || [".js", ".jsx", ".es6", ".es"];
   var ext = path.extname(filename);
   return _.contains(exts, ext);
 };

package.json

@@ -1,7 +1,7 @@
 {
   "name": "6to5",
   "description": "Turn ES6 code into readable vanilla ES5 with source maps",
-  "version": "2.4.2",
+  "version": "2.6.0",
   "author": "Sebastian McKenzie <sebmck@gmail.com>",
   "homepage": "https://github.com/6to5/6to5",
   "repository": {
@@ -18,6 +18,10 @@
     "6to5-node": "./bin/6to5-node",
     "6to5-runtime": "./bin/6to5-runtime"
   },
+  "browser": {
+    "./lib/6to5/index.js": "./lib/6to5/browser.js",
+    "./lib/6to5/register.js": "./lib/6to5/register-browser.js"
+  },
   "keywords": [
     "harmony",
     "classes",
@@ -35,19 +39,20 @@
     "test": "make test"
   },
   "dependencies": {
-    "acorn-6to5": "0.11.1-2",
+    "acorn-6to5": "0.11.1-11",
     "ast-types": "~0.6.1",
     "chokidar": "0.11.1",
     "commander": "2.5.0",
-    "core-js": "^0.3.3",
+    "core-js": "^0.4.0",
     "estraverse": "1.8.0",
     "esutils": "1.1.6",
+    "esvalid": "^1.1.0",
     "fs-readdir-recursive": "0.1.0",
     "jshint": "^2.5.10",
     "lodash": "2.4.1",
     "mkdirp": "0.5.0",
     "private": "0.1.6",
-    "regenerator": "^0.8.2",
+    "regenerator": "^0.8.3",
     "regexpu": "0.3.0",
     "roadrunner": "^1.0.4",
     "source-map": "0.1.40",

test/_helper.js

@@ -1,8 +1,9 @@
-var fs = require("fs");
-var _  = require("lodash");
+var path = require("path");
+var fs   = require("fs");
+var _    = require("lodash");
 
 var humanise = function (val) {
-  return val.replace(/-/g, " ");
+  return path.basename(val, path.extname(val)).replace(/-/g, " ");
 };
 
 var readFile = exports.readFile = function (filename) {
@@ -15,11 +16,11 @@ var readFile = exports.readFile = function (filename) {
   }
 };
 
-exports.get = function (entryName) {
+exports.get = function (entryName, entryLoc) {
   if (exports.cache[entryName]) return exports.cache[entryName];
 
   var suites = [];
-  var entryLoc = __dirname + "/fixtures/" + entryName;
+  var entryLoc = entryLoc || __dirname + "/fixtures/" + entryName;
 
   _.each(fs.readdirSync(entryLoc), function (suiteName) {
     if (suiteName[0] === ".") return;
@@ -35,9 +36,18 @@ exports.get = function (entryName) {
     var suiteOptsLoc = suite.filename + "/options.json";
     if (fs.existsSync(suiteOptsLoc)) suite.options = require(suiteOptsLoc);
 
-    _.each(fs.readdirSync(suite.filename), function (taskName) {
-      var taskDir = suite.filename + "/" + taskName;
-      if (fs.statSync(taskDir).isFile()) return;
+    if (fs.statSync(suite.filename).isFile()) {
+      push(suiteName, suite.filename);
+    } else {
+      _.each(fs.readdirSync(suite.filename), function (taskName) {
+        var taskDir = suite.filename + "/" + taskName;
+        push(taskName, taskDir);
+      });
+    }
+
+    function push(taskName, taskDir) {
+      // tracuer error tests
+      if (taskName.indexOf("Error_") >= 0) return;
 
       var actualLocAlias = suiteName + "/" + taskName + "/actual.js";
       var expectLocAlias = suiteName + "/" + taskName + "/expected.js";
@@ -47,6 +57,13 @@ exports.get = function (entryName) {
       var expectLoc = taskDir + "/expected.js";
       var execLoc   = taskDir + "/exec.js";
 
+      if (fs.statSync(taskDir).isFile()) {
+        var ext = path.extname(taskDir);
+        if (ext !== ".js" && ext !== ".module.js") return;
+
+        execLoc = taskDir;
+      }
+
       var taskOpts = _.merge({
         filenameRelative: expectLocAlias,
         sourceFileName:   actualLocAlias,
@@ -77,6 +94,18 @@ exports.get = function (entryName) {
         }
       };
 
+      // traceur checks
+
+      var shouldSkip = function (code) {
+        return code.indexOf("// Error:") >= 0 || code.indexOf("// Skip.") >= 0;
+      };
+
+      if (shouldSkip(test.actual.code) || shouldSkip(test.exec.code)) {
+        return;
+      } else if (test.exec.code.indexOf("// Async.") >= 0) {
+        //test.options.asyncExec = true;
+      }
+
       suite.tests.push(test);
 
       var sourceMappingsLoc = taskDir + "/source-mappings.json";
@@ -90,7 +119,7 @@ exports.get = function (entryName) {
         test.options.sourceMap = true;
         test.sourceMap = require(sourceMap);
       }
-    });
+    }
   });
 
   return exports.cache[entryName] = suites;
@@ -104,4 +133,5 @@ try {
   var cache = exports.cache = {};
   cache.transformation = exports.get("transformation");
   cache.generation     = exports.get("generation");
+  cache.esnext         = exports.get("esnext");
 }

test/_transformation-helper.js

@@ -0,0 +1,168 @@
+var genHelpers = require("./_generator-helpers");
+var transform  = require("../lib/6to5/transformation/transform");
+var sourceMap  = require("source-map");
+var esvalid    = require("esvalid");
+var Module     = require("module");
+var helper     = require("./_helper");
+var assert     = require("assert");
+var chai       = require("chai");
+var path       = require("path");
+var util       = require("../lib/6to5/util");
+var _          = require("lodash");
+
+require("../lib/6to5/polyfill");
+
+global.assertNoOwnProperties = function (obj) {
+  assert.equal(Object.getOwnPropertyNames(obj).length, 0);
+};
+
+global.assertArrayEquals = assert.deepEqual;
+global.assert = chai.assert;
+global.chai = chai;
+global.genHelpers = genHelpers;
+
+// Different Traceur generator message
+chai.assert._throw = chai.assert.throw;
+chai.assert.throw = function (fn, msg) {
+  if (msg === '"throw" on executing generator' ||
+      msg === '"next" on executing generator') {
+    msg = "Generator is already running";
+  } else if (msg === "Sent value to newborn generator") {
+    msg = /^attempt to send (.*?) to newborn generator$/;
+  }
+
+  return chai.assert._throw(fn, msg);
+};
+
+var run = function (task, done) {
+  var actual = task.actual;
+  var expect = task.expect;
+  var exec   = task.exec;
+  var opts   = task.options;
+
+  var getOpts = function (self) {
+    return _.merge({
+      filename: self.loc
+    }, opts);
+  };
+
+  var execCode = exec.code;
+  var result;
+
+  var checkAst = function (result) {
+    if (opts.noCheckAst) return;
+
+    var errors = esvalid.errors(result.ast.program);
+    if (errors.length) {
+      var msg = [];
+      _.each(errors, function (err) {
+        msg.push(err.message + " - " + JSON.stringify(err.node));
+      });
+      throw new Error(msg.join(". "));
+    }
+  };
+
+  if (execCode) {
+    result = transform(execCode, getOpts(exec));
+    checkAst(result);
+    execCode = result.code;
+
+    try {
+      var fakeRequire = function (loc) {
+        if (loc === "../../../src/runtime/polyfills/Number.js") {
+          return Number;
+        } else if (loc === "../../../src/runtime/polyfills/Math.js") {
+          return Math;
+        } else {
+          return require(path.resolve(exec.loc, "..", loc));
+        }
+      };
+
+      var fn = new Function("require", "done", execCode);
+      fn.call(global, fakeRequire, chai.assert, done);
+    } catch (err) {
+      err.message = exec.loc + ": " + err.message;
+      err.message += util.codeFrame(execCode);
+      throw err;
+    }
+  }
+
+  var actualCode = actual.code;
+  var expectCode = expect.code;
+  if (!execCode || actualCode) {
+    result     = transform(actualCode, getOpts(actual));
+    checkAst(result);
+    actualCode = result.code;
+
+    chai.expect(actualCode).to.be.equal(expectCode, actual.loc + " !== " + expect.loc);
+  }
+
+  if (task.sourceMap) {
+    chai.expect(result.map).to.deep.equal(task.sourceMap);
+  }
+
+  if (task.sourceMappings) {
+    var consumer = new sourceMap.SourceMapConsumer(result.map);
+
+    _.each(task.sourceMappings, function (mapping, i) {
+      var expect = mapping.original;
+
+      var actual = consumer.originalPositionFor(mapping.generated);
+      chai.expect({ line: actual.line, column: actual.column }).to.deep.equal(expect);
+    });
+  }
+};
+
+module.exports = function (suiteOpts, taskOpts, dynamicOpts) {
+  taskOpts = taskOpts || {};
+
+  require("../register")(taskOpts);
+
+  _.each(helper.get(suiteOpts.name, suiteOpts.loc), function (testSuite) {
+    if (_.contains(suiteOpts.ignoreSuites, testSuite.title)) return;
+
+    suite(suiteOpts.name + "/" + testSuite.title, function () {
+      _.each(testSuite.tests, function (task) {
+        if (_.contains(suiteOpts.ignoreTasks, task.title) || _.contains(suiteOpts.ignoreTasks, testSuite.title + "/" + task.title)) return;
+
+        var runTest = function (done) {
+          var runTask = function () {
+            try {
+              run(task, done);
+            } catch (err) {
+              if (task.options.after) task.options.after();
+              throw err;
+            }
+          };
+
+          _.extend(task.options, taskOpts);
+          if (dynamicOpts) dynamicOpts(task.options, task);
+
+          var throwMsg = task.options.throws;
+          if (throwMsg) {
+            // internal api doesn't have this option but it's best not to pollute
+            // the options object with useless options
+            delete task.options.throws;
+
+            assert.throws(runTask, function (err) {
+              return throwMsg === true || err.message.indexOf(throwMsg) >= 0;
+            });
+          } else {
+            runTask();
+          }
+        };
+
+        var callback;
+        if (task.options.asyncExec) {
+          callback = runTest;
+        } else {
+          callback = function () {
+            return runTest();
+          };
+        }
+
+        test(task.title, !task.disabled && callback);
+      });
+    });
+  });
+};

test/api.js

@@ -13,10 +13,10 @@ suite("api", function () {
     assert.ok(!result.ast);
   });
 
-  test("addDeclaration unknown", function () {
+  test("addHelper unknown", function () {
     var file = new File;
     assert.throws(function () {
-      file.addDeclaration("foob");
+      file.addHelper("foob");
     }, /unknown declaration foob/);
   });
 });

test/browserify.js

@@ -0,0 +1,19 @@
+var browserify = require("browserify");
+var assert = require("assert");
+var path = require("path");
+var vm = require("vm");
+
+suite("browserify", function() {
+  test("6to5/register may be used without breaking browserify", function(done) {
+    var bundler = browserify(path.join(__dirname, "fixtures/browserify/register.js"));
+
+    bundler.bundle(function(err, bundle) {
+      if (err) return done(err);
+      assert.ok(bundle.length, "bundle output code");
+
+      // ensure that the code runs without throwing an exception
+      vm.runInNewContext(bundle, {});
+      done();
+    })
+  })
+});

test/esnext.js

@@ -0,0 +1,5 @@
+if (!process.env.ALL_6TO5_TESTS) return;
+
+require("./_transformation-helper")({
+  name: "esnext"
+});

test/fixtures/browserify/register.js

@@ -0,0 +1,3 @@
+require("../../../register")({
+  ignore: false
+});

test/fixtures/esnext/es6-arrow-functions/arguments-refers-to-parent-function.js

@@ -0,0 +1,57 @@
+function makeMultiplier() {
+  // `arguments` should refer to `makeMultiplier`'s arguments.
+  return (n) => [].slice.call(arguments).reduce((a, b) => a * b) * n;
+}
+
+function toArray() {
+  // Intentionally nest arrow functions to ensure `arguments` is put inside
+  // `toArray`'s scope.
+  return (() => (arguments, (() => [].slice.call(arguments)).call())).call();
+}
+
+function returnDotArguments(object) {
+  // Ensure `arguments` is not treated as a reference to the magic value.
+  return (() => object.arguments).call();
+}
+
+function returnArgumentsObject() {
+  // Ensure `arguments` is not treated as a reference to the magic value.
+  return (() => ({arguments: 1})).call();
+}
+
+function makeArgumentsReturner() {
+  return (() => function() {
+    return [].slice.call(arguments);
+  }).call();
+}
+
+// i.e. 2 * 3 * 4 == 24, not 16 (4 * 4)
+assert.equal(
+  makeMultiplier(2, 3)(4),
+  24,
+  'ensure `arguments` is hoisted out to the first non-arrow scope'
+);
+
+assert.deepEqual(
+  toArray(1, 2, 3),
+  [1, 2, 3],
+  'ensure `arguments` is hoisted out to the first non-arrow scope'
+);
+
+assert.equal(
+  returnDotArguments({arguments: 1}),
+  1,
+  'member accesses with `arguments` property should not be replaced'
+);
+
+assert.deepEqual(
+  returnArgumentsObject(),
+  {arguments: 1},
+  'object property keys named `arguments` should not be replaced'
+);
+
+assert.deepEqual(
+  makeArgumentsReturner()(1, 2, 3),
+  [1, 2, 3],
+  'arguments should not be hoisted from inside non-arrow functions'
+);

test/fixtures/esnext/es6-arrow-functions/does-not-bind-this-from-standard-function.js

@@ -0,0 +1,5 @@
+var dynamicThisGetter = () => function () { return this; };
+assert.equal(
+  '(' + dynamicThisGetter.toString() + ')',
+  '(function () {\n  return function () {\n    return this;\n  };\n})'
+);

test/fixtures/esnext/es6-arrow-functions/empty-arrow-function.js

@@ -0,0 +1,2 @@
+var empty = () => {};
+assert.equal(empty(), undefined);

test/fixtures/esnext/es6-arrow-functions/handles-nested-context-bindings.js

@@ -0,0 +1,12 @@
+var obj = {
+  method: function() {
+    return () => (this, () => this);
+  },
+
+  method2: function() {
+    return () => () => this;
+  }
+};
+
+assert.strictEqual(obj.method()()(), obj);
+assert.strictEqual(obj.method2()()(), obj);

test/fixtures/esnext/es6-arrow-functions/no-parens-for-low-precedence-expression-body.js

@@ -0,0 +1,2 @@
+var square = x => x * x;
+assert.equal(square(4), 16);

test/fixtures/esnext/es6-arrow-functions/object-literal-needs-parens.js

@@ -0,0 +1,2 @@
+var keyMaker = val => ({ key: val });
+assert.deepEqual(keyMaker(9), { key: 9 });

test/fixtures/esnext/es6-arrow-functions/only-lexical-this-not-dynamic-this.js

@@ -0,0 +1,7 @@
+var obj = {
+  method: function() {
+    return () => this;
+  }
+};
+
+assert.strictEqual(obj.method()(), obj);

test/fixtures/esnext/es6-arrow-functions/passed-to-function.js

@@ -0,0 +1,2 @@
+var odds = [0, 2, 4].map(v => v + 1);
+assert.deepEqual(odds, [1, 3, 5]);

test/fixtures/esnext/es6-arrow-functions/single-param-does-not-need-parens.js

@@ -0,0 +1,2 @@
+var identity = x => x;
+assert.equal(identity(1), 1);

test/fixtures/esnext/es6-classes/anonymous-class.js

@@ -0,0 +1,29 @@
+var Animal = class {
+  sayHi() {
+    return 'Hi, I am a '+this.type()+'.';
+  }
+
+  static getName() {
+    return 'Animal';
+  }
+};
+
+var Dog = class extends Animal {
+  type() { return 'dog'; }
+
+  sayHi() {
+    return super() + ' WOOF!';
+  }
+
+  static getName() {
+    return super() + '/Dog';
+  }
+};
+
+assert.equal(new Dog().sayHi(), 'Hi, I am a dog. WOOF!');
+assert.equal(Dog.getName(), 'Animal/Dog');
+
+var count = 0;
+var Cat = class extends (function(){ count++; return Animal; })() {};
+
+assert.equal(count, 1);

test/fixtures/esnext/es6-classes/call-super-function.js

@@ -0,0 +1,21 @@
+class Animal {
+  sayHi() {
+    return 'I am an animal.'
+  }
+
+  sayOther() {
+    return 'WAT?!';
+  }
+}
+
+class Horse extends Animal {
+  sayHi() {
+    return super.sayOther();
+  }
+
+  sayOther() {
+    return 'I see dead objects.';
+  }
+}
+
+assert.equal(new Horse().sayHi(), 'WAT?!');

test/fixtures/esnext/es6-classes/class-expressions.js

@@ -0,0 +1,9 @@
+var Person = (class Person {});
+assert.equal(typeof Person, 'function');
+
+assert.equal(
+  (function(){ return (class Person {}); })().name,
+  'Person'
+);
+
+assert.equal(typeof (class {}), 'function');

test/fixtures/esnext/es6-classes/class-extend.js

@@ -0,0 +1,15 @@
+class Animal {
+  sayHi() {
+    return 'Hi, I am a '+this.type()+'.';
+  }
+}
+
+class Dog extends Animal {
+  type() { return 'dog'; }
+
+  sayHi() {
+    return super() + ' WOOF!';
+  }
+}
+
+assert.equal(new Dog().sayHi(), 'Hi, I am a dog. WOOF!');

test/fixtures/esnext/es6-classes/class-with-constructor.js

@@ -0,0 +1,14 @@
+class Multiplier {
+  constructor(n=1) {
+    this.n = n;
+  }
+
+  multiply(n=1) {
+    return n * this.n;
+  }
+}
+
+assert.equal(new Multiplier().n, 1);
+assert.equal(new Multiplier(6).n, 6);
+assert.equal(new Multiplier().multiply(), 1);
+assert.equal(new Multiplier(2).multiply(3), 6);

test/fixtures/esnext/es6-classes/class-with-method-declaration.js

@@ -0,0 +1,10 @@
+class Person {
+  getName() {
+    return this.firstName + ' ' + this.lastName;
+  }
+}
+
+var me = new Person();
+me.firstName = 'Brian';
+me.lastName = 'Donovan';
+assert.equal(me.getName(), 'Brian Donovan');

test/fixtures/esnext/es6-classes/empty-named-class.js

@@ -0,0 +1,5 @@
+class Foo {
+}
+
+assert.equal(new Foo().constructor, Foo, 'Foo instances should have Foo as constructor');
+assert.ok(new Foo() instanceof Foo, 'Foo instances should be `instanceof` Foo');

test/fixtures/esnext/es6-classes/enumerable.js

@@ -0,0 +1,20 @@
+class Point {
+  constructor(x, y) {
+    this.x = x;
+    this.y = y;
+  }
+
+  toString() {
+    return '(' + this.x + ', ' + this.y + ')';
+  }
+}
+
+var point = new Point(1, 2);
+var keys = [];
+
+for (var key in point) {
+  keys.push(key);
+}
+
+assert.equal(point.toString(), '(1, 2)');
+assert.deepEqual(keys.sort(), ['toString', 'x', 'y']);

test/fixtures/esnext/es6-classes/explicit-super-in-constructor.js

@@ -0,0 +1,15 @@
+class Point {
+  constructor(x, y) {
+    this.x = x;
+    this.y = y;
+  }
+}
+
+class ZeroPoint extends Point {
+  constructor() {
+    super(0, 0);
+  }
+}
+
+assert.equal(new ZeroPoint().x, 0);
+assert.equal(new ZeroPoint().y, 0);

test/fixtures/esnext/es6-classes/extends-null.js

@@ -0,0 +1,4 @@
+class Obj extends null {}
+
+assert.strictEqual(Obj.toString, Function.toString);
+assert.strictEqual(new Obj().toString, undefined);

test/fixtures/esnext/es6-classes/getter-setter-super.js

@@ -0,0 +1,15 @@
+class Animal {
+  get sound() {
+    return 'I am a ' + this.type + '.';
+  }
+}
+
+class Cat extends Animal {
+  get type() { return 'cat'; }
+
+  get sound() {
+    return super.sound + ' MEOW!';
+  }
+}
+
+assert.equal(new Cat().sound, 'I am a cat. MEOW!');

test/fixtures/esnext/es6-classes/getter-setter.js

@@ -0,0 +1,28 @@
+class Person {
+  constructor(firstName, lastName) {
+    this.firstName = firstName;
+    this.lastName = lastName;
+  }
+
+  get name() {
+    return this.firstName + ' ' + this.lastName;
+  }
+
+  set name(name) {
+    var parts = name.split(' ');
+    this.firstName = parts[0];
+    this.lastName = parts[1];
+  }
+}
+
+var mazer = new Person('Mazer', 'Rackham');
+assert.equal(mazer.name, 'Mazer Rackham');
+mazer.name = 'Ender Wiggin';
+assert.equal(mazer.firstName, 'Ender');
+assert.equal(mazer.lastName, 'Wiggin');
+
+var forLoopProperties = [];
+for (var key in mazer) {
+  forLoopProperties.push(key);
+}
+assert.ok(forLoopProperties.indexOf('name') >= 0, 'getters/setters are enumerable');