v1.12.21

Added an interop commonjs loader.

.gitignore

@@ -4,5 +4,9 @@ test/tmp
 *.log
 *.cache
 /templates.json
+/tests.json
+/browser.js
+/browser-polyfill.js
+/runtime.js
 coverage
 dist

.hound.yml

@@ -0,0 +1,3 @@
+java_script:
+  enabled: true
+  config_file: .jshintrc

.jshintrc

@@ -17,5 +17,13 @@
   "loopfunc": true,
   "white": true,
   "maxparams": 5,
-  "maxdepth": 4
+  "maxdepth": 4,
+
+  "globals": {
+    "window": true,
+    "suite": true,
+    "set": true,
+    "before": true,
+    "bench": true
+  }
 }

.npmignore

@@ -7,4 +7,5 @@ benchmark
 Makefile
 .*
 dist
-!README.md
+tests.json
+CHANGELOG.md

.travis.yml

@@ -3,10 +3,17 @@ node_js:
   - "0.10"
   - "0.11"
 
+branches:
+  except:
+   - experimental
+
 before_script: "npm install -g codeclimate-test-reporter"
 script: "make test-travis"
 
-addons:
-  code_climate:
-    repo_token:
-      secure: "PfP9sDUJzSznDb+ZEPO2cignXabSTXJxEVm5ESRPgEcFr+/4b0pt3hI8R9b+9mLtBEwtw3DLUq48MOeqEKnq29csQmpjPVcN6gT4uR2DdNa1JpVgDuwxT05NB3fBea9U2reM73iV8ylCgPHExr2uGR9/87JzR2beY/56EUL5NjY="
+notifications:
+  webhooks:
+    urls:
+      - https://webhooks.gitter.im/e/acf1870e9d223c65e8d5
+    on_success: always
+    on_failure: always
+    on_start: false

CHANGELOG.md

@@ -0,0 +1,120 @@
+# 1.12.21
+
+ * Fix unneccesary let scoping replacement.
+ * Add `commonInterop` module formatter. Thanks [@Naddiseo](https://github.com/Naddiseo).
+ * Fix `return` outside of function body bug. Thanks [@brentburg](https://github.com/brentburg).
+ * Add more flexible option types.
+
+# 1.12.20
+
+ * Append `sourceMappingURL` when using `bin/6to5` and output sourcemaps.
+
+# 1.12.19
+
+ * Add `comments` option and `--remove-comments` flag. Thanks [@webpro](htps://github.com/webpro).
+ * Embed `regenerator`.
+
+# 1.12.18
+
+ * Use `global` reference instead of `window`.
+
+# 1.12.17
+
+ * Add `moduleName`, `sourceRoot` and `filenameRelative` options. Thanks [@darvelo](https://github.com/darvelo).
+ * Traversal optimisations.
+
+# 1.12.16
+
+ * Fix comments not being retained from `MethodDefinition` in classes.
+ * Add temporal dead zone in default parameters.
+
+# 1.12.15
+
+ * Update `acorn-6to5`.
+
+# 1.12.14
+
+ * Fix duplicate let scoping in functions.
+ * Make JSX whitespace more React-compliant.
+ * Add `_memberExpressionKeywords` transformer that turns keyword identifiers to computed literals.
+ * Upgrade `regenerator-6to5`.
+
+# 1.12.13
+
+ * Support duplicate constants within different block scopes.
+ * Fix for-head duplication testing and replacement.
+ * Support `raw` property on tagged template literals.
+
+# 1.12.12
+
+ * Make scope tracker more reliable to handle all edgecases.
+
+# 1.12.11
+
+ * Block scope classes.
+ * Fix generation of integer `Literal`s in `MemberExpression`.
+
+# 1.12.10
+
+ * Fix let scoping var hoisting.
+
+# 1.12.9
+
+ * Escape unicode characters when generating string `Literal`s.
+ * Fix semicolons being output for statements in `ExportDeclaration`.
+ * Fix `WithStatement` missing parenthesis.
+
+# 1.12.8
+
+ * Temporarily forbid `AssignmentExpression` destructuring outside of `ExpressionStatement`.
+
+# 1.12.7
+
+ * Update to latest `acorn-6to5`.
+
+# 1.12.6
+
+ * Update to latest `acorn-6to5`.
+
+# 1.12.5
+
+ * Fix excessive whitespace trimming resulting in innaccurate sourcemap line.
+
+# 1.12.4
+
+ * Add `doc` folder for documentation.
+
+# 1.12.3
+
+ * Support generator comprehensions.
+ * Use `Array.from` instead of `Array.prototype.slice` in spread transformer.
+ * Support spread in `NewExpression`s.
+
+# 1.12.2
+
+ * Upgrade `matcha` to `0.6.0` and `browserify` to `6.3.2`.
+ * Add own `trimRight` helper instead of relying on the string instance method.
+ * Support JSX spreads that aren't the first.
+
+# 1.12.1
+
+ * Fix `this` and `arguments` mapping in the `_aliasFunctions` transformer.
+
+# 1.12.0
+
+ * Combine `jsx` and `react` transformers to `react`.
+ * Update `react` syntax output to React v0.12.
+
+# 1.11.15
+
+ * Fix JSX literal whitespace generation.
+
+# 1.11.14
+
+ * Avoid using a switch for let-scoping continue and break statements and use an if statement instead.
+ * Remove excess whitespace and newlines from JSX literals.
+
+# 1.11.13
+
+ * Update regenerator-6to5
+ * Add support for most escodegen formatting options

CONTRIBUTING.md

@@ -0,0 +1,31 @@
+# Contributing
+
+ * **General**
+   * No ES6 syntax features or methods, exclusively ES5.
+   * Max of five arguments for functions
+   * Max depth of four nested blocks
+   * 2-spaced soft tabs
+ * **Naming**
+   * CamelCase all class names
+   * camelBack all variable names
+ * **Spacing**
+   * 80 character line max
+   * Spaces after all keywords
+   * Spaces before all left curly braces
+ * **Comments**
+   * Use JSDoc-style comments for methods
+   * Single-line comments for ambiguous code
+ * **Quotes**
+   * Always use double quotes
+   * Only use single quotes when the string contains a double quote
+ * **Declaration**
+   * No unused variables
+   * No pollution of global variables and prototypes
+
+## Testing
+
+    $ make test
+
+## Linting
+
+    $ make lint

FEATURES.md

@@ -1,162 +0,0 @@
-# Features
-
-## Array comprehension
-
-```javascript
-[for (i of [1, 2, 3]) i * i]; // [1, 4, 9]
-```
-
-## Arrow functions
-
-```javascript
-arr.map(x => x * x);
-```
-
-## Let scoping
-
-```javascript
-for (let i in arr) {
-  let v = arr[i];
-}
-```
-
-## Classes
-
-```javascript
-class Foo extends Bar {
-  constructor() { }
-
-  foo() { }
-
-  get bar() { }
-
-  set bar() { }
-}
-```
-
-## Computed property names
-
-```javascript
-var foo = "foo";
-var bar = "bar";
-var obj = {
-  ["foo" + bar]: "heh",
-  ["bar" + foo]: "noo",
-  foo: "foo",
-  bar: "bar"
-};
-```
-
-## Constants
-
-```javascript
-const MULTIPLIER = 5;
-console.log(2 * MULTIPLIER);
-
-MULTIPLIER = 6; // error
-var MULTIPLIER; // error
-```
-
-## Default parameters
-
-```javascript
-function foo(bar = "foo") {
-  return bar + "bar";
-}
-```
-
-## Destructuring
-
-```javascript
-var [a, [b], c, d] = ["hello", [", ", "junk"], ["world"]];
-console.log(a + b + c); // hello, world
-```
-
-## For-of
-
-```javascript
-for (var i of [1, 2, 3]) {
-  console.log(i * i);
-}
-```
-
-## Generators
-
-```javascript
-```
-
-## Modules
-
-```javascript
-```
-
-## Numeric literals
-
-```javascript
-0b111110111 === 503; // true
-0o767 === 503; // true
-```
-
-## Property method assignment
-
-```javascript
-var obj = {
-  foo() {
-    return "foobar";
-  },
-
-  get bar() {
-    return this._bar;
-  },
-
-  set bar(val) {
-    this._bar = val;
-  }
-};
-```
-
-## Property name shorthand
-
-```javascript
-function f(x, y) {
-  return { x, y };
-}
-```
-
-## Rest parameters
-
-```javascript
-function printList(name, ...items) {
-  console.log("list %s has the following items", name);
-  items.forEach(function (item) {
-    console.log(item);
-  });
-}
-```
-
-## Spread
-
-```javascript
-function add(x, y) {
-  return x + y;
-}
-
-var numbers = [5, 10];
-add(...numbers); // 15
-```
-
-## Template literals
-
-```javascript
-var x = 5;
-var y = 10;
-console.log(`${x} + ${y} = ${x + y}`); // "5 + 10 = 15"
-```
-
-## Unicode regex
-
-```javascript
-var string = 'foo💩bar';
-var match = string.match(/foo(.)bar/u);
-console.log(match[1]);
-```

Makefile

@@ -1,10 +1,12 @@
+BROWSERIFY_CMD = node_modules/browserify/bin/cmd.js
 ISTANBUL_CMD = node_modules/istanbul/lib/cli.js cover
+UGLIFY_CMD = node_modules/uglify-js/bin/uglifyjs
 JSHINT_CMD = node_modules/jshint/bin/jshint
 MOCHA_CMD = node_modules/mocha/bin/_mocha
 
 export NODE_ENV = test
 
-.PHONY: clean test test-cov test-travis test-browser publish bench build
+.PHONY: clean test test-cov test-clean lint test-travis test-spec test-browser publish bench build
 
 clean:
 	rm -rf coverage templates.json test/tmp dist
@@ -13,21 +15,36 @@ bench:
 	npm install es6-transpiler traceur esnext es6now jstransform
 	node node_modules/matcha/bin/_matcha
 
+lint:
+	$(JSHINT_CMD) lib bin benchmark/index.js
+
+test-clean:
+	rm -rf test/tmp
+
 test:
-	$(JSHINT_CMD) lib
+	make lint
 	$(MOCHA_CMD)
+	make test-clean
 
 test-cov:
 	rm -rf coverage
 	node $(ISTANBUL_CMD) $(MOCHA_CMD) --
 
-test-travis:
+test-spec:
 	node $(ISTANBUL_CMD) $(MOCHA_CMD) -- --reporter spec
+
+test-travis:
+	make test-spec
 	if test -n "$$CODECLIMATE_REPO_TOKEN"; then codeclimate < coverage/lcov.info; fi
 
 test-browser:
-	make build
-	node bin/generate-browser-test >dist/6to5-test.js
+	mkdir -p dist
+
+	node bin/cache-templates
+	node bin/cache-tests
+	node $(BROWSERIFY_CMD) -e test/_browser.js >dist/6to5-test.js
+	rm -rf templates.json tests.json
+
 	test -n "`which open`" && open test/browser.html
 
 build:
@@ -35,8 +52,14 @@ build:
 
 	node bin/cache-templates
 
-	browserify lib/6to5/transform.js -s to5 >dist/6to5.js
-	uglifyjs dist/6to5.js >dist/6to5.min.js
+	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
 
@@ -45,6 +68,11 @@ publish:
 
 	make test
 
+	make build
+	cp dist/6to5.min.js browser.js
+	cp dist/polyfill.min.js browser-polyfill.js
+	cp dist/runtime.min.js runtime.js
+
 	node bin/cache-templates
 	test -f templates.json
 
@@ -54,4 +82,4 @@ publish:
 
 	git push --follow-tags
 
-	rm -rf templates.json
+	rm -rf templates.json browser.js runtime.js browser-polyfill.js

README.md

@@ -1,385 +1,29 @@
 <p align="center">
-  <img alt="6to5" src="http://i.imgur.com/hVl9KRw.png">
+  <img alt="6to5" src="https://raw.githubusercontent.com/6to5/logo/master/logo.png" width="546">
 </p>
 
 <p align="center">
-  <a href="https://travis-ci.org/sebmck/6to5">
-    <img alt="Travis Status" src="http://img.shields.io/travis/sebmck/6to5.svg?style=flat&amp;label=travis">
+  <a href="https://travis-ci.org/6to5/6to5">
+    <img alt="Travis Status" src="http://img.shields.io/travis/6to5/6to5.svg?branch=master&amp;style=flat&amp;label=travis">
   </a>
 
-  <a href="https://codeclimate.com/github/sebmck/6to5">
-    <img alt="Code Climate Score" src="http://img.shields.io/codeclimate/github/sebmck/6to5.svg?style=flat">
+  <a href="https://ci.appveyor.com/project/sebmck/6to5">
+    <img alt="Appveyor Status" src="http://img.shields.io/appveyor/ci/sebmck/6to5.svg?style=flat&amp;label=appveyor">
   </a>
 
-  <a href="https://codeclimate.com/github/sebmck/6to5">
-    <img alt="Coverage" src="http://img.shields.io/codeclimate/coverage/github/sebmck/6to5.svg?style=flat">
+  <a href="https://codeclimate.com/github/6to5/6to5">
+    <img alt="Code Climate Score" src="http://img.shields.io/codeclimate/github/6to5/6to5.svg?style=flat">
   </a>
 
-  <a href="https://david-dm.org/sebmck/6to5">
-    <img alt="Dependency Status" src="http://img.shields.io/david/sebmck/6to5.svg?style=flat">
+  <a href="https://codeclimate.com/github/6to5/6to5">
+    <img alt="Coverage" src="http://img.shields.io/codeclimate/coverage/github/6to5/6to5.svg?style=flat">
+  </a>
+
+  <a href="https://david-dm.org/6to5/6to5">
+    <img alt="Dependency Status" src="http://img.shields.io/david/6to5/6to5.svg?style=flat">
   </a>
 </p>
 
-**6to5** turns ES6 code into vanilla ES5, so you can use ES6 features **today.**
+**6to5** turns ES6+ code into vanilla ES5, so you can use next generation features **today.**
 
- - **Readable** - formatting is retained if possible so your generated code is as similar as possible.
- - **Extensible** - with a large range of [plugins](#plugins) and **browser support**.
- - **Lossless** - **source map support** so you can debug your compiled code with ease.
- - **Compact** - maps directly to the equivalent ES5 with **no runtime**[\*](#generators).
-
-## Installation
-
-It's as easy as:
-
-    $ npm install -g 6to5
-
-## Table of Contents
-
-- [Features](#features)
-- [Usage](#usage)
-  - [Plugins](#plugins)
-  - [CLI](#cli)
-  - [Node](#node-1)
-  - [Browser](#browser)
-- [Modules](#modules)
-- [Caveats](#caveats)
-- [Differences](#differences)
-
-## [Features](FEATURES.md)
-
- - [Array comprehension](FEATURES.md#array-comprehension)
- - [Arrow functions](FEATURES.md#arrow-functions)
- - [Classes](FEATURES.md#classes)
- - [Computed property names](FEATURES.md#computed-property-names)
- - [Constants](FEATURES.md#constants)
- - [Default parameters](FEATURES.md#default-parameters)
- - [Destructuring](FEATURES.md#destructuring)
- - [For-of](FEATURES.md#for-of)
- - [Generators](FEATURES.md#generators) via [regenerator](https://github.com/facebook/regenerator)
- - [Let scoping](FEATURES.md#let-scoping)
- - [Modules](FEATURES.md#modules)
- - [Numeric literals](FEATURES.md#numeric-literals)
- - [Property method assignment](FEATURES.md#property-method-assignment)
- - [Property name shorthand](FEATURES.md#property-name-shorthand)
- - [Rest parameters](FEATURES.md#rest-parameters)
- - [Spread](FEATURES.md#spread)
- - [Template literals](FEATURES.md#template-literals)
- - [Unicode regex](FEATURES.md#unicode-regex)
-
-## Usage
-
-### Plugins
-
- - [Broccoli](https://github.com/very-geek/broccoli-6to5-transpiler)
- - [Browserify](https://github.com/sebmck/6to5-browserify)
- - [Brunch](https://github.com/es128/6to5-brunch)
- - [Connect](https://github.com/sebmck/6to5-connect)
- - [Gulp](https://github.com/sindresorhus/gulp-6to5)
- - [Grunt](https://github.com/sindresorhus/grunt-6to5)
- - [Jade](https://github.com/Apoxx/jade-6to5)
- - [webpack](https://github.com/Couto/6to5-loader)
-
-### CLI
-
-Compile the file `script.js` and output it to stdout.
-
-    $ 6to5 script.js
-
-Compile the file `script.js` and output it to `script-compiled.js`.
-
-    $ 6to5 script.js --out-file script-compiled.js
-
-Compile the file `script.js` and output it to `script-compiled.js` and save a
-source map to `script-compiled.js.map`.
-
-    $ 6to5 script.js --source-maps --out-file script-compiled.js
-
-Compile the file `script.js` and output it to `script-compiled.js` with a source
-map embedded in a comment at the bottom.
-
-    $ 6to5 script.js --source-maps-inline --out-file script-compiled.js
-
-Compile the entire `src` directory and output it to the `lib` directory.
-
-    $ 6to5 src --out-dir lib
-
-Pipe a file in via stdin and output it to `script-compiled.js`
-
-    $ 6to5 --out-file script-compiled.js < script.js
-
-#### Node
-
-Launch a repl.
-
-    $ 6to5-node
-
-Evaluate code.
-
-    $ 6to5-node -e "class Test { }"
-
-Compile and run `test.js`.
-
-    $ 6to5-node test
-
-### Node
-
-```javascript
-var to5 = require("6to5");
-
-var result = to5.transform("code();", options);
-result.code;
-result.map;
-result.ast;
-
-to5.transformFileSync("filename.js", options).code;
-
-to5.transformFile("filename.js", options, function (err, result) {
-
-});
-```
-
-##### Options
-
-```javascript
-{
-  // Filename for use in errors etc.
-  // Default: "unknown"
-  filename: "filename",
-
-  // List of transformers to EXCLUDE.
-  // Run `6to5 --help` to see a full list of transformers.
-  blacklist: [],
-
-  // List of transformers to ONLY use.
-  // Run `6to5 --help` to see a full list of transformers.
-  whitelist: [],
-
-  // Module formatter to use
-  // Run `6to5 --help` to see a full list of module formatters.
-  // Default: "common"
-  modules: "common",
-
-  // If truthy, adds a `map` property to returned output.
-  // If set to "inline", a comment with a sourceMappingURL directive is added to
-  // the bottom of the returned code.
-  // Default: false
-  sourceMap: true,
-
-  // Set `file` on returned source map.
-  // Default: `filename` option.
-  sourceMapName: "filename",
-
-  // Set `sources[0]` on returned source map.
-  // Default: `filename` option.
-  sourceFileName: "filename"
-}
-```
-
-#### Require hook
-
-All subsequent files required by node with the extensions `.es6` and `.js` will
-be transformed by 6to5. The polyfill specified in [Polyfill](#polyfill) is also
-required.
-
-```javascript
-require("6to5/register");
-```
-
-**NOTE:** By default all requires to `node_modules` will be ignored. You can
-override this by passing an ignore regex via:
-
-```javascript
-require("6to5/register")(/regex/);
-```
-
-You can also customise the file extensions that the require hook will use via:
-
-```javascript
-require("6to5/register")({
-  // optional ignore regex
-  ignoreRegex: /regex/,
-
-  // this will remove the currently hooked extensions of .es6 and .js so you'll
-  // have to add them back if you want them to be used again
-  extensions: [".js", ".es6"]
-});
-```
-
-### Browser
-
-You can build a browser version of the compiler by running the following in the
-6to5 directory:
-
-    $ make build
-
-This will output the files `dist/6to5.js` and `dist/6to5.min.js`.
-
-Just include one of those in the browser and access the transform method via the
-global `to5`.
-
-```javascript
-to5("class Test {}").code;
-```
-
-#### Test
-
-To test 6to5 in your browser run:
-
-    $ make test-browser
-
-And open `test/browser.html` in your browser if it doesn't open automatically.
-
-## [Modules](MODULES.md)
-
-See [Modules - Common](MODULES.md#common-default) for documentation on the
-default module formatting.
-
-Alternatively see [Modules](MODULES.md) for all other supported module formatting types.
-
-## Caveats
-
-### Polyfill
-
-6to5 does not include a runtime nor polyfill and it's up to the developer to
-include one in compiled browser code.
-
-#### Node
-
-A polyfill is included with the 6to5 module that can be included in node like
-so:
-
-```javascript
-require("6to5/polyfill");
-```
-
-This is simply a wrapper around the
-[regenerator runtime](https://github.com/facebook/regenerator/blob/master/runtime.js) and the
-[es6-shim](https://github.com/paulmillr/es6-shim) and
-[es6-symbol](https://github.com/medikoo/es6-symbol) polyfills.
-
-#### Browser
-
-If you're planning on using 6to5 output in the browser then it's up to you
-to include polyfills. [es6-symbol](https://github.com/medikoo/es6-symbol#browser)
-and [es6-shim](https://raw.githubusercontent.com/paulmillr/es6-shim/master/es6-shim.js)
-fill the vast majority of polyfill concerns.
-
-### For-of
-
-A polyfill is required for for-of functionality that implements `Symbol` and
-adds `prototype[Symbol.iterator]` behaviour to built-ins. Using the polyfills
-specified in [polyfill](#polyfill) suffices.
-
-### Classes
-
-Built-in classes such as `Date`, `Array` and `DOM` cannot be subclassed due to
-limitations in ES5 implementations.
-
-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.
-
-### Generators
-
-The [regenerator runtime](https://github.com/facebook/regenerator/blob/master/runtime.js)
-and an [ES6 polyfill](#polyfill) are required in order for generators to work.
-
-## Differences
-
-### Philosophy
-
-The fundamental concept behind 6to5 is that the generated code must be close as
-possible to the original, retaining all the same formatting and readability.
-
-Many other transpilers are just concerned with making the code work while 6to5
-is concerned with making sure it works **and** is readable at the same time.
-
-For example, given the following array comprehension:
-
-```javascript
-var seattlers = [for (c of customers) if (c.city == "Seattle") { name: c.name, age: c.age }];
-```
-
-is generated to the following with 6to5:
-
-```javascript
-var seattlers = customers.filter(function (c) {
-  return c.city == "Seattle";
-}).map(function (c) {
-  return {
-    name: c.name,
-    age: c.age
-  };
-});
-```
-
-The following is what Traceur generates:
-
-```javascript
-var seattlers = (function() {
-  var c;
-  var $__20 = 0,
-      $__21 = [];
-  for (var $__22 = customers[$traceurRuntime.toProperty(Symbol.iterator)](),
-      $__23; !($__23 = $__22.next()).done; ) {
-    c = $__23.value;
-    if (c.city == "Seattle")
-      $traceurRuntime.setProperty($__21, $__20++, {
-        name: c.name,
-        age: c.age
-      });
-  }
-  return $__21;
-}());
-```
-
-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.
-
-I'm not saying 6to5 is for everyone or even suited for everything. Traceur is
-better suited if you'd like a full ES6 environment with polyfills and all.
-
-### Comparison to other transpilers
-
-|                              | 6to5 | Traceur | esnext | es6now | es6-transpiler | jstransform |
-| ---------------------------- | ---- | ------- | ------ | ------ | -------------- | ----------- |
-| No runtime                   | ✓    |         |        |        | ✓              | ✓           |
-| Source maps                  | ✓    | ✓       | ✓      |        | ✓              | ✓           |
-| No compiler global pollution | ✓    |         | ✓      |        | ✓              | ✓           |
-| Arrow functions              | ✓    | ✓       | ✓      | ✓      | ✓              | ✓           |
-| Classes                      | ✓    | ✓       | ✓      | ✓      | ✓              | ✓           |
-| Computed property names      | ✓    | ✓       | ✓      | ✓      | ✓              |             |
-| Constants                    | ✓    | ✓       |        |        | ✓              |             |
-| Default parameters           | ✓    | ✓       | ✓      | ✓      | ✓              |             |
-| Destructuring                | ✓    | ✓       | ✓      | ✓      | ✓              | ✓           |
-| For-of                       | ✓    | ✓       | ✓      | ✓      | ✓              |             |
-| Generators                   | ✓    | ✓       | ✓      |        |                |             |
-| Let scoping                  | ✓    | ✓       |        |        | ✓              |             |
-| Modules                      | ✓    | ✓       |        | ✓      |                |             |
-| Property method assignment   | ✓    | ✓       | ✓      | ✓      | ✓              | ✓           |
-| Property name shorthand      | ✓    | ✓       | ✓      | ✓      | ✓              | ✓           |
-| Rest parameters              | ✓    | ✓       | ✓      | ✓      | ✓              | ✓           |
-| Spread                       | ✓    | ✓       | ✓      | ✓      | ✓              |             |
-| Template literals            | ✓    | ✓       | ✓      | ✓      | ✓              | ✓           |
-| Unicode regex                | ✓    | ✓       |        |        | ✓              |             |
-
-#### [Traceur](https://github.com/google/traceur-compiler)
-
-Traceur requires quite a bulky runtime (~75KB) and produces quite verbose code.
-While this can be trimmed down by selectively building the runtime, it's an
-unneccesary step when a runtime can be eliminated entirely.
-
-#### [es6now](https://github.com/zenparsing/es6now)
-
-es6now doesn't output sourcemaps. This is cited as a positive as line-to-line
-mapping is the goal. This however obviously doesn't retain column mapping
-resulting in the output code not being very pleasant.
-
-#### [es6-transpiler](https://github.com/termi/es6-transpiler)
-
-The es6-transpiler compiler requires shims to operate which pollutes the global
-scope resulting in possible collisions.
-
-es6-transpiler maps line-by-line, just like es6now, this results in the same
-issues such as lack of column information and unpleasant code output.
+For more information view the [documentation](https://6to5.github.io).

appveyor.yml

@@ -0,0 +1,17 @@
+environment:
+  matrix:
+    - nodejs_version: "0.10"
+    - nodejs_version: "0.11"
+
+install:
+ - "npm install"
+ - "cinst make"
+
+test_script:
+ - "node --version"
+ - "npm --version"
+ - "make test-spec"
+
+build: "off"
+
+version: "{build}"

benchmark/index.js

@@ -7,13 +7,10 @@ var es6now  = require("es6now");
 var esnext  = require("esnext");
 var to5     = require("../lib/6to5");
 
-var uglify  = require("uglify-js");
+//var uglify  = require("uglify-js");
 var matcha  = require("matcha");
-var stream  = require("stream");
 var path    = require("path");
-var zlib    = require("zlib");
 var fs      = require("fs");
-var vm      = require("vm");
 var _       = require("lodash");
 
 var readResolve = function (filename) {
@@ -51,7 +48,7 @@ var compilers = {
 
   traceur: {
     runtime: readResolve("traceur/bin/traceur-runtime.js"),
-    compile: function (code, filename) {
+    compile: function (code) {
       return traceur.compile(code, {
         modules: "commonjs",
         experimental: true
@@ -61,20 +58,20 @@ var compilers = {
 
   esnext: {
     runtime: readResolve("esnext/node_modules/regenerator/runtime.js") || readResolve("regenerator/runtime.js"),
-    compile: function (code, filename) {
+    compile: function (code) {
       return esnext.compile(code).code;
     }
   },
 
   es6now: {
     runtime: readResolve("es6now/runtime/ES6.js"),
-    compile: function (code, filename) {
+    compile: function (code) {
       return es6now.translate(code);
     }
   },
 
   "es6-transpiler": {
-    compile: function (code, filename) {
+    compile: function (code) {
       var result = es6tr.run({ src: code });
       if (result.errors.length) throw new Error(result.join("; "));
       return result.src;
@@ -82,7 +79,7 @@ var compilers = {
   },
 
   jstransform: {
-    compile: function (code, filename) {
+    compile: function (code) {
       return jsTrans.transform(jsTransVisitors, code).code;
     }
   }
@@ -90,7 +87,7 @@ var compilers = {
 
 // versions
 
-var uglifyTitle = "uglify v" + getVersion("uglify-js");
+//var uglifyTitle = "uglify v" + getVersion("uglify-js");
 
 _.each(compilers, function (compiler, name) {
   compiler.title = name + " v" + (compiler.version || getVersion(name));
@@ -162,7 +159,7 @@ _.each(fs.readdirSync(__dirname + "/fixtures"), function (name) {
       });
     });
 
-    _.each(compilers, function (compiler, name) {
+    _.each(compilers, function (compiler) {
       bench(compiler.title, function () {
         compiler.compile(code, loc);
       });

bin/6to5-node

@@ -1,84 +1,56 @@
 #!/usr/bin/env node
 
-var commander = require("commander");
-var Module    = require("module");
-var util      = require("../lib/6to5/util");
-var path      = require("path");
-var repl      = require("repl");
-var to5       = require("../lib/6to5");
-var vm        = require("vm");
-var _         = require("lodash");
+/**
+ * This tiny wrapper file checks for known node flags and appends them
+ * when found, before invoking the "real" _6to5-node(1) executable.
+ */
 
-commander.option("-e, --eval [script]", "evaluate script");
-commander.option("-p, --print", "evaluate script and print result");
-commander.option("-i, --ignore [regex]", "ignore all files that match this regex when using the require hook");
-commander.option("-x, --extensions [extensions]", "list of extensions to hook into [.es6,.js]", util.list);
+var spawn = require("child_process").spawn;
+var args  = ["--harmony", __dirname + "/_6to5-node"];
 
-var pkg = require("../package.json");
-commander.version(pkg.version);
-commander.usage("[options] [ -e script | script.js ] [arguments]");
-commander.parse(process.argv);
+process.argv.slice(2).forEach(function(arg){
+  var flag = arg.split("=")[0];
 
-//
-
-var registerOpts = {};
-
-if (commander.ignore) {
-  registerOpts.ignoreRegex = new RegExp(commander.ignore);
-}
-
-if (commander.extensions && commander.extensions.length) {
-  registerOpts.extensions = commander.extensions
-}
-
-to5.register(registerOpts);
-
-//
-
-var _eval = function (code, filename) {
-  code = to5.transform(code, { filename: filename }).code;
-  return vm.runInThisContext(code, filename);
-};
-
-if (commander.eval) {
-  var result = _eval(commander.eval, "eval");
-  if (commander.print) console.log(result);
-} else {
-  var filenames = commander.args;
-
-  if (filenames.length) {
-    _.each(filenames, function (filename) {
-      if (!util.isAbsolute(filename)) {
-        filename = path.join(process.cwd(), filename);
-      }
-
-      require(require.resolve(filename));
-    });
-  } else {
-    replStart();
+  switch (flag) {
+    case "-d":
+      args.unshift("--debug");
+      args.push("--no-timeouts");
+      break;
+    case "debug":
+    case "--debug":
+    case "--debug-brk":
+      args.unshift(arg);
+      args.push("--no-timeouts");
+      break;
+    case "-gc":
+    case "--expose-gc":
+      args.unshift("--expose-gc");
+      break;
+    case "--gc-global":
+    case "--harmony":
+    case "--harmony-proxies":
+    case "--harmony-collections":
+    case "--harmony-generators":
+    case "--no-deprecation":
+    case "--prof":
+    case "--throw-deprecation":
+    case "--trace-deprecation":
+      args.unshift(arg);
+      break;
+    default:
+      if (0 == arg.indexOf("--trace")) args.unshift(arg);
+      else args.push(arg);
+      break;
   }
-}
+});
 
-function replStart() {
-  repl.start({
-    prompt: "> ",
-    input: process.stdin,
-    output: process.stdout,
-    eval: replEval,
-    useGlobal: true
+var proc = spawn(process.argv[0], args, { stdio: "inherit" });
+proc.on("exit", function (code, signal) {
+  process.on("exit", function (){
+    if (signal) {
+      process.kill(process.pid, signal);
+    } else {
+      process.exit(code);
+    }
   });
-}
-
-function replEval(code, context, filename, callback) {
-  var err;
-  var result;
-
-  try {
-    code = code.slice(1, -2); // remove "(" and "\n)"
-    result = _eval(code, filename);
-  } catch (e) {
-    err = e;
-  }
-
-  callback(err, result);
-}
+});

bin/6to5-runtime

@@ -0,0 +1,4 @@
+#!/usr/bin/env node
+
+var runtime = require("../lib/6to5/runtime");
+console.log(runtime(process.argv[2]));

bin/6to5/dir.js

@@ -19,7 +19,9 @@ module.exports = function (commander, filenames, opts) {
     mkdirp.sync(up);
 
     if (commander.sourceMaps) {
-      fs.writeFileSync(dest + ".map", JSON.stringify(data.map));
+      var mapLoc = dest + ".map";
+      data.code = util.addSourceMappingUrl(data.code, mapLoc);
+      fs.writeFileSync(mapLoc, JSON.stringify(data.map));
     }
 
     fs.writeFileSync(dest, data.code);

bin/6to5/file.js

@@ -6,7 +6,7 @@ var util      = require("./util");
 var fs        = require("fs");
 var _         = require("lodash");
 
-module.exports = function (commander, filenames, opts) {
+module.exports = function (commander, filenames) {
   var results = [];
 
   var buildResult = function () {
@@ -48,7 +48,7 @@ module.exports = function (commander, filenames, opts) {
     return {
       map: map,
       code: code
-    }
+    };
   };
 
   var output = function () {
@@ -56,7 +56,9 @@ module.exports = function (commander, filenames, opts) {
 
     if (commander.outFile) {
       if (commander.sourceMaps) {
-        fs.writeFileSync(commander.outFile + ".map", JSON.stringify(result.map));
+        var mapLoc = commander.outFile + ".map";
+        result.code = util.addSourceMappingUrl(result.code, mapLoc);
+        fs.writeFileSync(mapLoc, JSON.stringify(result.map));
       }
 
       fs.writeFileSync(commander.outFile, result.code);
@@ -100,8 +102,8 @@ module.exports = function (commander, filenames, opts) {
       }
     });
 
-    _.each(_filenames, function (filename, i) {
-      results.push(util.compile(filename, { _noStrict: i != 0 }));
+    _.each(_filenames, function (filename) {
+      results.push(util.compile(filename));
     });
 
     output();

bin/6to5/index.js

@@ -1,13 +1,8 @@
 #!/usr/bin/env node
 
 var commander = require("commander");
-var sourceMap = require("source-map");
-var transform = require("../../lib/6to5/transform");
-var chokidar  = require("chokidar");
-var mkdirp    = require("mkdirp");
-var util2     = require("../../lib/6to5/util");
-var util      = require("./util");
-var path      = require("path");
+var transform = require("../../lib/6to5/transformation/transform");
+var util      = require("../../lib/6to5/util");
 var fs        = require("fs");
 var _         = require("lodash");
 
@@ -15,12 +10,14 @@ commander.option("-t, --source-maps-inline", "Append sourceMappingURL comment to
 commander.option("-s, --source-maps", "Save source map alongside the compiled code");
 commander.option("-f, --filename [filename]", "Filename to use when reading from stdin - this will be used in source-maps, errors etc [stdin]", "stdin");
 commander.option("-w, --watch", "Recompile files on changes");
+commander.option("-r, --runtime", "Replace 6to5 declarations with references to a runtime");
 
 commander.option("-m, --modules [modules]", "Module formatter type to use [common]", "common");
-commander.option("-w, --whitelist [whitelist]", "Whitelist of transformers to ONLY use", util2.list);
-commander.option("-b, --blacklist [blacklist]", "Blacklist of transformers to NOT use", util2.list);
+commander.option("-w, --whitelist [whitelist]", "Whitelist of transformers to ONLY use", util.list);
+commander.option("-b, --blacklist [blacklist]", "Blacklist of transformers to NOT use", util.list);
 commander.option("-o, --out-file [out]", "Compile all input files into a single file");
 commander.option("-d, --out-dir [out]", "Compile an input directory of modules into an output directory");
+commander.option("-c, --remove-comments", "Remove comments from the compiled code", false);
 
 commander.on("--help", function(){
   var outKeys = function (title, obj) {
@@ -92,6 +89,8 @@ exports.opts = {
   blacklist:     commander.blacklist,
   whitelist:     commander.whitelist,
   sourceMap:     commander.sourceMaps || commander.sourceMapsInline,
+  comments:      !commander.removeComments,
+  runtime:       commander.runtime,
   modules:       commander.modules
 };
 

bin/6to5/util.js

@@ -1,12 +1,19 @@
 var readdir = require("fs-readdir-recursive");
 var index   = require("./index");
 var util    = require("../../lib/6to5/util");
+var path    = require("path");
 var to5     = require("../../lib/6to5");
 var fs      = require("fs");
 var _       = require("lodash");
 
 exports.readdirFilter = function (filename) {
-  return readdir(filename).filter(util.canCompile);
+  return readdir(filename).filter(function (filename) {
+    return util.canCompile(filename);
+  });
+};
+
+exports.addSourceMappingUrl = function (code, loc) {
+  return code + "\n//# sourceMappingURL=" + path.basename(loc);
 };
 
 exports.transform = function (filename, code, opts) {

bin/_6to5-node

@@ -0,0 +1,86 @@
+#!/usr/bin/env node
+
+var commander = require("commander");
+var path      = require("path");
+var repl      = require("repl");
+var to5       = require("../lib/6to5");
+var util      = require("../lib/6to5/util");
+var vm        = require("vm");
+var _         = require("lodash");
+
+commander.option("-e, --eval [script]", "evaluate script");
+commander.option("-p, --print", "evaluate script and print result");
+commander.option("-i, --ignore [regex]", "ignore all files that match this regex when using the require hook");
+commander.option("-x, --extensions [extensions]", "list of extensions to hook into [.es6,.js]", util.list);
+
+var pkg = require("../package.json");
+commander.version(pkg.version);
+commander.usage("[options] [ -e script | script.js ] [arguments]");
+commander.parse(process.argv);
+
+//
+
+var registerOpts = {};
+
+if (commander.ignore) {
+  registerOpts.ignoreRegex = new RegExp(commander.ignore);
+}
+
+if (commander.extensions && commander.extensions.length) {
+  registerOpts.extensions = commander.extensions;
+}
+
+to5.register(registerOpts);
+
+//
+
+var _eval = function (code, filename) {
+  code = to5.transform(code, { filename: filename, blacklist: ["useStrict"] }).code;
+  return vm.runInThisContext(code, filename);
+};
+
+if (commander.eval) {
+  var result = _eval(commander.eval, "eval");
+  if (commander.print) console.log(result);
+} else {
+  var filenames = commander.args;
+
+  if (filenames.length) {
+    _.each(filenames, function (filename) {
+      if (!util.isAbsolute(filename)) {
+        filename = path.join(process.cwd(), filename);
+      }
+
+      require(require.resolve(filename));
+    });
+  } else {
+    replStart();
+  }
+}
+
+function replStart() {
+  repl.start({
+    prompt: "> ",
+    input: process.stdin,
+    output: process.stdout,
+    eval: replEval,
+    useGlobal: true
+  });
+}
+
+function replEval(code, context, filename, callback) {
+  var err;
+  var result;
+
+  try {
+    if (/^\((.*?)\n\)$/.test(code)) {
+      code = code.slice(1, -2); // remove "(" and "\n)"
+    }
+
+    result = _eval(code, filename);
+  } catch (e) {
+    err = e;
+  }
+
+  callback(err, result);
+}

bin/cache-tests

@@ -0,0 +1,5 @@
+#!/usr/bin/env node
+
+var fs = require("fs");
+var cache = require("../test/_helper").cache;
+fs.writeFileSync("tests.json", JSON.stringify(cache));

bin/generate-browser-test

@@ -1,6 +0,0 @@
-#!/usr/bin/env node
-
-var helper = require("../test/_helper");
-var util   = require("../lib/6to5/util");
-
-console.log("(" + helper.run + ")(" + JSON.stringify(helper.getTests()) + ", to5, proclaim)");

doc/browser.md

@@ -0,0 +1,61 @@
+# Browser
+
+A browser version of 6to5 is available from `browser.js` inside the 6to5
+directory in an npm release.
+
+## Scripts
+
+While it's not recommended for serious use, when the browser version is included
+all scripts with the type `text/ecmascript-6` and `text/6to5` are automatically
+compiled and ran.
+
+For example:
+
+```html
+<script src="node_modules/6to5/browser.js"></script>
+<script type="text/6to5">
+class Test {
+  test() {
+    return "test";
+  }
+}
+
+var test = new Test;
+test.test();
+</script>
+```
+
+## Build
+
+You can build a browser version of the compiler by running the following in the
+6to5 directory:
+
+    $ make build
+
+This will output the files `dist/6to5.js` and `dist/6to5.min.js`.
+
+## Test
+
+To test 6to5 in your browser run:
+
+    $ make test-browser
+
+And open `test/browser.html` in your browser if it doesn't open automatically.
+
+## API
+
+### to5.transform(code, [opts])
+
+See [options](usage.md#options) for additional documentation.
+
+```javascript
+to5.transform("class Test {}").code;
+```
+
+### to5.run(code, [opts])
+
+See [options](usage.md#options) for additional documentation.
+
+```javascript
+to5.run("class Test {}");
+```

doc/caveats.md

@@ -0,0 +1,43 @@
+# Caveats
+
+## Async/Generators
+
+The [regenerator runtime](https://github.com/facebook/regenerator/blob/master/runtime.js)
+and an [ES6 polyfill](polyfill.md) are required in order for generators to work.
+
+## Classes
+
+Built-in classes such as `Date`, `Array` and `DOM` cannot be subclassed due to
+limitations in ES5 implementations.
+
+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
+**will not** be inherited. A possible workaround is to use `super();`:
+
+```javascript
+class Foo {
+  static foo() {
+
+  }
+}
+
+class Bar extends Foo {
+  static foo() {
+    super();
+  }
+}
+```
+
+## For-of
+
+A polyfill is required for for-of functionality that implements `Symbol` and
+adds `prototype[Symbol.iterator]` behaviour to built-ins. Using the polyfills
+specified in [polyfill](polyfill.md) suffices.
+
+## Spread
+
+An [ES6 polyfill](polyfill.md) is required in order for spread to work. More
+specifically a polyfill for `Array.from`.

doc/differences.md

@@ -0,0 +1,114 @@
+# Differences
+
+## Philosophy
+
+The fundamental concept behind 6to5 is that the generated code must be close as
+possible to the original, retaining all the same formatting and readability.
+
+Many other transpilers are just concerned with making the code work while 6to5
+is concerned with making sure it works **and** is readable at the same time.
+
+For example, given the following array comprehension:
+
+```javascript
+var seattlers = [for (c of customers) if (c.city == "Seattle") { name: c.name, age: c.age }];
+```
+
+is generated to the following with 6to5:
+
+```javascript
+var seattlers = customers.filter(function (c) {
+  return c.city == "Seattle";
+}).map(function (c) {
+  return {
+    name: c.name,
+    age: c.age
+  };
+});
+```
+
+The following is what Traceur generates:
+
+```javascript
+var seattlers = (function() {
+  var c;
+  var $__20 = 0,
+      $__21 = [];
+  for (var $__22 = customers[$traceurRuntime.toProperty(Symbol.iterator)](),
+      $__23; !($__23 = $__22.next()).done; ) {
+    c = $__23.value;
+    if (c.city == "Seattle")
+      $traceurRuntime.setProperty($__21, $__20++, {
+        name: c.name,
+        age: c.age
+      });
+  }
+  return $__21;
+}());
+```
+
+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.
+
+I'm not saying 6to5 is for everyone or even suited for everything. Traceur is
+better suited if you'd like a full ES6 environment with polyfills and all.
+
+## Comparison to other transpilers
+
+### Features
+
+|                              | 6to5 | Traceur | es6-transpiler | esnext | es6now | jstransform |
+| ---------------------------- | ---- | ------- | -------------- | ------ | ------ | ----------- |
+| Source maps                  | ✓    | ✓       | ✓              | ✓      |        | ✓           |
+| No compiler global pollution | ✓    |         | ✓              | ✓      |        | ✓           |
+| No runtime                   | ✓    |         | ✓              |        |        | ✓           |
+| Browser support              | ✓    | ✓       |                | ✓      |        |             |
+
+### Language Support
+
+|                              | 6to5  | Traceur | es6-transpiler | esnext | es6now | jstransform |
+| ---------------------------- | ----- | ------- | -------------- | ------ | ------ | ----------- |
+| Array comprehension          | ✓     | ✓       | ✓              |        |        |             |
+| Arrow functions              | ✓     | ✓       | ✓              | ✓      | ✓      | ✓           |
+| Async functions              | ✓     | ✓       |                | ✓      |        |             |
+| Classes                      | ✓     | ✓       | ✓              | ✓      | ✓      | ✓           |
+| Computed property names      | ✓     | ✓       | ✓              | ✓      | ✓      |             |
+| Constants                    | ✓     | ✓       | ✓              |        |        |             |
+| Default parameters           | ✓     | ✓       | ✓              | ✓      | ✓      |             |
+| Destructuring                | ✓     | ✓       | ✓              | ✓      | ✓      | ✓           |
+| For-of                       | ✓     | ✓       | ✓              | ✓      | ✓      |             |
+| Generators                   | ✓     | ✓       |                | ✓      |        |             |
+| Generator comprehension      | ✓     | ✓       |                |        |        |             |
+| Let scoping                  | ✓     | ✓       | ✓              |        |        |             |
+| Modules                      | ✓     | ✓       |                |        | ✓      |             |
+| Property method assignment   | ✓     | ✓       | ✓              | ✓      | ✓      | ✓           |
+| Property name shorthand      | ✓     | ✓       | ✓              | ✓      | ✓      | ✓           |
+| Rest parameters              | ✓     | ✓       | ✓              | ✓      | ✓      | ✓           |
+| Spread                       | ✓     | ✓       | ✓              | ✓      | ✓      |             |
+| Template literals            | ✓     | ✓       | ✓              | ✓      | ✓      | ✓           |
+| Unicode regex                | ✓     | ✓       | ✓              |        |        |             |
+
+
+
+
+
+### [Traceur](https://github.com/google/traceur-compiler)
+
+Traceur requires quite a bulky runtime (~75KB) and produces quite verbose code.
+While this can be trimmed down by selectively building the runtime, it's an
+unneccesary step when a runtime can be eliminated entirely.
+
+### [es6now](https://github.com/zenparsing/es6now)
+
+es6now doesn't output sourcemaps. This is cited as a positive as line-to-line
+mapping is the goal. This however obviously doesn't retain column mapping
+resulting in the output code not being very pleasant.
+
+### [es6-transpiler](https://github.com/termi/es6-transpiler)
+
+The es6-transpiler compiler requires shims to operate which pollutes the global
+scope resulting in possible collisions.
+
+es6-transpiler maps line-by-line, just like es6now, this results in the same
+issues such as lack of column information and unpleasant code output.

doc/features.md

@@ -0,0 +1,226 @@
+# Features
+
+## Array comprehension
+
+```javascript
+var results = [for (c of customers) if (c.city == "Seattle") { name: c.name, age: c.age }]
+```
+
+## Arrow functions
+
+```javascript
+// Expression bodies
+var odds = evens.map(v => v + 1);
+var nums = evens.map((v, i) => v + i);
+
+// Statement bodies
+nums.forEach(v => {
+  if (v % 5 === 0)
+    fives.push(v);
+});
+
+// Lexical this
+var bob = {
+  _name: "Bob",
+  _friends: [],
+  printFriends() {
+    this._friends.forEach(f => {
+      console.log(this._name + " knows " + f);
+    });
+  }
+};
+```
+
+## Async functions
+
+```javascript
+async function chainAnimationsAsync(elem, animations) {
+  for (var anim of animations) {
+    await anim(elem);
+  }
+}
+```
+
+## Classes
+
+```javascript
+class SkinnedMesh extends THREE.Mesh {
+  constructor(geometry, materials) {
+    super(geometry, materials);
+
+    this.idMatrix = SkinnedMesh.defaultMatrix();
+    this.bones = [];
+    this.boneMatrices = [];
+    //...
+  }
+
+  update(camera) {
+    //...
+    super.update();
+  }
+
+  static defaultMatrix() {
+    return new THREE.Matrix4();
+  }
+}
+```
+
+## Computed property names
+
+```javascript
+var foo = "foo";
+var bar = "bar";
+var obj = {
+  ["foo" + bar]: "heh",
+  ["bar" + foo]: "noo",
+  foo: "foo",
+  bar: "bar"
+};
+```
+
+## Constants
+
+```javascript
+const MULTIPLIER = 5;
+console.log(2 * MULTIPLIER);
+
+MULTIPLIER = 6; // error
+var MULTIPLIER; // error
+```
+
+## Default parameters
+
+```javascript
+function f(x, y = 12) {
+  // y is 12 if not passed (or passed as undefined)
+  return x + y;
+}
+f(3) == 15
+```
+
+## Destructuring
+
+```javascript
+// list matching
+var [a, , b] = [1,2,3];
+
+// object matching
+var { op: a, lhs: { op: b }, rhs: c } = getASTNode();
+
+// object matching shorthand
+// binds `op`, `lhs` and `rhs` in scope
+var { op, lhs, rhs } = getASTNode();
+
+// Can be used in parameter position
+function g({ name: x }) {
+  console.log(x);
+}
+g({ name: 5 });
+
+// Fail-soft destructuring
+var [a] = [];
+a === undefined;
+```
+
+## For-of
+
+```javascript
+for (var i of [1, 2, 3]) {
+  console.log(i * i);
+}
+```
+
+## Generators
+
+```javascript
+
+```
+
+## Generator comprehension
+
+```javascript
+
+```
+
+## Let scoping
+
+```javascript
+for (let i in arr) {
+  let v = arr[i];
+}
+```
+
+## Modules
+
+```javascript
+
+```
+
+## Numeric literals
+
+```javascript
+0b111110111 === 503; // true
+0o767 === 503; // true
+```
+
+## Property method assignment
+
+```javascript
+var obj = {
+  foo() {
+    return "foobar";
+  },
+
+  get bar() {
+    return this._bar;
+  },
+
+  set bar(val) {
+    this._bar = val;
+  }
+};
+```
+
+## Property name shorthand
+
+```javascript
+function f(x, y) {
+  return { x, y };
+}
+```
+
+## Rest parameters
+
+```javascript
+function f(x, ...y) {
+  // y is an Array
+  return x * y.length;
+}
+f(3, "hello", true) == 6
+```
+
+## Spread
+
+```javascript
+function f(x, y, z) {
+  return x + y + z;
+}
+// Pass each elem of array as argument
+f(...[1,2,3]) == 6
+```
+
+## Template literals
+
+```javascript
+var x = 5;
+var y = 10;
+console.log(`${x} + ${y} = ${x + y}`); // "5 + 10 = 15"
+```
+
+## Unicode regex
+
+```javascript
+var string = 'foo💩bar';
+var match = string.match(/foo(.)bar/u);
+console.log(match[1]);
+```

doc/index.md

@@ -0,0 +1,54 @@
+**6to5** turns ES6+ code into vanilla ES5, so you can use next generation features **today.**
+
+ - **Readable** - formatting is retained if possible so your generated code is as similar as possible.
+ - **Extensible** - with a large range of [plugins](plugins.md) and **browser support**.
+ - **Lossless** - **source map support** so you can debug your compiled code with ease.
+ - **Compact** - maps directly to the equivalent ES5 with **no runtime**[\*](caveats.md#generators).
+
+## Installation
+
+It's as easy as:
+
+    $ npm install -g 6to5
+
+## Usage
+
+Once you've installed 6to5, there are multiple paths you can take depending on
+how you want to use it.
+
+6to5 will simply compile your ES6+ script to ES5 if you pass it as an argument
+to the command-line tool `6to5`:
+
+    $ 6to5 script.js
+
+If you have a file written using ES6+ and you just want to run it, `6to5-node`
+has you covered:
+
+    $ 6to5-node script.js
+
+And it doesn't end here! To see all the ways you can use 6to5, check out the
+[Usage](http://6to5.github.io/usage.html) page.
+
+## [Features](features.md)
+
+ - [Array comprehension](features.md#array-comprehension)
+ - [Async functions](features.md#async-functions) via [regenerator](https://github.com/facebook/regenerator)
+ - [Arrow functions](features.md#arrow-functions)
+ - [Classes](features.md#classes)
+ - [Computed property names](features.md#computed-property-names)
+ - [Constants](features.md#constants)
+ - [Default parameters](features.md#default-parameters)
+ - [Destructuring](features.md#destructuring)
+ - [For-of](features.md#for-of)
+ - [Generators](features.md#generators) via [regenerator](https://github.com/facebook/regenerator)
+ - [Generator comprehension](features.md#generator-comprehension)
+ - [Let scoping](features.md#let-scoping)
+ - [Modules](features.md#modules)
+ - [Numeric literals](features.md#numeric-literals)
+ - [Property method assignment](features.md#property-method-assignment)
+ - [Property name shorthand](features.md#property-name-shorthand)
+ - [React/JSX](react.md)
+ - [Rest parameters](features.md#rest-parameters)
+ - [Spread](features.md#spread)
+ - [Template literals](features.md#template-literals)
+ - [Unicode regex](features.md#unicode-regex)

doc/modules.md

@@ -66,7 +66,7 @@ export function bar() {
 **Out**
 
 ```javascript
-define(["exports", "foo"], function (exports, _foo) {
+define("filename", ["exports", "foo"], function (exports, _foo) {
   exports.bar = bar;
 
   var foo = _foo.default;
@@ -94,7 +94,7 @@ export function bar() {
 ```javascript
 (function (factory) {
   if (typeof define === "function" && define.amd) {
-    define(["exports", "foo"], factory);
+    define("filename", ["exports", "foo"], factory);
   } else if (typeof exports !== "undefined") {
     factory(exports, require("foo"));
   }
@@ -109,10 +109,34 @@ export function bar() {
 });
 ```
 
+### Ignore
+
+**In**
+
+```javascript
+import foo from "foo";
+
+export function bar() {
+  return foo("foobar");
+}
+```
+
+**Out**
+
+```javascript
+function bar() {
+  return foo("foobar");
+}
+```
+
 ## Custom
 
 You can alternatively specify module names instead of one of the built-in types.
 
+    $ 6to5 --modules custom-module-formatter
+
+**node_modules/custom-module-formatter/index.js**
+
 ```javascript
 module.exports = ModuleFormatter;
 

doc/optional-runtime.md

@@ -0,0 +1,51 @@
+# Optional runtime
+
+6to5 has a few helper functions that'll be placed at the top of the generated
+code if needed so it's not inlined multiple times throughout that file. This may
+become an issue if you have multiple files, especially when you're sending them
+to the browser. gzip alleviates most of this concern but it's still not ideal.
+
+You can tell 6to5 to not place any declarations at the top of your files and
+instead just point them to a reference contained within the runtime.
+
+Simply use the following option if you're using the [Node API](usage.md#node):
+
+```javascript
+{
+  runtime: true
+}
+```
+
+or the following flag if you're using the [CLI](usage.md#cli):
+
+    $ 6to5 --runtime
+
+Then just include the runtime before your generated code.
+
+## Getting the runtime
+
+You can get the runtime via either:
+
+    $ 6to5-runtime
+
+or
+
+```javascript
+require("6to5").runtime();
+```
+
+or from an npm release in `runtime.js` from the 6to5 directory.
+
+## Customising namespace
+
+You can also customise the runtime namespace by passing an optional namespace
+argument:
+
+```javascript
+require("6to5").runtime("myCustomNamespace");
+```
+
+    $ 6to5-runtime myCustomNamespace
+
+See [Options - runtime](usage.md#options) for documentation on changing the
+reference in generated code.

doc/plugins.md

@@ -0,0 +1,17 @@
+# Plugins
+
+ - [Broccoli](https://github.com/very-geek/broccoli-6to5-transpiler)
+ - [Browserify](https://github.com/6to5/6to5-browserify)
+ - [Brunch](https://github.com/es128/6to5-brunch)
+ - [Duo](https://github.com/bdo-labs/duo6to5)
+ - [Connect](https://github.com/6to5/6to5-connect)
+ - [Gobble](https://github.com/gobblejs/gobble-6to5)
+ - [Gulp](https://github.com/sindresorhus/gulp-6to5)
+ - [Grunt](https://github.com/sindresorhus/grunt-6to5)
+ - [Jade](https://github.com/Apoxx/jade-6to5)
+ - [Jest](https://github.com/6to5/6to5-jest)
+ - [JSXHint](https://github.com/STRML/JSXHint) (A wrapper around JSHint to allow linting of JSX files)
+ - [Karma](https://github.com/shuhei/karma-6to5-preprocessor)
+ - [Mocha](https://github.com/6to5/6to5-mocha)
+ - [Rails](https://github.com/josh/sprockets-es6) or via [browserify-rails](https://github.com/6to5/6to5-rails)
+ - [webpack](https://github.com/Couto/6to5-loader)

doc/polyfill.md

@@ -0,0 +1,17 @@
+# Polyfill
+
+6to5 includes a polyfill that includes the
+[regenerator runtime](https://github.com/facebook/regenerator/blob/master/runtime.js) and the
+[es6-shim](https://github.com/paulmillr/es6-shim) and
+[es6-symbol](https://github.com/medikoo/es6-symbol) polyfills.
+
+## Node
+
+```javascript
+require("6to5/polyfill");
+```
+
+## Browser
+
+Available from the `browser-polyfill.js` file within the 6to5 directory of an
+npm release.

doc/react.md

@@ -0,0 +1,16 @@
+# React/JSX
+
+6to5 has built-in support for React v0.12. Tags are automatically transformed to
+their equivalent `React.createElement(...)` and `displayName` is automatically
+inferred and added to all `React.createClass` calls.
+
+## Blacklist
+
+To disable this behaviour add `react` to your blacklist:
+
+```javascript
+to5.transform("code", { blacklist: ["react"] });
+```
+
+
+    $ 6to5 --blacklist react

doc/usage.md

@@ -0,0 +1,176 @@
+# Usage
+
+## CLI
+
+Compile the file `script.js` and output it to stdout.
+
+    $ 6to5 script.js
+
+Compile the file `script.js` and output it to `script-compiled.js`.
+
+    $ 6to5 script.js --out-file script-compiled.js
+
+Compile the file `script.js` and output it to `script-compiled.js` and save a
+source map to `script-compiled.js.map`.
+
+    $ 6to5 script.js --source-maps --out-file script-compiled.js
+
+Compile the file `script.js` and output it to `script-compiled.js` with a source
+map embedded in a comment at the bottom.
+
+    $ 6to5 script.js --source-maps-inline --out-file script-compiled.js
+
+Compile the entire `src` directory and output it to the `lib` directory.
+
+    $ 6to5 src --out-dir lib
+
+Compile the entire `src` directory and output it to the one concatenated file.
+
+    $ 6to5 src --out-file script-compiled.js
+
+Pipe a file in via stdin and output it to `script-compiled.js`
+
+    $ 6to5 --out-file script-compiled.js < script.js
+
+### Node
+
+Launch a repl.
+
+    $ 6to5-node
+
+Evaluate code.
+
+    $ 6to5-node -e "class Test { }"
+
+Compile and run `test.js`.
+
+    $ 6to5-node test
+
+## Node
+
+```javascript
+var to5 = require("6to5");
+```
+
+### to5.transform(code, [opts]);
+
+```javascript
+var result = to5.transform("code();", options);
+result.code;
+result.map;
+result.ast;
+```
+
+### to5.transformFileSync(filename, [opts])
+
+```javascript
+to5.transformFileSync("filename.js", options).code;
+```
+
+### to5.transformFile(filename, [opts], callback)
+
+```javascript
+to5.transformFile("filename.js", options, function (err, result) {
+  result.code;
+});
+```
+
+#### Options
+
+```javascript
+{
+  // Filename for use in errors etc.
+  // Default: "unknown"
+  filename: "filename",
+
+  // Filename relative to `sourceRoot`
+  // Default: `filename` option.
+  filenameRelative: "",
+
+  // List of transformers to EXCLUDE.
+  // Run `6to5 --help` to see a full list of transformers.
+  blacklist: [],
+
+  // List of transformers to ONLY use.
+  // Run `6to5 --help` to see a full list of transformers.
+  whitelist: [],
+
+  // Module formatter to use
+  // Run `6to5 --help` to see a full list of module formatters.
+  // Default: "common"
+  modules: "common",
+
+  // If truthy, adds a `map` property to returned output.
+  // If set to "inline", a comment with a sourceMappingURL directive is added to
+  // the bottom of the returned code.
+  // Default: false
+  sourceMap: true,
+
+  // Set `file` on returned source map.
+  // Default: `filenameRelative` option.
+  sourceMapName: "filename",
+
+  // Set `sources[0]` on returned source map.
+  // Default: `filenameRelative` option.
+  sourceFileName: "filename",
+
+  // The root from which all sources are relative
+  sourceRoot: "assets/scripts",
+
+  // Optional prefix for the AMD module formatter that will be prepend to the
+  // filename on module definitions
+  moduleRoot: "my-app",
+
+  // Optionally replace all 6to5 helper declarations with a referenece to this
+  // variable. If set to `true` then the default namespace is used "to5Runtime".
+  // Default: false
+  runtime: true,
+
+  // Output comments in generated output
+  // Default: true
+  comments: false
+}
+```
+
+### Require hook
+
+All subsequent files required by node with the extensions `.es6` and `.js` will
+be transformed by 6to5. The polyfill specified in [Polyfill](polyfill.md) is
+also required.
+
+```javascript
+require("6to5/register");
+```
+
+**NOTE:** By default all requires to `node_modules` will be ignored. You can
+override this by passing an ignore regex via:
+
+```javascript
+require("6to5/register")({
+  // This will override `node_modules` ignoring - you can alternatively pass
+  // a regex
+  ignore: false
+});
+```
+
+#### Options
+
+```javascript
+require("6to5/register")({
+  // Optional ignore regex - if any filenames **do** match this regex then they
+  // aren't compiled
+  ignore: /regex/,
+
+  // Optional only regex - if any filenames **don't** match this regex then they
+  // aren't compiled
+  only: /my_es6_folder/,
+
+  // See options above for usage
+  whitelist: [],
+  blacklist: [],
+
+  // This will remove the currently hooked extensions of .es6 and .js so you'll
+  // have to add them back if you want them to be used again.
+  extensions: [".js", ".es6"]
+});
+```

lib/6to5/browser.js

@@ -0,0 +1,80 @@
+var transform = module.exports = require("./transformation/transform");
+
+transform.transform = transform;
+
+transform.run = function (code, opts) {
+  opts = opts || {};
+  opts.sourceMap = "inline";
+  return new Function(transform(code, opts).code)();
+};
+
+transform.load = function (url, callback, opts, hold) {
+  opts = opts || {};
+  opts.filename = opts.filename || url;
+
+  var xhr = global.ActiveXObject ? new global.ActiveXObject("Microsoft.XMLHTTP") : new global.XMLHttpRequest();
+  xhr.open("GET", url, true);
+  if ("overrideMimeType" in xhr) xhr.overrideMimeType("text/plain");
+
+  xhr.onreadystatechange = function () {
+    if (xhr.readyState !== 4) return;
+
+    var status = xhr.status;
+    if (status === 0 || status === 200) {
+      var param = [xhr.responseText, opts];
+      if (!hold) transform.run.apply(transform, param);
+      if (callback) callback(param);
+    } else {
+      throw new Error("Could not load " + url);
+    }
+  };
+
+  xhr.send(null);
+};
+
+var runScripts = function () {
+  var scripts = [];
+  var types   = ["text/ecmascript-6", "text/6to5"];
+  var index   = 0;
+
+  var exec = function () {
+    var param = scripts[index];
+    if (param instanceof Array) {
+      transform.run.apply(transform, param);
+      index++;
+      exec();
+    }
+  };
+
+  var run = function (script, i) {
+    var opts = {};
+
+    if (script.src) {
+      transform.load(script.src, function (param) {
+        scripts[i] = param;
+        exec();
+      }, opts, true);
+    } else {
+      opts.filename = "embedded";
+      scripts[i] = [script.innerHTML, opts];
+    }
+  };
+
+  var _scripts = global.document.getElementsByTagName("script");
+  for (var i in _scripts) {
+    var _script = _scripts[i];
+    if (types.indexOf(_script.type) >= 0) scripts.push(_script);
+  }
+
+  for (i in scripts) {
+    run(scripts[i], i);
+  }
+
+  exec();
+};
+
+if (global.addEventListener) {
+  global.addEventListener("DOMContentLoaded", runScripts, false);
+} else if (global.attachEvent) {
+  global.attachEvent("onload", runScripts);
+}

lib/6to5/file.js

@@ -2,37 +2,67 @@ module.exports = File;
 
 var SHEBANG_REGEX = /^\#\!.*/;
 
-var transform = require("./transform");
-var recast    = require("acorn-recast");
+var transform = require("./transformation/transform");
+var generate  = require("./generation/generator");
+var Scope     = require("./traverse/scope");
 var util      = require("./util");
-var b         = require("acorn-ast-types").builders;
+var t         = require("./types");
 var _         = require("lodash");
 
 function File(opts) {
   this.opts            = File.normaliseOptions(opts);
-  this.moduleFormatter = this.getModuleFormatter(opts.modules);
+  this.moduleFormatter = this.getModuleFormatter(this.opts.modules);
 
   this.declarations = {};
   this.uids         = {};
   this.ast          = {};
 }
 
+File.declarations = ["extends", "class-props", "slice", "apply-constructor",
+                     "tagged-template-literal", "interop-require"];
+
 File.normaliseOptions = function (opts) {
-  opts = opts || {};
+  opts = _.cloneDeep(opts || {});
 
   _.defaults(opts, {
-    blacklist: [],
-    whitelist: [],
-    sourceMap: false,
-    filename:  "unknown",
-    modules:   "common"
+    whitespace: true,
+    blacklist:  [],
+    whitelist:  [],
+    sourceMap:  false,
+    comments:   true,
+    filename:   "unknown",
+    modules:    "common",
+    runtime:    false,
+    code:       true
+  });
+
+  // normalise windows path separators to unix
+  opts.filename = opts.filename.replace(/\\/g, "/");
+
+  opts.blacklist = util.arrayify(opts.blacklist);
+  opts.whitelist = util.arrayify(opts.whitelist);
+
+  _.defaults(opts, {
+    moduleRoot: opts.sourceRoot
   });
 
   _.defaults(opts, {
-    sourceFileName: opts.filename,
-    sourceMapName:  opts.filename
+    sourceRoot: opts.moduleRoot
   });
 
+  _.defaults(opts, {
+    filenameRelative: opts.filename
+  });
+
+  _.defaults(opts, {
+    sourceFileName: opts.filenameRelative,
+    sourceMapName:  opts.filenameRelative
+  });
+
+  if (opts.runtime === true) {
+    opts.runtime = "to5Runtime";
+  }
+
   transform._ensureTransformerNames("blacklist", opts.blacklist);
   transform._ensureTransformerNames("whitelist", opts.whitelist);
 
@@ -40,18 +70,18 @@ File.normaliseOptions = function (opts) {
 };
 
 File.prototype.getModuleFormatter = function (type) {
-  var ModuleLoader = transform.moduleFormatters[type];
+  var ModuleFormatter = _.isFunction(type) ? type : transform.moduleFormatters[type];
 
-  if (!ModuleLoader) {
+  if (!ModuleFormatter) {
     var loc = util.resolve(type);
-    if (loc) ModuleLoader = require(loc);
+    if (loc) ModuleFormatter = require(loc);
   }
 
-  if (!ModuleLoader) {
+  if (!ModuleFormatter) {
     throw new ReferenceError("unknown module formatter type " + type);
   }
 
-  return new ModuleLoader(this);
+  return new ModuleFormatter(this);
 };
 
 File.prototype.parseShebang = function (code) {
@@ -67,20 +97,46 @@ File.prototype.parseShebang = function (code) {
 };
 
 File.prototype.addDeclaration = function (name) {
+  if (!_.contains(File.declarations, name)) {
+    throw new ReferenceError("unknown declaration " + name);
+  }
+
   var declar = this.declarations[name];
   if (declar) return declar.uid;
 
-  var uid = b.identifier(this.generateUid(name));
+  var ref;
+  var runtimeNamespace = this.opts.runtime;
+  if (runtimeNamespace) {
+    name = t.identifier(t.toIdentifier(name));
+    return t.memberExpression(t.identifier(runtimeNamespace), name);
+  } else {
+    ref = util.template(name);
+  }
+
+  var uid = t.identifier(this.generateUid(name));
   this.declarations[name] = {
     uid: uid,
-    node: util.template(name)
+    node: ref
   };
   return uid;
 };
 
+File.prototype.errorWithNode = function (node, msg, Error) {
+  Error = Error || SyntaxError;
+
+  var loc = node.loc.start;
+  var err = new Error("Line " + loc.line + ": " + msg);
+  err.loc = loc;
+  return err;
+};
+
 File.prototype.parse = function (code) {
+  code = (code || "") + "";
+
   var self = this;
 
+  this.code = code;
+
   code = this.parseShebang(code);
 
   return util.parse(this.opts, code, function (tree) {
@@ -91,6 +147,7 @@ File.prototype.parse = function (code) {
 
 File.prototype.transform = function (ast) {
   this.ast = ast;
+  this.scope = new Scope(null, ast.program);
 
   var self = this;
 
@@ -103,43 +160,43 @@ File.prototype.generate = function () {
   var opts = this.opts;
   var ast  = this.ast;
 
-  var printOpts = { tabWidth: 2 };
-
-  if (opts.sourceMap) {
-    printOpts.sourceMapName = opts.sourceMapName;
+  if (!opts.code) {
+    return {
+      code: "",
+      map:  null,
+      ast:  ast
+    };
   }
 
-  var result = recast.print(ast, printOpts);
-  var code   = result.code;
+  var result = generate(ast, opts, this.code);
 
   if (this.shebang) {
     // add back shebang
-    code = this.shebang + code;
+    result.code = this.shebang + "\n" + result.code;
   }
 
   if (opts.sourceMap === "inline") {
-    code += "\n" + util.sourceMapToComment(result.map);
+    result.code += "\n" + util.sourceMapToComment(result.map);
   }
 
-  return {
-    code: code,
-    map:  result.map || null,
-    ast:  ast
-  };
+  result.ast = result;
+
+  return result;
 };
 
-File.prototype.generateUid = function (name) {
-  // replace all non-valid identifiers with dashes
-  name = name.replace(/[^a-zA-Z0-9]/g, "-");
+File.prototype.generateUid = function (name, scope) {
+  name = t.toIdentifier(name);
 
-  // remove all dashes and numbers from start of name
-  name = name.replace(/^[-0-9]+/, "");
+  scope = scope || this.scope;
 
-  // camel case
-  name = name.replace(/[-_\s]+(.)?/g, function (match, c) {
-    return c ? c.toUpperCase() : "";
-  });
+  var uid;
+  do {
+    uid = this._generateUid(name);
+  } while (scope.has(uid));
+  return uid;
+};
 
+File.prototype._generateUid = function (name) {
   var uids = this.uids;
   var i = uids[name] || 1;
 

lib/6to5/generation/buffer.js

@@ -0,0 +1,125 @@
+module.exports = Buffer;
+
+var util = require("../util");
+var _    = require("lodash");
+
+function Buffer(position, format) {
+  this.position = position;
+  this._indent  = format.indent.base;
+  this.format   = format;
+  this.buf      = "";
+}
+
+Buffer.prototype.get = function () {
+  return util.trimRight(this.buf);
+};
+
+Buffer.prototype.getIndent = function () {
+  if (this.format.compact) {
+    return "";
+  } else {
+    return util.repeat(this._indent, this.format.indent.style);
+  }
+};
+
+Buffer.prototype.indentSize = function () {
+  return this.getIndent().length;
+};
+
+Buffer.prototype.indent = function () {
+  this._indent++;
+};
+
+Buffer.prototype.dedent = function () {
+  this._indent--;
+};
+
+Buffer.prototype.semicolon = function () {
+  if (this.format.semicolons) this.push(";");
+};
+
+Buffer.prototype.ensureSemicolon = function () {
+  if (!this.isLast(";")) this.semicolon();
+};
+
+Buffer.prototype.rightBrace = function () {
+  this.newline(true);
+  this.push("}");
+};
+
+Buffer.prototype.keyword = function (name) {
+  this.push(name);
+  this.push(" ");
+};
+
+Buffer.prototype.space = function () {
+  if (this.buf && !this.isLast([" ", "\n"])) {
+    this.push(" ");
+  }
+};
+
+Buffer.prototype.removeLast = function (cha) {
+  if (!this.isLast(cha)) return;
+
+  this.buf = this.buf.slice(0, -1);
+  this.position.unshift(cha);
+};
+
+Buffer.prototype.newline = function (i, removeLast) {
+  if (!this.buf) return;
+  if (this.format.compact) return;
+  if (this.endsWith("{\n")) return;
+
+  if (_.isBoolean(i)) {
+    removeLast = i;
+    i = null;
+  }
+
+  if (_.isNumber(i)) {
+    if (this.endsWith(util.repeat(i, "\n"))) return;
+
+    var self = this;
+    _.times(i, function () {
+      self.newline(null, removeLast);
+    });
+    return;
+  }
+
+  if (removeLast && this.isLast("\n")) this.removeLast("\n");
+
+  this.removeLast(" ");
+  this.buf = this.buf.replace(/\n +$/, "\n");
+  this._push("\n");
+};
+
+Buffer.prototype.push = function (str, noIndent) {
+  if (this._indent && !noIndent && str !== "\n") {
+    // we have an indent level and we aren't pushing a newline
+    var indent = this.getIndent();
+
+    // replace all newlines with newlines with the indentation
+    str = str.replace(/\n/g, "\n" + indent);
+
+    // we've got a newline before us so prepend on the indentation
+    if (this.isLast("\n")) str = indent + str;
+  }
+
+  this._push(str);
+};
+
+Buffer.prototype._push = function (str) {
+  this.position.push(str);
+  this.buf += str;
+};
+
+Buffer.prototype.endsWith = function (str) {
+  return this.buf.slice(-str.length) === str;
+};
+
+Buffer.prototype.isLast = function (cha, trimRight) {
+  var buf = this.buf;
+  if (trimRight) buf = util.trimRight(buf);
+
+  var chars = [].concat(cha);
+  return _.contains(chars, _.last(buf));
+};

lib/6to5/generation/generator.js

@@ -0,0 +1,296 @@
+module.exports = function (ast, opts, code) {
+  var gen = new CodeGenerator(ast, opts, code);
+  return gen.generate();
+};
+
+module.exports.CodeGenerator = CodeGenerator;
+
+var Whitespace = require("./whitespace");
+var SourceMap  = require("./source-map");
+var Position   = require("./position");
+var Buffer     = require("./buffer");
+var util       = require("../util");
+var n          = require("./node");
+var t          = require("../types");
+var _          = require("lodash");
+
+function CodeGenerator(ast, opts, code) {
+  opts = opts || {};
+
+  this.comments = ast.comments || [];
+  this.tokens   = ast.tokens || [];
+  this.format   = CodeGenerator.normaliseOptions(opts);
+  this.ast      = ast;
+
+  this.whitespace = new Whitespace(this.tokens, this.comments);
+  this.position   = new Position;
+  this.map        = new SourceMap(this.position, opts, code);
+  this.buffer     = new Buffer(this.position, this.format);
+}
+
+_.each(Buffer.prototype, function (fn, key) {
+  CodeGenerator.prototype[key] = function () {
+    return fn.apply(this.buffer, arguments);
+  };
+});
+
+CodeGenerator.normaliseOptions = function (opts) {
+  return _.merge({
+    parentheses: true,
+    semicolons: true,
+    comments: opts.comments == null || opts.comments,
+    compact: false,
+    indent: {
+      adjustMultilineComment: true,
+      style: "  ",
+      base: 0
+    }
+  }, opts.format || {});
+};
+
+CodeGenerator.generators = {
+  templateLiterals: require("./generators/template-literals"),
+  comprehensions:   require("./generators/comprehensions"),
+  expressions:      require("./generators/expressions"),
+  statements:       require("./generators/statements"),
+  classes:          require("./generators/classes"),
+  methods:          require("./generators/methods"),
+  modules:          require("./generators/modules"),
+  types:            require("./generators/types"),
+  base:             require("./generators/base"),
+  jsx:              require("./generators/jsx")
+};
+
+_.each(CodeGenerator.generators, function (generator) {
+  _.extend(CodeGenerator.prototype, generator);
+});
+
+CodeGenerator.prototype.generate = function () {
+  var ast = this.ast;
+
+  this.print(ast);
+
+  return {
+    map:  this.map.get(),
+    code: this.buffer.get()
+  };
+};
+
+CodeGenerator.prototype.buildPrint = function (parent) {
+  var self = this;
+
+  var print = function (node, opts) {
+    return self.print(node, parent, opts);
+  };
+
+  print.sequence = function (nodes, opts) {
+    opts = opts || {};
+    opts.statement = true;
+    return self.printJoin(print, nodes, opts);
+  };
+
+  print.join = function (nodes, opts) {
+    return self.printJoin(print, nodes, opts);
+  };
+
+  print.block = function (node) {
+    return self.printBlock(print, node);
+  };
+
+  print.indentOnComments = function (node) {
+    return self.printAndIndentOnComments(print, node);
+  };
+
+  return print;
+};
+
+CodeGenerator.prototype.print = function (node, parent, opts) {
+  if (!node) return "";
+
+  var self = this;
+  opts = opts || {};
+
+  var newline = function (leading) {
+    if (!opts.statement && !n.isUserWhitespacable(node, parent)) {
+      return;
+    }
+
+    var lines = 0;
+
+    if (node.start != null) {
+      // user node
+      if (leading) {
+        lines = self.whitespace.getNewlinesBefore(node);
+      } else {
+        lines = self.whitespace.getNewlinesAfter(node);
+      }
+    } else {
+      // generated node
+      if (!leading) lines++; // always include at least a single line after
+
+      var needs = n.needsWhitespaceAfter;
+      if (leading) needs = n.needsWhitespaceBefore;
+      lines += needs(node, parent);
+    }
+
+    self.newline(lines);
+  };
+
+  if (this[node.type]) {
+    this.printLeadingComments(node, parent);
+
+    newline(true);
+
+    if (opts.before) opts.before();
+    this.map.mark(node, "start");
+
+    // only compute if this node needs parens if our parent has been changed
+    // since acorn would've wrapped us in a ParanthesizedExpression
+    var needsParens = parent !== node._parent && n.needsParens(node, parent);
+    if (needsParens) this.push("(");
+
+    this[node.type](node, this.buildPrint(node), parent);
+
+    if (needsParens) this.push(")");
+
+    this.map.mark(node, "end");
+    if (opts.after) opts.after();
+
+    newline(false);
+
+    this.printTrailingComments(node, parent);
+  } else {
+    throw new ReferenceError("unknown node " + node.type + " " + JSON.stringify(node));
+  }
+};
+
+CodeGenerator.prototype.printJoin = function (print, nodes, opts) {
+  if (!nodes || !nodes.length) return;
+
+  opts = opts || {};
+
+  var self = this;
+  var len  = nodes.length;
+
+  if (opts.indent) self.indent();
+
+  _.each(nodes, function (node, i) {
+    print(node, {
+      statement: opts.statement,
+      after: function () {
+        if (opts.iterator) {
+          opts.iterator(node, i);
+        }
+
+        if (opts.separator && i < len - 1) {
+          self.push(opts.separator);
+        }
+      }
+    });
+  });
+
+  if (opts.indent) self.dedent();
+};
+
+CodeGenerator.prototype.printAndIndentOnComments = function (print, node) {
+  var indent = !!node.leadingComments;
+  if (indent) this.indent();
+  print(node);
+  if (indent) this.dedent();
+};
+
+CodeGenerator.prototype.printBlock = function (print, node) {
+  if (t.isEmptyStatement(node)) {
+    this.semicolon();
+  } else {
+    this.push(" ");
+    print(node);
+  }
+};
+
+CodeGenerator.prototype.generateComment = function (comment) {
+  var val = comment.value;
+  if (comment.type === "Line") {
+    val = "//" + val;
+  } else {
+    val = "/*" + val + "*/";
+  }
+  return val;
+};
+
+CodeGenerator.prototype.printTrailingComments = function (node, parent) {
+  this._printComments(this.getComments("trailingComments", node, parent));
+};
+
+CodeGenerator.prototype.printLeadingComments = function (node, parent) {
+  this._printComments(this.getComments("leadingComments", node, parent));
+};
+
+CodeGenerator.prototype.getComments = function (key, node, parent) {
+  if (t.isExpressionStatement(parent)) {
+    return [];
+  }
+
+  var comments = [];
+  var nodes    = [node];
+  var self     = this;
+
+  if (t.isExpressionStatement(node)) {
+    nodes.push(node.argument);
+  }
+
+  _.each(nodes, function (node) {
+    comments = comments.concat(self._getComments(key, node));
+  });
+
+  return comments;
+};
+
+CodeGenerator.prototype._getComments = function (key, node) {
+  return (node && node[key]) || [];
+};
+
+CodeGenerator.prototype._printComments = function (comments) {
+  if (this.format.compact) return;
+  if (!this.format.comments) return;
+  if (!comments || !comments.length) return;
+
+  var self = this;
+
+  _.each(comments, function (comment) {
+    // whitespace before
+    self.newline(self.whitespace.getNewlinesBefore(comment));
+
+    var column = self.position.column;
+    var val    = self.generateComment(comment);
+
+    if (column && !self.isLast(["\n", " ", "[", "{"])) {
+      self._push(" ");
+      column++;
+    }
+
+    //
+
+    if (comment.type === "Block" && self.format.indent.adjustMultilineComment) {
+      var offset = comment.loc.start.column;
+      if (offset) {
+        var newlineRegex = new RegExp("\\n\\s{1," + offset + "}", "g");
+        val = val.replace(newlineRegex, "\n");
+      }
+
+      var indent = Math.max(self.indentSize(), column);
+      val = val.replace(/\n/g, "\n" + util.repeat(indent));
+    }
+
+    if (column === 0) {
+      val = self.getIndent() + val;
+    }
+
+    //
+
+    self._push(val);
+
+    // whitespace after
+    self.newline(self.whitespace.getNewlinesAfter(comment));
+  });
+};

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

@@ -0,0 +1,19 @@
+exports.File = function (node, print) {
+  print(node.program);
+};
+
+exports.Program = function (node, print) {
+  print.sequence(node.body);
+};
+
+exports.BlockStatement = function (node, print) {
+  if (node.body.length === 0) {
+    this.push("{}");
+  } else {
+    this.push("{");
+    this.newline();
+    print.sequence(node.body, { indent: true });
+    this.removeLast("\n");
+    this.rightBrace();
+  }
+};

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

@@ -0,0 +1,40 @@
+exports.ClassExpression =
+exports.ClassDeclaration = function (node, print) {
+  this.push("class");
+
+  if (node.id) {
+    this.space();
+    print(node.id);
+  }
+
+  if (node.superClass) {
+    this.push(" extends ");
+    print(node.superClass);
+  }
+
+  this.space();
+  print(node.body);
+};
+
+exports.ClassBody = function (node, print) {
+  if (node.body.length === 0) {
+    this.push("{}");
+  } else {
+    this.push("{");
+    this.newline();
+
+    this.indent();
+    print.sequence(node.body);
+    this.dedent();
+
+    this.rightBrace();
+  }
+};
+
+exports.MethodDefinition = function (node, print) {
+  if (node.static) {
+    this.push("static ");
+  }
+
+  this._method(node, print);
+};

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

@@ -0,0 +1,27 @@
+exports.ComprehensionBlock = function (node, print) {
+  this.keyword("for");
+  this.push("(");
+  print(node.left);
+  this.push(" of ");
+  print(node.right);
+  this.push(")");
+};
+
+exports.ComprehensionExpression = function (node, print) {
+  this.push(node.generator ? "(" : "[");
+
+  print.join(node.blocks, { separator: " " });
+  this.space();
+
+  if (node.filter) {
+    this.keyword("if");
+    this.push("(");
+    print(node.filter);
+    this.push(")");
+    this.space();
+  }
+
+  print(node.body);
+
+  this.push(node.generator ? ")" : "]");
+};

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

@@ -0,0 +1,117 @@
+var util = require("../../util");
+var t    = require("../../types");
+
+exports.UnaryExpression = function (node, print) {
+  var hasSpace = /[a-z]$/.test(node.operator);
+  var arg = node.argument;
+
+  if (t.isUpdateExpression(arg) || t.isUnaryExpression(arg)) {
+    hasSpace = true;
+  }
+
+  if (t.isUnaryExpression(arg) && arg.operator === "!") {
+    hasSpace = false;
+  }
+
+  this.push(node.operator);
+  if (hasSpace) this.space();
+  print(node.argument);
+};
+
+exports.ParenthesizedExpression = function (node, print) {
+  this.push("(");
+  print(node.expression);
+  this.push(")");
+};
+
+exports.UpdateExpression = function (node, print) {
+  if (node.prefix) {
+    this.push(node.operator);
+    print(node.argument);
+  } else {
+    print(node.argument);
+    this.push(node.operator);
+  }
+};
+
+exports.ConditionalExpression = function (node, print) {
+  print(node.test);
+  this.push(" ? ");
+  print(node.consequent);
+  this.push(" : ");
+  print(node.alternate);
+};
+
+exports.NewExpression = function (node, print) {
+  this.push("new ");
+  print(node.callee);
+  if (node.arguments.length || this.format.parentheses) {
+    this.push("(");
+    print.join(node.arguments, { separator: ", " });
+    this.push(")");
+  }
+};
+
+exports.SequenceExpression = function (node, print) {
+  print.join(node.expressions, { separator: ", " });
+};
+
+exports.ThisExpression = function () {
+  this.push("this");
+};
+
+exports.CallExpression = function (node, print) {
+  print(node.callee);
+  this.push("(");
+  print.join(node.arguments, { separator: ", " });
+  this.push(")");
+};
+
+var buildYieldAwait = function (keyword) {
+  return function (node, print) {
+    this.push(keyword);
+    if (node.delegate) this.push("*");
+    if (node.argument) {
+      this.space();
+      print(node.argument);
+    }
+  };
+};
+
+exports.YieldExpression = buildYieldAwait("yield");
+exports.AwaitExpression = buildYieldAwait("await");
+
+exports.EmptyStatement = function () {
+  this.semicolon();
+};
+
+exports.ExpressionStatement = function (node, print) {
+  print(node.expression);
+  this.semicolon();
+};
+
+exports.BinaryExpression =
+exports.LogicalExpression =
+exports.AssignmentExpression = function (node, print) {
+  print(node.left);
+  this.push(" " + node.operator + " ");
+  print(node.right);
+};
+
+exports.MemberExpression = function (node, print) {
+  print(node.object);
+
+  if (node.computed) {
+    this.push("[");
+    print(node.property);
+    this.push("]");
+  } else {
+    // 5..toFixed(2);
+    if (t.isLiteral(node.object) && util.isInteger(node.object.value)) {
+      this.push(".");
+    }
+
+    this.push(".");
+    print(node.property);
+  }
+};

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

@@ -0,0 +1,78 @@
+var t = require("../../types");
+var _ = require("lodash");
+
+exports.XJSAttribute = function (node, print) {
+  print(node.name);
+  if (node.value) {
+    this.push("=");
+    print(node.value);
+  }
+};
+
+exports.XJSIdentifier = function (node) {
+  this.push(node.name);
+};
+
+exports.XJSNamespacedName = function (node, print) {
+  print(node.namespace);
+  this.push(":");
+  print(node.name);
+};
+
+exports.XJSMemberExpression = function (node, print) {
+  print(node.object);
+  this.push(".");
+  print(node.property);
+};
+
+exports.XJSSpreadAttribute = function (node, print) {
+  this.push("{...");
+  print(node.argument);
+  this.push("}");
+};
+
+exports.XJSExpressionContainer = function (node, print) {
+  this.push("{");
+  print(node.expression);
+  this.push("}");
+};
+
+exports.XJSElement = function (node, print) {
+  var self = this;
+
+  var open = node.openingElement;
+  print(open);
+  if (open.selfClosing) return;
+
+  this.indent();
+  _.each(node.children, function (child) {
+    if (t.isLiteral(child)) {
+      self.push(child.value);
+    } else {
+      print(child);
+    }
+  });
+  this.dedent();
+
+  print(node.closingElement);
+};
+
+exports.XJSOpeningElement = function (node, print) {
+  this.push("<");
+  print(node.name);
+  if (node.attributes.length > 0) {
+    this.space();
+    print.join(node.attributes, { separator: " " });
+  }
+  this.push(node.selfClosing ? " />" : ">");
+};
+
+exports.XJSClosingElement = function (node, print) {
+  this.push("</");
+  print(node.name);
+  this.push(">");
+};
+
+exports.XJSEmptyExpression = function () {
+
+};

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

@@ -0,0 +1,82 @@
+var t = require("../../types");
+
+exports._params = function (node, print) {
+  var self = this;
+
+  this.push("(");
+
+  print.join(node.params, {
+    separator: ", ",
+    iterator: function (param, i) {
+      var def = node.defaults && node.defaults[i];
+      if (def) {
+        self.push(" = ");
+        print(def);
+      }
+    }
+  });
+
+  if (node.rest) {
+    if (node.params.length) {
+      this.push(", ");
+    }
+
+    this.push("...");
+    print(node.rest);
+  }
+
+  this.push(")");
+};
+
+exports._method = function (node, print) {
+  var value = node.value;
+  var kind  = node.kind;
+  var key   = node.key;
+
+  if (!kind || kind === "init") {
+    if (value.generator) {
+      this.push("*");
+    }
+  } else {
+    this.push(kind + " ");
+  }
+
+  if (value.async) this.push("async ");
+
+  if (node.computed) {
+    this.push("[");
+    print(key);
+    this.push("]");
+  } else {
+    print(key);
+  }
+
+  this._params(value, print);
+  this.space();
+  print(value.body);
+};
+
+exports.FunctionDeclaration =
+exports.FunctionExpression = function (node, print) {
+  if (node.async) this.push("async ");
+  this.push("function");
+  if (node.generator) this.push("*");
+  this.space();
+  if (node.id) print(node.id);
+  this._params(node, print);
+  this.space();
+  print(node.body);
+};
+
+exports.ArrowFunctionExpression = function (node, print) {
+  if (node.async) this.push("async ");
+
+  if (node.params.length === 1 && !node.defaults.length && !node.rest && t.isIdentifier(node.params[0])) {
+    print(node.params[0]);
+  } else {
+    this._params(node, print);
+  }
+
+  this.push(" => ");
+  print(node.body);
+};

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

@@ -0,0 +1,87 @@
+var t = require("../../types");
+var _ = require("lodash");
+
+exports.ImportSpecifier =
+exports.ExportSpecifier = function (node, print) {
+  print(node.id);
+  if (node.name) {
+    this.push(" as ");
+    print(node.name);
+  }
+};
+
+exports.ExportBatchSpecifier = function () {
+  this.push("*");
+};
+
+exports.ExportDeclaration = function (node, print) {
+  this.push("export ");
+
+  var specifiers = node.specifiers;
+
+  if (node.default) {
+    this.push("default ");
+  }
+
+  if (node.declaration) {
+    print(node.declaration);
+    if (t.isStatement(node.declaration)) return;
+  } else {
+    if (specifiers.length === 1 && t.isExportBatchSpecifier(specifiers[0])) {
+      print(specifiers[0]);
+    } else {
+      this.push("{");
+      if (specifiers.length) {
+        this.space();
+        print.join(specifiers, { separator: ", " });
+        this.space();
+      }
+      this.push("}");
+    }
+
+    if (node.source) {
+      this.push(" from ");
+      print(node.source);
+    }
+  }
+
+  this.ensureSemicolon();
+};
+
+exports.ImportDeclaration = function (node, print) {
+  var self = this;
+
+  this.push("import ");
+
+  var specfiers = node.specifiers;
+  if (specfiers && specfiers.length) {
+    var foundImportSpecifier = false;
+
+    _.each(node.specifiers, function (spec, i) {
+      if (+i > 0) {
+        self.push(", ");
+      }
+
+      if (!spec.default && spec.type !== "ImportBatchSpecifier" && !foundImportSpecifier) {
+        foundImportSpecifier = true;
+        self.push("{ ");
+      }
+
+      print(spec);
+    });
+
+    if (foundImportSpecifier) {
+      this.push(" }");
+    }
+
+    this.push(" from ");
+  }
+
+  print(node.source);
+  this.semicolon();
+};
+
+exports.ImportBatchSpecifier = function (node, print) {
+  this.push("* as ");
+  print(node.name);
+};

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

@@ -0,0 +1,175 @@
+var t = require("../../types");
+
+exports.WithStatement = function (node, print) {
+  this.keyword("with");
+  this.push("(");
+  print(node.object);
+  this.push(")");
+  print.block(node.body);
+};
+
+exports.IfStatement = function (node, print) {
+  this.keyword("if");
+  this.push("(");
+  print(node.test);
+  this.push(") ");
+
+  print.indentOnComments(node.consequent);
+
+  if (node.alternate) {
+    if (this.isLast("}")) this.space();
+    this.keyword("else");
+    print.indentOnComments(node.alternate);
+  }
+};
+
+exports.ForStatement = function (node, print) {
+  this.keyword("for");
+  this.push("(");
+
+  print(node.init);
+  this.push(";");
+
+  if (node.test) {
+    this.space();
+    print(node.test);
+  }
+  this.push(";");
+
+  if (node.update) {
+    this.space();
+    print(node.update);
+  }
+
+  this.push(")");
+  print.block(node.body);
+};
+
+exports.WhileStatement = function (node, print) {
+  this.keyword("while");
+  this.push("(");
+  print(node.test);
+  this.push(")");
+  print.block(node.body);
+};
+
+var buildForXStatement = function (op) {
+  return function (node, print) {
+    this.keyword("for");
+    this.push("(");
+    print(node.left);
+    this.push(" " + op + " ");
+    print(node.right);
+    this.push(")");
+    print.block(node.body);
+  };
+};
+
+exports.ForInStatement = buildForXStatement("in");
+exports.ForOfStatement = buildForXStatement("of");
+
+exports.DoWhileStatement = function (node, print) {
+  this.keyword("do");
+  print(node.body);
+  this.space();
+  this.keyword("while");
+  this.push("(");
+  print(node.test);
+  this.push(");");
+};
+
+var buildLabelStatement = function (prefix, key) {
+  return function (node, print) {
+    this.push(prefix);
+
+    var label = node[key || "label"];
+    if (label) {
+      this.space();
+      print(label);
+    }
+
+    this.semicolon();
+  };
+};
+
+exports.ContinueStatement = buildLabelStatement("continue");
+exports.ReturnStatement   = buildLabelStatement("return", "argument");
+exports.BreakStatement    = buildLabelStatement("break");
+
+exports.LabeledStatement = function (node, print) {
+  print(node.label);
+  this.push(": ");
+  print(node.body);
+};
+
+exports.TryStatement = function (node, print) {
+  this.keyword("try");
+  print(node.block);
+  this.space();
+  print(node.handler);
+  if (node.finalizer) {
+    this.space();
+    this.push("finally ");
+    print(node.finalizer);
+  }
+};
+
+exports.CatchClause = function (node, print) {
+  this.keyword("catch");
+  this.push("(");
+  print(node.param);
+  this.push(") ");
+  print(node.body);
+};
+
+exports.ThrowStatement = function (node, print) {
+  this.push("throw ");
+  print(node.argument);
+  this.semicolon();
+};
+
+exports.SwitchStatement = function (node, print) {
+  this.keyword("switch");
+  this.push("(");
+  print(node.discriminant);
+  this.push(") {");
+  print.sequence(node.cases, { indent: true });
+  this.push("}");
+};
+
+exports.SwitchCase = function (node, print) {
+  if (node.test) {
+    this.push("case ");
+    print(node.test);
+    this.push(":");
+  } else {
+    this.push("default:");
+  }
+
+  this.space();
+  print.sequence(node.consequent, { indent: true });
+};
+
+exports.DebuggerStatement = function () {
+  this.push("debugger;");
+};
+
+exports.VariableDeclaration = function (node, print, parent) {
+  this.push(node.kind + " ");
+
+  print.join(node.declarations, { separator: ", " });
+
+  if (!t.isFor(parent)) {
+    this.semicolon();
+  }
+};
+
+exports.VariableDeclarator = function (node, print) {
+  if (node.init) {
+    print(node.id);
+    this.push(" = ");
+    print(node.init);
+  } else {
+    print(node.id);
+  }
+};

lib/6to5/generation/generators/template-literals.js

@@ -0,0 +1,30 @@
+var _ = require("lodash");
+
+exports.TaggedTemplateExpression = function (node, print) {
+  print(node.tag);
+  print(node.quasi);
+};
+
+exports.TemplateElement = function (node) {
+  this._push(node.value.raw);
+};
+
+exports.TemplateLiteral = function (node, print) {
+  this.push("`");
+
+  var quasis = node.quasis;
+  var self   = this;
+  var len    = quasis.length;
+
+  _.each(quasis, function (quasi, i) {
+    print(quasi);
+
+    if (i + 1 < len) {
+      self.push("${ ");
+      print(node.expressions[i]);
+      self.push(" }");
+    }
+  });
+
+  this._push("`");
+};

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

@@ -0,0 +1,93 @@
+var _ = require("lodash");
+
+exports.Identifier = function (node) {
+  this.push(node.name);
+};
+
+exports.SpreadElement = function (node, print) {
+  this.push("...");
+  print(node.argument);
+};
+
+exports.ObjectExpression =
+exports.ObjectPattern = function (node, print) {
+  var props = node.properties;
+
+  if (props.length) {
+    this.push("{");
+    this.space();
+
+    print.join(props, { separator: ", ", indent: true });
+
+    this.space();
+    this.push("}");
+  } else {
+    this.push("{}");
+  }
+};
+
+exports.Property = function (node, print) {
+  if (node.method || node.kind === "get" || node.kind === "set") {
+    this._method(node, print);
+  } else {
+    if (node.computed) {
+      this.push("[");
+      print(node.key);
+      this.push("]");
+    } else {
+      print(node.key);
+      if (node.shorthand) return;
+    }
+
+    this.push(": ");
+    print(node.value);
+  }
+};
+
+exports.ArrayExpression =
+exports.ArrayPattern = function (node, print) {
+  var elems = node.elements;
+  var self  = this;
+  var len   = elems.length;
+
+  this.push("[");
+
+  _.each(elems, function (elem, i) {
+    if (!elem) {
+      // If the array expression ends with a hole, that hole
+      // will be ignored by the interpreter, but if it ends with
+      // two (or more) holes, we need to write out two (or more)
+      // commas so that the resulting code is interpreted with
+      // both (all) of the holes.
+      self.push(",");
+    } else {
+      if (i > 0) self.push(" ");
+      print(elem);
+      if (i < len - 1) self.push(",");
+    }
+  });
+
+  this.push("]");
+};
+
+exports.Literal = function (node) {
+  var val  = node.value;
+  var type = typeof val;
+
+  if (type === "string") {
+    val = JSON.stringify(val);
+
+    // escape unicode characters
+    val = val.replace(/[\u007f-\uffff]/g, function(c) {
+      return "\\u" + ("0000" + c.charCodeAt(0).toString(16)).slice(-4);
+    });
+
+    this.push(val);
+  } else if (type === "boolean" || type === "number") {
+    this.push(JSON.stringify(val));
+  } else if (node.regex) {
+    this.push("/" + node.regex.pattern + "/" + node.regex.flags);
+  } else if (val === null) {
+    this.push("null");
+  }
+};

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

@@ -0,0 +1,87 @@
+module.exports = Node;
+
+var whitespace = require("./whitespace");
+var parens     = require("./parentheses");
+var t          = require("../../types");
+var _          = require("lodash");
+
+var find = function (obj, node, parent) {
+  var result;
+
+  _.each(obj, function (fn, type) {
+    if (t["is" + type](node)) {
+      result = fn(node, parent);
+      if (result != null) return false;
+    }
+  });
+
+  return result;
+};
+
+function Node(node, parent) {
+  this.parent = parent;
+  this.node   = node;
+}
+
+Node.prototype.isUserWhitespacable = function () {
+  var parent = this.parent;
+  var node = this.node;
+
+  if (t.isUserWhitespacable(node) ||
+      t.isSequenceExpression(parent)) {
+    return true;
+  }
+
+  return false;
+};
+
+Node.prototype.needsWhitespace = function (type) {
+  var parent = this.parent;
+  var node   = this.node;
+  if (!node) return 0;
+
+  if (t.isExpressionStatement(node)) {
+    node = node.expression;
+  }
+
+  var lines = find(whitespace[type].nodes, node, parent);
+  if (lines) return lines;
+
+  _.each(find(whitespace[type].list, node, parent), function (expr) {
+    lines = Node.needsWhitespace(expr, node, type);
+    if (lines) return false;
+  });
+  return lines || 0;
+};
+
+Node.prototype.needsWhitespaceBefore = function () {
+  return this.needsWhitespace("before");
+};
+
+Node.prototype.needsWhitespaceAfter = function () {
+  return this.needsWhitespace("after");
+};
+
+Node.prototype.needsParens = function () {
+  var parent = this.parent;
+  var node   = this.node;
+
+  if (!parent) return false;
+
+  if (t.isNewExpression(parent) && parent.callee === node) {
+    return t.isCallExpression(node) || _.some(node, function (val) {
+      return t.isCallExpression(val);
+    });
+  }
+
+  return find(parens, node, parent);
+};
+
+_.each(Node.prototype, function (fn, key) {
+  Node[key] = function (node, parent) {
+    var n = new Node(node, parent);
+
+    var args = _.toArray(arguments).slice(2);
+    return n[key].apply(n, args);
+  };
+});

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

@@ -0,0 +1,150 @@
+var t = require("../../types");
+var _ = require("lodash");
+
+var PRECEDENCE = {};
+
+_.each([
+  ["||"],
+  ["&&"],
+  ["|"],
+  ["^"],
+  ["&"],
+  ["==", "===", "!=", "!=="],
+  ["<", ">", "<=", ">=", "in", "instanceof"],
+  [">>", "<<", ">>>"],
+  ["+", "-"],
+  ["*", "/", "%"]
+], function (tier, i) {
+  _.each(tier, function (op) {
+    PRECEDENCE[op] = i;
+  });
+});
+
+exports.Binary = function (node, parent) {
+  if (t.isCallExpression(parent) && parent.callee === node) {
+    return true;
+  }
+
+  if (t.isUnaryLike(parent)) {
+    return true;
+  }
+
+  if (t.isMemberExpression(parent) && parent.object === node) {
+    return true;
+  }
+
+  if (t.isBinary(parent)) {
+    var parentOp  = parent.operator;
+    var parentPos = PRECEDENCE[parentOp];
+
+    var nodeOp = node.operator;
+    var nodePos = PRECEDENCE[nodeOp];
+
+    if (parentPos > nodePos) {
+      return true;
+    }
+
+    if (parentPos === nodePos && parent.right === node) {
+      return true;
+    }
+  }
+};
+
+exports.BinaryExpression = function (node, parent) {
+  if (node.operator === "in") {
+    // var i = (1 in []);
+    if (t.isVariableDeclarator(parent)) {
+      return true;
+    }
+
+    // for ((1 in []);;);
+    if (t.isFor(parent)) {
+      return true;
+    }
+  }
+};
+
+exports.SequenceExpression = function (node, parent) {
+  if (t.isForStatement(parent)) {
+    // Although parentheses wouldn't hurt around sequence
+    // expressions in the head of for loops, traditional style
+    // dictates that e.g. i++, j++ should not be wrapped with
+    // parentheses.
+    return false;
+  }
+
+  if (t.isExpressionStatement(parent) && parent.expression === node) {
+    return false;
+  }
+
+  // Otherwise err on the side of overparenthesization, adding
+  // explicit exceptions above if this proves overzealous.
+  return true;
+};
+
+exports.YieldExpression = function (node, parent) {
+  return t.isBinary(parent) ||
+         t.isUnaryLike(parent) ||
+         t.isCallExpression(parent) ||
+         t.isMemberExpression(parent) ||
+         t.isNewExpression(parent) ||
+         t.isConditionalExpression(parent) ||
+         t.isYieldExpression(parent);
+};
+
+exports.Literal = function (node, parent) {
+  // (1).valueOf()
+  if (_.isNumber(node.value) && t.isMemberExpression(parent) && parent.object === node) {
+    return true;
+  }
+};
+
+exports.ClassExpression = function (node, parent) {
+  return t.isExpressionStatement(parent);
+};
+
+exports.UnaryLike = function (node, parent) {
+  return t.isMemberExpression(parent) && parent.object === node;
+};
+
+exports.FunctionExpression = function (node, parent) {
+  // function () {};
+  if (t.isExpressionStatement(parent)) {
+    return true;
+  }
+
+  // (function test() {}).name;
+  if (t.isMemberExpression(parent) && parent.object === node) {
+    return true;
+  }
+
+  // (function () {})();
+  if (t.isCallExpression(parent) && parent.callee === node) {
+    return true;
+  }
+};
+
+exports.AssignmentExpression =
+exports.ConditionalExpression = function (node, parent) {
+  if (t.isUnaryLike(parent)) {
+    return true;
+  }
+
+  if (t.isBinary(parent)) {
+    return true;
+  }
+
+  if (t.isCallExpression(parent) && parent.callee === node) {
+    return true;
+  }
+
+  if (t.isConditionalExpression(parent) && parent.test === node) {
+    return true;
+  }
+
+  if (t.isMemberExpression(parent) && parent.object === node) {
+    return true;
+  }
+
+  return false;
+};

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

@@ -0,0 +1,60 @@
+var _ = require("lodash");
+var t = require("../../types");
+
+exports.before = {
+  nodes: {
+    Property: function (node, parent) {
+      if (parent.properties[0] === node) {
+        return 1;
+      }
+    },
+
+    SwitchCase: function (node, parent) {
+      if (parent.cases[0] === node) {
+        return 1;
+      }
+    },
+
+    CallExpression: function (node) {
+      if (t.isFunction(node.callee)) {
+        return 1;
+      }
+    }
+  }
+};
+
+exports.after = {
+  nodes: {},
+
+  list: {
+    VariableDeclaration: function (node) {
+      return _.map(node.declarations, "init");
+    },
+
+    ArrayExpression: function (node) {
+      return node.elements;
+    },
+
+    ObjectExpression: function (node) {
+      return node.properties;
+    }
+  }
+};
+
+_.each({
+  Function: 1,
+  Class: 1,
+  For: 1,
+  SwitchStatement: 1,
+  IfStatement: { before: 1 },
+  CallExpression: { after: 1 },
+  Literal: { after: 1 }
+}, function (amounts, type) {
+  if (_.isNumber(amounts)) amounts = { after: amounts, before: amounts };
+
+  _.each(amounts, function (amount, key) {
+    exports[key].nodes[type] = function () {
+      return amount;
+    };
+  });
+});

lib/6to5/generation/position.js

@@ -0,0 +1,33 @@
+module.exports = Position;
+
+var _ = require("lodash");
+
+function Position() {
+  this.line = 1;
+  this.column = 0;
+}
+
+Position.prototype.push = function (str) {
+  var self = this;
+
+  _.each(str, function (cha) {
+    if (cha === "\n") {
+      self.line++;
+      self.column = 0;
+    } else {
+      self.column++;
+    }
+  });
+};
+
+Position.prototype.unshift = function (str) {
+  var self = this;
+
+  _.each(str, function (cha) {
+    if (cha === "\n") {
+      self.line--;
+    } else {
+      self.column--;
+    }
+  });
+};

lib/6to5/generation/source-map.js

@@ -0,0 +1,56 @@
+module.exports = SourceMap;
+
+var sourceMap = require("source-map");
+var t         = require("../types");
+
+function SourceMap(position, opts, code) {
+  this.position = position;
+  this.opts     = opts;
+
+  if (opts.sourceMap) {
+    this.map = new sourceMap.SourceMapGenerator({
+      file: opts.sourceMapName,
+      sourceRoot: opts.sourceRoot
+    });
+
+    this.map.setSourceContent(opts.sourceFileName, code);
+  } else {
+    this.map = null;
+  }
+}
+
+SourceMap.prototype.get = function () {
+  var map = this.map;
+  if (map) {
+    return map.toJSON();
+  } else {
+    return map;
+  }
+};
+
+SourceMap.prototype.mark = function (node, type) {
+  var loc = node.loc;
+  if (!loc) return; // no location info
+
+  var map = this.map;
+  if (!map) return; // no source map
+
+  if (t.isProgram(node) || t.isFile(node)) return; // illegal mapping nodes
+
+  var position = this.position;
+
+  var generated = {
+    line: position.line,
+    column: position.column
+  };
+
+  var original = loc[type];
+
+  if (generated.line === original.line && generated.column === original.column) return; // nothing to map
+
+  map.addMapping({
+    source: this.opts.sourceFileName,
+    generated: generated,
+    original: original
+  });
+};

lib/6to5/generation/whitespace.js

@@ -0,0 +1,58 @@
+module.exports = Whitespace;
+
+var _ = require("lodash");
+
+function Whitespace(tokens, comments) {
+  this.tokens = _.sortBy(tokens.concat(comments), "start");
+  this.used   = [];
+}
+
+Whitespace.prototype.getNewlinesBefore = function (node) {
+  var startToken;
+  var endToken;
+  var tokens = this.tokens;
+
+  _.each(tokens, function (token, i) {
+    // this is the token this node starts with
+    if (node.start === token.start) {
+      startToken = tokens[i - 1];
+      endToken = token;
+      return false;
+    }
+  });
+
+  return this.getNewlinesBetween(startToken, endToken);
+};
+
+Whitespace.prototype.getNewlinesAfter = function (node) {
+  var startToken;
+  var endToken;
+  var tokens = this.tokens;
+
+  _.each(tokens, function (token, i) {
+    // this is the token this node ends with
+    if (node.end === token.end) {
+      startToken = token;
+      endToken = tokens[i + 1];
+      return false;
+    }
+  });
+
+  return this.getNewlinesBetween(startToken, endToken);
+};
+
+Whitespace.prototype.getNewlinesBetween = function (startToken, endToken) {
+  var start = startToken ? startToken.loc.end.line : 1;
+  var end   = endToken.loc.start.line;
+
+  var lines = 0;
+
+  for (var line = start; line < end; line++) {
+    if (!_.contains(this.used, line)) {
+      this.used.push(line);
+      lines++;
+    }
+  }
+
+  return lines;
+};

lib/6to5/index.js

@@ -1,8 +1,9 @@
-var transform = require("./transform");
+var transform = require("./transformation/transform");
+var util      = require("./util");
 var fs        = require("fs");
 var _         = require("lodash");
 
-exports.util = require("./util");
+exports.runtime = require("./runtime");
 
 exports.register = function (opts) {
   var register = require("./register");
@@ -14,6 +15,11 @@ exports.polyfill = function () {
   require("./polyfill");
 };
 
+exports.canCompile = util.canCompile;
+
+// do not use this - this is for use by official maintained 6to5 plugins
+exports._util = util;
+
 exports.transform = transform;
 
 exports.transformFile = function (filename, opts, callback) {

lib/6to5/modules/amd.js

@@ -1,82 +0,0 @@
-module.exports = AMDFormatter;
-
-var CommonJSFormatter = require("./common");
-var util              = require("../util");
-var b                 = require("acorn-ast-types").builders;
-var _                 = require("lodash");
-
-function AMDFormatter(file) {
-  this.file = file;
-  this.ids  = {};
-}
-
-util.inherits(AMDFormatter, CommonJSFormatter);
-
-AMDFormatter.prototype.transform = function (ast) {
-  var program = ast.program;
-  var body    = program.body;
-
-  // build an array of module names
-
-  var names = [b.literal("exports")];
-  _.each(this.ids, function (id, name) {
-    names.push(b.literal(name));
-  });
-  names = b.arrayExpression(names);
-
-  // build up define container
-
-  var params = _.values(this.ids);
-  params.unshift(b.identifier("exports"));
-
-  var container = b.functionExpression(null, params, b.blockStatement(body));
-  var call = b.callExpression(b.identifier("define"), [names, container]);
-
-  program.body = [b.expressionStatement(call)];
-};
-
-AMDFormatter.prototype._push = function (node) {
-  var id  = node.source.value;
-  var ids = this.ids;
-
-  if (ids[id]) {
-    return ids[id];
-  } else {
-    return this.ids[id] = b.identifier(this.file.generateUid(id));
-  }
-};
-
-AMDFormatter.prototype.import = function (node) {
-  this._push(node);
-};
-
-AMDFormatter.prototype.importSpecifier = function (specifier, node, nodes) {
-  var key = util.getSpecifierName(specifier);
-  var id  = specifier.id;
-
-  // import foo from "foo";
-  if (specifier.default) {
-    id = b.identifier("default");
-  }
-
-  var ref;
-
-  if (specifier.type === "ImportBatchSpecifier") {
-    // import * as bar from "foo";
-    ref = this._push(node);
-  } else {
-    // import foo from "foo";
-    ref = b.memberExpression(this._push(node), id, false);
-  }
-
-  nodes.push(b.variableDeclaration("var", [
-    b.variableDeclarator(key, ref)
-  ]));
-};
-
-AMDFormatter.prototype.exportSpecifier = function (specifier, node, nodes) {
-  var self = this;
-  return this._exportSpecifier(function () {
-    return self._push(node);
-  }, specifier, node, nodes);
-};

lib/6to5/patch.js

@@ -0,0 +1,28 @@
+var t = require("./types");
+var _ = require("lodash");
+
+var types = require("ast-types");
+var def   = types.Type.def;
+
+// Program wrapper
+def("File")
+  .bases("Node")
+  .build("program")
+  .field("program", def("Program"));
+
+// Non-standard Acorn type
+def("ParenthesizedExpression")
+  .bases("Expression")
+  .build("expression")
+  .field("expression", def("Expression"));
+
+// Same as ImportNamespaceSpecifier but `id` is `name`
+def("ImportBatchSpecifier")
+  .bases("Specifier")
+  .build("name")
+  .field("name", def("Identifier"));
+
+types.finalize();
+
+var estraverse = require("estraverse");
+_.extend(estraverse.VisitorKeys, t.VISITOR_KEYS);

lib/6to5/polyfill.js

@@ -1,3 +1,6 @@
-require("es6-symbol/implement");
+if (typeof Symbol === "undefined") {
+  require("es6-symbol/implement");
+}
+
 require("es6-shim");
-require("regenerator/runtime");
+require("./transformation/transformers/generators/runtime");

lib/6to5/register.js

@@ -1,12 +1,13 @@
 require("./polyfill");
 
 var sourceMapSupport = require("source-map-support");
+var util             = require("./util");
 var to5              = require("./index");
 var _                = require("lodash");
 
 sourceMapSupport.install({
   retrieveSourceMap: function (source) {
-    var map = maps[source];
+    var map = maps && maps[source];
     if (map) {
       return {
         url: null,
@@ -20,18 +21,59 @@ sourceMapSupport.install({
 
 //
 
+var blacklist  = [];
+
+var blacklistTest = function (transformer, code) {
+  try {
+    if (_.isFunction(code)) {
+      code();
+    } else {
+      new Function(code);
+    }
+    blacklist.push(transformer);
+  } catch (err) {
+    if (err.name !== "SyntaxError") throw err;
+  }
+};
+
+blacklistTest("arrayComprehension", "var foo = [for (foo of bar) foo * foo];");
+//blacklistTest("generatorComprehension", "");
+blacklistTest("arrowFunctions", "var foo = x => x * x;");
+blacklistTest("classes", "class Foo {}");
+blacklistTest("computedPropertyNames", "var foo = { [foo]: bar };");
+//blacklistTest("constants", "const foo = 0;");
+blacklistTest("defaultParamaters", "var foo = function (bar = 0) {};");
+blacklistTest("destructuring", "var { x, y } = { x: 0, y: 0 };");
+blacklistTest("forOf", "for (var foo of bar) {}");
+blacklistTest("generators", "function* foo() {}");
+blacklistTest("letScoping", "let foo = 0;");
+blacklistTest("modules", 'import foo from "from";');
+blacklistTest("propertyMethodAssignment", "{ get foo() {} }");
+blacklistTest("propertyNameShorthand", "var foo = { x, y };");
+blacklistTest("restParameters", "function foo(...bar) {}");
+blacklistTest("spread", "foo(...bar);");
+blacklistTest("templateLiterals", "var foo = `foo`;");
+blacklistTest("unicodeRegex", function () { new RegExp("foo", "u"); });
+
+//
+
 var ignoreRegex = /node_modules/;
+var onlyRegex;
+var whitelist   = [];
 var exts        = {};
 var maps        = {};
 var old         = require.extensions[".js"];
 
 var loader = function (m, filename) {
-  if (ignoreRegex && ignoreRegex.test(filename)) {
+  if ((ignoreRegex && ignoreRegex.test(filename)) || (onlyRegex && !onlyRegex.test(filename))) {
     return old.apply(this, arguments);
   }
 
   var result = to5.transformFileSync(filename, {
-    sourceMap: true
+    whitelist: whitelist,
+    blacklist: blacklist,
+    sourceMap: true,
+    modules:   "commonInterop"
   });
 
   maps[filename] = result.map;
@@ -55,12 +97,16 @@ var hookExtensions = function (_exts) {
 hookExtensions([".es6", ".js"]);
 
 module.exports = function (opts) {
+  // normalise options
   opts = opts || {};
-  if (_.isRegExp(opts)) opts = { ignoreRegex: opts };
+  if (_.isRegExp(opts)) opts = { ignore: opts };
+  if (opts.ignoreRegex != null) opts.ignore = opts.ignoreRegex;
 
-  if (opts.ignoreRegex != null) {
-    ignoreRegex = opts.ignoreRegex;
-  }
+  if (opts.only != null) onlyRegex = util.regexify(opts.only);
+  if (opts.ignore != null) ignoreRegex = util.regexify(opts.ignore);
 
-  if (opts.extensions) hookExtensions(opts.extensions);
+  if (opts.extensions) hookExtensions(util.arrayify(opts.extensions));
+
+  if (opts.blacklist) blacklist = util.arrayify(opts.blacklist);
+  if (opts.whitelist) whitelist = util.arrayify(opts.whitelist);
 };

lib/6to5/runtime.js

@@ -0,0 +1,31 @@
+var generator = require("./generation/generator");
+var util      = require("./util");
+var File      = require("./file");
+var t         = require("./types");
+var _         = require("lodash");
+
+module.exports = function (namespace) {
+  namespace = t.identifier(t.toIdentifier(namespace || "to5Runtime"));
+
+  var body      = [];
+  var container = t.functionExpression(null, [], t.blockStatement(body));
+  var tree      = t.program([t.expressionStatement(t.callExpression(container, []))]);
+
+  body.push(util.template("self-global", true));
+
+  body.push(t.variableDeclaration("var", [
+    t.variableDeclarator(
+      namespace,
+      t.assignmentExpression("=", t.memberExpression(t.identifier("self"), namespace), t.objectExpression([]))
+    )
+  ]));
+
+  _.each(File.declarations, function (name) {
+    var key = t.identifier(t.toIdentifier(name));
+    body.push(t.expressionStatement(
+      t.assignmentExpression("=", t.memberExpression(namespace, key), util.template(name))
+    ));
+  });
+
+  return generator(tree).code;
+};

lib/6to5/templates/apply-constructor.js

@@ -0,0 +1,5 @@
+(function (Constructor, args) {
+  var bindArgs = [null].concat(args);
+  var Factory = Constructor.bind.apply(Constructor, bindArgs);
+  return new Factory;
+});

lib/6to5/templates/class-props.js

@@ -0,0 +1,4 @@
+(function (child, staticProps, instanceProps) {
+  if (staticProps) Object.defineProperties(child, staticProps);
+  if (instanceProps) Object.defineProperties(child.prototype, instanceProps);
+})

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

@@ -0,0 +1,3 @@
+(function (obj) {
+  return obj && (obj["default"] || obj);
+})

lib/6to5/templates/let-scoping-return.js

@@ -0,0 +1 @@
+if (typeof RETURN === "object") return RETURN.v;

lib/6to5/templates/self-global.js

@@ -0,0 +1 @@
+var self = typeof global === "undefined" ? window : global;

lib/6to5/templates/tagged-template-literal.js

@@ -0,0 +1,4 @@
+(function (strings, raw) {
+  return Object.defineProperties(strings, { raw: { value: raw } });
+});
+

lib/6to5/transform.js

@@ -1,118 +0,0 @@
-module.exports = transform;
-
-var Transformer = require("./transformer");
-var sourceMap   = require("source-map");
-var recast      = require("acorn-recast");
-var File        = require("./file");
-var util        = require("./util");
-var _           = require("lodash");
-
-function transform(code, opts) {
-  opts = opts || {};
-  code = (code || "") + "";
-
-  var file = new File(opts);
-  return file.parse(code);
-}
-
-transform.test = function (task, assert) {
-  var actual = task.actual;
-  var expect = task.expect;
-  var opts   = task.options;
-  var exec   = task.exec;
-
-  var getOpts = function (filename) {
-    return _.merge({ filename: filename }, opts);
-  };
-
-  var execCode = exec.code.trim();
-  var result;
-
-  if (execCode) {
-    result = transform(execCode, getOpts(exec.filename));
-    execCode = result.code;
-
-    require("./polyfill");
-    var fn = new Function("assert", execCode);
-    fn(assert);
-  } else {
-    var actualCode = actual.code.trim();
-    var expectCode = expect.code.trim();
-
-    var printOpts = { tabWidth: 2 };
-
-    result     = transform(actualCode, getOpts(actual.filename));
-    actualCode = recast.prettyPrint(result.ast, printOpts).code;
-
-    var expectAst    = util.parse(expect, expectCode);
-    var expectResult = recast.prettyPrint(expectAst, printOpts);
-    expectCode       = expectResult.code;
-
-    assert.equal(actualCode, expectCode);
-  }
-
-  if (task.sourceMap) {
-    assert.deepEqual(task.sourceMap, result.map);
-  }
-
-  if (task.sourceMappings) {
-    var consumer = new sourceMap.SourceMapConsumer(result.map);
-
-    _.each(task.sourceMappings, function (mapping, i) {
-      var generated = mapping.generated;
-      var original  = mapping.original;
-
-      var pos = consumer.originalPositionFor(generated);
-      var msg = "source mapping " + i + " - generated: " + generated.line + ":" + generated.column;
-      assert.equal(pos.line + ":" + pos.column, original.line + ":" + original.column, msg);
-    });
-  }
-};
-
-transform._ensureTransformerNames = function (type, keys) {
-  _.each(keys, function (key) {
-    if (!_.has(transform.transformers, key)) {
-      throw new ReferenceError("unknown transformer " + key + " specified in " + type);
-    }
-  });
-};
-
-transform.transformers = {
-  modules:                  require("./transformers/modules"),
-  computedPropertyNames:    require("./transformers/computed-property-names"),
-  propertyNameShorthand:    require("./transformers/property-name-shorthand"),
-  constants:                require("./transformers/constants"),
-  arrayComprehension:       require("./transformers/array-comprehension"),
-  arrowFunctions:           require("./transformers/arrow-functions"),
-  classes:                  require("./transformers/classes"),
-  spread:                   require("./transformers/spread"),
-  templateLiterals:         require("./transformers/template-literals"),
-  propertyMethodAssignment: require("./transformers/property-method-assignment"),
-  defaultParameters:        require("./transformers/default-parameters"),
-  letScoping:               require("./transformers/let-scoping"),
-  restParameters:           require("./transformers/rest-parameters"),
-  destructuring:            require("./transformers/destructuring"),
-  forOf:                    require("./transformers/for-of"),
-  unicodeRegex:             require("./transformers/unicode-regex"),
-  generators:               require("./transformers/generators"),
-
-  react:                    require("./transformers/react"),
-  jsx:                      require("./transformers/jsx"),
-
-  _aliasFunctions:          require("./transformers/_alias-functions"),
-  _blockHoist:              require("./transformers/_block-hoist"),
-  _declarations:            require("./transformers/_declarations"),
-  _moduleFormatter:         require("./transformers/_module-formatter"),
-
-  useStrict:                require("./transformers/use-strict")
-};
-
-transform.moduleFormatters = {
-  common: require("./modules/common"),
-  amd:    require("./modules/amd"),
-  umd:    require("./modules/umd")
-};
-
-_.each(transform.transformers, function (transformer, key) {
-  transform.transformers[key] = new Transformer(key, transformer);
-});

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

@@ -0,0 +1,111 @@
+module.exports = AMDFormatter;
+
+var CommonJSFormatter = require("./common");
+var util              = require("../../util");
+var t                 = require("../../types");
+var _                 = require("lodash");
+
+function AMDFormatter(file) {
+  this.file = file;
+  this.ids  = {};
+}
+
+util.inherits(AMDFormatter, CommonJSFormatter);
+
+AMDFormatter.prototype.transform = function (ast) {
+  var program = ast.program;
+  var body    = program.body;
+
+  // build an array of module names
+
+  var names = [t.literal("exports")];
+  _.each(this.ids, function (id, name) {
+    names.push(t.literal(name));
+  });
+  names = t.arrayExpression(names);
+
+  // build up define container
+
+  var params = _.values(this.ids);
+  params.unshift(t.identifier("exports"));
+
+  var moduleName = this.getModuleName();
+
+  var container = t.functionExpression(null, params, t.blockStatement(body));
+  var call = t.callExpression(t.identifier("define"), [t.literal(moduleName), names, container]);
+
+  program.body = [t.expressionStatement(call)];
+};
+
+AMDFormatter.prototype.getModuleName = function () {
+  var opts = this.file.opts;
+  var filenameRelative = opts.filenameRelative;
+  var moduleName = "";
+
+  if (opts.moduleRoot) {
+    moduleName = opts.moduleRoot + "/";
+  }
+
+  if (!opts.filenameRelative) {
+    return moduleName + opts.filename.replace(/^\//, "");
+  }
+
+  if (opts.sourceRoot) {
+    // remove sourceRoot from filename
+    var sourceRootRegEx = new RegExp("^" + opts.sourceRoot + "\/?");
+    filenameRelative = filenameRelative.replace(sourceRootRegEx, "");
+  }
+
+  // remove extension
+  filenameRelative = filenameRelative.replace(/\.(.*?)$/, "");
+
+  moduleName += filenameRelative;
+
+  return moduleName;
+};
+
+AMDFormatter.prototype._push = function (node) {
+  var id  = node.source.value;
+  var ids = this.ids;
+
+  if (ids[id]) {
+    return ids[id];
+  } else {
+    return this.ids[id] = t.identifier(this.file.generateUid(id));
+  }
+};
+
+AMDFormatter.prototype.import = function (node) {
+  this._push(node);
+};
+
+AMDFormatter.prototype.importSpecifier = function (specifier, node, nodes) {
+  var key = t.getSpecifierName(specifier);
+  var id  = specifier.id;
+
+  // import foo from "foo";
+  if (specifier.default) {
+    id = t.identifier("default");
+  }
+
+  var ref;
+
+  if (t.isImportBatchSpecifier(specifier)) {
+    // import * as bar from "foo";
+    ref = this._push(node);
+  } else {
+    // import foo from "foo";
+    ref = t.memberExpression(this._push(node), id, false);
+  }
+
+  nodes.push(t.variableDeclaration("var", [
+    t.variableDeclarator(key, ref)
+  ]));
+};
+
+AMDFormatter.prototype.exportSpecifier = function (specifier, node, nodes) {
+  var self = this;
+  return this._exportSpecifier(function () {
+    return self._push(node);
+  }, specifier, node, nodes);
+};

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

@@ -0,0 +1,29 @@
+module.exports = CommonJSInteropFormatter;
+
+var CommonJSFormatter = require("./common");
+var util              = require("../../util");
+var t                 = require("../../types");
+
+function CommonJSInteropFormatter(file) {
+  this.file = file;
+}
+
+util.inherits(CommonJSInteropFormatter, CommonJSFormatter);
+
+CommonJSInteropFormatter.prototype.importSpecifier = function (specifier, node, nodes) {
+  var variableName = t.getSpecifierName(specifier);
+
+  // import foo from "foo";
+   if (specifier.default) {
+    nodes.push(t.variableDeclaration("var", [
+      t.variableDeclarator(variableName,
+        t.callExpression(this.file.addDeclaration("interop-require"), [util.template("require", {
+          MODULE_NAME: node.source.raw
+        })])
+      )
+    ]));
+    return;
+  }
+
+  CommonJSFormatter.prototype.importSpecifier.apply(this, arguments);
+};

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

@@ -1,7 +1,7 @@
 module.exports = CommonJSFormatter;
 
-var util = require("../util");
-var b    = require("acorn-ast-types").builders;
+var util = require("../../util");
+var t    = require("../../types");
 
 function CommonJSFormatter(file) {
   this.file = file;
@@ -10,16 +10,18 @@ function CommonJSFormatter(file) {
 CommonJSFormatter.prototype.import = function (node, nodes) {
   // import "foo";
   nodes.push(util.template("require", {
+    //inherits: node,
+
     MODULE_NAME: node.source.raw
   }, true));
 };
 
 CommonJSFormatter.prototype.importSpecifier = function (specifier, node, nodes) {
-  var variableName = util.getSpecifierName(specifier);
+  var variableName = t.getSpecifierName(specifier);
 
   // import foo from "foo";
   if (specifier.default) {
-    specifier.id = b.identifier("default");
+    specifier.id = t.identifier("default");
   }
 
   var templateName = "require-assign";
@@ -28,6 +30,8 @@ CommonJSFormatter.prototype.importSpecifier = function (specifier, node, nodes)
   if (specifier.type !== "ImportBatchSpecifier") templateName += "-key";
 
   nodes.push(util.template(templateName, {
+    //inherits: node.specifiers.length === 1 && node,
+
     VARIABLE_NAME: variableName,
     MODULE_NAME:   node.source.raw,
     KEY:           specifier.id
@@ -38,44 +42,73 @@ CommonJSFormatter.prototype.export = function (node, nodes) {
   var declar = node.declaration;
 
   if (node.default) {
-    util.ensureExpressionType(declar);
+    var ref = declar;
+
+    if (t.isClass(ref) || t.isFunction(ref)) {
+      if (ref.id) {
+        nodes.push(t.toStatement(ref));
+        ref = ref.id;
+      }
+    }
 
     nodes.push(util.template("exports-default", {
-      VALUE: declar
+      //inherits: node,
+
+      VALUE: ref
     }, true));
   } else {
-    var id = declar.id;
-    if (declar.type === "VariableDeclaration") {
-      id = declar.declarations[0].id;
+    var assign;
+
+    if (t.isVariableDeclaration(declar)) {
+      var decl = declar.declarations[0];
+
+      if (decl.init) {
+        decl.init = util.template("exports-assign", {
+          //inherits: node,
+
+          VALUE: decl.init,
+          KEY:   decl.id
+        });
+      }
+
+      nodes.push(declar);
+    } else {
+      assign = util.template("exports-assign", {
+        //inherits: node,
+
+        VALUE: declar.id,
+        KEY:   declar.id
+      }, true);
+
+      nodes.push(t.toStatement(declar));
+      nodes.push(assign);
+
+      if (t.isFunctionDeclaration(declar)) {
+        assign._blockHoist = true;
+      }
     }
-
-    var assign = util.template("exports-assign", {
-      VALUE: id,
-      KEY:   id
-    }, true);
-
-    nodes.push(declar);
-
-    if (declar.type === "FunctionDeclaration") {
-      assign._blockHoist = true;
-    }
-
-    nodes.push(assign);
   }
 };
 
 CommonJSFormatter.prototype._exportSpecifier = function (getRef, specifier, node, nodes) {
-  var variableName = util.getSpecifierName(specifier);
+  var variableName = t.getSpecifierName(specifier);
+
+  var inherits = false;
+  if (node.specifiers.length === 1) inherits = node;
 
   if (node.source) {
-    if (specifier.type === "ExportBatchSpecifier") {
+    if (t.isExportBatchSpecifier(specifier)) {
       // export * from "foo";
       nodes.push(util.template("exports-wildcard", {
+        //inherits: inherits,
+
         OBJECT: getRef()
       }, true));
     } else {
       // export { foo } from "test";
       nodes.push(util.template("exports-assign-key", {
+        //inherits: inherits,
+
         VARIABLE_NAME: variableName.name,
         OBJECT:        getRef(),
         KEY:           specifier.id
@@ -84,6 +117,8 @@ CommonJSFormatter.prototype._exportSpecifier = function (getRef, specifier, node
   } else {
     // export { foo };
     nodes.push(util.template("exports-assign", {
+      //inherits: inherits,
+
       VALUE: specifier.id,
       KEY:   variableName
     }, true));
@@ -92,6 +127,6 @@ CommonJSFormatter.prototype._exportSpecifier = function (getRef, specifier, node
 
 CommonJSFormatter.prototype.exportSpecifier = function (specifier, node, nodes) {
   return this._exportSpecifier(function () {
-    return b.callExpression(b.identifier("require"), [node.source]);
+    return t.callExpression(t.identifier("require"), [node.source]);
   }, specifier, node, nodes);
 };

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

@@ -0,0 +1,24 @@
+module.exports = IgnoreFormatter;
+
+var t = require("../../types");
+
+function IgnoreFormatter() {
+
+}
+
+IgnoreFormatter.prototype.import = function () {
+
+};
+
+IgnoreFormatter.prototype.importSpecifier = function () {
+
+};
+
+IgnoreFormatter.prototype.export = function (node, nodes) {
+  var declar = t.toStatement(node.declaration, true);
+  if (declar) nodes.push(t.inherits(declar, node));
+};
+
+IgnoreFormatter.prototype.exportSpecifier = function () {
+
+};

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

@@ -1,8 +1,8 @@
 module.exports = UMDFormatter;
 
 var AMDFormatter = require("./amd");
-var util         = require("../util");
-var b            = require("acorn-ast-types").builders;
+var util         = require("../../util");
+var t            = require("../../types");
 var _            = require("lodash");
 
 function UMDFormatter(file) {
@@ -20,28 +20,30 @@ UMDFormatter.prototype.transform = function (ast) {
 
   var names = [];
   _.each(this.ids, function (id, name) {
-    names.push(b.literal(name));
+    names.push(t.literal(name));
   });
 
   // factory
 
   var ids  = _.values(this.ids);
-  var args = [b.identifier("exports")].concat(ids);
+  var args = [t.identifier("exports")].concat(ids);
 
-  var factory = b.functionExpression(null, args, b.blockStatement(body));
+  var factory = t.functionExpression(null, args, t.blockStatement(body));
 
   // runner
 
+  var moduleName = this.getModuleName();
+
   var runner = util.template("umd-runner-body", {
-    AMD_ARGUMENTS: b.arrayExpression([b.literal("exports")].concat(names)),
+    AMD_ARGUMENTS: [t.literal(moduleName), t.arrayExpression([t.literal("exports")].concat(names))],
 
     COMMON_ARGUMENTS: names.map(function (name) {
-      return b.callExpression(b.identifier("require"), [name]);
+      return t.callExpression(t.identifier("require"), [name]);
     })
   });
 
   //
 
-  var call = b.callExpression(runner, [factory]);
-  program.body = [b.expressionStatement(call)];
+  var call = t.callExpression(runner, [factory]);
+  program.body = [t.expressionStatement(call)];
 };

lib/6to5/transformation/transform.js

@@ -0,0 +1,66 @@
+module.exports = transform;
+
+var Transformer = require("./transformer");
+var File        = require("../file");
+var _           = require("lodash");
+
+function transform(code, opts) {
+  var file = new File(opts);
+  return file.parse(code);
+}
+
+transform._ensureTransformerNames = function (type, keys) {
+  _.each(keys, function (key) {
+    if (!_.has(transform.transformers, key)) {
+      throw new ReferenceError("unknown transformer " + key + " specified in " + type);
+    }
+  });
+};
+
+transform.transformers = {};
+
+transform.moduleFormatters = {
+  common:        require("./modules/common"),
+  commonInterop: require("./modules/common-interop"),
+  ignore:        require("./modules/ignore"),
+  amd:           require("./modules/amd"),
+  umd:           require("./modules/umd")
+};
+
+_.each({
+  modules:                   require("./transformers/modules"),
+  propertyNameShorthand:     require("./transformers/property-name-shorthand"),
+  arrayComprehension:        require("./transformers/array-comprehension"),
+  generatorComprehension:    require("./transformers/generator-comprehension"),
+  arrowFunctions:            require("./transformers/arrow-functions"),
+  classes:                   require("./transformers/classes"),
+
+  _propertyLiterals:         require("./transformers/_property-literals"),
+  computedPropertyNames:     require("./transformers/computed-property-names"),
+
+  spread:                    require("./transformers/spread"),
+  templateLiterals:          require("./transformers/template-literals"),
+  propertyMethodAssignment:  require("./transformers/property-method-assignment"),
+  defaultParameters:         require("./transformers/default-parameters"),
+  restParameters:            require("./transformers/rest-parameters"),
+  destructuring:             require("./transformers/destructuring"),
+  forOf:                     require("./transformers/for-of"),
+  unicodeRegex:              require("./transformers/unicode-regex"),
+  react:                     require("./transformers/react"),
+
+  constants:                 require("./transformers/constants"),
+  letScoping:                require("./transformers/let-scoping"),
+
+  generators:                require("./transformers/generators"),
+
+  _blockHoist:               require("./transformers/_block-hoist"),
+  _declarations:             require("./transformers/_declarations"),
+  _aliasFunctions:           require("./transformers/_alias-functions"),
+
+  useStrict:                 require("./transformers/use-strict"),
+
+  _memberExpressionKeywords: require("./transformers/_member-expression-keywords"),
+  _moduleFormatter:          require("./transformers/_module-formatter")
+}, function (transformer, key) {
+  transform.transformers[key] = new Transformer(key, transformer);
+});

lib/6to5/transformation/transformer.js

@@ -1,6 +1,7 @@
 module.exports = Transformer;
 
-var traverse = require("./traverse");
+var traverse = require("../traverse");
+var t        = require("../types");
 var _        = require("lodash");
 
 function Transformer(key, transformer) {
@@ -14,6 +15,7 @@ Transformer.normalise = function (transformer) {
   }
 
   _.each(transformer, function (fns, type) {
+    if (type[0] === "_") return;
     if (_.isFunction(fns)) fns = { enter: fns };
     transformer[type] = fns;
   });
@@ -27,14 +29,18 @@ Transformer.prototype.transform = function (file) {
   var transformer = this.transformer;
   var ast         = file.ast;
 
-  if (transformer.ast && transformer.ast.enter) {
-    transformer.ast.enter(ast, file);
-  }
+  var astRun = function (key) {
+    if (transformer.ast && transformer.ast[key]) {
+      transformer.ast[key](ast, file);
+    }
+  };
+
+  astRun("enter");
 
   var build = function (exit) {
-    return function (node, parent) {
+    return function (node, parent, scope) {
       // add any node type aliases that exist
-      var types = [node.type].concat(traverse.aliases[node.type] || []);
+      var types = [node.type].concat(t.ALIAS_KEYS[node.type] || []);
 
       var fns = transformer.all;
 
@@ -49,7 +55,7 @@ Transformer.prototype.transform = function (file) {
       if (exit) fn = fns.exit;
       if (!fn) return;
 
-      return fn(node, parent, file);
+      return fn(node, parent, file, scope);
     };
   };
 
@@ -58,19 +64,20 @@ Transformer.prototype.transform = function (file) {
     exit:  build(true)
   });
 
-  if (transformer.ast && transformer.ast.exit) {
-    transformer.ast.exit(ast, file);
-  }
+  astRun("exit");
 };
 
 Transformer.prototype.canRun = function (file) {
   var opts = file.opts;
+  var key  = this.key;
 
   var blacklist = opts.blacklist;
-  if (blacklist.length && _.contains(blacklist, this.key)) return false;
+  if (blacklist.length && _.contains(blacklist, key)) return false;
 
-  var whitelist = opts.whitelist;
-  if (whitelist.length && !_.contains(whitelist, this.key)) return false;
+  if (key[0] !== "_") {
+    var whitelist = opts.whitelist;
+    if (whitelist.length && !_.contains(whitelist, key)) return false;
+  }
 
   return true;
 };

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

@@ -0,0 +1,82 @@
+var traverse = require("../../traverse");
+var t        = require("../../types");
+
+var go = function (getBody, node, file, scope) {
+  var argumentsId;
+  var thisId;
+
+  var getArgumentsId = function () {
+    return argumentsId = argumentsId || t.identifier(file.generateUid("arguments", scope));
+  };
+
+  var getThisId = function () {
+    return thisId = thisId || t.identifier(file.generateUid("this", scope));
+  };
+
+  // traverse the function and find all alias functions so we can alias
+  // `arguments` and `this` if necessary
+  traverse(node, function (node) {
+    if (!node._aliasFunction) {
+      if (t.isFunction(node)) {
+        // stop traversal of this node as it'll be hit again by this transformer
+        return false;
+      } else {
+        return;
+      }
+    }
+
+    // traverse all child nodes of this function and find `arguments` and `this`
+    traverse(node, function (node, parent) {
+      if (t.isFunction(node) && !node._aliasFunction) {
+        return false;
+      }
+
+      if (node._ignoreAliasFunctions) return;
+
+      var getId;
+
+      if (t.isIdentifier(node) && node.name === "arguments") {
+        getId = getArgumentsId;
+      } else if (t.isThisExpression(node)) {
+        getId = getThisId;
+      } else {
+        return;
+      }
+
+      if (t.isReferenced(node, parent)) return getId();
+    });
+
+    return false;
+  });
+
+  var body;
+
+  var pushDeclaration = function (id, init) {
+    body = body || getBody();
+    body.unshift(t.variableDeclaration("var", [
+      t.variableDeclarator(id, init)
+    ]));
+  };
+
+  if (argumentsId) {
+    pushDeclaration(argumentsId, t.identifier("arguments"));
+  }
+
+  if (thisId) {
+    pushDeclaration(thisId, t.identifier("this"));
+  }
+};
+
+exports.Program = function (node, parent, file, scope) {
+  go(function () {
+    return node.body;
+  }, node, file, scope);
+};
+
+exports.FunctionDeclaration =
+exports.FunctionExpression = function (node, parent, file, scope) {
+  go(function () {
+    t.ensureBlock(node);
+    return node.body.body;
+  }, node, file, scope);
+};

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

@@ -1,12 +1,12 @@
-var b = require("acorn-ast-types").builders;
+var t = require("../../types");
 var _ = require("lodash");
 
 module.exports = function (ast, file) {
   var body = ast.program.body;
 
   _.each(file.declarations, function (declar) {
-    body.unshift(b.variableDeclaration("var", [
-      b.variableDeclarator(declar.uid, declar.node)
+    body.unshift(t.variableDeclaration("var", [
+      t.variableDeclarator(declar.uid, declar.node)
     ]));
   });
 };

lib/6to5/transformation/transformers/_member-expression-keywords.js

@@ -0,0 +1,10 @@
+var esutils = require("esutils");
+var t = require("../../types");
+
+exports.MemberExpression = function (node) {
+  var prop = node.property;
+  if (t.isIdentifier(prop) && esutils.keyword.isKeywordES6(prop.name, true)) {
+    node.property = t.literal(prop.name);
+    node.computed = true;
+  }
+};

lib/6to5/transformation/transformers/_property-literals.js

@@ -0,0 +1,15 @@
+var esutils = require("esutils");
+var t       = require("../../types");
+var _       = require("lodash");
+
+exports.Property = function (node) {
+  // ignore key literals that are valid identifiers
+  var key = node.key;
+  if (t.isLiteral(key) && _.isString(key.value) && esutils.keyword.isIdentifierName(key.value)) {
+    key.type = "Identifier";
+    key.name = key.value;
+    delete key.value;
+
+    node.computed = false;
+  }
+};

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

@@ -0,0 +1,81 @@
+var util = require("../../util");
+var t    = require("../../types");
+var _    = require("lodash");
+
+var singleArrayExpression = function (node) {
+  var block = node.blocks[0];
+
+  var templateName = "array-expression-comprehension-map";
+  if (node.filter) templateName = "array-expression-comprehension-filter";
+
+  var result = util.template(templateName, {
+    STATEMENT: node.body,
+    FILTER:    node.filter,
+    ARRAY:     block.right,
+    KEY:       block.left
+  });
+
+  _.each([result.callee.object, result], function (call) {
+    if (t.isCallExpression(call)) {
+      call.arguments[0]._aliasFunction = true;
+    }
+  });
+
+  return result;
+};
+
+var multiple = function (node, file) {
+  var uid = file.generateUid("arr");
+
+  var container = util.template("array-comprehension-container", {
+    KEY: uid
+  });
+  container.callee.expression._aliasFunction = true;
+
+  var block = container.callee.expression.body;
+  var body  = block.body;
+
+  var returnStatement = body.pop();
+
+  body.push(exports._build(node, function () {
+    return util.template("array-push", {
+      STATEMENT: node.body,
+      KEY:       uid
+    }, true);
+  }));
+  body.push(returnStatement);
+
+  return container;
+};
+
+exports._build = function (node, buildBody) {
+  var self = node.blocks.shift();
+  if (!self) return;
+
+  var child = exports._build(node, buildBody);
+  if (!child) {
+    // last item
+    child = buildBody();
+
+    // add a filter as this is our final stop
+    if (node.filter) {
+      child = t.ifStatement(node.filter, t.blockStatement([child]));
+    }
+  }
+
+  return t.forOfStatement(
+    t.variableDeclaration("var", [t.variableDeclarator(self.left)]),
+    self.right,
+    t.blockStatement([child])
+  );
+};
+
+exports.ComprehensionExpression = function (node, parent, file) {
+  if (node.generator) return;
+
+  if (node.blocks.length === 1 && t.isArrayExpression(node.blocks[0].right)) {
+    return singleArrayExpression(node);
+  } else {
+    return multiple(node, file);
+  }
+};

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

@@ -1,9 +1,9 @@
-var util = require("../util");
+var t = require("../../types");
 
 exports.ArrowFunctionExpression = function (node) {
-  util.ensureBlock(node);
+  t.ensureBlock(node);
 
-  node._aliasFunction = "arrows";
+  node._aliasFunction = true;
   node.expression = false;
   node.type = "FunctionExpression";
 

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

@@ -0,0 +1,263 @@
+var traverse = require("../../traverse");
+var util     = require("../../util");
+var t        = require("../../types");
+var _        = require("lodash");
+
+exports.ClassDeclaration = function (node, parent, file, scope) {
+  return t.variableDeclaration("let", [
+    t.variableDeclarator(node.id, new Class(node, file, scope).run())
+  ]);
+};
+
+exports.ClassExpression = function (node, parent, file, scope) {
+  return new Class(node, file, scope).run();
+};
+
+var getMemberExpressionObject = function (node) {
+  while (t.isMemberExpression(node)) {
+    node = node.object;
+  }
+  return node;
+};
+
+/**
+ * Description
+ *
+ * @param {Node} node
+ * @param {File} file
+ * @param {Scope} scope
+ */
+
+function Class(node, file, scope) {
+  this.scope = scope;
+  this.node  = node;
+  this.file  = file;
+
+  this.instanceMutatorMap = {};
+  this.staticMutatorMap   = {};
+  this.hasConstructor     = false;
+  this.className          = node.id || t.identifier(file.generateUid("class", scope));
+  this.superName          = node.superClass;
+}
+
+/**
+ * Description
+ *
+ * @returns {Array}
+ */
+
+Class.prototype.run = function () {
+  var superClassArgument = this.superName;
+  var superClassCallee   = this.superName;
+  var superName          = this.superName;
+  var className          = this.className;
+  var file               = this.file;
+
+  if (superName) {
+    if (t.isMemberExpression(superName)) {
+      superClassArgument = superClassCallee = getMemberExpressionObject(superName);
+    } else if (!t.isIdentifier(superName)) {
+      superClassArgument = superName;
+      superClassCallee   = superName = t.identifier(file.generateUid("ref", this.scope));
+    }
+  }
+
+  this.superName = superName;
+
+  var container = util.template("class", {
+    CLASS_NAME: className
+  });
+
+  var block       = container.callee.expression.body;
+  var body        = this.body = block.body;
+  var constructor = this.constructor = body[0].declarations[0].init;
+
+  if (this.node.id) constructor.id = className;
+
+  var returnStatement = body.pop();
+
+  if (superName) {
+    body.push(t.expressionStatement(t.callExpression(file.addDeclaration("extends"), [className, superName])));
+
+    container.arguments.push(superClassArgument);
+    container.callee.expression.params.push(superClassCallee);
+  }
+
+  this.buildBody();
+
+  if (body.length === 1) {
+    // only a constructor so no need for a closure container
+    return constructor;
+  } else {
+    body.push(returnStatement);
+    return container;
+  }
+};
+
+/**
+ * Description
+ */
+
+Class.prototype.buildBody = function () {
+  var constructor = this.constructor;
+  var className   = this.className;
+  var superName   = this.superName;
+  var classBody   = this.node.body.body;
+  var body        = this.body;
+  var self        = this;
+
+  _.each(classBody, function (node) {
+    self.replaceInstanceSuperReferences(node);
+
+    if (node.key.name === "constructor") {
+      self.pushConstructor(node);
+    } else {
+      self.pushMethod(node);
+    }
+  });
+
+  if (!this.hasConstructor && superName) {
+    constructor.body.body.push(util.template("class-super-constructor-call", {
+      SUPER_NAME: superName
+    }, true));
+  }
+
+  var instanceProps;
+  var staticProps;
+
+  if (!_.isEmpty(this.instanceMutatorMap)) {
+    var protoId = util.template("prototype-identifier", {
+      CLASS_NAME: className
+    });
+
+    instanceProps = util.buildDefineProperties(this.instanceMutatorMap, protoId);
+  }
+
+  if (!_.isEmpty(this.staticMutatorMap)) {
+    staticProps = util.buildDefineProperties(this.staticMutatorMap, className);
+  }
+
+  if (instanceProps || staticProps) {
+    staticProps = staticProps || t.literal(null);
+
+    var args = [className, staticProps];
+    if (instanceProps) args.push(instanceProps);
+
+    body.push(t.expressionStatement(
+      t.callExpression(this.file.addDeclaration("class-props"), args)
+    ));
+  }
+};
+
+/**
+ * Push a method to it's respective mutatorMap.
+ *
+ * @param {Node} node MethodDefinition
+ */
+
+Class.prototype.pushMethod = function (node) {
+  var methodName = node.key;
+
+  var mutatorMap = this.instanceMutatorMap;
+  if (node.static) mutatorMap = this.staticMutatorMap;
+
+  var kind = node.kind;
+
+  if (kind === "") {
+    kind = "value";
+    util.pushMutatorMap(mutatorMap, methodName, "writable", t.identifier("true"));
+  }
+
+  util.pushMutatorMap(mutatorMap, methodName, kind, node);
+};
+
+/**
+ * Given a `methodNode`, produce a `MemberExpression` super class reference.
+ *
+ * @param {Node} methodNode MethodDefinition
+ * @param {Node} node Identifier
+ * @param {Node} parent
+ *
+ * @returns {Node}
+ */
+
+Class.prototype.superIdentifier = function (methodNode, id, parent) {
+  var methodName = methodNode.key;
+  var superName  = this.superName || t.identifier("Function");
+
+  if (parent.property === id) {
+    return;
+  } else if (t.isCallExpression(parent, { callee: id })) {
+    // super(); -> ClassName.prototype.MethodName.call(this);
+    parent.arguments.unshift(t.thisExpression());
+
+    if (methodName.name === "constructor") {
+      // constructor() { super(); }
+      return t.memberExpression(superName, t.identifier("call"));
+    } else {
+      id = superName;
+
+      // foo() { super(); }
+      if (!methodNode.static) {
+        id = t.memberExpression(id, t.identifier("prototype"));
+      }
+
+      id = t.memberExpression(id, methodName, methodNode.computed);
+      return t.memberExpression(id, t.identifier("call"));
+    }
+  } else if (t.isMemberExpression(parent) && !methodNode.static) {
+    // super.test -> ClassName.prototype.test
+    return t.memberExpression(superName, t.identifier("prototype"));
+  } else {
+    return superName;
+  }
+};
+
+/**
+ * Replace all `super` references with a reference to our `superClass`.
+ *
+ * @param {Node} methodNode MethodDefinition
+ */
+
+Class.prototype.replaceInstanceSuperReferences = function (methodNode) {
+  var method = methodNode.value;
+  var self = this;
+
+  traverse(method, function (node, parent) {
+    if (t.isIdentifier(node, { name: "super" })) {
+      return self.superIdentifier(methodNode, node, parent);
+    } else if (t.isCallExpression(node)) {
+      var callee = node.callee;
+      if (!t.isMemberExpression(callee)) return;
+      if (callee.object.name !== "super") return;
+
+      // super.test(); -> ClassName.prototype.MethodName.call(this);
+      callee.property = t.memberExpression(callee.property, t.identifier("call"));
+      node.arguments.unshift(t.thisExpression());
+    }
+  });
+};
+
+/**
+ * Replace the constructor body of our class.
+ *
+ * @param {Node} method MethodDefinition
+ */
+
+Class.prototype.pushConstructor = function (method) {
+  if (method.kind !== "") {
+    throw this.file.errorWithNode(method, "illegal kind for constructor method");
+  }
+
+  var construct = this.constructor;
+  var fn        = method.value;
+
+  this.hasConstructor = true;
+  t.inherits(construct, fn);
+  t.inheritsComments(construct, method);
+
+  construct.defaults = fn.defaults;
+  construct.params   = fn.params;
+  construct.body     = fn.body;
+  construct.rest     = fn.rest;
+};

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

@@ -1,5 +1,5 @@
-var util = require("../util");
-var b    = require("acorn-ast-types").builders;
+var util = require("../../util");
+var t    = require("../../types");
 var _    = require("lodash");
 
 exports.ObjectExpression = function (node, parent, file) {
@@ -26,17 +26,17 @@ exports.ObjectExpression = function (node, parent, file) {
     OBJECT: node
   });
 
-  var containerCallee = container.callee;
+  var containerCallee = container.callee.expression;
   var containerBody = containerCallee.body.body;
 
-  containerCallee._aliasFunction = "arrows";
+  containerCallee._aliasFunction = true;
 
   _.each(computed, function (prop) {
     containerBody.unshift(
-      b.expressionStatement(
-        b.assignmentExpression(
+      t.expressionStatement(
+        t.assignmentExpression(
           "=",
-          b.memberExpression(objId, prop.key, true),
+          t.memberExpression(objId, prop.key, true),
           prop.value
         )
       )

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

@@ -0,0 +1,54 @@
+var traverse = require("../../traverse");
+var t        = require("../../types");
+var _        = require("lodash");
+
+exports.Program =
+exports.BlockStatement =
+exports.ForInStatement =
+exports.ForOfStatement =
+exports.ForStatement = function (node, parent, file) {
+  var constants = {};
+
+  var check = function (parent, names) {
+    _.each(names, function (nameNode, name) {
+      if (!_.has(constants, name)) return;
+      if (parent && t.isBlockStatement(parent) && parent !== constants[name]) return;
+
+      throw file.errorWithNode(nameNode, name + " is read-only");
+    });
+  };
+
+  var getIds = function (node) {
+    return t.getIds(node, true, ["MemberExpression"]);
+  };
+
+  _.each(node.body, function (child, parent) {
+    if (child && t.isVariableDeclaration(child, { kind: "const" })) {
+      _.each(child.declarations, function (declar) {
+        _.each(getIds(declar), function (nameNode, name) {
+          var names = {};
+          names[name] = nameNode;
+          check(parent, names);
+
+          constants[name] = parent;
+        });
+
+        declar._ignoreConstant = true;
+      });
+
+      child._ignoreConstant = true;
+      child.kind = "let";
+    }
+  });
+
+  if (_.isEmpty(constants)) return;
+
+  traverse(node, function (child, parent) {
+    if (child._ignoreConstant) return;
+    if (t.isVariableDeclaration(child)) return;
+
+    if (t.isVariableDeclarator(child) || t.isDeclaration(child) || t.isAssignmentExpression(child)) {
+      check(parent, getIds(child));
+    }
+  });
+};

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

@@ -0,0 +1,70 @@
+var traverse = require("../../traverse");
+var util     = require("../../util");
+var t        = require("../../types");
+var _        = require("lodash");
+
+exports.Function = function (node, parent, file, scope) {
+  if (!node.defaults || !node.defaults.length) return;
+  t.ensureBlock(node);
+
+  var ids = node.params.map(function (param) {
+    return t.getIds(param);
+  });
+
+  var closure = false;
+
+  _.each(node.defaults, function (def, i) {
+    if (!def) return;
+
+    var param = node.params[i];
+
+    // temporal dead zone check - here we prevent accessing of params that
+    // are to the right - ie. uninitialized parameters
+    _.each(ids.slice(i), function (ids) {
+      var check = function (node, parent) {
+        if (!t.isIdentifier(node) || !t.isReferenced(node, parent)) return;
+
+        if (_.contains(ids, node.name)) {
+          throw file.errorWithNode(node, "Temporal dead zone - accessing a variable before it's initialized");
+        }
+
+        if (scope.has(node.name)) {
+          closure = true;
+        }
+      };
+
+      check(def, node);
+      traverse(def, check);
+    });
+
+    // we're accessing a variable that's already defined within this function
+    var has = scope.get(param.name);
+    if (has && !_.contains(node.params, has)) {
+      closure = true;
+    }
+  });
+
+  var body = [];
+
+  _.each(node.defaults, function (def, i) {
+    if (!def) return;
+
+    body.push(util.template("if-undefined-set-to", {
+      VARIABLE: node.params[i],
+      DEFAULT:  def
+    }, true));
+  });
+
+  if (closure) {
+    var container = t.functionExpression(null, [], node.body, node.generator);
+    container._aliasFunction = true;
+
+    body.push(t.returnStatement(t.callExpression(container, [])));
+
+    node.body = t.blockStatement(body);
+  } else {
+    node.body.body = body.concat(node.body.body);
+  }
+
+  node.defaults = [];
+};

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

@@ -0,0 +1,204 @@
+var t = require("../../types");
+var _ = require("lodash");
+
+var buildVariableAssign = function (kind, id, init) {
+  if (kind === false) {
+    return t.expressionStatement(t.assignmentExpression("=", id, init));
+  } else {
+    return t.variableDeclaration(kind, [
+      t.variableDeclarator(id, init)
+    ]);
+  }
+};
+
+var push = function (kind, nodes, elem, parentId) {
+  if (t.isObjectPattern(elem)) {
+    pushObjectPattern(kind, nodes, elem, parentId);
+  } else if (t.isArrayPattern(elem)) {
+    pushArrayPattern(kind, nodes, elem, parentId);
+  } else if (t.isMemberExpression(elem)) {
+    nodes.push(buildVariableAssign(false, elem, parentId));
+  } else {
+    nodes.push(buildVariableAssign(kind, elem, parentId));
+  }
+};
+
+var pushObjectPattern = function (kind, nodes, pattern, parentId) {
+  _.each(pattern.properties, function (prop) {
+    var pattern2   = prop.value;
+    var patternId2 = t.memberExpression(parentId, prop.key);
+
+    if (t.isPattern(pattern2)) {
+      push(kind, nodes, pattern2, patternId2);
+    } else {
+      nodes.push(buildVariableAssign(kind, pattern2, patternId2));
+    }
+  });
+};
+
+var pushArrayPattern = function (kind, nodes, pattern, parentId) {
+  _.each(pattern.elements, function (elem, i) {
+    if (!elem) return;
+
+    var newPatternId;
+
+    if (t.isSpreadElement(elem)) {
+      newPatternId = t.callExpression(t.memberExpression(parentId, t.identifier("slice")), [t.literal(i)]);
+      elem = elem.argument;
+    } else {
+      newPatternId = t.memberExpression(parentId, t.literal(i), true);
+    }
+
+    push(kind, nodes, elem, newPatternId);
+  });
+};
+
+var pushPattern = function (opts) {
+  var kind = opts.kind;
+  var nodes = opts.nodes;
+  var pattern = opts.pattern;
+  var parentId = opts.id;
+  var file = opts.file;
+  var scope = opts.scope;
+
+  if (!t.isMemberExpression(parentId) && !t.isIdentifier(parentId)) {
+    var key = t.identifier(file.generateUid("ref", scope));
+
+    nodes.push(t.variableDeclaration("var", [
+      t.variableDeclarator(key, parentId)
+    ]));
+
+    parentId = key;
+  }
+
+  push(kind, nodes, pattern, parentId);
+};
+
+exports.ForInStatement =
+exports.ForOfStatement = function (node, parent, file, scope) {
+  var declar = node.left;
+  if (!t.isVariableDeclaration(declar)) return;
+
+  var pattern = declar.declarations[0].id;
+  if (!t.isPattern(pattern)) return;
+
+  var key = t.identifier(file.generateUid("ref", scope));
+  node.left = t.variableDeclaration(declar.kind, [
+    t.variableDeclarator(key, null)
+  ]);
+
+  var nodes = [];
+
+  push(declar.kind, nodes, pattern, key);
+
+  t.ensureBlock(node);
+
+  var block = node.body;
+  block.body = nodes.concat(block.body);
+};
+
+exports.Function = function (node, parent, file, scope) {
+  var nodes = [];
+
+  var hasDestructuring = false;
+
+  node.params = node.params.map(function (pattern) {
+    if (!t.isPattern(pattern)) return pattern;
+
+    hasDestructuring = true;
+    var parentId = t.identifier(file.generateUid("ref", scope));
+
+    pushPattern({
+      kind:    "var",
+      nodes:   nodes,
+      pattern: pattern,
+      id:      parentId,
+      file:    file,
+      scope:   scope
+    });
+
+    return parentId;
+  });
+
+  if (!hasDestructuring) return;
+
+  t.ensureBlock(node);
+
+  var block = node.body;
+  block.body = nodes.concat(block.body);
+};
+
+exports.ExpressionStatement = function (node, parent, file, scope) {
+  var expr = node.expression;
+  if (expr.type !== "AssignmentExpression") return;
+
+  if (!t.isPattern(expr.left)) return;
+
+  var nodes = [];
+
+  var ref = t.identifier(file.generateUid("ref", scope));
+  nodes.push(t.variableDeclaration("var", [
+    t.variableDeclarator(ref, expr.right)
+  ]));
+
+  push(false, nodes, expr.left, ref);
+
+  return nodes;
+};
+
+exports.AssignmentExpression = function (node, parent, file) {
+  if (parent.type === "ExpressionStatement") return;
+  if (!t.isPattern(node.left)) return;
+  throw file.errorWithNode(node, "AssignmentExpression destructuring outside of a ExpressionStatement is forbidden due to current 6to5 limitations");
+};
+
+exports.VariableDeclaration = function (node, parent, file, scope) {
+  if (t.isForInStatement(parent) || t.isForOfStatement(parent)) return;
+
+  var nodes = [];
+
+  var hasPattern = false;
+  _.each(node.declarations, function (declar) {
+    if (t.isPattern(declar.id)) {
+      hasPattern = true;
+      return false;
+    }
+  });
+  if (!hasPattern) return;
+
+  _.each(node.declarations, function (declar) {
+    var patternId = declar.init;
+    var pattern   = declar.id;
+    if (t.isPattern(pattern) && patternId) {
+      pushPattern({
+        kind:    node.kind,
+        nodes:   nodes,
+        pattern: pattern,
+        id:      patternId,
+        file:    file,
+        scope:   scope
+      });
+    } else {
+      nodes.push(buildVariableAssign(node.kind, declar.id, declar.init));
+    }
+  });
+
+  if (!t.isProgram(parent) && !t.isBlockStatement(parent)) {
+    var declar;
+
+    _.each(nodes, function (node) {
+      declar = declar || t.variableDeclaration(node.kind, []);
+
+      if (!t.isVariableDeclaration(node) && declar.kind !== node.kind) {
+        throw file.errorWithNode(node, "Cannot use this node within the current parent");
+      }
+
+      declar.declarations = declar.declarations.concat(node.declarations);
+    });
+
+    return declar;
+  }
+
+  return nodes;
+};
+

lib/6to5/transformation/transformers/for-of.js

@@ -0,0 +1,34 @@
+var util = require("../../util");
+var t    = require("../../types");
+
+exports.ForOfStatement = function (node, parent, file, scope) {
+  var left = node.left;
+  var declar;
+
+  var stepKey   = t.identifier(file.generateUid("step", scope));
+  var stepValue = t.memberExpression(stepKey, t.identifier("value"));
+
+  if (t.isIdentifier(left)) {
+    declar = t.expressionStatement(t.assignmentExpression("=", left, stepValue));
+  } else if (t.isVariableDeclaration(left)) {
+    declar = t.variableDeclaration(left.kind, [
+      t.variableDeclarator(left.declarations[0].id, stepValue)
+    ]);
+  } else {
+    throw file.errorWithNode(left, "Unknown node type " + left.type + " in ForOfStatement");
+  }
+
+  var node2 = util.template("for-of", {
+    ITERATOR_KEY: file.generateUid("iterator", scope),
+    STEP_KEY:     stepKey,
+    OBJECT:       node.right
+  });
+
+  t.ensureBlock(node);
+
+  var block = node2.body;
+  block.body.push(declar);
+  block.body = block.body.concat(node.body.body);
+
+  return node2;
+};

lib/6to5/transformation/transformers/generator-comprehension.js

@@ -0,0 +1,15 @@
+var arrayComprehension = require("./array-comprehension");
+var t                  = require("../../types");
+
+exports.ComprehensionExpression = function (node) {
+  if (!node.generator) return;
+
+  var body = [];
+  var container = t.functionExpression(null, [], t.blockStatement(body), true);
+
+  body.push(arrayComprehension._build(node, function () {
+    return t.expressionStatement(t.yieldExpression(node.body));
+  }));
+
+  return t.callExpression(container, []);
+};

lib/6to5/transformation/transformers/generators/hoist.js

@@ -0,0 +1,151 @@
+/**
+ * Copyright (c) 2014, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * https://raw.githut.com/facebook/regenerator/master/LICENSE file. An
+ * additional grant of patent rights can be found in the PATENTS file in
+ * the same directory.
+ */
+
+var assert = require("assert");
+var types  = require("ast-types");
+var t      = require("../../../types");
+var _      = require("lodash");
+
+// The hoist function takes a FunctionExpression or FunctionDeclaration
+// and replaces any Declaration nodes in its body with assignments, then
+// returns a VariableDeclaration containing just the names of the removed
+// declarations.
+exports.hoist = function(funPath) {
+  assert.ok(funPath instanceof types.NodePath);
+  t.assertFunction(funPath.value);
+
+  var vars = {};
+
+  function varDeclToExpr(vdec, includeIdentifiers) {
+    t.assertVariableDeclaration(vdec);
+    var exprs = [];
+
+    vdec.declarations.forEach(function(dec) {
+      vars[dec.id.name] = dec.id;
+
+      if (dec.init) {
+        exprs.push(t.assignmentExpression(
+          "=", dec.id, dec.init
+        ));
+      } else if (includeIdentifiers) {
+        exprs.push(dec.id);
+      }
+    });
+
+    if (exprs.length === 0)
+      return null;
+
+    if (exprs.length === 1)
+      return exprs[0];
+
+    return t.sequenceExpression(exprs);
+  }
+
+  types.visit(funPath.get("body"), {
+    visitVariableDeclaration: function(path) {
+      var expr = varDeclToExpr(path.value, false);
+      if (expr === null) {
+        path.replace();
+      } else {
+        // We don't need to traverse this expression any further because
+        // there can't be any new declarations inside an expression.
+        return t.expressionStatement(expr);
+      }
+
+      // Since the original node has been either removed or replaced,
+      // avoid traversing it any further.
+      return false;
+    },
+
+    visitForStatement: function(path) {
+      var init = path.value.init;
+      if (t.isVariableDeclaration(init)) {
+        path.get("init").replace(varDeclToExpr(init, false));
+      }
+      this.traverse(path);
+    },
+
+    visitForInStatement: function(path) {
+      var left = path.value.left;
+      if (t.isVariableDeclaration(left)) {
+        path.get("left").replace(varDeclToExpr(left, true));
+      }
+      this.traverse(path);
+    },
+
+    visitFunctionDeclaration: function(path) {
+      var node = path.value;
+      vars[node.id.name] = node.id;
+
+      var assignment = t.expressionStatement(
+        t.assignmentExpression(
+          "=",
+          node.id,
+          t.functionExpression(
+            node.id,
+            node.params,
+            node.body,
+            node.generator,
+            node.expression
+          )
+        )
+      );
+
+      if (t.isBlockStatement(path.parent.node)) {
+        // Insert the assignment form before the first statement in the
+        // enclosing block.
+        path.parent.get("body").unshift(assignment);
+
+        // Remove the function declaration now that we've inserted the
+        // equivalent assignment form at the beginning of the block.
+        path.replace();
+
+      } else {
+        // If the parent node is not a block statement, then we can just
+        // replace the declaration with the equivalent assignment form
+        // without worrying about hoisting it.
+        path.replace(assignment);
+      }
+
+      // Don't hoist variables out of inner functions.
+      return false;
+    },
+
+    visitFunctionExpression: function() {
+      // Don't descend into nested function expressions.
+      return false;
+    }
+  });
+
+  var paramNames = {};
+  funPath.get("params").each(function(paramPath) {
+    var param = paramPath.value;
+    if (t.isIdentifier(param)) {
+      paramNames[param.name] = param;
+    } else {
+      // Variables declared by destructuring parameter patterns will be
+      // harmlessly re-declared.
+    }
+  });
+
+  var declarations = [];
+
+  Object.keys(vars).forEach(function(name) {
+    if (!_.has(paramNames, name)) {
+      declarations.push(t.variableDeclarator(vars[name], null));
+    }
+  });
+
+  if (declarations.length === 0) {
+    return null; // Be sure to handle this case!
+  }
+
+  return t.variableDeclaration("var", declarations);
+};

lib/6to5/transformation/transformers/generators/index.js

@@ -0,0 +1 @@
+module.exports = require("./visit").transform;

lib/6to5/transformation/transformers/generators/leap.js

@@ -0,0 +1,163 @@
+/**
+ * Copyright (c) 2014, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * https://raw.github.com/facebook/regenerator/master/LICENSE file. An
+ * additional grant of patent rights can be found in the PATENTS file in
+ * the same directory.
+ */
+
+exports.FunctionEntry = FunctionEntry;
+exports.FinallyEntry  = FinallyEntry;
+exports.SwitchEntry   = SwitchEntry;
+exports.LeapManager   = LeapManager;
+exports.CatchEntry    = CatchEntry;
+exports.LoopEntry     = LoopEntry;
+exports.TryEntry      = TryEntry;
+
+var assert = require("assert");
+var util   = require("util");
+var t      = require("../../../types");
+
+var inherits = util.inherits;
+
+function Entry() {
+  assert.ok(this instanceof Entry);
+}
+
+function FunctionEntry(returnLoc) {
+  Entry.call(this);
+
+  t.assertLiteral(returnLoc);
+
+  this.returnLoc = returnLoc;
+}
+
+inherits(FunctionEntry, Entry);
+
+function LoopEntry(breakLoc, continueLoc, label) {
+  Entry.call(this);
+
+  t.assertLiteral(breakLoc);
+  t.assertLiteral(continueLoc);
+
+  if (label) {
+    t.assertIdentifier(label);
+  } else {
+    label = null;
+  }
+
+  this.breakLoc = breakLoc;
+  this.continueLoc = continueLoc;
+  this.label = label;
+}
+
+inherits(LoopEntry, Entry);
+
+function SwitchEntry(breakLoc) {
+  Entry.call(this);
+
+  t.assertLiteral(breakLoc);
+
+  this.breakLoc = breakLoc;
+}
+
+inherits(SwitchEntry, Entry);
+
+function TryEntry(firstLoc, catchEntry, finallyEntry) {
+  Entry.call(this);
+
+  t.assertLiteral(firstLoc);
+
+  if (catchEntry) {
+    assert.ok(catchEntry instanceof CatchEntry);
+  } else {
+    catchEntry = null;
+  }
+
+  if (finallyEntry) {
+    assert.ok(finallyEntry instanceof FinallyEntry);
+  } else {
+    finallyEntry = null;
+  }
+
+  // Have to have one or the other (or both).
+  assert.ok(catchEntry || finallyEntry);
+
+  this.firstLoc = firstLoc;
+  this.catchEntry = catchEntry;
+  this.finallyEntry = finallyEntry;
+}
+
+inherits(TryEntry, Entry);
+
+function CatchEntry(firstLoc, paramId) {
+  Entry.call(this);
+
+  t.assertLiteral(firstLoc);
+  t.assertIdentifier(paramId);
+
+  this.firstLoc = firstLoc;
+  this.paramId = paramId;
+}
+
+inherits(CatchEntry, Entry);
+
+function FinallyEntry(firstLoc) {
+  Entry.call(this);
+
+  t.assertLiteral(firstLoc);
+
+  this.firstLoc = firstLoc;
+}
+
+inherits(FinallyEntry, Entry);
+
+function LeapManager(emitter) {
+  assert.ok(this instanceof LeapManager);
+
+  var Emitter = require("./emit").Emitter;
+  assert.ok(emitter instanceof Emitter);
+
+  this.emitter = emitter;
+  this.entryStack = [new FunctionEntry(emitter.finalLoc)];
+}
+
+LeapManager.prototype.withEntry = function(entry, callback) {
+  assert.ok(entry instanceof Entry);
+  this.entryStack.push(entry);
+  try {
+    callback.call(this.emitter);
+  } finally {
+    var popped = this.entryStack.pop();
+    assert.strictEqual(popped, entry);
+  }
+};
+
+LeapManager.prototype._findLeapLocation = function(property, label) {
+  for (var i = this.entryStack.length - 1; i >= 0; --i) {
+    var entry = this.entryStack[i];
+    var loc = entry[property];
+    if (loc) {
+      if (label) {
+        if (entry.label &&
+            entry.label.name === label.name) {
+          return loc;
+        }
+      } else {
+        return loc;
+      }
+    }
+  }
+
+  return null;
+};
+
+LeapManager.prototype.getBreakLoc = function(label) {
+  return this._findLeapLocation("breakLoc", label);
+};
+
+LeapManager.prototype.getContinueLoc = function(label) {
+  return this._findLeapLocation("continueLoc", label);
+};

lib/6to5/transformation/transformers/generators/meta.js

@@ -0,0 +1,98 @@
+/**
+ * Copyright (c) 2014, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * https://raw.github.com/facebook/regenerator/master/LICENSE file. An
+ * additional grant of patent rights can be found in the PATENTS file in
+ * the same directory.
+ */
+
+var assert = require("assert");
+var types  = require("ast-types");
+var m      = require("private").makeAccessor();
+var _      = require("lodash");
+
+var isArray = types.builtInTypes.array;
+var n       = types.namedTypes;
+
+function makePredicate(propertyName, knownTypes) {
+  function onlyChildren(node) {
+    n.Node.check(node);
+
+    // Assume no side effects until we find out otherwise.
+    var result = false;
+
+    function check(child) {
+      if (result) {
+        // Do nothing.
+      } else if (isArray.check(child)) {
+        child.some(check);
+      } else if (n.Node.check(child)) {
+        assert.strictEqual(result, false);
+        result = predicate(child);
+      }
+      return result;
+    }
+
+    types.eachField(node, function(name, child) {
+      check(child);
+    });
+
+    return result;
+  }
+
+  function predicate(node) {
+    n.Node.check(node);
+
+    var meta = m(node);
+    if (_.has(meta, propertyName)) return meta[propertyName];
+
+    // Certain types are "opaque," which means they have no side
+    // effects or leaps and we don't care about their subexpressions.
+    if (_.has(opaqueTypes, node.type)) return meta[propertyName] = false;
+
+    if (_.has(knownTypes, node.type)) return meta[propertyName] = true;
+
+    return meta[propertyName] = onlyChildren(node);
+  }
+
+  predicate.onlyChildren = onlyChildren;
+
+  return predicate;
+}
+
+var opaqueTypes = {
+  FunctionExpression: true
+};
+
+// These types potentially have side effects regardless of what side
+// effects their subexpressions have.
+var sideEffectTypes = {
+  CallExpression: true, // Anything could happen!
+  ForInStatement: true, // Modifies the key variable.
+  UnaryExpression: true, // Think delete.
+  BinaryExpression: true, // Might invoke .toString() or .valueOf().
+  AssignmentExpression: true, // Side-effecting by definition.
+  UpdateExpression: true, // Updates are essentially assignments.
+  NewExpression: true // Similar to CallExpression.
+};
+
+// These types are the direct cause of all leaps in control flow.
+var leapTypes = {
+  YieldExpression: true,
+  BreakStatement: true,
+  ContinueStatement: true,
+  ReturnStatement: true,
+  ThrowStatement: true
+};
+
+// All leap types are also side effect types.
+for (var type in leapTypes) {
+  if (_.has(leapTypes, type)) {
+    sideEffectTypes[type] = leapTypes[type];
+  }
+}
+
+exports.hasSideEffects = makePredicate("hasSideEffects", sideEffectTypes);
+exports.containsLeap = makePredicate("containsLeap", leapTypes);

lib/6to5/transformation/transformers/generators/runtime.js

@@ -0,0 +1,454 @@
+/**
+* Copyright (c) 2014, Facebook, Inc.
+* All rights reserved.
+*
+* This source code is licensed under the BSD-style license found in the
+* https://raw.github.com/facebook/regenerator/master/LICENSE file. An
+* additional grant of patent rights can be found in the PATENTS file in
+* the same directory.
+*/
+
+var iteratorSymbol = typeof Symbol === "function" && Symbol.iterator || "@@iterator";
+var runtime = global.regeneratorRuntime = exports;
+var hasOwn = Object.prototype.hasOwnProperty;
+
+var wrap = runtime.wrap = function wrap(innerFn, outerFn, self, tryList) {
+  return new Generator(innerFn, outerFn, self || null, tryList || []);
+};
+
+var GenStateSuspendedStart = "suspendedStart";
+var GenStateSuspendedYield = "suspendedYield";
+var GenStateExecuting = "executing";
+var GenStateCompleted = "completed";
+
+// Returning this object from the innerFn has the same effect as
+// breaking out of the dispatch switch statement.
+var ContinueSentinel = {};
+
+// Dummy constructor that we use as the .constructor property for
+// functions that return Generator objects.
+var GF = function GeneratorFunction() {};
+var GFp = function GeneratorFunctionPrototype() {};
+var Gp = GFp.prototype = Generator.prototype;
+(GFp.constructor = GF).prototype =
+  Gp.constructor = GFp;
+
+// Ensure isGeneratorFunction works when Function#name not supported.
+var GFName = "GeneratorFunction";
+if (GF.name !== GFName) GF.name = GFName;
+if (GF.name !== GFName) throw new Error(GFName + " renamed?");
+
+runtime.isGeneratorFunction = function(genFun) {
+  var ctor = genFun && genFun.constructor;
+  return ctor ? GF.name === ctor.name : false;
+};
+
+runtime.mark = function(genFun) {
+  genFun.__proto__ = GFp;
+  genFun.prototype = Object.create(Gp);
+  return genFun;
+};
+
+runtime.async = function(innerFn, outerFn, self, tryList) {
+  return new Promise(function(resolve, reject) {
+    var generator = wrap(innerFn, outerFn, self, tryList);
+    var callNext = step.bind(generator.next);
+    var callThrow = step.bind(generator["throw"]);
+
+    function step(arg) {
+      var info;
+      var value;
+
+      try {
+        info = this(arg);
+        value = info.value;
+      } catch (error) {
+        return reject(error);
+      }
+
+      if (info.done) {
+        resolve(value);
+      } else {
+        Promise.resolve(value).then(callNext, callThrow);
+      }
+    }
+
+    callNext();
+  });
+};
+
+function Generator(innerFn, outerFn, self, tryList) {
+  var generator = outerFn ? Object.create(outerFn.prototype) : this;
+  var context = new Context(tryList);
+  var state = GenStateSuspendedStart;
+
+  function invoke(method, arg) {
+    if (state === GenStateExecuting) {
+      throw new Error("Generator is already running");
+    }
+
+    if (state === GenStateCompleted) {
+      throw new Error("Generator has already finished");
+    }
+
+    while (true) {
+      var delegate = context.delegate;
+      var info;
+
+      if (delegate) {
+        try {
+          info = delegate.iterator[method](arg);
+
+          // Delegate generator ran and handled its own exceptions so
+          // regardless of what the method was, we continue as if it is
+          // "next" with an undefined arg.
+          method = "next";
+          arg = undefined;
+
+        } catch (uncaught) {
+          context.delegate = null;
+
+          // Like returning generator.throw(uncaught), but without the
+          // overhead of an extra function call.
+          method = "throw";
+          arg = uncaught;
+
+          continue;
+        }
+
+        if (info.done) {
+          context[delegate.resultName] = info.value;
+          context.next = delegate.nextLoc;
+        } else {
+          state = GenStateSuspendedYield;
+          return info;
+        }
+
+        context.delegate = null;
+      }
+
+      if (method === "next") {
+        if (state === GenStateSuspendedStart &&
+            typeof arg !== "undefined") {
+          // https://people.mozilla.org/~jorendorff/es6-draft.html#sec-generatorresume
+          throw new TypeError(
+            "attempt to send " + JSON.stringify(arg) + " to newborn generator"
+          );
+        }
+
+        if (state === GenStateSuspendedYield) {
+          context.sent = arg;
+        } else {
+          delete context.sent;
+        }
+
+      } else if (method === "throw") {
+        if (state === GenStateSuspendedStart) {
+          state = GenStateCompleted;
+          throw arg;
+        }
+
+        if (context.dispatchException(arg)) {
+          // If the dispatched exception was caught by a catch block,
+          // then let that catch block handle the exception normally.
+          method = "next";
+          arg = undefined;
+        }
+
+      } else if (method === "return") {
+        context.abrupt("return", arg);
+      }
+
+      state = GenStateExecuting;
+
+      try {
+        var value = innerFn.call(self, context);
+
+        // If an exception is thrown from innerFn, we leave state ===
+        // GenStateExecuting and loop back for another invocation.
+        state = context.done ? GenStateCompleted : GenStateSuspendedYield;
+
+        info = {
+          value: value,
+          done: context.done
+        };
+
+        if (value === ContinueSentinel) {
+          if (context.delegate && method === "next") {
+            // Deliberately forget the last sent value so that we don't
+            // accidentally pass it on to the delegate.
+            arg = undefined;
+          }
+        } else {
+          return info;
+        }
+
+      } catch (thrown) {
+        state = GenStateCompleted;
+
+        if (method === "next") {
+          context.dispatchException(thrown);
+        } else {
+          arg = thrown;
+        }
+      }
+    }
+  }
+
+  generator.next = invoke.bind(generator, "next");
+  generator["throw"] = invoke.bind(generator, "throw");
+  generator["return"] = invoke.bind(generator, "return");
+
+  return generator;
+}
+
+Gp[iteratorSymbol] = function() {
+  return this;
+};
+
+Gp.toString = function() {
+  return "[object Generator]";
+};
+
+function pushTryEntry(triple) {
+  var entry = { tryLoc: triple[0] };
+
+  if (1 in triple) {
+    entry.catchLoc = triple[1];
+  }
+
+  if (2 in triple) {
+    entry.finallyLoc = triple[2];
+  }
+
+  this.tryEntries.push(entry);
+}
+
+function resetTryEntry(entry, i) {
+  var record = entry.completion || {};
+  record.type = i === 0 ? "normal" : "return";
+  delete record.arg;
+  entry.completion = record;
+}
+
+function Context(tryList) {
+  // The root entry object (effectively a try statement without a catch
+  // or a finally block) gives us a place to store values thrown from
+  // locations where there is no enclosing try statement.
+  this.tryEntries = [{ tryLoc: "root" }];
+  tryList.forEach(pushTryEntry, this);
+  this.reset();
+}
+
+runtime.keys = function(object) {
+  var keys = [];
+  for (var key in object) {
+    keys.push(key);
+  }
+  keys.reverse();
+
+  // Rather than returning an object with a next method, we keep
+  // things simple and return the next function itself.
+  return function next() {
+    while (keys.length) {
+      var key = keys.pop();
+      if (key in object) {
+        next.value = key;
+        next.done = false;
+        return next;
+      }
+    }
+
+    // To avoid creating an additional object, we just hang the .value
+    // and .done properties off the next function object itself. This
+    // also ensures that the minifier will not anonymize the function.
+    next.done = true;
+    return next;
+  };
+};
+
+function values(iterable) {
+  var iterator = iterable;
+  if (iteratorSymbol in iterable) {
+    iterator = iterable[iteratorSymbol]();
+  } else if (!isNaN(iterable.length)) {
+    var i = -1;
+    iterator = function next() {
+      while (++i < iterable.length) {
+        if (i in iterable) {
+          next.value = iterable[i];
+          next.done = false;
+          return next;
+        }
+      }
+      next.done = true;
+      return next;
+    };
+    iterator.next = iterator;
+  }
+  return iterator;
+}
+runtime.values = values;
+
+Context.prototype = {
+  constructor: Context,
+
+  reset: function() {
+    this.prev = 0;
+    this.next = 0;
+    this.sent = undefined;
+    this.done = false;
+    this.delegate = null;
+
+    this.tryEntries.forEach(resetTryEntry);
+
+    // Pre-initialize at least 20 temporary variables to enable hidden
+    // class optimizations for simple generators.
+    for (var tempIndex = 0, tempName;
+         hasOwn.call(this, tempName = "t" + tempIndex) || tempIndex < 20;
+         ++tempIndex) {
+      this[tempName] = null;
+    }
+  },
+
+  stop: function() {
+    this.done = true;
+
+    var rootEntry = this.tryEntries[0];
+    var rootRecord = rootEntry.completion;
+    if (rootRecord.type === "throw") {
+      throw rootRecord.arg;
+    }
+
+    return this.rval;
+  },
+
+  dispatchException: function(exception) {
+    if (this.done) {
+      throw exception;
+    }
+
+    var context = this;
+    function handle(loc, caught) {
+      record.type = "throw";
+      record.arg = exception;
+      context.next = loc;
+      return !!caught;
+    }
+
+    for (var i = this.tryEntries.length - 1; i >= 0; --i) {
+      var entry = this.tryEntries[i];
+      var record = entry.completion;
+
+      if (entry.tryLoc === "root") {
+        // Exception thrown outside of any try block that could handle
+        // it, so set the completion value of the entire function to
+        // throw the exception.
+        return handle("end");
+      }
+
+      if (entry.tryLoc <= this.prev) {
+        var hasCatch = hasOwn.call(entry, "catchLoc");
+        var hasFinally = hasOwn.call(entry, "finallyLoc");
+
+        if (hasCatch && hasFinally) {
+          if (this.prev < entry.catchLoc) {
+            return handle(entry.catchLoc, true);
+          } else if (this.prev < entry.finallyLoc) {
+            return handle(entry.finallyLoc);
+          }
+
+        } else if (hasCatch) {
+          if (this.prev < entry.catchLoc) {
+            return handle(entry.catchLoc, true);
+          }
+
+        } else if (hasFinally) {
+          if (this.prev < entry.finallyLoc) {
+            return handle(entry.finallyLoc);
+          }
+
+        } else {
+          throw new Error("try statement without catch or finally");
+        }
+      }
+    }
+  },
+
+  _findFinallyEntry: function(finallyLoc) {
+    for (var i = this.tryEntries.length - 1; i >= 0; --i) {
+      var entry = this.tryEntries[i];
+      if (entry.tryLoc <= this.prev &&
+          hasOwn.call(entry, "finallyLoc") && (
+            entry.finallyLoc === finallyLoc ||
+            this.prev < entry.finallyLoc)) {
+        return entry;
+      }
+    }
+  },
+
+  abrupt: function(type, arg) {
+    var entry = this._findFinallyEntry();
+    var record = entry ? entry.completion : {};
+
+    record.type = type;
+    record.arg = arg;
+
+    if (entry) {
+      this.next = entry.finallyLoc;
+    } else {
+      this.complete(record);
+    }
+
+    return ContinueSentinel;
+  },
+
+  complete: function(record) {
+    if (record.type === "throw") {
+      throw record.arg;
+    }
+
+    if (record.type === "break" || record.type === "continue") {
+      this.next = record.arg;
+    } else if (record.type === "return") {
+      this.rval = record.arg;
+      this.next = "end";
+    }
+
+    return ContinueSentinel;
+  },
+
+  finish: function(finallyLoc) {
+    var entry = this._findFinallyEntry(finallyLoc);
+    return this.complete(entry.completion);
+  },
+
+  "catch": function(tryLoc) {
+    for (var i = this.tryEntries.length - 1; i >= 0; --i) {
+      var entry = this.tryEntries[i];
+      if (entry.tryLoc === tryLoc) {
+        var record = entry.completion;
+        var thrown;
+        if (record.type === "throw") {
+          thrown = record.arg;
+          resetTryEntry(entry, i);
+        }
+        return thrown;
+      }
+    }
+
+    // The context.catch method must only be called with a location
+    // argument that corresponds to a known catch block.
+    throw new Error("illegal catch attempt");
+  },
+
+  delegateYield: function(iterable, resultName, nextLoc) {
+    this.delegate = {
+      iterator: values(iterable),
+      resultName: resultName,
+      nextLoc: nextLoc
+    };
+
+    return ContinueSentinel;
+  }
+};

lib/6to5/transformation/transformers/generators/util.js

@@ -0,0 +1,18 @@
+/**
+ * Copyright (c) 2014, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * https://raw.github.com/facebook/regenerator/master/LICENSE file. An
+ * additional grant of patent rights can be found in the PATENTS file in
+ * the same directory.
+ */
+
+var t = require("../../../types");
+
+exports.runtimeProperty = function (name) {
+  return t.memberExpression(
+    t.identifier("regeneratorRuntime"),
+    t.identifier(name)
+  );
+};

lib/6to5/transformation/transformers/generators/visit.js

@@ -0,0 +1,219 @@
+/**
+ * Copyright (c) 2014, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * https://raw.githut.com/facebook/regenerator/master/LICENSE file. An
+ * additional grant of patent rights can be found in the PATENTS file in
+ * the same directory.
+ */
+
+var runtimeProperty = require("./util").runtimeProperty;
+var Emitter         = require("./emit").Emitter;
+var hoist           = require("./hoist").hoist;
+var types           = require("ast-types");
+var t               = require("../../../types");
+
+var runtimeAsyncMethod = runtimeProperty("async");
+var runtimeWrapMethod  = runtimeProperty("wrap");
+var runtimeMarkMethod  = runtimeProperty("mark");
+
+exports.transform = function transform(node) {
+  return types.visit(node, visitor);
+};
+
+var visitor = types.PathVisitor.fromMethodsObject({
+  visitFunction: function(path) {
+    // Calling this.traverse(path) first makes for a post-order traversal.
+    this.traverse(path);
+
+    var node = path.value;
+
+    if (!node.generator && !node.async) {
+      return;
+    }
+
+    node.generator = false;
+
+    if (node.expression) {
+      // Transform expression lambdas into normal functions.
+      node.expression = false;
+      node.body = t.blockStatement([
+        t.returnStatement(node.body)
+      ]);
+    }
+
+    if (node.async) {
+      awaitVisitor.visit(path.get("body"));
+    }
+
+    var outerFnId = node.id || (
+      node.id = path.scope.parent.declareTemporary("callee$")
+    );
+
+    var innerFnId = t.identifier(node.id.name + "$");
+    var contextId = path.scope.declareTemporary("context$");
+    var vars = hoist(path);
+
+    var emitter = new Emitter(contextId);
+    emitter.explode(path.get("body"));
+
+    var outerBody = [];
+
+    if (vars && vars.declarations.length > 0) {
+      outerBody.push(vars);
+    }
+
+    var wrapArgs = [
+      emitter.getContextFunction(innerFnId),
+      // Async functions don't care about the outer function because they
+      // don't need it to be marked and don't inherit from its .prototype.
+      node.async ? t.literal(null) : outerFnId,
+      t.thisExpression()
+    ];
+
+    var tryEntryList = emitter.getTryEntryList();
+    if (tryEntryList) {
+      wrapArgs.push(tryEntryList);
+    }
+
+    var wrapCall = t.callExpression(
+      node.async ? runtimeAsyncMethod : runtimeWrapMethod,
+      wrapArgs
+    );
+
+    outerBody.push(t.returnStatement(wrapCall));
+    node.body = t.blockStatement(outerBody);
+
+    if (node.async) {
+      node.async = false;
+      return;
+    }
+
+    if (t.isFunctionDeclaration(node)) {
+      var pp = path.parent;
+
+      while (pp && !(t.isBlockStatement(pp.value) || t.isProgram(pp.value))) {
+        pp = pp.parent;
+      }
+
+      if (!pp) {
+        return;
+      }
+
+      // Here we turn the FunctionDeclaration into a named
+      // FunctionExpression that will be assigned to a variable of the
+      // same name at the top of the enclosing block. This is important
+      // for a very subtle reason: named function expressions can refer to
+      // themselves by name without fear that the binding may change due
+      // to code executing outside the function, whereas function
+      // declarations are vulnerable to the following rebinding:
+      //
+      //   function f() { return f }
+      //   var g = f;
+      //   f = "asdf";
+      //   g(); // "asdf"
+      //
+      // One way to prevent the problem illustrated above is to transform
+      // the function declaration thus:
+      //
+      //   var f = function f() { return f };
+      //   var g = f;
+      //   f = "asdf";
+      //   g(); // f
+      //   g()()()()(); // f
+      //
+      // In the code below, we transform generator function declarations
+      // in the following way:
+      //
+      //   gen().next(); // { value: gen, done: true }
+      //   function *gen() {
+      //     return gen;
+      //   }
+      //
+      // becomes something like
+      //
+      //   var gen = runtime.mark(function *gen() {
+      //     return gen;
+      //   });
+      //   gen().next(); // { value: gen, done: true }
+      //
+      // which ensures that the generator body can always reliably refer
+      // to gen by name.
+
+      // Remove the FunctionDeclaration so that we can add it back as a
+      // FunctionExpression passed to runtime.mark.
+      path.replace();
+
+      // Change the type of the function to be an expression instead of a
+      // declaration. Note that all the other fields are the same.
+      node.type = "FunctionExpression";
+
+      var varDecl = t.variableDeclaration("var", [
+        t.variableDeclarator(
+          node.id,
+          t.callExpression(runtimeMarkMethod, [node])
+        )
+      ]);
+
+      if (node.comments) {
+        // Copy any comments preceding the function declaration to the
+        // variable declaration, to avoid weird formatting consequences.
+        varDecl.comments = node.comments;
+        node.comments = null;
+      }
+
+      var bodyPath = pp.get("body");
+      var bodyLen = bodyPath.value.length;
+
+      for (var i = 0; i < bodyLen; ++i) {
+        var firstStmtPath = bodyPath.get(i);
+        if (!shouldNotHoistAbove(firstStmtPath)) {
+          firstStmtPath.insertBefore(varDecl);
+          return;
+        }
+      }
+
+      bodyPath.push(varDecl);
+
+    } else {
+      t.assertFunctionExpression(node);
+      return t.callExpression(runtimeMarkMethod, [node]);
+    }
+  }
+});
+
+function shouldNotHoistAbove(stmtPath) {
+  var value = stmtPath.value;
+  t.assertStatement(value);
+
+  // If the first statement is a "use strict" declaration, make sure to
+  // insert hoisted declarations afterwards.
+  if (t.isExpressionStatement(value) &&
+      t.isLiteral(value.expression) &&
+      value.expression.value === "use strict") {
+    return true;
+  }
+
+  if (t.isVariableDeclaration(value)) {
+    for (var i = 0; i < value.declarations.length; ++i) {
+      var decl = value.declarations[i];
+      if (t.isCallExpression(decl.init) && types.astNodesAreEquivalent(decl.init.callee, runtimeMarkMethod)) {
+        return true;
+      }
+    }
+  }
+
+  return false;
+}
+
+var awaitVisitor = types.PathVisitor.fromMethodsObject({
+  visitFunction: function() {
+    return false; // Don't descend into nested function scopes.
+  },
+
+  visitAwaitExpression: function(path) {
+    // Convert await expressions to yield expressions.
+    return t.yieldExpression(path.value.argument, false);
+  }
+});

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

@@ -0,0 +1,474 @@
+var traverse = require("../../traverse");
+var util     = require("../../util");
+var t        = require("../../types");
+var _        = require("lodash");
+
+var isLet = function (node) {
+  if (!t.isVariableDeclaration(node)) return false;
+  if (node._let) return true;
+  if (node.kind !== "let") return false;
+
+  node._let = true;
+  node.kind = "var";
+  return true;
+};
+
+var isVar = function (node) {
+  return t.isVariableDeclaration(node, { kind: "var" }) && !isLet(node);
+};
+
+var standardiseLets = function (declars) {
+  _.each(declars, function (declar) {
+    delete declar._let;
+  });
+};
+
+exports.VariableDeclaration = function (node) {
+  isLet(node);
+};
+
+exports.For = function (node, parent, file, scope) {
+  var init = node.left || node.init;
+  if (isLet(init)) {
+    t.ensureBlock(node);
+    node.body._letDeclars = [init];
+  }
+
+  if (t.isLabeledStatement(parent)) {
+    // set label so `run` has access to it
+    node.label = parent.label;
+  }
+
+  var letScoping = new LetScoping(node, node.body, parent, file, scope);
+  letScoping.run();
+
+  if (node.label && !t.isLabeledStatement(parent)) {
+    // we've been given a label so let's wrap ourselves
+    return t.labeledStatement(node.label, node);
+  }
+};
+
+exports.BlockStatement = function (block, parent, file, scope) {
+  if (!t.isFor(parent)) {
+    var letScoping = new LetScoping(false, block, parent, file, scope);
+    letScoping.run();
+  }
+};
+
+/**
+ * Description
+ *
+ * @param {Boolean|Node} forParent
+ * @param {Node} block
+ * @param {Node} parent
+ * @param {File} file
+ * @param {Scope} scope
+ */
+
+function LetScoping(forParent, block, parent, file, scope) {
+  this.forParent = forParent;
+  this.parent    = parent;
+  this.scope     = scope;
+  this.block     = block;
+  this.file      = file;
+
+  this.letReferences = {};
+  this.body          = [];
+}
+
+/**
+ * Start the ball rolling.
+ */
+
+LetScoping.prototype.run = function () {
+  var block = this.block;
+
+  if (block._letDone) return;
+  block._letDone = true;
+
+  this.info = this.getInfo();
+
+  // remap all let references that exist in upper scopes to their uid
+  this.remap();
+
+  // this is a block within a `Function` so we can safely leave it be
+  if (t.isFunction(this.parent)) return this.noClosure();
+
+  // this block has no let references so let's clean up
+  if (!this.info.keys.length) return this.noClosure();
+
+  // returns whether or not there are any outside let references within any
+  // functions
+  var referencesInClosure = this.getLetReferences();
+
+  // no need for a closure so let's clean up
+  if (!referencesInClosure) return this.noClosure();
+
+  // if we're inside of a for loop then we search to see if there are any
+  // `break`s, `continue`s, `return`s etc
+  this.has = this.checkFor();
+
+  // hoist var references to retain scope
+  this.hoistVarDeclarations();
+
+  // set let references to plain var references
+  standardiseLets(this.info.declarators);
+
+  // turn letReferences into an array
+  var letReferences = _.values(this.letReferences);
+
+  // build the closure that we're going to wrap the block with
+  var fn = t.functionExpression(null, letReferences, t.blockStatement(block.body));
+  fn._aliasFunction = true;
+
+  // replace the current block body with the one we're going to build
+  block.body = this.body;
+
+  // change upper scope references with their uid if they have one
+  var params = this.getParams(letReferences);
+
+  // build a call and a unique id that we can assign the return value to
+  var call = t.callExpression(fn, params);
+  var ret  = t.identifier(this.file.generateUid("ret", this.scope));
+
+  var hasYield = traverse.hasType(fn.body, "YieldExpression", t.FUNCTION_TYPES);
+  if (hasYield) {
+    fn.generator = true;
+    call = t.yieldExpression(call, true);
+  }
+
+  this.build(ret, call);
+};
+
+/**
+ * There are no let references accessed within a closure so we can just turn the
+ * lets into vars.
+ */
+
+LetScoping.prototype.noClosure = function () {
+  standardiseLets(this.info.declarators);
+};
+
+/**
+ * Traverse through block and replace all references that exist in a higher
+ * scope to their uids.
+ */
+
+LetScoping.prototype.remap = function () {
+  var replacements = this.info.duplicates;
+  var block        = this.block;
+
+  if (_.isEmpty(replacements)) return;
+
+  var replace = function (node, parent, scope) {
+    if (!t.isIdentifier(node)) return;
+    if (!t.isReferenced(node, parent)) return;
+    if (scope && scope.hasOwn(node.name)) return;
+    node.name = replacements[node.name] || node.name;
+  };
+
+  var traverseReplace = function (node, parent) {
+    replace(node, parent);
+    traverse(node, replace);
+  };
+
+  var forParent = this.forParent;
+  if (forParent) {
+    traverseReplace(forParent.right, forParent);
+    traverseReplace(forParent.test, forParent);
+    traverseReplace(forParent.update, forParent);
+  }
+
+  traverse(block, replace);
+};
+
+/**
+ * Description
+ *
+ * @returns {Object}
+ */
+
+LetScoping.prototype.getInfo = function () {
+  var block = this.block;
+  var scope = this.scope;
+  var file  = this.file;
+
+  var opts = {
+    // array of `Identifier` names of let variables that appear lexically out of
+    // this scope but should be accessible - eg. `ForOfStatement`.left
+    outsideKeys: [],
+
+    // array of let `VariableDeclarator`s that are a part of this block
+    declarators: block._letDeclars || [],
+
+    // object of duplicate ids and their aliases - if there's an `Identifier`
+    // name that's used in an upper scope we generate a unique id and replace
+    // all references with it
+    duplicates:  {},
+
+    // array of `Identifier` names of let variables that are accessible within
+    // the current block
+    keys:        []
+  };
+
+  var duplicates = function (id, key) {
+    var has = scope.parentGet(key);
+
+    if (has && has !== id) {
+      // there's a variable with this exact name in an upper scope so we need
+      // to generate a new name
+      opts.duplicates[key] = id.name = file.generateUid(key, scope);
+    }
+  };
+
+  _.each(opts.declarators, function (declar) {
+    opts.declarators.push(declar);
+
+    var keys = t.getIds(declar, true);
+    _.each(keys, duplicates);
+    keys = _.keys(keys);
+
+    opts.outsideKeys = opts.outsideKeys.concat(keys);
+    opts.keys = opts.keys.concat(keys);
+  });
+
+  _.each(block.body, function (declar) {
+    if (!isLet(declar)) return;
+
+    _.each(t.getIds(declar, true), function (id, key) {
+      duplicates(id, key);
+      opts.keys.push(key);
+    });
+  });
+
+  return opts;
+};
+
+/**
+ * If we're inside of a `For*Statement` then traverse it and check if it has one
+ * of the following node types `ReturnStatement`, `BreakStatement`,
+ * `ContinueStatement` and replace it with a return value that we can track
+ * later on.
+ *
+ * @returns {Object}
+ */
+
+LetScoping.prototype.checkFor = function () {
+  var has = {
+    hasContinue: false,
+    hasReturn:   false,
+    hasBreak:    false,
+  };
+
+  var forParent = this.forParent;
+
+  traverse(this.block, function (node) {
+    var replace;
+
+    if (t.isFunction(node) || t.isFor(node)) {
+      return false;
+    }
+
+    if (forParent && node && !node.label) {
+      if (t.isBreakStatement(node)) {
+        has.hasBreak = true;
+        replace = t.returnStatement(t.literal("break"));
+      } else if (t.isContinueStatement(node)) {
+        has.hasContinue = true;
+        replace = t.returnStatement(t.literal("continue"));
+      }
+    }
+
+    if (t.isReturnStatement(node)) {
+      has.hasReturn = true;
+      replace = t.returnStatement(t.objectExpression([
+        t.property("init", t.identifier("v"), node.argument || t.identifier("undefined"))
+      ]));
+    }
+
+    if (replace) return t.inherits(replace, node);
+  });
+
+  return has;
+};
+
+/**
+ * Hoist all var declarations in this block to before it so they retain scope
+ * once we wrap everything in a closure.
+ */
+
+LetScoping.prototype.hoistVarDeclarations = function () {
+  var self = this;
+  traverse(this.block, function (node) {
+    if (t.isForStatement(node)) {
+      if (isVar(node.init)) {
+        node.init = t.sequenceExpression(self.pushDeclar(node.init));
+      }
+    } else if (t.isFor(node)) {
+      if (isVar(node.left)) {
+        node.left = node.left.declarations[0].id;
+      }
+    } else if (isVar(node)) {
+      return self.pushDeclar(node).map(t.expressionStatement);
+    } else if (t.isFunction(node)) {
+      return false;
+    }
+  });
+};
+
+/**
+ * Build up a parameter list that we'll call our closure wrapper with, replacing
+ * all duplicate ids with their uid.
+ *
+ * @param {Array} params
+ * @returns {Array}
+ */
+
+LetScoping.prototype.getParams = function (params) {
+  var info = this.info;
+  params = _.cloneDeep(params);
+  _.each(params, function (param) {
+    param.name = info.duplicates[param.name] || param.name;
+  });
+  return params;
+};
+
+/**
+ * Get all let references within this block. Stopping whenever we reach another
+ * block.
+ */
+
+LetScoping.prototype.getLetReferences = function () {
+  var closurify = false;
+  var self = this;
+
+  // traverse through this block, stopping on functions and checking if they
+  // contain any outside let references
+  traverse(this.block, function (node, parent, scope) {
+    if (t.isFunction(node)) {
+      traverse(node, function (node, parent) {
+        // not an identifier so we have no use
+        if (!t.isIdentifier(node)) return;
+
+        // not a direct reference
+        if (!t.isReferenced(node, parent)) return;
+
+        // this scope has a variable with the same name so it couldn't belong
+        // to our let scope
+        if (scope.hasOwn(node.name)) return;
+
+        closurify = true;
+
+        // this key doesn't appear just outside our scope
+        if (!_.contains(self.info.outsideKeys, node.name)) return;
+
+        // push this badboy
+        self.letReferences[node.name] = node;
+      });
+
+      return false;
+    } else if (t.isFor(node)) {
+      return false;
+    }
+  });
+
+  return closurify;
+};
+
+/**
+ * Turn a `VariableDeclaration` into an array of `AssignmentExpressions` with
+ * their declarations hoisted to before the closure wrapper.
+ *
+ * @param {Node} node VariableDeclaration
+ * @returns {Array}
+ */
+
+LetScoping.prototype.pushDeclar = function (node) {
+  this.body.push(t.variableDeclaration(node.kind, node.declarations.map(function (declar) {
+    return t.variableDeclarator(declar.id);
+  })));
+
+  var replace = [];
+
+  _.each(node.declarations, function (declar) {
+    if (!declar.init) return;
+
+    var expr = t.assignmentExpression("=", declar.id, declar.init);
+    replace.push(t.inherits(expr, declar));
+  });
+
+  return replace;
+};
+
+/**
+ * Push the closure to the body.
+ *
+ * @param {Node} ret Identifier
+ * @param {Node} call CallExpression
+ */
+
+LetScoping.prototype.build = function (ret, call) {
+  var has = this.has;
+  if (has.hasReturn || has.hasBreak || has.hasContinue) {
+    this.buildHas(ret, call);
+  } else {
+    this.body.push(t.expressionStatement(call));
+  }
+};
+
+/**
+ * Description
+ *
+ * @param {Node} ret Identifier
+ * @param {Node} call CallExpression
+ */
+
+LetScoping.prototype.buildHas = function (ret, call) {
+  var body = this.body;
+
+  body.push(t.variableDeclaration("var", [
+    t.variableDeclarator(ret, call)
+  ]));
+
+  var forParent = this.forParent;
+  var retCheck;
+  var has = this.has;
+  var cases = [];
+
+  if (has.hasReturn) {
+    // typeof ret === "object"
+    retCheck = util.template("let-scoping-return", {
+      RETURN: ret
+    });
+  }
+
+  if (has.hasBreak || has.hasContinue) {
+    // ensure that the parent has a label as we're building a switch and we
+    // need to be able to access it
+    var label = forParent.label = forParent.label || t.identifier(this.file.generateUid("loop", this.scope));
+
+    if (has.hasBreak) {
+      cases.push(t.switchCase(t.literal("break"), [t.breakStatement(label)]));
+    }
+
+    if (has.hasContinue) {
+      cases.push(t.switchCase(t.literal("continue"), [t.continueStatement(label)]));
+    }
+
+    if (has.hasReturn) {
+      cases.push(t.switchCase(null, [retCheck]));
+    }
+
+    if (cases.length === 1) {
+      var single = cases[0];
+      body.push(t.ifStatement(
+        t.binaryExpression("===", ret, single.test),
+        single.consequent[0]
+      ));
+    } else {
+      body.push(t.switchStatement(ret, cases));
+    }
+  } else {
+    if (has.hasReturn) body.push(retCheck);
+  }
+};

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

@@ -1,4 +1,4 @@
-var util = require("../util");
+var util = require("../../util");
 var _    = require("lodash");
 
 exports.Property = function (node) {
@@ -10,7 +10,7 @@ exports.ObjectExpression = function (node, parent, file) {
 
   node.properties = node.properties.filter(function (prop) {
     if (prop.kind === "get" || prop.kind === "set") {
-      util.pushMutatorMap(mutatorMap, prop.key.name, prop.kind, prop.value);
+      util.pushMutatorMap(mutatorMap, prop.key, prop.kind, prop.value);
       return false;
     } else {
       return true;
@@ -24,6 +24,9 @@ exports.ObjectExpression = function (node, parent, file) {
   return util.template("object-define-properties-closure", {
     KEY: objId,
     OBJECT: node,
-    CONTENT: util.buildDefineProperties(mutatorMap, objId).expression
+    CONTENT: util.template("object-define-properties", {
+      OBJECT: objId,
+      PROPS:  util.buildDefineProperties(mutatorMap)
+    })
   });
 };