v2.4.4

fix incorrect scripts reference in browser
add 2.4.4 changelog
2015-01-02 19:24:56 +11:00 · 2015-01-02 19:23:50 +11:00 · 2015-01-02 19:22:03 +11:00 · 2015-01-02 19:20:14 +11:00 · 2015-01-02 19:20:05 +11:00 · 2015-01-02 16:46:58 +11:00
194 changed files with 1837 additions and 805 deletions
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,51 @@

 Gaps between patch versions are faulty/broken releases.

+## 2.4.4
+
+ * Add `module` type to browser build `<script>` handler.
+ * Fix some `MemberExpression` modifying incorrectly setting `property` to a `MemberExpression`.
+
+## 2.4.3
+
+ * Upgrade `acorn-6to5`.
+ * Add support for `FunctionDeclaration`s in `bluebirdCoroutines` and `asyncToGenerators` transformers.
+
+## 2.4.2
+
+ * Upgrade `acorn-6to5`.
+ * Better uids generated for various transformers based on parent node.
+ * Alias flat references in `coreAliasing` transformer.
+
+## 2.4.1
+
+ * Better whitespace handling of parenthesized expressions due to trailing comments.
+ * Fix `yield` inside of comprehensions.
+
+## 2.4.0
+
+ * Use a closure always for classes with a super.
+ * Always use native loops for array comprehensions.
+ * Allow `yield` inside of comprehensions.
+ * Add optional `bluebirdCoroutine` transformer.
+ * Add optional `asyncToGenerator` transformer.
+ * Move `useStrict` transformer to before `_moduleFormatter` causing `"use strict";` to always be placed the very top.
+
+## 2.3.2
+
+ * Add parens on expressions with trailing comments.
+
+## 2.3.1
+
+ * Add `undefinedToVoid` optional transformer.
+ * Use `Object.defineProperty` for computed properties.
+
+## 2.3.0
+
+ * Upgrade `acorn-6to5`.
+ * Support circular references and hoist variable declarations in `system` module formatter.
+ * Add optional transformers, including a new `coreAliasing` transformer that aliases native ES6 static properties to their `core-js` equivalent.
+
 ## 2.2.0

 * Make `system` module formatter modules anonymous by default.
--- a/2
+++ b/2
@@ -1,4 +1,4 @@
-Copyright (c) 2014 Sebastian McKenzie
+Copyright (c) 2014-2015 Sebastian McKenzie

 MIT License

--- a/6
+++ b/6
@@ -21,8 +21,7 @@ lint:
 test-clean:
 	rm -rf test/tmp

-test:
-	make lint
+test: lint
 	$(MOCHA_CMD)
 	make test-clean

@@ -33,8 +32,7 @@ test-cov:
 test-spec:
 	node $(ISTANBUL_CMD) $(MOCHA_CMD) -- --reporter spec

-test-travis:
-	make test-spec
+test-travis: test-spec
 	if test -n "$$CODECLIMATE_REPO_TOKEN"; then codeclimate < coverage/lcov.info; fi

 test-browser:
--- a/README.md
+++ b/README.md
@@ -11,10 +11,6 @@
    <img alt="Travis Status" src="http://img.shields.io/travis/6to5/6to5/master.svg?style=flat&amp;label=travis">
  </a>

-  <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/6to5/6to5">
    <img alt="Code Climate Score" src="http://img.shields.io/codeclimate/github/6to5/6to5.svg?style=flat">
  </a>
--- a/bin/6to5/index.js
+++ b/bin/6to5/index.js
@@ -17,6 +17,7 @@ commander.option("-p, --playground", "Enable playground support");
 commander.option("-m, --modules [modules]", "Module formatter type to use [common]", "common");
 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("-i, --optional [list]", "List of optional transformers to enable", 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);
@@ -28,8 +29,16 @@ commander.on("--help", function(){
    console.log("  " + title + ":");
    console.log();

+    var hasOptional = true;
+
    _.each(_.keys(obj).sort(), function (key) {
      if (key[0] === "_") return;
+
+      if (obj[key].optional) {
+        hasOptional = true;
+        key = "[" + key + "]";
+      }
+
      console.log("    - " + key);
    });

@@ -96,6 +105,7 @@ exports.opts = {
  blacklist:     commander.blacklist,
  whitelist:     commander.whitelist,
  sourceMap:     commander.sourceMaps || commander.sourceMapsInline,
+  optional:      commander.optional,
  comments:      !commander.removeComments,
  runtime:       commander.runtime,
  modules:       commander.modules
--- a/doc/caveats.md
+++ b/doc/caveats.md
@@ -9,12 +9,12 @@ You may alternatively selectively include what you need:
 | Feature                     | Requirements                                                                                                           |
 | --------------------------- | ---------------------------------------------------------------------------------------------------------------------- |
 | Abstract References         | [experimental](experimental.md), `Symbol`                                                                              |
-| Array destructuring         | `Array.isArray`, `Array.from`                                                                                          |
+| Array destructuring         | `Array.from`                                                                                                           |
 | Async functions, Generators | [experimental](experimental.md), [regenerator runtime](https://github.com/facebook/regenerator/blob/master/runtime.js) |
-| Comprehensions              | [experimental](experimental.md), `Array.isArray`, `Array.from`                                                         |
+| Comprehensions              | [experimental](experimental.md), `Array.from`                                                                          |
 | For Of                      | `Symbol`, `prototype[Symbol.iterator]`                                                                                 |
 | Object spread/rest          | [experimental](experimental.md), `Object.assign`                                                                       |
-| Spread                      | `Array.isArray`, `Array.from`                                                                                          |
+| Spread                      | `Array.from`                                                                                                           |

 ## ES5

@@ -26,13 +26,13 @@ ES5 such as lower versions of IE then using the

 ## Internet Explorer

-### Classes (9 and below)
+### Classes (10 and below)

 If you're inheriting from a class then static properties are inherited from it
 via [\_\_proto\_\_](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/proto),
 this is widely supported but you may run into problems with much older browsers.

-**NOTE:** `__proto__` is not supported on IE <= 9 so static properties
+**NOTE:** `__proto__` is not supported in IE <= 10 so static properties
 **will not** be inherited. A possible workaround is to use `super();`:

 ```javascript
@@ -56,4 +56,4 @@ unfortunate as it's required to set getters and setters. Due to this if
 you plan on supporting IE8 or below then the user of getters and setters
 isn't recommended.

-Reference: [MDN](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty#Internet_Explorer_8_specific_notes).
+**Reference**: [MDN](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty#Internet_Explorer_8_specific_notes).
--- a/doc/index.md
+++ b/doc/index.md
@@ -52,7 +52,7 @@ And it doesn't end here! To see all the ways you can use 6to5, check out the
 - [Let scoping](features.md#let-scoping)
 - [Modules](features.md#modules)
 - [Numeric literals](features.md#numeric-literals)
- - [Object Rest/Spread](features.md#object-rest-spread) ([experimental](experimental.md))
+ - [Object rest/spread](features.md#object-rest-spread) ([experimental](experimental.md))
 - [Property method assignment](features.md#property-method-assignment)
 - [Property name shorthand](features.md#property-name-shorthand)
 - [React/JSX](react.md)
--- a/doc/playground.md
+++ b/doc/playground.md
@@ -18,11 +18,19 @@ to5.transform("code", { playground: true });

 * [Memoization operator](#memoization-operator)
 * [Method binding](#method-binding)
+ * [Method binding function shorthand](#method-binding-function-shorthand)
 * [Object getter memoization](#object-getter-memoization)
 * [This shorthand](#this-shorthand)

 ### Memoization assignment operator

+The memoization assignment operator allows you to lazily set an object property.
+It checks whether there's a property defined on the object and if there isn't then
+the right hand value is set.
+
+This means that `obj.x` in the following `var x = { x: undefined }; obj.x ?= 2;`
+will still be `undefined` because it's already been defined on the object.
+
 ```javascript
 var obj = {};
 obj.x ?= 2;
@@ -42,7 +50,7 @@ var obj = {};
 obj.x ?= 2;
 ```

-equivalent to:
+equivalent to

 ```javascript
 var obj = {};
@@ -54,17 +62,25 @@ if (!Object.prototype.hasOwnProperty.call(obj, "x")) obj.x = 2;
 ```javascript
 var fn = obj#method;
 var fn = obj#method("foob");
-
-["foo", "bar"].map(#toUpperCase); // ["FOO", "BAR"]
-[1.1234, 23.53245, 3].map(#toFixed(2)); // ["1.12", "23.53", "3.00"]
 ```

-equivalent to:
+equivalent to

 ```javascript
 var fn = obj.method.bind(obj);
 var fn = obj.method.bind(obj, "foob");
+```

+### Method binding function shorthand
+
+```javascript
+["foo", "bar"].map(#toUpperCase); // ["FOO", "BAR"]
+[1.1234, 23.53245, 3].map(#toFixed(2)); // ["1.12", "23.53", "3.00"]
+```
+
+equivalent to
+
+```javascript
 ["foo", "bar"].map(function (val) { return val.toUpperCase(); });
 [1.1234, 23.53245, 3].map(function (val) { return val.toFixed(2); });
 ```
@@ -90,23 +106,27 @@ equivalent to
 ```javascript
 var foo = {
  get bar() {
-    if (this._barRan) return this._bar;
-    this._barRan = true;
-    return this._bar = complex();
+    return Object.defineProperty(this, "bar", {
+      value: complex(),
+      enumerable: true,
+      configurable: true,
+      writable: true
+    }).bar;
  }
 };

 class Foo {
  get bar() {
-    if (this._barRan) return this._bar;
-    this._barRan = true;
-    return this._bar = complex();
+    return Object.defineProperty(this, "bar", {
+      value: complex(),
+      enumerable: true,
+      configurable: true,
+      writable: true
+    }).bar;
  }
 }
 ```

-**NOTE:** Memoised functions will return the result of the **first** execution, regardless of arguments.
-
 ### This shorthand

 ```javascript
--- a/lib/6to5/browser.js
+++ b/lib/6to5/browser.js
@@ -34,7 +34,7 @@ transform.load = function (url, callback, opts, hold) {

 var runScripts = function () {
  var scripts = [];
-  var types   = ["text/ecmascript-6", "text/6to5"];
+  var types   = ["text/ecmascript-6", "text/6to5", "module"];
  var index   = 0;

  var exec = function () {
@@ -60,8 +60,9 @@ var runScripts = function () {
    }
  };

-  var _scripts = global.document.getElementsByTagName("script");
-  for (var i in _scripts) {
+  var _scripts = global.document .getElementsByTagName("script");
+
+  for (var i = 0; i < _scripts.length; ++i) {
    var _script = _scripts[i];
    if (types.indexOf(_script.type) >= 0) scripts.push(_script);
  }
--- a/lib/6to5/file.js
+++ b/lib/6to5/file.js
@@ -10,9 +10,11 @@ var t         = require("./types");
 var _         = require("lodash");

 function File(opts) {
-  this.opts = File.normaliseOptions(opts);
-  this.uids = {};
-  this.ast  = {};
+  this.dynamicImports = [];
+  this.opts           = File.normaliseOptions(opts);
+  this.transformers   = this.getTransformers();
+  this.uids           = {};
+  this.ast            = {};
 }

 File.declarations = [
@@ -25,7 +27,13 @@ File.declarations = [
  "sliced-to-array",
  "object-without-properties",
  "has-own",
-  "slice"
+  "slice",
+  "define-property",
+  "async-to-generator"
+];
+
+File.excludeDeclarationsFromRuntime = [
+  "async-to-generator"
 ];

 File.normaliseOptions = function (opts) {
@@ -39,6 +47,7 @@ File.normaliseOptions = function (opts) {
    blacklist:    [],
    whitelist:    [],
    sourceMap:    false,
+    optional:     [],
    comments:     true,
    filename:     "unknown",
    modules:      "common",
@@ -80,10 +89,28 @@ File.normaliseOptions = function (opts) {

  transform._ensureTransformerNames("blacklist", opts.blacklist);
  transform._ensureTransformerNames("whitelist", opts.whitelist);
+  transform._ensureTransformerNames("optional", opts.optional);

  return opts;
 };

+File.prototype.getTransformers = function () {
+  var file = this;
+  var transformers = [];
+
+  _.each(transform.transformers, function (transformer) {
+    if (transformer.canRun(file)) {
+      transformers.push(transformer);
+
+      if (transformer.manipulateOptions) {
+        transformer.manipulateOptions(file.opts, file);
+      }
+    }
+  });
+
+  return transformers;
+};
+
 File.prototype.toArray = function (node, i) {
  if (t.isArrayExpression(node)) {
    return node;
@@ -127,6 +154,13 @@ File.prototype.parseShebang = function (code) {
  return code;
 };

+File.prototype.addImport = function (id, source) {
+  var specifiers = [t.importSpecifier(t.identifier("default"), id)];
+  var declar = t.importDeclaration(specifiers, t.literal(source));
+  declar._blockHoist = 3;
+  this.dynamicImports.push(declar);
+};
+
 File.prototype.addDeclaration = function (name) {
  if (!_.contains(File.declarations, name)) {
    throw new ReferenceError("unknown declaration " + name);
@@ -139,7 +173,7 @@ File.prototype.addDeclaration = function (name) {

  var ref;
  var runtimeNamespace = this.opts.runtime;
-  if (runtimeNamespace) {
+  if (runtimeNamespace && !_.contains(File.excludeDeclarationsFromRuntime, name)) {
    name = t.identifier(t.toIdentifier(name));
    return t.memberExpression(t.identifier(runtimeNamespace), name);
  } else {
@@ -182,15 +216,25 @@ File.prototype.parse = function (code) {
 };

 File.prototype.transform = function (ast) {
+  var self = this;
+
  this.ast = ast;
  this.scope = new Scope(ast.program);
  this.moduleFormatter = this.getModuleFormatter(this.opts.modules);

-  var self = this;
+  var astRun = function (key) {
+    _.each(self.transformers, function (transformer) {
+      transformer.astRun(self, key);
+    });
+  };

-  _.each(transform.transformers, function (transformer) {
+  astRun("enter");
+
+  _.each(this.transformers, function (transformer) {
    transformer.transform(self);
  });
+
+  astRun("exit");
 };

 File.prototype.generate = function () {
--- a/lib/6to5/generation/generator.js
+++ b/lib/6to5/generation/generator.js
@@ -115,6 +115,7 @@ CodeGenerator.prototype.print = function (node, parent, opts) {
  if (!node) return "";

  var self = this;
+
  opts = opts || {};

  var newline = function (leading) {
@@ -147,6 +148,12 @@ CodeGenerator.prototype.print = function (node, parent, opts) {
  };

  if (this[node.type]) {
+    var needsCommentParens = t.isExpression(node) && node.leadingComments && node.leadingComments.length;
+    var needsParens        = needsCommentParens || n.needsParens(node, parent);
+
+    if (needsParens) this.push("(");
+    if (needsCommentParens) this.indent();
+
    this.printLeadingComments(node, parent);

    newline(true);
@@ -154,13 +161,12 @@ CodeGenerator.prototype.print = function (node, parent, opts) {
    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 = n.needsParens(node, parent);
-    if (needsParens) this.push("(");
-
    this[node.type](node, this.buildPrint(node), parent);

+    if (needsCommentParens) {
+      this.newline();
+      this.dedent();
+    }
    if (needsParens) this.push(")");

    this.map.mark(node, "end");
@@ -170,7 +176,7 @@ CodeGenerator.prototype.print = function (node, parent, opts) {

    this.printTrailingComments(node, parent);
  } else {
-    throw new ReferenceError("unknown node " + node.type);
+    throw new ReferenceError("unknown node of type " + JSON.stringify(node.type) + " with constructor " + JSON.stringify(node && node.constructor.name));
  }
 };

--- a/lib/6to5/generation/generators/expressions.js
+++ b/lib/6to5/generation/generators/expressions.js
@@ -98,6 +98,10 @@ exports.MemberExpression = function (node, print) {
  var obj = node.object;
  print(obj);

+  if (!node.computed && t.isMemberExpression(node.property)) {
+    throw new TypeError("Got a MemberExpression for MemberExpression property");
+  }
+
  if (node.computed) {
    this.push("[");
    print(node.property);
--- a/lib/6to5/generation/node/whitespace.js
+++ b/lib/6to5/generation/node/whitespace.js
@@ -55,6 +55,8 @@ _.each({
  Function: 1,
  Class: 1,
  For: 1,
+  ArrayExpression: { after: 1 },
+  ObjectExpression: { after: 1 },
  SwitchStatement: 1,
  IfStatement: { before: 1 },
  CallExpression: { after: 1 },
--- a/lib/6to5/index.js
+++ b/lib/6to5/index.js
@@ -3,8 +3,6 @@ var util      = require("./util");
 var fs        = require("fs");
 var _         = require("lodash");

-exports.Transformer = require("./transformation/transformer");
-
 exports.types = require("./types");

 exports.runtime = require("./runtime-generator");
--- a/lib/6to5/runtime-generator.js
+++ b/lib/6to5/runtime-generator.js
@@ -19,6 +19,10 @@ module.exports = function (namespace) {
  ]));

  _.each(File.declarations, function (name) {
+    if (_.contains(File.excludeDeclarationsFromRuntime, name)) {
+      return false;
+    }
+
    var key = t.identifier(t.toIdentifier(name));
    body.push(t.expressionStatement(
      t.assignmentExpression("=", t.memberExpression(namespace, key), util.template(name))
--- a/lib/6to5/transformation/modules/_default.js
+++ b/lib/6to5/transformation/modules/_default.js
@@ -124,9 +124,9 @@ DefaultFormatter.prototype._pushStatement = function (ref, nodes) {
  return ref;
 };

-DefaultFormatter.prototype._hoistExport = function (declar, assign) {
+DefaultFormatter.prototype._hoistExport = function (declar, assign, priority) {
  if (t.isFunctionDeclaration(declar)) {
-    assign._blockHoist = true;
+    assign._blockHoist = priority || 2;
  }

  return assign;
@@ -139,17 +139,18 @@ DefaultFormatter.prototype._exportSpecifier = function (getRef, specifier, node,
  if (node.source) {
    if (t.isExportBatchSpecifier(specifier)) {
      // export * from "foo";
-      nodes.push(this._exportsWildcard(getRef()));
+      nodes.push(this._exportsWildcard(getRef(), node));
    } else {
      // export { foo } from "test";
      nodes.push(this._exportsAssign(
        t.getSpecifierName(specifier),
-        t.memberExpression(getRef(), specifier.id)
+        t.memberExpression(getRef(), specifier.id),
+        node
      ));
    }
  } else {
    // export { foo };
-    nodes.push(this._exportsAssign(t.getSpecifierName(specifier), specifier.id));
+    nodes.push(this._exportsAssign(t.getSpecifierName(specifier), specifier.id, node));
  }
 };

@@ -181,7 +182,7 @@ DefaultFormatter.prototype.exportDeclaration = function (node, nodes) {
    for (var i in declar.declarations) {
      var decl = declar.declarations[i];

-      decl.init = this._exportsAssign(decl.id, decl.init).expression;
+      decl.init = this._exportsAssign(decl.id, decl.init, node).expression;

      var newDeclar = t.variableDeclaration(declar.kind, [decl]);
      if (i === "0") t.inherits(newDeclar, declar);
@@ -195,7 +196,7 @@ DefaultFormatter.prototype.exportDeclaration = function (node, nodes) {
      nodes.push(declar);
    }

-    assign = this._exportsAssign(id, ref);
+    assign = this._exportsAssign(id, ref, node);

    nodes.push(assign);

--- a/lib/6to5/transformation/modules/common.js
+++ b/lib/6to5/transformation/modules/common.js
@@ -57,6 +57,7 @@ CommonJSFormatter.prototype.importDeclaration = function (node, nodes) {
 CommonJSFormatter.prototype.exportDeclaration = function (node, nodes) {
  if (node.default) {
    var declar = node.declaration;
+    var assign;

    // module.exports = VALUE;
    var templateName = "exports-default-module";
@@ -64,15 +65,29 @@ CommonJSFormatter.prototype.exportDeclaration = function (node, nodes) {
    // exports = module.exports = VALUE;
    if (this.hasNonDefaultExports) templateName = "exports-default-module-override";

-    var assign = util.template(templateName, {
-      VALUE: this._pushStatement(declar, nodes)
-    }, true);
+    if (t.isFunction(declar) || !this.hasNonDefaultExports) {
+      assign = util.template(templateName, {
+        VALUE: this._pushStatement(declar, nodes)
+      }, true);

-    // hoist to the top if this default is a function
-    nodes.push(this._hoistExport(declar, assign));
-  } else {
-    DefaultFormatter.prototype.exportDeclaration.apply(this, arguments);
+      // hoist to the top if this default is a function
+      nodes.push(this._hoistExport(declar, assign, 3));
+      return;
+    } else {
+      // this export isn't a function so we can't hoist it to the top so we need to set it
+      // at the very end of the file with something like:
+      //
+      //   module.exports = Object.assign(exports["default"], exports)
+      //
+
+      assign = util.template("common-export-default-assign", true);
+      assign._blockHoist = 0;
+
+      nodes.push(assign);
+    }
  }
+
+  DefaultFormatter.prototype.exportDeclaration.apply(this, arguments);
 };

 CommonJSFormatter.prototype.exportSpecifier = function (specifier, node, nodes) {
--- a/lib/6to5/transformation/modules/system.js
+++ b/lib/6to5/transformation/modules/system.js
@@ -15,8 +15,13 @@ function SystemFormatter(file) {

 util.inherits(SystemFormatter, AMDFormatter);

-SystemFormatter.prototype._exportsWildcard = function (objectIdentifier) {
-  var leftIdentifier = t.identifier("i");
+SystemFormatter.prototype._addImportSource = function (node, exportNode) {
+  node._importSource = exportNode.source && exportNode.source.value;
+  return node;
+};
+
+SystemFormatter.prototype._exportsWildcard = function (objectIdentifier, node) {
+  var leftIdentifier = this.file.generateUidIdentifier("key");
  var valIdentifier  = t.memberExpression(objectIdentifier, leftIdentifier, true);

  var left = t.variableDeclaration("var", [
@@ -29,11 +34,12 @@ SystemFormatter.prototype._exportsWildcard = function (objectIdentifier) {
    this.buildExportCall(leftIdentifier, valIdentifier)
  ]);

-  return t.forInStatement(left, right, block);
+  return this._addImportSource(t.forInStatement(left, right, block), node);
 };

-SystemFormatter.prototype._exportsAssign = function (id, init) {
-  return this.buildExportCall(t.literal(id.name), init, true);
+SystemFormatter.prototype._exportsAssign = function (id, init, node) {
+  var call = this.buildExportCall(t.literal(id.name), init, true);
+  return this._addImportSource(call, node);
 };

 SystemFormatter.prototype.remapExportAssignment = function (node) {
@@ -49,28 +55,53 @@ SystemFormatter.prototype.buildExportCall = function (id, init, isStatement) {
  }
 };

-SystemFormatter.prototype.buildRunnerSetters = function () {
-  return t.arrayExpression(_.map(this.ids, function (uid) {
-    var moduleIdentifier = t.identifier("m");
+SystemFormatter.prototype.importSpecifier = function (specifier, node, nodes) {
+  AMDFormatter.prototype.importSpecifier.apply(this, arguments);
+  this._addImportSource(_.last(nodes), node);
+};

-    return t.functionExpression(null, [moduleIdentifier], t.blockStatement([
-      t.assignmentExpression("=", uid, moduleIdentifier)
-    ]));
+SystemFormatter.prototype.buildRunnerSetters = function (block, hoistDeclarators) {
+  return t.arrayExpression(_.map(this.ids, function (uid, source) {
+    var nodes = [];
+
+    traverse(block, {
+      enter: function (node) {
+        if (node._importSource === source) {
+          if (t.isVariableDeclaration(node)) {
+            _.each(node.declarations, function (declar) {
+              hoistDeclarators.push(t.variableDeclarator(declar.id));
+              nodes.push(t.expressionStatement(
+                t.assignmentExpression("=", declar.id, declar.init)
+              ));
+            });
+          } else {
+            nodes.push(node);
+          }
+
+          this.remove();
+        }
+      }
+    });
+
+    return t.functionExpression(null, [uid], t.blockStatement(nodes));
  }));
 };

 SystemFormatter.prototype.transform = function (ast) {
  var program = ast.program;

+  var hoistDeclarators = [];
  var moduleName = this.getModuleName();
  var moduleNameLiteral = t.literal(moduleName);

+  var block = t.blockStatement(program.body);
+
  var runner = util.template("system", {
    MODULE_NAME: moduleNameLiteral,
    MODULE_DEPENDENCIES: t.arrayExpression(this.buildDependencyLiterals()),
    EXPORT_IDENTIFIER: this.exportIdentifier,
-    SETTERS: this.buildRunnerSetters(),
-    EXECUTE: t.functionExpression(null, [], t.blockStatement(program.body))
+    SETTERS: this.buildRunnerSetters(block, hoistDeclarators),
+    EXECUTE: t.functionExpression(null, [], block)
  }, true);

  var handlerBody = runner.expression.arguments[2].body.body;
@@ -78,8 +109,55 @@ SystemFormatter.prototype.transform = function (ast) {

  var returnStatement = handlerBody.pop();

+  // hoist up all variable declarations
+  traverse(block, {
+    enter: function (node, parent, scope) {
+      if (t.isFunction(node)) {
+        // nothing inside is accessible
+        return this.stop();
+      }
+
+      if (t.isVariableDeclaration(node)) {
+        if (node.kind !== "var" && !t.isProgram(parent)) { // let, const
+          // can't be accessed
+          return;
+        }
+
+        var nodes = [];
+
+        _.each(node.declarations, function (declar) {
+          hoistDeclarators.push(t.variableDeclarator(declar.id));
+          if (declar.init) {
+            // no initializer so we can just hoist it as-is
+            var assign = t.expressionStatement(t.assignmentExpression("=", declar.id, declar.init));
+            nodes.push(assign);
+          }
+        });
+
+        // for (var i in test)
+        // for (var i = 0;;)
+        if (t.isFor(parent)) {
+          if (parent.left === node) {
+            return node.declarations[0].id;
+          }
+
+          if (parent.init === node) {
+            return t.toSequenceExpression(nodes, scope);
+          }
+        }
+
+        return nodes;
+      }
+    }
+  });
+  if (hoistDeclarators.length) {
+    var hoistDeclar = t.variableDeclaration("var", hoistDeclarators);
+    hoistDeclar._blockHoist = true;
+    handlerBody.unshift(hoistDeclar);
+  }
+
  // hoist up function declarations for circular references
-  traverse(program, {
+  traverse(block, {
    enter: function (node) {
      if (t.isFunction(node)) this.stop();

@@ -90,12 +168,6 @@ SystemFormatter.prototype.transform = function (ast) {
    }
  });

-  if (!_.isEmpty(this.ids)) {
-    handlerBody.push(t.variableDeclaration("var", _.map(this.ids, function (uid) {
-      return t.variableDeclarator(uid);
-    })));
-  }
-
  handlerBody.push(returnStatement);

  program.body = [runner];
--- a/lib/6to5/transformation/templates/array-expression-comprehension-filter.js
+++ b/lib/6to5/transformation/templates/array-expression-comprehension-filter.js
@@ -1,5 +0,0 @@
-ARRAY.filter(function (KEY) {
-  return FILTER;
-}).map(function (KEY) {
-  return STATEMENT;
-});
--- a/lib/6to5/transformation/templates/array-expression-comprehension-map.js
+++ b/lib/6to5/transformation/templates/array-expression-comprehension-map.js
@@ -1,3 +0,0 @@
-ARRAY.map(function (KEY) {
-  return STATEMENT;
-});
--- a/lib/6to5/transformation/templates/async-to-generator.js
+++ b/lib/6to5/transformation/templates/async-to-generator.js
@@ -0,0 +1,37 @@
+(function (fn) {
+  return function () {
+    var gen = fn.apply(this, arguments);
+
+    return new Promise(function (resolve, reject) {
+      function step(getNext) {
+        var next;
+
+        try {
+          next = getNext();
+        } catch(e) {
+          reject(e);
+          return;
+        }
+
+        if (next.done) {
+          resolve(next.value);
+          return;
+        }
+
+        Promise.resolve(next.value).then(function (v) {
+          step(function () {
+            return gen.next(v);
+          });
+        }, function (e) {
+          step(function () {
+            return gen["throw"](e);
+          });
+        });
+      }
+
+      step(function () {
+        return gen.next();
+      });
+    });
+  }
+})
--- a/lib/6to5/transformation/templates/common-export-default-assign.js
+++ b/lib/6to5/transformation/templates/common-export-default-assign.js
@@ -0,0 +1 @@
+module.exports = Object.assign(exports["default"], exports);
--- a/lib/6to5/transformation/templates/corejs-iterator.js
+++ b/lib/6to5/transformation/templates/corejs-iterator.js
@@ -0,0 +1 @@
+CORE_ID.$for.getIterator(VALUE);
--- a/lib/6to5/transformation/templates/define-property.js
+++ b/lib/6to5/transformation/templates/define-property.js
@@ -0,0 +1,8 @@
+(function (obj, key, value) {
+  return Object.defineProperty(obj, key, {
+    value: value,
+    enumerable: true,
+    configurable: true,
+    writable: true
+  });
+});
--- a/lib/6to5/transformation/templates/function-return-obj.js
+++ b/lib/6to5/transformation/templates/function-return-obj.js
@@ -1,3 +0,0 @@
-(function (KEY) {
-  return KEY;
-})(OBJECT)
--- a/lib/6to5/transformation/templates/object-define-properties-closure.js
+++ b/lib/6to5/transformation/templates/object-define-properties-closure.js
@@ -1,4 +0,0 @@
-(function (KEY) {
-  CONTENT;
-  return KEY;
-})(OBJECT);
--- a/lib/6to5/transformation/transform.js
+++ b/lib/6to5/transformation/transform.js
@@ -49,6 +49,9 @@ _.each({
  memoizationOperator:       require("./transformers/playground-memoization-operator"),
  objectGetterMemoization:   require("./transformers/playground-object-getter-memoization"),

+  asyncToGenerator:          require("./transformers/optional-async-to-generator"),
+  bluebirdCoroutines:        require("./transformers/optional-bluebird-coroutines"),
+
  react:                     require("./transformers/react"),
  modules:                   require("./transformers/es6-modules"),
  propertyNameShorthand:     require("./transformers/es6-property-name-shorthand"),
@@ -80,10 +83,13 @@ _.each({

  _declarations:             require("./transformers/_declarations"),

+  coreAliasing:              require("./transformers/optional-core-aliasing"),
+  undefinedToVoid:           require("./transformers/optional-undefined-to-void"),
+
  // wrap up
  _aliasFunctions:           require("./transformers/_alias-functions"),
-  useStrict:                 require("./transformers/use-strict"),
  _moduleFormatter:          require("./transformers/_module-formatter"),
+  useStrict:                 require("./transformers/use-strict"),

  // spec
  specPropertyLiterals:         require("./transformers/spec-property-literals"),
--- a/lib/6to5/transformation/transformer.js
+++ b/lib/6to5/transformation/transformer.js
@@ -5,9 +5,12 @@ var t        = require("../types");
 var _        = require("lodash");

 function Transformer(key, transformer, opts) {
-  this.transformer = Transformer.normalise(transformer);
-  this.opts        = opts || {};
-  this.key         = key;
+  this.manipulateOptions = transformer.manipulateOptions;
+  this.experimental      = !!transformer.experimental;
+  this.transformer       = Transformer.normalise(transformer);
+  this.optional          = !!transformer.optional;
+  this.opts              = opts || {};
+  this.key               = key;
 }

 Transformer.normalise = function (transformer) {
@@ -16,8 +19,13 @@ Transformer.normalise = function (transformer) {
  }

  _.each(transformer, function (fns, type) {
+    // hidden property
    if (type[0] === "_") return;
+
    if (_.isFunction(fns)) fns = { enter: fns };
+
+    if (!_.isObject(fns)) return;
+
    transformer[type] = fns;

    var aliases = t.FLIPPED_ALIAS_KEYS[type];
@@ -41,13 +49,9 @@ Transformer.prototype.astRun = function (file, key) {
 };

 Transformer.prototype.transform = function (file) {
-  if (!this.canRun(file)) return;
-
  var transformer = this.transformer;
  var ast         = file.ast;

-  this.astRun(file, "enter");
-
  var build = function (exit) {
    return function (node, parent, scope) {
      var fns = transformer[node.type];
@@ -61,12 +65,14 @@ Transformer.prototype.transform = function (file) {
    };
  };

+  this.astRun(file, "before");
+
  traverse(ast, {
    enter: build(),
    exit:  build(true)
  });

-  this.astRun(file, "exit");
+  this.astRun(file, "after");
 };

 Transformer.prototype.canRun = function (file) {
@@ -80,5 +86,9 @@ Transformer.prototype.canRun = function (file) {
  var whitelist = opts.whitelist;
  if (whitelist.length && !_.contains(whitelist, key)) return false;

+  if (this.optional && !_.contains(opts.optional, key)) return false;
+
+  if (this.experimental && !opts.experimental) return false;
+
  return true;
 };
--- a/lib/6to5/transformation/transformers/_alias-functions.js
+++ b/lib/6to5/transformation/transformers/_alias-functions.js
@@ -20,7 +20,7 @@ var go = function (getBody, node, file, scope) {
      if (!node._aliasFunction) {
        if (t.isFunction(node)) {
          // stop traversal of this node as it'll be hit again by this transformer
-          return false;
+          return this.stop();
        } else {
          return;
        }
@@ -30,10 +30,10 @@ var go = function (getBody, node, file, scope) {
      traverse(node, {
        enter: function (node, parent) {
          if (t.isFunction(node) && !node._aliasFunction) {
-            return false;
+            return this.stop();
          }

-          if (node._ignoreAliasFunctions) return false;
+          if (node._ignoreAliasFunctions) return this.stop();

          var getId;

@@ -49,7 +49,7 @@ var go = function (getBody, node, file, scope) {
        }
      });

-      return false;
+      return this.stop();
    }
  });

--- a/lib/6to5/transformation/transformers/_block-hoist.js
+++ b/lib/6to5/transformation/transformers/_block-hoist.js
@@ -1,17 +1,29 @@
+var _ = require("lodash");
+
+// Priority:
+//
+//  - 0 We want this to be at the **very** bottom
+//  - 1 Default node position
+//  - 2 Priority over normal nodes
+//  - 3 We want this to be at the **very** top
+
 exports.BlockStatement =
 exports.Program = {
  exit: function (node) {
-    var unshift = [];
+    var hasChange = false;
+    for (var i in node.body) {
+      var bodyNode = node.body[i];
+      if (bodyNode && bodyNode._blockHoist != null) hasChange = true;
+    }
+    if (!hasChange) return;

-    node.body = node.body.filter(function (bodyNode) {
-      if (bodyNode._blockHoist) {
-        unshift.push(bodyNode);
-        return false;
-      } else {
-        return true;
-      }
+    var nodePriorities = _.groupBy(node.body, function (bodyNode) {
+      var priority = bodyNode._blockHoist;
+      if (priority == null) priority = 1;
+      if (priority === true) priority = 2;
+      return priority;
    });

-    node.body = unshift.concat(node.body);
+    node.body = _.flatten(_.values(nodePriorities).reverse());
  }
 };
--- a/lib/6to5/transformation/transformers/es5-property-method-assignment.js
+++ b/lib/6to5/transformation/transformers/es5-property-method-assignment.js
@@ -1,4 +1,5 @@
 var util = require("../../util");
+var t    = require("../../types");

 exports.Property = function (node) {
  if (node.method) node.method = false;
@@ -20,14 +21,21 @@ exports.ObjectExpression = function (node, parent, file) {

  if (!hasAny) return;

-  var objId = util.getUid(parent, file);
+  if (node.properties.length) {
+    var objId = t.getUid(parent, file);

-  return util.template("object-define-properties-closure", {
-    KEY: objId,
-    OBJECT: node,
-    CONTENT: util.template("object-define-properties", {
-      OBJECT: objId,
+    return util.template("object-define-properties-closure", {
+      KEY: objId,
+      OBJECT: node,
+      CONTENT: util.template("object-define-properties", {
+        OBJECT: objId,
+        PROPS:  util.buildDefineProperties(mutatorMap)
+      })
+    });
+  } else {
+    return util.template("object-define-properties", {
+      OBJECT: node,
      PROPS:  util.buildDefineProperties(mutatorMap)
-    })
-  });
+    });
+  }
 };
--- a/lib/6to5/transformation/transformers/es6-classes.js
+++ b/lib/6to5/transformation/transformers/es6-classes.js
@@ -21,7 +21,7 @@ exports.ClassDeclaration = function (node, parent, file, scope) {
      });
      return t.assignmentExpression("=", node.id, newNode);
    } else {
-      // likely has a PrivateDeclaration etc
+      // has a super class or PrivateDeclaration etc
      return t.variableDeclaration("let", [
        t.variableDeclarator(node.id, newNode)
      ]);
@@ -85,23 +85,17 @@ Class.prototype.run = function () {

  //

-  if (superName && t.isDynamic(superName)) {
-    // so we're only evaluating it once
-    var superRefName = "super";
-    if (className) superRefName = className.name + "Super";
+  if (superName) {
+    this.closure = true;

-    var superRef = file.generateUidIdentifier(superRefName, this.scope);
+    // so we're only evaluating it once
+    var superRef = t.getUid(superName, this.file);
    body.unshift(t.variableDeclaration("var", [
      t.variableDeclarator(superRef, superName)
    ]));
    superName = superRef;
-  }

-  this.superName = superName;
-
-  //
-
-  if (superName) {
+    this.superName = superName;
    body.push(t.expressionStatement(t.callExpression(file.addDeclaration("inherits"), [className, superName])));
  }

@@ -153,7 +147,7 @@ Class.prototype.buildBody = function () {
    }
  }

-  if (!this.hasConstructor && superName) {
+  if (!this.hasConstructor && superName && !t.isFalsyExpression(superName)) {
    constructor.body.body.push(util.template("class-super-constructor-call", {
      SUPER_NAME: superName
    }, true));
@@ -282,7 +276,7 @@ Class.prototype.replaceInstanceSuperReferences = function (methodNode) {
        if (callee.object.name !== "super") return;

        // super.test(); -> ClassName.prototype.MethodName.call(this);
-        callee.property = t.memberExpression(callee.property, t.identifier("call"));
+        t.appendToMemberExpression(callee, t.identifier("call"));
        node.arguments.unshift(t.thisExpression());
      }
    }
--- a/lib/6to5/transformation/transformers/es6-computed-property-names.js
+++ b/lib/6to5/transformation/transformers/es6-computed-property-names.js
@@ -1,47 +1,96 @@
-var util = require("../../util");
-var t    = require("../../types");
+var t = require("../../types");

 exports.ObjectExpression = function (node, parent, file) {
  var hasComputed = false;
+  var prop;
+  var key;
+  var i;

-  var computed = [];
-
-  node.properties = node.properties.filter(function (prop) {
-    if (prop.computed) {
-      hasComputed = true;
-      computed.unshift(prop);
-      return false;
-    } else {
-      return true;
-    }
-  });
+  for (i in node.properties) {
+    hasComputed = t.isProperty(node.properties[i], { computed: true });
+    if (hasComputed) break;
+  }

  if (!hasComputed) return;

-  var objId = util.getUid(parent, file);
+  var objId = t.getUid(parent, file);

-  var container = util.template("function-return-obj", {
-    KEY: objId,
-    OBJECT: node
-  });
+  var body = [];
+  var container = t.functionExpression(null, [], t.blockStatement(body));
+  container._aliasFunction = true;

-  var containerCallee = container.callee;
-  var containerBody = containerCallee.body.body;
+  var props = node.properties;

-  containerCallee._aliasFunction = true;
+  // normalise key

-  for (var i in computed) {
-    var prop = computed[i];
-    containerBody.unshift(
-      t.expressionStatement(
-        t.assignmentExpression(
-          "=",
-          t.memberExpression(objId, prop.key, true),
-          prop.value
-        )
-      )
-    );
+  for (i in props) {
+    prop = props[i];
+    key = prop.key;
+
+    if (!prop.computed && t.isIdentifier(key)) {
+      prop.key = t.literal(key.name);
+    }
  }

-  return container;
+  // add all non-computed properties and `__proto__` properties to the initializer
+
+  var initProps = [];
+  var broken = false;
+
+  for (i in props) {
+    prop = props[i];
+
+    if (prop.computed) {
+      broken = true;
+    }
+
+    if (!broken || t.isLiteral(prop.key, { value: "__proto__" })) {
+      initProps.push(prop);
+      props[i] = null;
+    }
+  }
+
+  // add a simple assignment for all Symbol member expressions due to symbol polyfill limitations
+  // otherwise use Object.defineProperty
+
+  for (i in props) {
+    prop = props[i];
+    if (!prop) continue;
+
+    key = prop.key;
+    var bodyNode;
+
+    if (prop.computed && t.isMemberExpression(key) && t.isIdentifier(key.object, { name: "Symbol" })) {
+      bodyNode = t.assignmentExpression(
+        "=",
+        t.memberExpression(objId, key, true),
+        prop.value
+      );
+    } else {
+      bodyNode = t.callExpression(file.addDeclaration("define-property"), [objId, key, prop.value]);
+    }
+
+    body.push(t.expressionStatement(bodyNode));
+  }
+
+  // only one node and it's a Object.defineProperty that returns the object
+
+  if (body.length === 1) {
+    var first = body[0].expression;
+
+    if (t.isCallExpression(first)) {
+      first.arguments[0] = t.objectExpression([]);
+      return first;
+    }
+  }
+
+  //
+
+  body.unshift(t.variableDeclaration("var", [
+    t.variableDeclarator(objId, t.objectExpression(initProps))
+  ]));
+
+  body.push(t.returnStatement(objId));
+
+  return t.callExpression(container, []);
 };
--- a/lib/6to5/transformation/transformers/es6-destructuring.js
+++ b/lib/6to5/transformation/transformers/es6-destructuring.js
@@ -75,7 +75,7 @@ var pushArrayPattern = function (opts, nodes, pattern, parentId) {

  var toArray = opts.file.toArray(parentId, !hasSpreadElement && pattern.elements.length);

-  var _parentId = opts.file.generateUidIdentifier("ref", opts.scope);
+  var _parentId = t.getUid(parentId, opts.file, opts.scope);
  nodes.push(t.variableDeclaration("var", [
    t.variableDeclarator(_parentId, toArray)
  ]));
@@ -113,7 +113,7 @@ var pushPattern = function (opts) {
  var scope = opts.scope;

  if (!t.isMemberExpression(parentId) && !t.isIdentifier(parentId)) {
-    var key = file.generateUidIdentifier("ref", scope);
+    var key = t.getUid(parentId, file, scope);

    nodes.push(t.variableDeclaration("var", [
      t.variableDeclarator(key, parentId)
--- a/lib/6to5/transformation/transformers/es6-generators.js
+++ b/lib/6to5/transformation/transformers/es6-generators.js
@@ -1 +1,3 @@
-module.exports = require("regenerator").transform;
+exports.ast = {
+  before: require("regenerator").transform
+};
--- a/lib/6to5/transformation/transformers/es6-let-scoping.js
+++ b/lib/6to5/transformation/transformers/es6-let-scoping.js
@@ -280,7 +280,7 @@ LetScoping.prototype.checkLoop = function () {
      var replace;

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

      if (node && !node.label) {
@@ -329,7 +329,7 @@ LetScoping.prototype.hoistVarDeclarations = function () {
      } else if (isVar(node, parent)) {
        return self.pushDeclar(node).map(t.expressionStatement);
      } else if (t.isFunction(node)) {
-        return false;
+        return this.stop();
      }
    }
  });
@@ -388,9 +388,9 @@ LetScoping.prototype.getLetReferences = function () {
          }
        });

-        return false;
+        return this.stop();
      } else if (t.isLoop(node)) {
-        return false;
+        return this.stop();
      }
    }
  });
--- a/lib/6to5/transformation/transformers/es6-modules.js
+++ b/lib/6to5/transformation/transformers/es6-modules.js
@@ -1,5 +1,11 @@
 var t = require("../../types");

+exports.ast = {
+  before: function (ast, file) {
+    ast.program.body = file.dynamicImports.concat(ast.program.body);
+  }
+};
+
 exports.ImportDeclaration = function (node, parent, file) {
  var nodes = [];

@@ -11,6 +17,12 @@ exports.ImportDeclaration = function (node, parent, file) {
    file.moduleFormatter.importDeclaration(node, nodes, parent);
  }

+  if (nodes.length === 1) {
+    // inherit `_blockHoist`
+    // this for `_blockHoist` in File.prototype.addImport
+    nodes[0]._blockHoist = node._blockHoist;
+  }
+
  return nodes;
 };

--- a/lib/6to5/transformation/transformers/es6-spread.js
+++ b/lib/6to5/transformation/transformers/es6-spread.js
@@ -87,13 +87,7 @@ exports.CallExpression = function (node, parent, file, scope) {
      callee.object = t.assignmentExpression("=", temp, callee.object);
    }

-    if (callee.computed) {
-      callee.object = t.memberExpression(callee.object, callee.property, true);
-      callee.property = t.identifier("apply");
-      callee.computed = false;
-    } else {
-      callee.property = t.memberExpression(callee.property, t.identifier("apply"));
-    }
+    t.appendToMemberExpression(callee, t.identifier("apply"));
  } else {
    node.callee = t.memberExpression(node.callee, t.identifier("apply"));
  }
--- a/lib/6to5/transformation/transformers/es7-abstract-references.js
+++ b/lib/6to5/transformation/transformers/es7-abstract-references.js
@@ -3,6 +3,8 @@
 var util = require("../../util");
 var t    = require("../../types");

+exports.experimental = true;
+
 var container = function (parent, call, ret) {
  if (t.isExpressionStatement(parent)) {
    // we don't need to worry about return values
--- a/lib/6to5/transformation/transformers/es7-array-comprehension.js
+++ b/lib/6to5/transformation/transformers/es7-array-comprehension.js
@@ -1,41 +1,25 @@
-var util = require("../../util");
-var t    = require("../../types");
+var traverse = require("../../traverse");
+var util     = require("../../util");
+var t        = require("../../types");

-var single = function (node, file) {
-  var block = node.blocks[0];
+exports.experimental = true;

-  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:     file.toArray(block.right),
-    KEY:       block.left
-  });
-
-  var aliasPossibles = [result.callee.object, result];
-  for (var i in aliasPossibles) {
-    var call = aliasPossibles[i];
-    if (t.isCallExpression(call)) {
-      call.arguments[0]._aliasFunction = true;
-    }
-  }
-
-  return result;
-};
-
-var multiple = function (node, file) {
-  var uid = file.generateUidIdentifier("arr");
+var build = function (node, parent, file, scope) {
+  var uid = t.getUid(parent, file, scope);

  var container = util.template("array-comprehension-container", {
    KEY: uid
  });
-  container.callee.expression._aliasFunction = true;
+  container.callee._aliasFunction = true;

  var block = container.callee.body;
  var body  = block.body;

+  if (traverse.hasType(node, "YieldExpression", t.FUNCTION_TYPES)) {
+    container.callee.generator = true;
+    container = t.yieldExpression(container, true);
+  }
+
  var returnStatement = body.pop();

  body.push(exports._build(node, function () {
@@ -71,12 +55,8 @@ exports._build = function (node, buildBody) {
  );
 };

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

-  if (node.blocks.length === 1) {
-    return single(node, file);
-  } else {
-    return multiple(node, file);
-  }
+  return build(node, parent, file, scope);
 };
--- a/lib/6to5/transformation/transformers/es7-exponentiation-operator.js
+++ b/lib/6to5/transformation/transformers/es7-exponentiation-operator.js
@@ -1,5 +1,7 @@
 // https://github.com/rwaldron/exponentiation-operator

+exports.experimental = true;
+
 var t = require("../../types");
 var pow = t.memberExpression(t.identifier("Math"), t.identifier("pow"));

--- a/lib/6to5/transformation/transformers/es7-generator-comprehension.js
+++ b/lib/6to5/transformation/transformers/es7-generator-comprehension.js
@@ -1,6 +1,8 @@
 var arrayComprehension = require("./es7-array-comprehension");
 var t                  = require("../../types");

+exports.experimental = true;
+
 exports.ComprehensionExpression = function (node) {
  if (!node.generator) return;

--- a/lib/6to5/transformation/transformers/es7-object-spread.js
+++ b/lib/6to5/transformation/transformers/es7-object-spread.js
@@ -2,6 +2,8 @@

 var t = require("../../types");

+exports.experimental = true;
+
 exports.ObjectExpression = function (node) {
  var hasSpread = false;
  var i;
--- a/lib/6to5/transformation/transformers/optional-async-to-generator.js
+++ b/lib/6to5/transformation/transformers/optional-async-to-generator.js
@@ -0,0 +1,11 @@
+var bluebirdCoroutines = require("./optional-bluebird-coroutines");
+
+exports.optional = true;
+
+exports.manipulateOptions = bluebirdCoroutines.manipulateOptions;
+
+exports.Function = function (node, parent, file) {
+  if (!node.async || node.generator) return;
+
+  return bluebirdCoroutines._Function(node, file.addDeclaration("async-to-generator"));
+};
--- a/lib/6to5/transformation/transformers/optional-bluebird-coroutines.js
+++ b/lib/6to5/transformation/transformers/optional-bluebird-coroutines.js
@@ -0,0 +1,45 @@
+var traverse = require("../../traverse");
+var t        = require("../../types");
+
+exports.manipulateOptions = function (opts) {
+  opts.experimental = true;
+  opts.blacklist.push("generators");
+};
+
+exports.optional = true;
+
+exports._Function = function (node, callId) {
+  node.async = false;
+  node.generator = true;
+
+  traverse(node, {
+    enter: function (node) {
+      if (t.isFunction(node)) this.stop();
+
+      if (t.isAwaitExpression(node)) {
+        node.type = "YieldExpression";
+      }
+    }
+  });
+
+  var call = t.callExpression(callId, [node]);
+
+  if (t.isFunctionDeclaration(node)) {
+    var declar = t.variableDeclaration("var", [
+      t.variableDeclarator(node.id, call)
+    ]);
+    declar._blockHoist = true;
+    return declar;
+  } else {
+    return call;
+  }
+};
+
+exports.Function = function (node, parent, file) {
+  if (!node.async || node.generator) return;
+
+  var id = t.identifier("Bluebird");
+  file.addImport(id, "bluebird");
+
+  return exports._Function(node, t.memberExpression(id, t.identifier("coroutine")));
+};
--- a/lib/6to5/transformation/transformers/optional-core-aliasing.js
+++ b/lib/6to5/transformation/transformers/optional-core-aliasing.js
@@ -0,0 +1,59 @@
+var traverse = require("../../traverse");
+var util     = require("../../util");
+var core     = require("core-js/library");
+var t        = require("../../types");
+var _        = require("lodash");
+
+var coreHas = function (node) {
+  return node.name !== "_" && _.has(core, node.name);
+};
+
+exports.optional = true;
+
+exports.ast = {
+  enter: function (ast, file) {
+    file._coreId = file.generateUidIdentifier("core");
+    file.addImport(file._coreId, "core-js/library");
+  },
+
+  exit: function (ast, file) {
+    traverse(ast, {
+      enter: function (node, parent) {
+        var prop;
+
+        if (t.isMemberExpression(node) && t.isReferenced(node, parent)) {
+          // Array.from -> _core.Array.from
+          var obj = node.object;
+          prop = node.property;
+
+          if (!t.isReferenced(obj, node)) return;
+
+          if (!node.computed && coreHas(obj) && _.has(core[obj.name], prop.name)) {
+            this.stop();
+            return t.prependToMemberExpression(node, file._coreId);
+          }
+        } else if (t.isIdentifier(node) && !t.isMemberExpression(parent) && t.isReferenced(node, parent) && coreHas(node)) {
+          // new Promise -> new _core.Promise
+          return t.memberExpression(file._coreId, node);
+        } else if (t.isCallExpression(node)) {
+          // arr[Symbol.iterator]() -> _core.$for.getIterator(arr)
+
+          if (node.arguments.length) return;
+
+          var callee = node.callee;
+          if (!t.isMemberExpression(callee)) return;
+          if (!callee.computed) return;
+
+          prop = callee.property;
+          if (!t.isIdentifier(prop.object, { name: "Symbol" })) return;
+          if (!t.isIdentifier(prop.property, { name: "iterator" })) return;
+
+          return util.template("corejs-iterator", {
+            CORE_ID: file._coreId,
+            VALUE:   callee.object
+          });
+        }
+      }
+    });
+  }
+};
--- a/lib/6to5/transformation/transformers/optional-undefined-to-void.js
+++ b/lib/6to5/transformation/transformers/optional-undefined-to-void.js
@@ -0,0 +1,9 @@
+var t = require("../../types");
+
+exports.optional = true;
+
+exports.Identifier = function (node, parent) {
+  if (node.name === "undefined" && t.isReferenced(node, parent)) {
+    return t.unaryExpression("void", t.literal(0), true);
+  }
+};
--- a/lib/6to5/transformation/transformers/playground-memoization-operator.js
+++ b/lib/6to5/transformation/transformers/playground-memoization-operator.js
@@ -10,7 +10,7 @@ var getPropRef = function (nodes, prop, file, scope) {
  if (t.isIdentifier(prop)) {
    return t.literal(prop.name);
  } else {
-    var temp = file.generateUidIdentifier("propKey", scope);
+    var temp = t.getUid(prop, file, scope);
    nodes.push(t.variableDeclaration("var", [
      t.variableDeclarator(temp, prop)
    ]));
@@ -20,7 +20,7 @@ var getPropRef = function (nodes, prop, file, scope) {

 var getObjRef = function (nodes, obj, file, scope) {
  if (t.isDynamic(obj)) {
-    var temp = file.generateUidIdentifier("obj", scope);
+    var temp = t.getUid(obj, file, scope);
    nodes.push(t.variableDeclaration("var", [
      t.variableDeclarator(temp, obj)
    ]));
--- a/lib/6to5/transformation/transformers/playground-object-getter-memoization.js
+++ b/lib/6to5/transformation/transformers/playground-object-getter-memoization.js
@@ -2,38 +2,30 @@ var traverse = require("../../traverse");
 var t        = require("../../types");

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

  var value = node.value;
  t.ensureBlock(value);

-  var body  = value.body.body;
-  var key   = node.key;
+  var key = node.key;

  if (t.isIdentifier(key) && !node.computed) {
-    key = "_" + key.name;
-  } else {
-    key = file.generateUid("memo", scope);
+    key = t.literal(key.name);
  }

-  var memoId = t.memberExpression(t.thisExpression(), t.identifier(key));
-  var doneId = t.memberExpression(t.thisExpression(), t.identifier(key + "Done"));
-
  traverse(value, {
    enter: function (node) {
      if (t.isFunction(node)) return;

      if (t.isReturnStatement(node) && node.argument) {
-        node.argument = t.assignmentExpression("=", memoId, node.argument);
+        node.argument = t.memberExpression(t.callExpression(file.addDeclaration("define-property"), [
+          t.thisExpression(),
+          key,
+          node.argument
+        ]), key, true);
      }
    }
  });
-
-  // this._barDone = true;
-  body.unshift(t.expressionStatement(t.assignmentExpression("=", doneId, t.literal(true))));
-
-  // if (this._barDone) return this._bar;
-  body.unshift(t.ifStatement(doneId, t.returnStatement(memoId)));
 };
--- a/lib/6to5/transformation/transformers/use-strict.js
+++ b/lib/6to5/transformation/transformers/use-strict.js
@@ -1,12 +1,14 @@
 var t = require("../../types");

-module.exports = function (ast) {
-  var body = ast.program.body;
-  var first = body[0];
+exports.ast = {
+  exit: function (ast) {
+    var body = ast.program.body;
+    var first = body[0];

-  var noStrict = !first || !t.isExpressionStatement(first) || !t.isLiteral(first.expression) || first.expression.value !== "use strict";
+    var noStrict = !first || !t.isExpressionStatement(first) || !t.isLiteral(first.expression) || first.expression.value !== "use strict";

-  if (noStrict) {
-    body.unshift(t.expressionStatement(t.literal("use strict")));
+    if (noStrict) {
+      body.unshift(t.expressionStatement(t.literal("use strict")));
+    }
  }
 };
--- a/lib/6to5/traverse/index.js
+++ b/lib/6to5/traverse/index.js
@@ -39,25 +39,23 @@ function traverse(parent, opts, scope) {
      // replace node
      var maybeReplace = function (result) {
        if (result === false) return;
+        if (result == null) return;

-        if (result != null) {
-          updated = true;
+        var isArray = _.isArray(result);

-          var isArray = _.isArray(result);
+        // inherit comments from original node to the first replacement node
+        var inheritTo = result;
+        if (isArray) inheritTo = result[0];
+        if (inheritTo) t.inheritsComments(inheritTo, node);

-          // inherit comments from original node to the first replacement node
-          var inheritTo = result;
-          if (isArray) inheritTo = result[0];
-          if (inheritTo) t.inheritsComments(inheritTo, node);
+        // replace the node
+        node = obj[key] = result;
+        updated = true;

-          // replace the node
-          node = obj[key] = result;
-
-          // we're replacing a statement or block node with an array of statements so we better
-          // ensure that it's a block
-          if (isArray && _.contains(t.STATEMENT_OR_BLOCK_KEYS, key) && !t.isBlockStatement(obj)) {
-            t.ensureBlock(obj, key);
-          }
+        // we're replacing a statement or block node with an array of statements so we better
+        // ensure that it's a block
+        if (isArray && _.contains(t.STATEMENT_OR_BLOCK_KEYS, key) && !t.isBlockStatement(obj)) {
+          t.ensureBlock(obj, key);
        }
      };

@@ -70,7 +68,8 @@ function traverse(parent, opts, scope) {
        },

        remove: function () {
-          stopped = removed = true;
+          this.stop();
+          removed = true;
        }
      };

@@ -84,12 +83,12 @@ function traverse(parent, opts, scope) {
        maybeReplace(result);

        if (removed) {
-          delete obj[key];
+          obj[key] = null;
          updated = true;
        }

        // stop iteration
-        if (stopped || result === false) return;
+        if (stopped) return;
      }

      // traverse node
@@ -106,7 +105,14 @@ function traverse(parent, opts, scope) {
        handle(nodes, i);
      }

-      if (updated) parent[key] = _.flatten(parent[key]);
+      if (updated) {
+        parent[key] = _.flatten(parent[key]);
+
+        if (key === "body") {
+          // we can safely compact this
+          parent[key] = _.compact(parent[key]);
+        }
+      }
    } else {
      handle(parent, key);
    }
@@ -155,7 +161,7 @@ traverse.hasType = function (tree, type, blacklistTypes) {
    enter: function (node) {
      if (node.type === type) {
        has = true;
-        return false;
+        this.stop();
      }
    }
  });
--- a/lib/6to5/traverse/scope.js
+++ b/lib/6to5/traverse/scope.js
@@ -93,7 +93,7 @@ Scope.prototype.getInfo = function () {

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

        // function identifier doesn't belong to this scope
        if (block.id && node === block.id) return;
--- a/lib/6to5/types/alias-keys.json
+++ b/lib/6to5/types/alias-keys.json
@@ -17,23 +17,23 @@
  "ExportDeclaration":   ["Statement", "Declaration"],
  "ImportDeclaration":   ["Statement", "Declaration"],

-  "ArrowFunctionExpression": ["Scope", "Function"],
+  "ArrowFunctionExpression": ["Scope", "Function", "Expression"],
  "FunctionDeclaration":     ["Statement", "Declaration", "Scope", "Function"],
-  "FunctionExpression":      ["Scope", "Function"],
+  "FunctionExpression":      ["Scope", "Function", "Expression"],

  "BlockStatement": ["Statement", "Scope"],
  "Program":        ["Scope"],
  "CatchClause":    ["Scope"],

-  "LogicalExpression": ["Binary"],
-  "BinaryExpression":  ["Binary"],
+  "LogicalExpression": ["Binary", "Expression"],
+  "BinaryExpression":  ["Binary", "Expression"],

-  "UnaryExpression": ["UnaryLike"],
+  "UnaryExpression": ["UnaryLike", "Expression"],
  "SpreadProperty":  ["UnaryLike"],
  "SpreadElement":   ["UnaryLike"],

  "ClassDeclaration": ["Statement", "Declaration", "Class"],
-  "ClassExpression":  ["Class"],
+  "ClassExpression":  ["Class", "Expression"],

  "ForOfStatement": ["Statement", "For", "Scope", "Loop"],
  "ForInStatement": ["Statement", "For", "Scope", "Loop"],
@@ -43,5 +43,27 @@
  "ArrayPattern":  ["Pattern"],

  "Property": ["UserWhitespacable"],
-  "XJSElement": ["UserWhitespacable"]
+  "XJSElement": ["UserWhitespacable", "Expression"],
+
+  "ArrayExpression": ["Expression"],
+  "AssignmentExpression": ["Expression"],
+  "AwaitExpression": ["Expression"],
+  "BindFunctionExpression": ["Expression"],
+  "BindMemberExpression": ["Expression"],
+  "CallExpression": ["Expression"],
+  "ComprehensionExpression": ["Expression"],
+  "ConditionalExpression": ["Expression"],
+  "Identifier": ["Expression"],
+  "Literal": ["Expression"],
+  "MemberExpression": ["Expression"],
+  "NewExpression": ["Expression"],
+  "ObjectExpression": ["Expression"],
+  "SequenceExpression": ["Expression"],
+  "TaggedTemplateExpression": ["Expression"],
+  "ThisExpression": ["Expression"],
+  "UpdateExpression": ["Expression"],
+  "VirtualPropertyExpression": ["Expression"],
+  "XJSEmptyExpression": ["Expression"],
+  "XJSMemberExpression": ["Expression"],
+  "YieldExpression": ["Expression"]
 }
--- a/lib/6to5/types/builder-keys.json
+++ b/lib/6to5/types/builder-keys.json
@@ -11,6 +11,8 @@
  "FunctionExpression":      ["id", "params", "body", "generator"],
  "Identifier":              ["name"],
  "IfStatement":             ["test", "consequent", "alternate"],
+  "ImportDeclaration":       ["specifiers", "source"],
+  "ImportSpecifier":         ["id", "name"],
  "Literal":                 ["value"],
  "LogicalExpression":       ["operator", "left", "right"],
  "MemberExpression":        ["object", "property", "computed"],
--- a/lib/6to5/types/index.js
+++ b/lib/6to5/types/index.js
@@ -64,15 +64,32 @@ _.each(t.FLIPPED_ALIAS_KEYS, function (types, type) {
  addAssert(type, is);
 });

-//
+/*
+ * Shallowly checks to see if the passed `node` will evaluate to a
+ * falsy. This is if `node` is a `Literal` and `value` is falsy or
+ * `node` is an `Identifier` with a name of `undefiend`.
+ *
+ * @param {Object} node
+ * @returns {Boolean}
+ */

-t.isExpression = function (node) {
-  return !t.isStatement(node);
+t.isFalsyExpression = function (node) {
+  if (t.isLiteral(node)) {
+    return !node.value;
+  } else if (t.isIdentifier(node)) {
+    return node.name === "undefined";
+  }
+  return false;
 };

-addAssert("Expression", t.isExpression);
-
-//
+/**
+ * Turn an array of statement `nodes` into a `SequenceExpression`.
+ *
+ * Variable declarations are turned into simple assignments and their
+ * declarations hoisted to the top of the current scope.
+ *
+ * Expression statements are just resolved to their standard expression.
+ */

 t.toSequenceExpression = function (nodes, scope) {
  var exprs = [];
@@ -113,7 +130,41 @@ t.shallowEqual = function (actual, expected) {
  return same;
 };

-//
+/**
+ * Description
+ *
+ * @param {Object} member
+ * @param {Object} append
+ * @param {Boolean} [computed]
+ * @returns {Object} member
+ */
+
+t.appendToMemberExpression = function (member, append, computed) {
+  member.object   = t.memberExpression(member.object, member.property, member.computed);
+  member.property = append;
+  member.computed = !!computed;
+  return member;
+};
+
+/**
+ * Description
+ *
+ * @param {Object} member
+ * @param {Object} append
+ * @returns {Object} member
+ */
+
+t.prependToMemberExpression = function (member, append) {
+  member.object = t.memberExpression(append, member.object);
+  return member;
+};
+
+/*
+ * Description
+ *
+ * @param {Object} node
+ * @returns {Boolean}
+ */

 t.isDynamic = function (node) {
  if (t.isExpressionStatement(node)) {
@@ -127,7 +178,14 @@ t.isDynamic = function (node) {
  }
 };

-// todo: https://github.com/eventualbuddha/ast-util/blob/9bf91c5ce8/lib/index.js#L454-L507
+/**
+ * Description
+ *
+ * @param {Object} node
+ * @param {Object} parent
+ * @returns {Boolean}
+ */
+
 t.isReferenced = function (node, parent) {
  // we're a property key and we aren't computed so we aren't referenced
  if (t.isProperty(parent) && parent.key === node && !parent.computed) return false;
@@ -149,11 +207,29 @@ t.isReferenced = function (node, parent) {
  return false;
 };

+/**
+ * Description
+ *
+ * @param {String} name
+ * @returns {Boolean}
+ */
+
+t.isValidIdentifier = function (name) {
+  return _.isString(name) && esutils.keyword.isIdentifierName(name) && !esutils.keyword.isKeywordES6(name, true);
+};
+
+/*
+ * Description
+ *
+ * @param {String} name
+ * @returns {String}
+ */
+
 t.toIdentifier = function (name) {
  if (t.isIdentifier(name)) return name.name;

  // replace all non-valid identifiers with dashes
-  name = name.replace(/[^a-zA-Z0-9]/g, "-");
+  name = name.replace(/[^a-zA-Z0-9$_]/g, "-");

  // remove all dashes and numbers from start of name
  name = name.replace(/^[-0-9]+/, "");
@@ -163,18 +239,32 @@ t.toIdentifier = function (name) {
    return c ? c.toUpperCase() : "";
  });

+  // remove underscores from start of name
+  name = name.replace(/^\_/, "");
+
  return name || '_';
 };

-t.isValidIdentifier = function (name) {
-  return _.isString(name) && esutils.keyword.isIdentifierName(name) && !esutils.keyword.isKeywordES6(name, true);
-};
+/**
+ * Description
+ *
+ * @param {Object} node
+ * @param {String} key
+ */

 t.ensureBlock = function (node, key) {
  key = key || "body";
  node[key] = t.toBlock(node[key], node);
 };

+/**
+ * Description
+ *
+ * @param {Object} node
+ * @param {Boolean} [ignore]
+ * @returns {Object|Boolean}
+ */
+
 t.toStatement = function (node, ignore) {
  if (t.isStatement(node)) {
    return node;
@@ -208,6 +298,14 @@ t.toStatement = function (node, ignore) {
  return node;
 };

+/**
+ * Description
+ *
+ * @param {Object} node
+ * @param {Object} parent
+ * @returns {Object}
+ */
+
 t.toBlock = function (node, parent) {
  if (t.isBlockStatement(node)) {
    return node;
@@ -228,6 +326,67 @@ t.toBlock = function (node, parent) {
  return t.blockStatement(node);
 };

+/*
+ * Description
+ *
+ * @param {Object} parent
+ * @param {File} file
+ * @param {Scope} scope
+ * @returns {Object}
+ */
+
+t.getUid = function (parent, file, scope) {
+  var node = parent;
+
+  if (t.isAssignmentExpression(parent)) {
+    node = parent.left;
+  } else if (t.isVariableDeclarator(parent)) {
+    node = parent.id;
+  }
+
+  var id = "ref";
+
+  if (t.isProperty(node)) {
+    node = node.key;
+  }
+
+  if (t.isIdentifier(node)) {
+    id = node.name;
+  } else if (t.isLiteral(node)) {
+    id = node.value;
+  } else if (t.isMemberExpression(node)) {
+    var parts = [];
+
+    var add = function (node) {
+      if (t.isMemberExpression(node)) {
+        add(node.object);
+        add(node.property);
+      } else if (t.isIdentifier(node)) {
+        parts.push(node.name);
+      } else if (t.isLiteral(node)) {
+        parts.push(node.value);
+      }
+    };
+
+    add(node);
+
+    id = parts.join("$");
+  }
+
+  id = id.replace(/^_/, "");
+
+  return file.generateUidIdentifier(id, scope);
+};
+
+/**
+ * Description
+ *
+ * @param {Object} node
+ * @param {Boolean} [map]
+ * @param {Array} [ignoreTypes]
+ * @returns {Array|Object}
+ */
+
 t.getIds = function (node, map, ignoreTypes) {
  ignoreTypes = ignoreTypes || [];

@@ -278,27 +437,69 @@ t.getIds.arrays = {
  ObjectPattern: ["properties"]
 };

+/**
+ * Description
+ *
+ * @param {Object} node
+ * @returns {Boolean}
+ */
+
 t.isLet = function (node) {
  return t.isVariableDeclaration(node) && (node.kind !== "var" || node._let);
 };

+/**
+ * Description
+ *
+ * @param {Object} node
+ * @returns {Boolean}
+ */
+
 t.isVar = function (node) {
  return t.isVariableDeclaration(node, { kind: "var" }) && !node._let;
 };

+//
+
+t.COMMENT_KEYS = ["leadingComments", "trailingComments"];
+
+/**
+ * Description
+ *
+ * @param {Object} child
+ * @returns {Object} child
+ */
+
 t.removeComments = function (child) {
-  delete child.leadingComments;
-  delete child.trailingComments;
+  _.each(t.COMMENT_KEYS, function (key) {
+    delete child[key];
+  });
  return child;
 };

+/**
+ * Description
+ *
+ * @param {Object} child
+ * @param {Object} parent
+ * @returns {Object} child
+ */
+
 t.inheritsComments = function (child, parent) {
-  _.each(["leadingComments", "trailingComments"], function (key) {
+  _.each(t.COMMENT_KEYS, function (key) {
    child[key]  = _.uniq(_.compact([].concat(child[key], parent[key])));
  });
  return child;
 };

+/**
+ * Description
+ *
+ * @param {Object} child
+ * @param {Object} parent
+ * @returns {Object} child
+ */
+
 t.inherits = function (child, parent) {
  child.loc   = parent.loc;
  child.end   = parent.end;
@@ -308,10 +509,24 @@ t.inherits = function (child, parent) {
  return child;
 };

+/**
+ * Description
+ *
+ * @param {Object} specifier
+ * @returns {String}
+ */
+
 t.getSpecifierName = function (specifier) {
  return specifier.name || specifier.id;
 };

+/**
+ * Description
+ *
+ * @param {Object} specifier
+ * @returns {Boolean}
+ */
+
 t.isSpecifierDefault = function (specifier) {
  return t.isIdentifier(specifier.id) && specifier.id.name === "default";
 };
--- a/lib/6to5/util.js
+++ b/lib/6to5/util.js
@@ -52,22 +52,6 @@ exports.arrayify = function (val) {
  throw new TypeError("illegal type for arrayify");
 };

-exports.getUid = function (parent, file) {
-  var node;
-
-  if (t.isAssignmentExpression(parent)) {
-    node = parent.left;
-  } else if (t.isVariableDeclarator(parent)) {
-    node = parent.id;
-  }
-
-  var id = "ref";
-
-  if (t.isIdentifier(node)) id = node.name;
-
-  return file.generateUidIdentifier(id);
-};
-
 exports.isAbsolute = function (loc) {
  if (!loc) return false;
  if (loc[0] === "/") return true; // unix
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
  "name": "6to5",
  "description": "Turn ES6 code into readable vanilla ES5 with source maps",
-  "version": "2.2.0",
+  "version": "2.4.4",
  "author": "Sebastian McKenzie <sebmck@gmail.com>",
  "homepage": "https://github.com/6to5/6to5",
  "repository": {
@@ -35,7 +35,7 @@
    "test": "make test"
  },
  "dependencies": {
-    "acorn-6to5": "0.9.1-16",
+    "acorn-6to5": "0.11.1-3",
    "ast-types": "~0.6.1",
    "chokidar": "0.11.1",
    "commander": "2.5.0",
--- a/test/fixtures/generation/comments/computed-property-comments-2/expected.js
+++ b/test/fixtures/generation/comments/computed-property-comments-2/expected.js
@@ -3,8 +3,9 @@ var test = {
   * Before bracket init
   */
  ["a"]: "1",
-  [/*
-    * Inside bracket init
-    */
-  "b"]: "2"
+  [( /*
+      * Inside bracket init
+      */
+    "b"
+  )]: "2"
 }, ok = 42;
--- a/test/fixtures/generation/comments/computed-property-comments/expected.js
+++ b/test/fixtures/generation/comments/computed-property-comments/expected.js
@@ -4,10 +4,11 @@ var test = {
   */
  ["a"]: "1",

-  [/*
-    * Inside bracket init
-    */
-  "b"]: "2",
+  [( /*
+      * Inside bracket init
+      */
+    "b"
+  )]: "2",

  ["c"
  /*
@@ -17,9 +18,10 @@ var test = {
  // Before bracket, line comment
  ["d"]: "4",

-  [
-  // Inside bracket, line comment
-  "e"]: "5",
+  [(
+    // Inside bracket, line comment
+    "e"
+  )]: "5",

  ["f"
  // After bracket, line comment
--- a/test/fixtures/generation/harmony-edgecase/class-declaration/actual.js
+++ b/test/fixtures/generation/harmony-edgecase/class-declaration/actual.js
@@ -2,8 +2,6 @@ class Test {
 }
 class Derived extends Super {
 }
-class Derived2 extends Super() {
-}
 class StaticMethods {
  static n1() {
  }
--- a/test/fixtures/generation/harmony-edgecase/class-declaration/expected.js
+++ b/test/fixtures/generation/harmony-edgecase/class-declaration/expected.js
@@ -1,6 +1,5 @@
 class Test {}
 class Derived extends Super {}
-class Derived2 extends Super() {}
 class StaticMethods {
  static n1() {}

--- a/test/fixtures/generation/harmony-edgecase/class-expression/actual.js
+++ b/test/fixtures/generation/harmony-edgecase/class-expression/actual.js
@@ -1,6 +1,5 @@
 (class Test { });
 (class Derived extends Super { });
-(class Derived2 extends Super() { });
 (class StaticMethods {
  static n1() {
  }
@@ -54,4 +53,3 @@
  }
 });
 (class { });
-(class extends Super() { });
--- a/test/fixtures/generation/harmony-edgecase/class-expression/expected.js
+++ b/test/fixtures/generation/harmony-edgecase/class-expression/expected.js
@@ -1,6 +1,5 @@
 (class Test {});
 (class Derived extends Super {});
-(class Derived2 extends Super() {});
 (class StaticMethods {
  static n1() {}

@@ -38,4 +37,3 @@
  *[gen1]() {}
 });
 (class {});
-(class extends Super() {});
--- a/test/fixtures/transformation/.es6-modules-system/exports-variable/expected.js
+++ b/test/fixtures/transformation/.es6-modules-system/exports-variable/expected.js
@@ -1,21 +0,0 @@
-System.register([], function (_export) {
-  _export("foo7", foo7);
-
-  function foo7() {}
-  return {
-    setters: [],
-    execute: function () {
-      "use strict";
-
-      var foo = _export("foo", 1);
-      var foo2 = _export("foo2", function () {});
-      var foo3 = _export("foo3", undefined);
-      var foo4 = _export("foo4", 2);
-      var foo5 = _export("foo5", undefined);
-      var foo6 = _export("foo6", 3);
-      var foo8 = function foo8() {};
-
-      _export("foo8", foo8);
-    }
-  };
-});
--- a/test/fixtures/transformation/.es6-modules-system/imports-default/expected.js
+++ b/test/fixtures/transformation/.es6-modules-system/imports-default/expected.js
@@ -1,14 +0,0 @@
-System.register([], function (_export) {
-  var _foo;
-  return {
-    setters: [function (m) {
-      _foo = m
-    }],
-    execute: function () {
-      "use strict";
-
-      var foo = _foo["default"];
-      var foo = _foo["default"];
-    }
-  };
-});
--- a/test/fixtures/transformation/.es6-modules-system/imports-glob/expected.js
+++ b/test/fixtures/transformation/.es6-modules-system/imports-glob/expected.js
@@ -1,13 +0,0 @@
-System.register(["foo"], function (_export) {
-  var _foo;
-  return {
-    setters: [function (m) {
-      _foo = m
-    }],
-    execute: function () {
-      "use strict";
-
-      var foo = _foo;
-    }
-  };
-});
--- a/test/fixtures/transformation/.es6-modules-system/imports-mixing/expected.js
+++ b/test/fixtures/transformation/.es6-modules-system/imports-mixing/expected.js
@@ -1,14 +0,0 @@
-System.register(["foo"], function (_export) {
-  var _foo;
-  return {
-    setters: [function (m) {
-      _foo = m
-    }],
-    execute: function () {
-      "use strict";
-
-      var foo = _foo["default"];
-      var xyz = _foo.baz;
-    }
-  };
-});
--- a/test/fixtures/transformation/.es6-modules-system/imports-named/expected.js
+++ b/test/fixtures/transformation/.es6-modules-system/imports-named/expected.js
@@ -1,18 +0,0 @@
-System.register(["foo"], function (_export) {
-  var _foo;
-  return {
-    setters: [function (m) {
-      _foo = m
-    }],
-    execute: function () {
-      "use strict";
-
-      var bar = _foo.bar;
-      var bar = _foo.bar;
-      var baz = _foo.baz;
-      var baz = _foo.bar;
-      var baz = _foo.bar;
-      var xyz = _foo.xyz;
-    }
-  };
-});
--- a/test/fixtures/transformation/.es6-modules-system/imports/expected.js
+++ b/test/fixtures/transformation/.es6-modules-system/imports/expected.js
@@ -1,15 +0,0 @@
-System.register(["foo", "foo-bar", "./directory/foo-bar"], function (_export) {
-  var _foo, _fooBar, _directoryFooBar;
-  return {
-    setters: [function (m) {
-      _foo = m
-    }, function (m) {
-      _fooBar = m
-    }, function (m) {
-      _directoryFooBar = m
-    }],
-    execute: function () {
-      "use strict";
-    }
-  };
-});
--- a/test/fixtures/transformation/.es6-modules-system/overview/expected.js
+++ b/test/fixtures/transformation/.es6-modules-system/overview/expected.js
@@ -1,25 +0,0 @@
-System.register(["foo", "foo-bar", "./directory/foo-bar"], function (_export) {
-  var _foo, _fooBar, _directoryFooBar;
-  return {
-    setters: [function (m) {
-      _foo = m
-    }, function (m) {
-      _fooBar = m
-    }, function (m) {
-      _directoryFooBar = m
-    }],
-    execute: function () {
-      "use strict";
-
-      var foo = _foo["default"];
-      var foo = _foo;
-      var bar = _foo.bar;
-      var bar = _foo.foo;
-      _export("test", test);
-
-      var test = _export("test", 5);
-
-      _export("default", test);
-    }
-  };
-});
--- a/test/fixtures/transformation/es5-property-methods-assignment/getter-and-setter/expected.js
+++ b/test/fixtures/transformation/es5-property-methods-assignment/getter-and-setter/expected.js
@@ -1,17 +1,13 @@
 "use strict";

-var obj = (function (_obj) {
-  Object.defineProperties(_obj, {
-    foo: {
-      get: function () {
-        return 5 + 5;
-      },
-      set: function (value) {
-        this._foo = value;
-      },
-      enumerable: true
-    }
-  });
-
-  return _obj;
-})({});
+var obj = Object.defineProperties({}, {
+  foo: {
+    get: function () {
+      return 5 + 5;
+    },
+    set: function (value) {
+      this._foo = value;
+    },
+    enumerable: true
+  }
+});
--- a/test/fixtures/transformation/es5-property-methods-assignment/getter/expected.js
+++ b/test/fixtures/transformation/es5-property-methods-assignment/getter/expected.js
@@ -1,14 +1,10 @@
 "use strict";

-var obj = (function (_obj) {
-  Object.defineProperties(_obj, {
-    foo: {
-      get: function () {
-        return 5 + 5;
-      },
-      enumerable: true
-    }
-  });
-
-  return _obj;
-})({});
+var obj = Object.defineProperties({}, {
+  foo: {
+    get: function () {
+      return 5 + 5;
+    },
+    enumerable: true
+  }
+});
--- a/test/fixtures/transformation/es5-property-methods-assignment/setter/expected.js
+++ b/test/fixtures/transformation/es5-property-methods-assignment/setter/expected.js
@@ -1,14 +1,10 @@
 "use strict";

-var obj = (function (_obj) {
-  Object.defineProperties(_obj, {
-    foo: {
-      set: function (value) {
-        this._foo = value;
-      },
-      enumerable: true
-    }
-  });
-
-  return _obj;
-})({});
+var obj = Object.defineProperties({}, {
+  foo: {
+    set: function (value) {
+      this._foo = value;
+    },
+    enumerable: true
+  }
+});
--- a/test/fixtures/transformation/es6-classes/accessing-super-class/expected.js
+++ b/test/fixtures/transformation/es6-classes/accessing-super-class/expected.js
@@ -13,29 +13,34 @@ var _inherits = function (child, parent) {
  if (parent) child.__proto__ = parent;
 };

-var Test = function Test() {
-  woops["super"].test();
-  Foo.call(this);
-  Foo.prototype.test.call(this);
-  foob(Foo);
+var Test = (function () {
+  var _Foo = Foo;
+  var Test = function Test() {
+    woops["super"].test();
+    _Foo.call(this);
+    _Foo.prototype.test.call(this);
+    foob(_Foo);

-  Foo.call.apply(Foo, [this].concat(_slice.call(arguments)));
-  Foo.call.apply(Foo, [this, "test"].concat(_slice.call(arguments)));
+    _Foo.call.apply(_Foo, [this].concat(_slice.call(arguments)));
+    _Foo.call.apply(_Foo, [this, "test"].concat(_slice.call(arguments)));

-  Foo.prototype.test.call.apply(Foo.prototype, [this].concat(_slice.call(arguments)));
-  Foo.prototype.test.call.apply(Foo.prototype, [this, "test"].concat(_slice.call(arguments)));
-};
+    _Foo.prototype.test.call.apply(_Foo.prototype.test, [this].concat(_slice.call(arguments)));
+    _Foo.prototype.test.call.apply(_Foo.prototype.test, [this, "test"].concat(_slice.call(arguments)));
+  };

-_inherits(Test, Foo);
+  _inherits(Test, _Foo);

-Test.prototype.test = function () {
-  Foo.prototype.test.call(this);
-  Foo.prototype.test.call.apply(Foo.prototype.test, [this].concat(_slice.call(arguments)));
-  Foo.prototype.test.call.apply(Foo.prototype.test, [this, "test"].concat(_slice.call(arguments)));
-};
+  Test.prototype.test = function () {
+    _Foo.prototype.test.call(this);
+    _Foo.prototype.test.call.apply(_Foo.prototype.test, [this].concat(_slice.call(arguments)));
+    _Foo.prototype.test.call.apply(_Foo.prototype.test, [this, "test"].concat(_slice.call(arguments)));
+  };

-Test.foo = function () {
-  Foo.foo.call(this);
-  Foo.foo.call.apply(Foo.foo, [this].concat(_slice.call(arguments)));
-  Foo.foo.call.apply(Foo.foo, [this, "test"].concat(_slice.call(arguments)));
-};
+  Test.foo = function () {
+    _Foo.foo.call(this);
+    _Foo.foo.call.apply(_Foo.foo, [this].concat(_slice.call(arguments)));
+    _Foo.foo.call.apply(_Foo.foo, [this, "test"].concat(_slice.call(arguments)));
+  };
+
+  return Test;
+})();
--- a/test/fixtures/transformation/es6-classes/accessing-super-properties/expected.js
+++ b/test/fixtures/transformation/es6-classes/accessing-super-properties/expected.js
@@ -12,9 +12,14 @@ var _inherits = function (child, parent) {
  if (parent) child.__proto__ = parent;
 };

-var Test = function Test() {
-  Foo.prototype.test;
-  Foo.prototype.test.whatever;
-};
+var Test = (function () {
+  var _Foo = Foo;
+  var Test = function Test() {
+    _Foo.prototype.test;
+    _Foo.prototype.test.whatever;
+  };

-_inherits(Test, Foo);
+  _inherits(Test, _Foo);
+
+  return Test;
+})();
--- a/test/fixtures/transformation/es6-classes/calling-super-properties/expected.js
+++ b/test/fixtures/transformation/es6-classes/calling-super-properties/expected.js
@@ -12,13 +12,18 @@ var _inherits = function (child, parent) {
  if (parent) child.__proto__ = parent;
 };

-var Test = function Test() {
-  Foo.prototype.test.whatever();
-  Foo.prototype.test.call(this);
-};
+var Test = (function () {
+  var _Foo = Foo;
+  var Test = function Test() {
+    _Foo.prototype.test.whatever();
+    _Foo.prototype.test.call(this);
+  };

-_inherits(Test, Foo);
+  _inherits(Test, _Foo);

-Test.test = function () {
-  return Foo.wow.call(this);
-};
+  Test.test = function () {
+    return _Foo.wow.call(this);
+  };
+
+  return Test;
+})();
--- a/test/fixtures/transformation/es6-classes/constructor/expected.js
+++ b/test/fixtures/transformation/es6-classes/constructor/expected.js
@@ -16,8 +16,13 @@ var Test = function Test() {
  this.state = "test";
 };

-var Foo = function Foo() {
-  this.state = "test";
-};
+var Foo = (function () {
+  var _Bar = Bar;
+  var Foo = function Foo() {
+    this.state = "test";
+  };

-_inherits(Foo, Bar);
+  _inherits(Foo, _Bar);
+
+  return Foo;
+})();
--- a/test/fixtures/transformation/es6-classes/super-class-id-member-expression/expected.js
+++ b/test/fixtures/transformation/es6-classes/super-class-id-member-expression/expected.js
@@ -12,18 +12,28 @@ var _inherits = function (child, parent) {
  if (parent) child.__proto__ = parent;
 };

-var BaseController = function BaseController() {
-  if (Chaplin.Controller) {
-    Chaplin.Controller.apply(this, arguments);
-  }
-};
+var BaseController = (function () {
+  var _Chaplin$Controller = Chaplin.Controller;
+  var BaseController = function BaseController() {
+    if (_Chaplin$Controller) {
+      _Chaplin$Controller.apply(this, arguments);
+    }
+  };

-_inherits(BaseController, Chaplin.Controller);
+  _inherits(BaseController, _Chaplin$Controller);

-var BaseController2 = function BaseController2() {
-  if (Chaplin.Controller.Another) {
-    Chaplin.Controller.Another.apply(this, arguments);
-  }
-};
+  return BaseController;
+})();

-_inherits(BaseController2, Chaplin.Controller.Another);
+var BaseController2 = (function () {
+  var _Chaplin$Controller$Another = Chaplin.Controller.Another;
+  var BaseController2 = function BaseController2() {
+    if (_Chaplin$Controller$Another) {
+      _Chaplin$Controller$Another.apply(this, arguments);
+    }
+  };
+
+  _inherits(BaseController2, _Chaplin$Controller$Another);
+
+  return BaseController2;
+})();
--- a/test/fixtures/transformation/es6-classes/super-class-id-non-identifiers/actual.js
+++ b/test/fixtures/transformation/es6-classes/super-class-id-non-identifiers/actual.js
@@ -1,3 +0,0 @@
-class Q extends function () {} {
-
-}
--- a/test/fixtures/transformation/es6-classes/super-class-id-non-identifiers/expected.js
+++ b/test/fixtures/transformation/es6-classes/super-class-id-non-identifiers/expected.js
@@ -1,23 +0,0 @@
-"use strict";
-
-var _inherits = function (child, parent) {
-  child.prototype = Object.create(parent && parent.prototype, {
-    constructor: {
-      value: child,
-      enumerable: false,
-      writable: true,
-      configurable: true
-    }
-  });
-  if (parent) child.__proto__ = parent;
-};
-
-var _QSuper = function () {};
-
-var Q = function Q() {
-  if (_QSuper) {
-    _QSuper.apply(this, arguments);
-  }
-};
-
-_inherits(Q, _QSuper);
--- a/test/fixtures/transformation/es6-classes/super-class/expected.js
+++ b/test/fixtures/transformation/es6-classes/super-class/expected.js
@@ -12,10 +12,15 @@ var _inherits = function (child, parent) {
  if (parent) child.__proto__ = parent;
 };

-var Test = function Test() {
-  if (Foo) {
-    Foo.apply(this, arguments);
-  }
-};
+var Test = (function () {
+  var _Foo = Foo;
+  var Test = function Test() {
+    if (_Foo) {
+      _Foo.apply(this, arguments);
+    }
+  };

-_inherits(Test, Foo);
+  _inherits(Test, _Foo);
+
+  return Test;
+})();
--- a/test/fixtures/transformation/es6-computed-property-names/argument/expected.js
+++ b/test/fixtures/transformation/es6-computed-property-names/argument/expected.js
@@ -1,6 +1,12 @@
 "use strict";

-foo((function (_ref) {
-  _ref[bar] = "foobar";
-  return _ref;
-})({}));
+var _defineProperty = function (obj, key, value) {
+  return Object.defineProperty(obj, key, {
+    value: value,
+    enumerable: true,
+    configurable: true,
+    writable: true
+  });
+};
+
+foo(_defineProperty({}, bar, "foobar"));
--- a/test/fixtures/transformation/es6-computed-property-names/assignment/expected.js
+++ b/test/fixtures/transformation/es6-computed-property-names/assignment/expected.js
@@ -1,6 +1,12 @@
 "use strict";

-foo = (function (_foo) {
-  _foo[bar] = "foobar";
-  return _foo;
-})({});
+var _defineProperty = function (obj, key, value) {
+  return Object.defineProperty(obj, key, {
+    value: value,
+    enumerable: true,
+    configurable: true,
+    writable: true
+  });
+};
+
+foo = _defineProperty({}, bar, "foobar");
--- a/test/fixtures/transformation/es6-computed-property-names/ignore-symbol/actual.js
+++ b/test/fixtures/transformation/es6-computed-property-names/ignore-symbol/actual.js
@@ -0,0 +1,3 @@
+var foo = {
+  [Symbol.iterator]: "foobar"
+};
--- a/test/fixtures/transformation/es6-computed-property-names/ignore-symbol/expected.js
+++ b/test/fixtures/transformation/es6-computed-property-names/ignore-symbol/expected.js
@@ -0,0 +1,8 @@
+"use strict";
+
+var foo = (function () {
+  var _foo = {};
+
+  _foo[Symbol.iterator] = "foobar";
+  return _foo;
+})();
--- a/test/fixtures/transformation/es6-computed-property-names/method/expected.js
+++ b/test/fixtures/transformation/es6-computed-property-names/method/expected.js
@@ -1,9 +1,14 @@
 "use strict";

-var obj = (function (_obj) {
-  _obj[foobar] = function () {
-    return "foobar";
-  };
+var _defineProperty = function (obj, key, value) {
+  return Object.defineProperty(obj, key, {
+    value: value,
+    enumerable: true,
+    configurable: true,
+    writable: true
+  });
+};

-  return _obj;
-})({});
+var obj = _defineProperty({}, foobar, function () {
+  return "foobar";
+});
--- a/test/fixtures/transformation/es6-computed-property-names/mixed/expected.js
+++ b/test/fixtures/transformation/es6-computed-property-names/mixed/expected.js
@@ -1,10 +1,24 @@
 "use strict";

-var obj = (function (_obj) {
-  _obj["x" + foo] = "heh";
-  _obj["y" + bar] = "noo";
+var _defineProperty = function (obj, key, value) {
+  return Object.defineProperty(obj, key, {
+    value: value,
+    enumerable: true,
+    configurable: true,
+    writable: true
+  });
+};
+
+var obj = (function () {
+  var _obj = {};
+
+  _defineProperty(_obj, "x" + foo, "heh");
+
+  _defineProperty(_obj, "y" + bar, "noo");
+
+  _defineProperty(_obj, "foo", "foo");
+
+  _defineProperty(_obj, "bar", "bar");
+
  return _obj;
-})({
-  foo: "foo",
-  bar: "bar"
-});
+})();
--- a/test/fixtures/transformation/es6-computed-property-names/multiple/expected.js
+++ b/test/fixtures/transformation/es6-computed-property-names/multiple/expected.js
@@ -1,7 +1,20 @@
 "use strict";

-var obj = (function (_obj) {
-  _obj["x" + foo] = "heh";
-  _obj["y" + bar] = "noo";
+var _defineProperty = function (obj, key, value) {
+  return Object.defineProperty(obj, key, {
+    value: value,
+    enumerable: true,
+    configurable: true,
+    writable: true
+  });
+};
+
+var obj = (function () {
+  var _obj = {};
+
+  _defineProperty(_obj, "x" + foo, "heh");
+
+  _defineProperty(_obj, "y" + bar, "noo");
+
  return _obj;
-})({});
+})();
--- a/test/fixtures/transformation/es6-computed-property-names/single/expected.js
+++ b/test/fixtures/transformation/es6-computed-property-names/single/expected.js
@@ -1,6 +1,12 @@
 "use strict";

-var obj = (function (_obj) {
-  _obj["x" + foo] = "heh";
-  return _obj;
-})({});
+var _defineProperty = function (obj, key, value) {
+  return Object.defineProperty(obj, key, {
+    value: value,
+    enumerable: true,
+    configurable: true,
+    writable: true
+  });
+};
+
+var obj = _defineProperty({}, "x" + foo, "heh");
--- a/test/fixtures/transformation/es6-computed-property-names/this/expected.js
+++ b/test/fixtures/transformation/es6-computed-property-names/this/expected.js
@@ -1,7 +1,12 @@
 "use strict";

-var _this = this;
-var obj = (function (_obj) {
-  _obj["x" + _this.foo] = "heh";
-  return _obj;
-})({});
+var _defineProperty = function (obj, key, value) {
+  return Object.defineProperty(obj, key, {
+    value: value,
+    enumerable: true,
+    configurable: true,
+    writable: true
+  });
+};
+
+var obj = _defineProperty({}, "x" + this.foo, "heh");
--- a/test/fixtures/transformation/es6-computed-property-names/variable/expected.js
+++ b/test/fixtures/transformation/es6-computed-property-names/variable/expected.js
@@ -1,6 +1,12 @@
 "use strict";

-var foo = (function (_foo) {
-  _foo[bar] = "foobar";
-  return _foo;
-})({});
+var _defineProperty = function (obj, key, value) {
+  return Object.defineProperty(obj, key, {
+    value: value,
+    enumerable: true,
+    configurable: true,
+    writable: true
+  });
+};
+
+var foo = _defineProperty({}, bar, "foobar");
--- a/test/fixtures/transformation/es6-constants/destructuring/expected.js
+++ b/test/fixtures/transformation/es6-constants/destructuring/expected.js
@@ -5,6 +5,7 @@ var _slicedToArray = function (arr, i) {
    return arr;
  } else {
    var _arr = [];
+
    for (var _iterator = arr[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
      _arr.push(_step.value);

@@ -23,13 +24,15 @@ var a = _ref2[0];
 var b = _ref2[1];
 var _ref3 = [3, 4];

-var _ref4 = _slicedToArray(_ref3, 2);
+var _ref3 = _slicedToArray(_ref3, 2);

-var c = _ref4[0];
-var d = _ref4[1];
-var _ref5 = { e: 5, f: 6 };
-var e = _ref5.e;
-var f = _ref5.f;
-var _ref6 = { a: 7, b: 8 };
-var g = _ref6.a;
-var h = _ref6.b;
+var c = _ref3[0];
+var d = _ref3[1];
+var _ref4 = { e: 5, f: 6 };
+
+var e = _ref4.e;
+var f = _ref4.f;
+var _ref5 = { a: 7, b: 8 };
+
+var g = _ref5.a;
+var h = _ref5.b;
--- a/test/fixtures/transformation/es6-destructuring/array/expected.js
+++ b/test/fixtures/transformation/es6-destructuring/array/expected.js
@@ -5,6 +5,7 @@ var _slicedToArray = function (arr, i) {
    return arr;
  } else {
    var _arr = [];
+
    for (var _iterator = arr[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
      _arr.push(_step.value);

@@ -20,10 +21,10 @@ var _ref = ["hello", [", ", "junk"], ["world"]];
 var _ref2 = _slicedToArray(_ref, 4);

 var a = _ref2[0];
-var _ref3 = _slicedToArray(_ref2[1], 1);
+var _ref2$1 = _slicedToArray(_ref2[1], 1);

-var b = _ref3[0];
-var _ref4 = _slicedToArray(_ref2[2], 1);
+var b = _ref2$1[0];
+var _ref2$2 = _slicedToArray(_ref2[2], 1);

-var c = _ref4[0];
+var c = _ref2$2[0];
 var d = _ref2[3];
--- a/test/fixtures/transformation/es6-destructuring/assignment-expression/expected.js
+++ b/test/fixtures/transformation/es6-destructuring/assignment-expression/expected.js
@@ -1,11 +1,12 @@
 "use strict";

-var _temp, _ref;
+var _temp, _temp2;
 var _slicedToArray = function (arr, i) {
  if (Array.isArray(arr)) {
    return arr;
  } else {
    var _arr = [];
+
    for (var _iterator = arr[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
      _arr.push(_step.value);

@@ -16,4 +17,4 @@ var _slicedToArray = function (arr, i) {
  }
 };

-console.log((_temp = [123], _ref = _slicedToArray(_temp, 1), x = _ref[0], _temp));
+console.log((_temp = [123], _temp2 = _slicedToArray(_temp, 1), x = _temp2[0], _temp));
--- a/test/fixtures/transformation/es6-destructuring/assignment-statement/expected.js
+++ b/test/fixtures/transformation/es6-destructuring/assignment-statement/expected.js
@@ -5,6 +5,7 @@ var _slicedToArray = function (arr, i) {
    return arr;
  } else {
    var _arr = [];
+
    for (var _iterator = arr[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
      _arr.push(_step.value);

--- a/test/fixtures/transformation/es6-destructuring/empty/expected.js
+++ b/test/fixtures/transformation/es6-destructuring/empty/expected.js
@@ -5,6 +5,7 @@ var _slicedToArray = function (arr, i) {
    return arr;
  } else {
    var _arr = [];
+
    for (var _iterator = arr[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
      _arr.push(_step.value);

@@ -20,10 +21,10 @@ var _ref = ["foo", "hello", [", ", "junk"], ["world"]];
 var _ref2 = _slicedToArray(_ref, 5);

 var a = _ref2[1];
-var _ref3 = _slicedToArray(_ref2[2], 1);
+var _ref2$2 = _slicedToArray(_ref2[2], 1);

-var b = _ref3[0];
-var _ref4 = _slicedToArray(_ref2[3], 1);
+var b = _ref2$2[0];
+var _ref2$3 = _slicedToArray(_ref2[3], 1);

-var c = _ref4[0];
+var c = _ref2$3[0];
 var d = _ref2[4];
--- a/test/fixtures/transformation/es6-destructuring/es7-object-rest/expected.js
+++ b/test/fixtures/transformation/es6-destructuring/es7-object-rest/expected.js
@@ -2,6 +2,7 @@

 var _objectWithoutProperties = function (obj, keys) {
  var target = {};
+
  for (var i in obj) {
    if (keys.indexOf(i) >= 0) continue;
    if (!Object.prototype.hasOwnProperty.call(obj, i)) continue;
--- a/test/fixtures/transformation/es6-destructuring/for-in/expected.js
+++ b/test/fixtures/transformation/es6-destructuring/for-in/expected.js
@@ -5,6 +5,7 @@ var _slicedToArray = function (arr, i) {
    return arr;
  } else {
    var _arr = [];
+
    for (var _iterator = arr[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
      _arr.push(_step.value);

--- a/test/fixtures/transformation/es6-destructuring/for-of/expected.js
+++ b/test/fixtures/transformation/es6-destructuring/for-of/expected.js
@@ -5,6 +5,7 @@ var _slicedToArray = function (arr, i) {
    return arr;
  } else {
    var _arr = [];
+
    for (var _iterator = arr[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
      _arr.push(_step.value);

--- a/test/fixtures/transformation/es6-destructuring/member-expression/expected.js
+++ b/test/fixtures/transformation/es6-destructuring/member-expression/expected.js
@@ -5,6 +5,7 @@ var _slicedToArray = function (arr, i) {
    return arr;
  } else {
    var _arr = [];
+
    for (var _iterator = arr[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
      _arr.push(_step.value);

--- a/Show More
+++ b/Show More
Author	SHA1	Message	Date
Sebastian McKenzie	d981c06444	v2.4.4	2015-01-02 19:24:56 +11:00
Sebastian McKenzie	8269e1488b	fix incorrect scripts reference in browser	2015-01-02 19:23:50 +11:00
Sebastian McKenzie	ddda7a020f	add 2.4.4 changelog	2015-01-02 19:22:03 +11:00
Sebastian McKenzie	7e9340864a	lowercase object rest/spread feature name in doc/index	2015-01-02 19:20:14 +11:00
Sebastian McKenzie	5ec19f23c3	add test skeleton for types and add jsdoc comments to types	2015-01-02 19:20:05 +11:00
Sebastian McKenzie	ba48b66458	add types.appendToMemberExpression and types.prependToMemberExpression helpers	2015-01-02 16:46:58 +11:00
Sebastian McKenzie	6e8c73f65f	fix incorrect member expression properties	2015-01-02 16:39:35 +11:00
Sebastian McKenzie	b34fcb0cd9	split up method binding and add description for memoization assignment operator	2015-01-02 14:33:51 +11:00
Sebastian McKenzie	ff7129f1aa	remove ES5 methods from caveats and change IE classes note to IE 10 and below	2015-01-02 14:33:38 +11:00
Sebastian McKenzie	fbabd193a4	add `module` type to 6to5 browser	2015-01-02 14:33:18 +11:00
Sebastian McKenzie	876d69798c	v2.4.3	2015-01-02 05:19:42 +11:00
Sebastian McKenzie	1a963ddc06	remove unused variable	2015-01-02 05:19:00 +11:00
Sebastian McKenzie	beb5acea6b	better addImport with good hoisting etc	2015-01-02 05:18:03 +11:00
Sebastian McKenzie	6a290f233e	add 2.4.3 changelog	2015-01-02 05:01:18 +11:00
Sebastian McKenzie	74563d88ed	upgrade acorn-6to5	2015-01-02 05:00:23 +11:00
Sebastian McKenzie	a18177026c	add support for statements in `asyncToGenerator` and `bluebirdCoroutines` transformers	2015-01-02 04:58:59 +11:00
Sebastian McKenzie	a813341433	v2.4.2	2015-01-02 04:25:44 +11:00
Sebastian McKenzie	4968de9803	fix linting errors	2015-01-02 04:24:56 +11:00
Sebastian McKenzie	0de2d33e8d	add 2.4.2 changelog	2015-01-02 04:24:19 +11:00
Sebastian McKenzie	6f81ddd0d5	upgrade acorn-6to5	2015-01-02 04:24:19 +11:00
Sebastian McKenzie	6b83055b12	alias flat references in `coreAliasing` transformer	2015-01-02 04:24:19 +11:00
Sebastian McKenzie	080c23d5ed	Merge pull request #360 from mquandalle/patch-1 Extend the license to the new year	2015-01-02 04:06:22 +11:00
Sebastian McKenzie	293bec58d7	remove appveyor badge	2015-01-02 03:53:33 +11:00
Sebastian McKenzie	93ceafc732	better uid names	2015-01-02 03:53:28 +11:00
Sebastian McKenzie	b2bac04b72	update object getter memoization docs to reflect new changes	2015-01-02 03:04:26 +11:00
Sebastian McKenzie	e549c37ca1	v2.4.1	2015-01-02 03:00:33 +11:00
Sebastian McKenzie	02512da38d	fix generation tests with parenthesized expressions and trailing comments	2015-01-02 02:59:53 +11:00
Sebastian McKenzie	abe9c4fd30	add 2.4.1 changelog	2015-01-02 02:57:16 +11:00
Sebastian McKenzie	af21c52cc6	set generator on correct node #252	2015-01-02 02:55:55 +11:00
Sebastian McKenzie	706626f79a	better whitespace handling of parenthesized comments due to trailing comments	2015-01-02 02:55:40 +11:00
Sebastian McKenzie	b8dd421073	v2.4.0	2015-01-02 02:26:14 +11:00
Sebastian McKenzie	5453c466d6	remove unused variable	2015-01-02 02:24:49 +11:00
Sebastian McKenzie	0cfb2e76b8	add 2.4.0 changelog	2015-01-02 02:24:01 +11:00
Sebastian McKenzie	ba67f57c1e	use simple loops always in array comprehensions, support yield inside of array comprehensions - closes #325 , fixes #252	2015-01-02 02:14:36 +11:00
Sebastian McKenzie	f1a178f8f9	compact body nodes in traversal	2015-01-02 01:59:49 +11:00
Sebastian McKenzie	b1d1909c64	forced closure on super classes - fixes #339	2015-01-02 01:59:42 +11:00
Sebastian McKenzie	9529f93690	move useStrict transformer to after `_moduleFormatter`	2015-01-02 01:58:56 +11:00
Sebastian McKenzie	925b1f7600	add optional asyncToGenerator transformer - closes #321	2015-01-02 01:31:14 +11:00
Sebastian McKenzie	40f8bc0a65	add optional bluebird coroutine transformer - @phpnode	2015-01-02 01:20:28 +11:00
Sebastian McKenzie	3a0dbabf5a	v2.3.2	2015-01-02 01:04:43 +11:00
Sebastian McKenzie	383912c11b	more reliable t.isExpression	2015-01-02 01:04:04 +11:00
Sebastian McKenzie	470c8fced0	add parens on expressions with trailing comments - fixes #349	2015-01-02 00:57:48 +11:00
Sebastian McKenzie	e3dc2355e8	v2.3.1	2015-01-02 00:46:14 +11:00
Sebastian McKenzie	9733cb58c9	remove unused variable	2015-01-02 00:45:26 +11:00
Sebastian McKenzie	edd5a3878a	fix redefined variables	2015-01-02 00:45:01 +11:00
Sebastian McKenzie	78d2c4fa8d	2.3.1 changelog	2015-01-02 00:43:54 +11:00
Sebastian McKenzie	e268dc6138	return Object.defineProperties without a closure in property methods assignment unless it's really necessary	2015-01-02 00:42:28 +11:00
Sebastian McKenzie	5b6c0fcacd	add whitespace after array and object expressions	2015-01-02 00:41:58 +11:00
Sebastian McKenzie	777f2be14e	add undefinedToVoid optional transformer	2015-01-02 00:41:33 +11:00
Sebastian McKenzie	41d60a85e9	simplify define property by using a helper in playground object getter memoization	2015-01-02 00:40:47 +11:00
Sebastian McKenzie	800c350db6	use Object.defineProperty on computed properties - fixes #357	2015-01-02 00:40:37 +11:00
Sebastian McKenzie	7b5b8ab6ed	add undefinedToVoid optional transformer	2015-01-02 00:25:17 +11:00
Maxime Quandalle	c7a02ca289	Extend the license to the new year	2015-01-01 13:03:38 +01:00
Sebastian McKenzie	52e23473ed	allow `export default` non-functions mapping to `module.exports` in common module formatter - fixes #356	2015-01-01 22:58:46 +11:00
Sebastian McKenzie	af412cae28	v2.3.0	2015-01-01 22:40:44 +11:00
Sebastian McKenzie	4c2c96366f	add 2.3.0 changelog	2015-01-01 22:40:02 +11:00
Sebastian McKenzie	de427936a6	remove invalid lval super classes in generation tests	2015-01-01 22:38:01 +11:00
Sebastian McKenzie	9d6850d576	fix linting errors	2015-01-01 22:35:08 +11:00
Sebastian McKenzie	20a0280a52	add support for optional transformers	2015-01-01 22:35:02 +11:00
Sebastian McKenzie	64b7d6fa93	more verbose unknown node error message in code generator	2015-01-01 22:34:51 +11:00
Sebastian McKenzie	d7ca7ebbb9	remove Transformer exposure	2015-01-01 22:34:29 +11:00
Sebastian McKenzie	9680730e24	remove forced closure on super classes	2015-01-01 22:34:22 +11:00
Sebastian McKenzie	07667d80ff	clean up traverse	2015-01-01 22:34:05 +11:00
Sebastian McKenzie	9a633ebd9c	update scope to use new traversal api	2015-01-01 22:33:40 +11:00
Sebastian McKenzie	fac4a61245	use Makefile command shortcuts	2015-01-01 22:33:30 +11:00
Sebastian McKenzie	0ebc073762	update traversal api, removing `return false;` in favor of `this.stop();`	2015-01-01 22:33:17 +11:00
Sebastian McKenzie	860432cdfd	hoist export default to very top	2015-01-01 22:31:59 +11:00
Sebastian McKenzie	c408432445	add support for circular references and hoist all variable declarations	2015-01-01 22:30:28 +11:00
Sebastian McKenzie	27e9f9d616	remove invalid lval super class test	2015-01-01 22:29:57 +11:00
Sebastian McKenzie	94a11cd602	add optional core aliasing transformer	2015-01-01 20:02:20 +11:00
Sebastian McKenzie	ab6e424cac	make experimental transformers declare that they're experimental	2015-01-01 20:01:24 +11:00
Sebastian McKenzie	9ee7b07cbf	add corejs aliasing transformer and support for optional transformers	2015-01-01 20:01:09 +11:00
Sebastian McKenzie	31fff092b6	upgrade acorn-6to5 - fixes #358 and #353	2014-12-31 11:56:04 +11:00
Sebastian McKenzie	e847ac11af	add object-getter-memoization template	2014-12-31 11:54:51 +11:00
Sebastian McKenzie	aee1ca45b0	add isFalsyExpression check to superName and make classes a closure if they're inheriting	2014-12-31 11:54:39 +11:00
Sebastian McKenzie	46632e1a97	better object getter memoization - closes #353	2014-12-31 11:54:13 +11:00
Sebastian McKenzie	961e0b9b6b	reenable system modules tests	2014-12-31 11:51:52 +11:00
				`@@ -0,0 +1 @@`
				`module.exports = Object.assign(exports["default"], exports);`