v3.6.2

Conflicts:
	lib/6to5/transformation/transformers/minification/dead-code-elimination.js

.6to5rc

@@ -0,0 +1,5 @@
+{
+  "experimental": true,
+  "playground": true,
+  "loose": true
+}

.editorconfig

@@ -6,6 +6,6 @@ charset = utf-8
 trim_trailing_whitespace = true
 insert_final_newline = true
 
-[*.js]
+[*.{js,json}]
 indent_style = space
 indent_size = 2

.jshintrc

@@ -2,6 +2,7 @@
   "esnext": true,
   "indent": 2,
   "freeze": true,
+  "validthis": true,
   "camelcase": true,
   "unused": true,
   "eqnull": true,

.travis.yml

@@ -3,6 +3,7 @@ language: node_js
 node_js:
   - "0.10"
   - "0.11"
+  - "0.12"
 
 branches:
   except:

CHANGELOG.md

@@ -11,6 +11,87 @@
 
 _Note: Gaps between patch versions are faulty/broken releases._
 
+## 3.6.1
+
+ * **Bug Fix**
+  * Multiline JSX string literals are now supported.
+  * Fix scope tracking import specifiers incorrectly.
+  * Fix templates incorrectly recursing into their replacements.
+ * **Internal**
+  * Type inferrence now extends to function return types.
+  * Upgrade `acorn-6to5`.
+
+## 3.6.0
+
+ * **New Feature**
+  * Add playground class property initializers.
+ * **Polish**
+  * Completely reimplemented scope tracking, can now track types and optimise certain helpers based on it.
+  * Extremely fast tail recursion optimisation implementation. Thanks [@RReverser](https://github.com/RReverser)!
+ * **Internal**
+  * `kexec` has been removed as an optional dependency and must be user installed.
+  * Upgrade `regenerator-6to5`.
+  * Upgrade `acorn-6to5`.
+  * Upgrade `core-js`.
+
+## 3.5.3
+
+ * Enable `es6.tailCall` transformer with the first implementation that only works with self referencing calls until we can implement nested tail calls elegantly.
+
+## 3.5.2
+
+ * Disable `es6.tailCall` temporairly after reports of it breaking.
+
+## 3.5.1
+
+ * **Polish**
+  * Allow tail calls to work across files without the runtime.
+ * **Internal**
+  * Upgrade `acorn-6to5`.
+
+## 3.5.0
+
+ * **Bug Fix**
+  * Destructuring patterns as the left operator in `ForInStatement`/`ForOfStatement`.
+ * **Polish**
+  * Make default parameter IIFE invocation smarter.
+  * Make `__esModule` flag non-enumerable. Thanks [@daliwali](https://github.com/daliwali)!
+ * **Internal**
+  * More performance improvements.
+  * Parsing is now ~30% faster thanks to [marijnh/acorn@7264bc0178e7e6af7cfe02e9e0c6b26ee0e6007f](https://github.com/marijnh/acorn/commit/7264bc0178e7e6af7cfe02e9e0c6b26ee0e6007f).
+ * **New Feature**
+  * Optional `es6.blockScopingTDZ` is now completely functional and handles all edgecases.
+  * `super` in object literals.
+  * Tail call optimisation. Thanks [@RReverser](https://github.com/RReverser)!
+
+## 3.4.1
+
+ * **Bug Fix**
+  * Fix conflicting `--module-ids` shorthand arg in `$ 6to5`.
+  * Add require hook options to cache key.
+  * Fix strict module formatter.
+
+## 3.4.0
+
+ * **New Feature**
+  * Add `commonStandard` module formatter.
+ * **Bug Fix**
+  * Fix conflicting `--module-ids` shorthand arg in `$ 6to5`.
+ * **Internal**
+  * Lots of internal refactoring with scope tracking and traversal.
+ * **Polish**
+  * Don't return `map` in the API result if `sourceMap` was set to `"inline"`.
+
+## 3.3.12
+
+ * **Bug Fix**
+  * Don't override `MemberExpression`s with `core-js` in `selfContained` if a local binding exists.
+
+## 3.3.11
+
+ * **Bug Fix**
+  * Fix the require cache.
+
 ## 3.3.10
 
  * **Internal**

CONTRIBUTING.md

@@ -1,6 +1,12 @@
 # Contributing
 
-Contributions are always welcome, no matter how large or small. Before contributing, please read the [code of conduct](https://github.com/6to5/6to5/blob/master/CODE_OF_CONDUCT.md).
+Contributions are always welcome, no matter how large or small. Before
+contributing, please read the
+[code of conduct](https://github.com/6to5/6to5/blob/master/CODE_OF_CONDUCT.md).
+
+**NOTE:** Please do not send pull requests that fix linting issues. It's highly
+likely that they've already been fixed by the time it's submitted and it just
+pollutes the git tree.
 
 ## Developing
 
@@ -12,7 +18,8 @@ Contributions are always welcome, no matter how large or small. Before contribut
 * Link your forked clone (`npm link`)
 * Develop your changes ensuring you're fetching updates from upstream often
 * Ensure the test are passing (`make test`)
-* Create new pull request explaining your proposed change or reference an issue in your commit message
+* Create new pull request explaining your proposed change or reference an issue
+  in your commit message
 
 #### Code Standards
 

Makefile

@@ -5,10 +5,17 @@ UGLIFY_CMD = node_modules/uglify-js/bin/uglifyjs
 JSHINT_CMD = node_modules/jshint/bin/jshint
 MOCHA_CMD = node_modules/mocha/bin/_mocha
 JSCS_CMD = node_modules/jscs/bin/jscs
+6TO5_CMD = node_modules/6to5/bin/6to5
 
 export NODE_ENV = test
 
-.PHONY: clean test test-cov test-clean lint test-travis test-simple test-all test-browser publish build bootstrap publish-core publish-runtime
+.PHONY: clean test test-cov test-clean lint test-travis test-simple test-all test-browser publish build bootstrap publish-core publish-runtime build-core watch-core
+
+build-core:
+	#node $(6TO5_CMD) src --out-dir lib
+
+watch-core:
+	#node $(6TO5_CMD) src --out-dir lib --watch
 
 build:
 	mkdir -p dist
@@ -18,7 +25,7 @@ build:
 	node $(BROWSERIFY_CMD) -e lib/6to5/polyfill.js >dist/polyfill.js
 	node $(UGLIFY_CMD) dist/polyfill.js >dist/polyfill.min.js
 
-	node $(BROWSERIFY_CMD) lib/6to5/browser.js -s to5 >dist/6to5.js
+	node $(BROWSERIFY_CMD) lib/6to5/api/browser.js -s to5 >dist/6to5.js
 	node $(UGLIFY_CMD) dist/6to5.js >dist/6to5.min.js
 
 	node bin/6to5-runtime >dist/runtime.js
@@ -55,7 +62,7 @@ test-cov:
 	export SIMPLE_6TO5_TESTS=1; \
 	node $(ISTANBUL_CMD) $(MOCHA_CMD) --
 
-test-travis: bootstrap
+test-travis: build-core bootstrap
 	node $(ISTANBUL_CMD) $(MOCHA_CMD) --
 	if test -n "$$CODECLIMATE_REPO_TOKEN"; then codeclimate < coverage/lcov.info; fi
 
@@ -92,7 +99,7 @@ publish:
 	make publish-core
 	make publish-runtime
 
-	rm -rf templates.json browser.js browser-polyfill.js
+	rm -rf templates.json browser.js browser-polyfill.js runtime.js
 
 publish-runtime:
 	cd packages; \

appveyor.yml

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

bin/6to5/dir.js

@@ -37,8 +37,13 @@ module.exports = function (commander, filenames, opts) {
     if (stat.isDirectory(filename)) {
       var dirname = filename;
 
-      _.each(util.readdirFilter(dirname), function (filename) {
-        write(path.join(dirname, filename), filename);
+      _.each(util.readdir(dirname), function (filename) {
+        var src = path.join(dirname, filename);
+        if (util.canCompile(filename)) {
+          write(src, filename);
+        } else {
+          outputFileSync(path.join(commander.outDir, filename), fs.readFileSync(src));
+        }
       });
     } else {
       write(filename, filename);

bin/6to5/index.js

@@ -23,7 +23,7 @@ commander.option("-L, --loose [list]", "List of transformers to enable loose mod
 commander.option("-o, --out-file [out]", "Compile all input files into a single file");
 commander.option("-d, --out-dir [out]", "Compile an input directory of modules into an output directory");
 commander.option("-c, --remove-comments", "Remove comments from the compiled code", false);
-commander.option("-m, --module-ids", "Insert module id in modules", false);
+commander.option("-M, --module-ids", "Insert module id in modules", false);
 commander.option("-R, --react-compat", "Makes the react transformer produce pre-v0.12 code");
 commander.option("--keep-module-id-extensions", "Keep extensions when generating module ids", false);
 

bin/6to5/util.js

@@ -2,7 +2,7 @@ var readdir = require("fs-readdir-recursive");
 var index   = require("./index");
 var util    = require("../../lib/6to5/util");
 var path    = require("path");
-var to5     = require("../../lib/6to5");
+var to5     = require("../../lib/6to5/api/node");
 var fs      = require("fs");
 var _       = require("lodash");
 
@@ -12,6 +12,10 @@ exports.readdirFilter = function (filename) {
   });
 };
 
+exports.readdir = readdir;
+
+exports.canCompile = util.canCompile;
+
 exports.addSourceMappingUrl = function (code, loc) {
   return code + "\n//# sourceMappingURL=" + path.basename(loc);
 };

bin/_6to5-node

@@ -4,7 +4,7 @@ var commander = require("commander");
 var Module    = require("module");
 var path      = require("path");
 var repl      = require("repl");
-var to5       = require("../lib/6to5");
+var to5       = require("../lib/6to5/api/node");
 var util      = require("../lib/6to5/util");
 var vm        = require("vm");
 var _         = require("lodash");

lib/6to5/api/browser.js

@@ -1,8 +1,8 @@
 "use strict";
 
-var transform = module.exports = require("./transformation");
+var transform = module.exports = require("../transformation");
 
-transform.version = require("../../package").version;
+transform.version = require("../../../package").version;
 
 transform.transform = transform;
 

lib/6to5/api/node.js

@@ -1,24 +1,24 @@
 "use strict";
 
-var transform  = require("./transformation");
-var util       = require("./util");
-var fs         = require("fs");
 var isFunction = require("lodash/lang/isFunction");
+var transform  = require("../transformation");
+var util       = require("../util");
+var fs         = require("fs");
 
-exports.version = require("../../package").version;
+exports.version = require("../../../package").version;
 
-exports.runtime = require("./build-runtime");
+exports.runtime = require("../build-runtime");
 
-exports.types = require("./types");
+exports.types = require("../types");
 
 exports.register = function (opts) {
-  var register = require("./register");
+  var register = require("./register/node");
   if (opts != null) register(opts);
   return register;
 };
 
 exports.polyfill = function () {
-  require("./polyfill");
+  require("../polyfill");
 };
 
 exports.canCompile = util.canCompile;

lib/6to5/api/register/browser.js

@@ -4,4 +4,4 @@
 
 module.exports = function () {};
 
-require("./polyfill");
+require("../../polyfill");

lib/6to5/api/register/node.js

@@ -1,14 +1,14 @@
 "use strict";
 
-require("./polyfill");
+require("../../polyfill");
 
 var sourceMapSupport = require("source-map-support");
-var registerCache    = require("./register-cache");
-var util             = require("./util");
-var to5              = require("./index");
-var fs               = require("fs");
+var registerCache    = require("./cache");
 var extend           = require("lodash/object/extend");
 var each             = require("lodash/collection/each");
+var util             = require("../../util");
+var to5              = require("../node");
+var fs               = require("fs");
 
 sourceMapSupport.install({
   retrieveSourceMap: function (source) {
@@ -44,8 +44,10 @@ var mtime = function (filename) {
 var compile = function (filename) {
   var result;
 
+  var cacheKey = filename + ":" + JSON.stringify(transformOpts);
+
   if (cache) {
-    var cached = cache[filename];
+    var cached = cache[cacheKey];
     if (cached && cached.mtime === mtime(filename)) {
       result = cached;
     }
@@ -60,7 +62,7 @@ var compile = function (filename) {
 
   if (cache) {
     result.mtime = mtime(filename);
-    cache[filename] = result;
+    cache[cacheKey] = result;
   }
 
   maps[filename] = result.map;

lib/6to5/build-helpers.js

@@ -1,4 +1,4 @@
-var File = require("./file");
+var File = require("./transformation/file");
 var util = require("./util");
 var each = require("lodash/collection/each");
 var t    = require("./types");

lib/6to5/detection/index.js

@@ -1,7 +1,7 @@
 module.exports = detect;
 
 var SYNTAX_KEYS = require("./syntax-keys");
-var traverse    = require("../traverse");
+var traverse    = require("../traversal");
 var visitors    = traverse.explode(require("./visitors"));
 
 function detect(ast) {

lib/6to5/detection/visitors.js

@@ -1,5 +1,5 @@
 var t = require("../types");
-var _ = require("lodash");
+var includes = require("lodash/collection/includes");
 
 exports.AssignmentExpression = function (node, parent, detected) {
   if (node.operator === "**=") {
@@ -38,7 +38,7 @@ exports.Property = function (node, parent, detected) {
 };
 
 exports.AssignmentPattern = function (node, parent, detected) {
-  if (t.isFunction(parent) && _.contains(parent.params, node)) {
+  if (t.isFunction(parent) && includes(parent.params, node)) {
     detected("es6.parameters.default");
   }
 };

lib/6to5/generation/buffer.js

@@ -2,10 +2,10 @@
 
 module.exports = Buffer;
 
-var util      = require("../util");
-var isNumber  = require("lodash/lang/isNumber");
 var isBoolean = require("lodash/lang/isBoolean");
-var contains  = require("lodash/collection/contains");
+var includes  = require("lodash/collection/includes");
+var isNumber  = require("lodash/lang/isNumber");
+var util      = require("../util");
 
 function Buffer(position, format) {
   this.position = position;
@@ -159,7 +159,7 @@ Buffer.prototype.isLast = function (cha, trimRight) {
   var last = buf[buf.length - 1];
 
   if (Array.isArray(cha)) {
-    return contains(cha, last);
+    return includes(cha, last);
   } else {
     return cha === last;
   }

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

@@ -21,7 +21,7 @@ exports.IfStatement = function (node, print) {
   print.indentOnComments(node.consequent);
 
   if (node.alternate) {
-    if (this.isLast("}")) this.push(" ");
+    if (this.isLast("}")) this.space();
     this.keyword("else");
 
     if (this.format.format && !t.isBlockStatement(node.alternate)) {

lib/6to5/generation/index.js

@@ -12,12 +12,12 @@ var Whitespace   = require("./whitespace");
 var SourceMap    = require("./source-map");
 var Position     = require("./position");
 var Buffer       = require("./buffer");
+var extend       = require("lodash/object/extend");
+var merge        = require("lodash/object/merge");
+var each         = require("lodash/collection/each");
 var util         = require("../util");
 var n            = require("./node");
 var t            = require("../types");
-var each         = require("lodash/collection/each");
-var extend       = require("lodash/object/extend");
-var merge        = require("lodash/object/merge");
 
 function CodeGenerator(ast, opts, code) {
   opts = opts || {};
@@ -25,6 +25,7 @@ function CodeGenerator(ast, opts, code) {
   this.comments = ast.comments || [];
   this.tokens   = ast.tokens || [];
   this.format   = CodeGenerator.normalizeOptions(code, opts);
+  this.opts     = opts;
   this.ast      = ast;
 
   this.whitespace = new Whitespace(this.tokens, this.comments);

lib/6to5/helpers/normalize-ast.js

@@ -0,0 +1,9 @@
+var t = require("../types");
+
+module.exports = function (ast, comments, tokens) {
+  if (ast && ast.type === "Program") {
+    return t.file(ast, comments || [], tokens || []);
+  } else {
+    throw new Error("Not a valid ast?");
+  }
+};

lib/6to5/helpers/parse.js

@@ -0,0 +1,49 @@
+var normalizeAst = require("./normalize-ast");
+var estraverse   = require("estraverse");
+var codeFrame    = require("./code-frame");
+var acorn        = require("acorn-6to5");
+
+module.exports = function (opts, code, callback) {
+  try {
+    var comments = [];
+    var tokens   = [];
+
+    var ast = acorn.parse(code, {
+      allowImportExportEverywhere: opts.allowImportExportEverywhere,
+      allowReturnOutsideFunction:  !opts._anal,
+      ecmaVersion:                 opts.experimental ? 7 : 6,
+      playground:                  opts.playground,
+      strictMode:                  opts.strictMode,
+      onComment:                   comments,
+      locations:                   true,
+      onToken:                     tokens,
+      ranges:                      true
+    });
+
+    estraverse.attachComments(ast, comments, tokens);
+
+    ast = normalizeAst(ast, comments, tokens);
+
+    if (callback) {
+      return callback(ast);
+    } else {
+      return ast;
+    }
+  } catch (err) {
+    if (!err._6to5) {
+      err._6to5 = true;
+      var message = opts.filename + ": " + err.message;
+
+      var loc = err.loc;
+      if (loc) {
+        var frame = codeFrame(code, loc.line, loc.column + 1);
+        message += frame;
+      }
+
+      if (err.stack) err.stack = err.stack.replace(err.message, message);
+      err.message = message;
+    }
+
+    throw err;
+  }
+};

lib/6to5/messages.js

@@ -0,0 +1,48 @@
+var util = require("util");
+
+exports.messages = {
+  tailCallReassignmentDeopt: "Function reference has been reassigned so it's probably be dereferenced so we can't optimise this with confidence",
+  JSXNamespacedTags: "Namespace tags are not supported. ReactJSX is not XML.",
+  classesIllegalBareSuper: "Illegal use of bare super",
+  classesIllegalSuperCall: "Direct super call is illegal in non-constructor, use super.$1() instead",
+  classesIllegalConstructorKind: "Illegal kind for constructor method",
+  scopeDuplicateDeclaration: "Duplicate declaration $1",
+  undeclaredVariable: "Reference to undeclared variable $1",
+  undeclaredVariableSuggestion: "Reference to undeclared variable $1 - did you mean $2?",
+  settersInvalidParamLength: "Setters must have only one parameter",
+  noAssignmentsInForHead: "No assignments allowed in for-in/of head",
+  expectedMemberExpressionOrIdentifier: "Expected type MemeberExpression or Identifier",
+  invalidParentForThisNode: "We don't know how to handle this node within the current parent - please open an issue",
+  readOnly: "$1 is read-only",
+  modulesIllegalExportName: "Illegal export $1",
+  unknownForHead: "Unknown node type $1 in ForStatement"
+};
+
+exports.get = function (key) {
+  var msg = exports.messages[key];
+  if (!msg) throw new ReferenceError("Unknown message `" + key + "`");
+
+  var args = [];
+  for (var i = 1; i < arguments.length; i++) {
+    args.push(arguments[i]);
+  }
+  args = exports.parseArgs(args);
+
+  return msg.replace(/\$(\d+)/g, function (str, i) {
+    return args[--i];
+  });
+};
+
+exports.parseArgs = function (args) {
+  return args.map(function (val) {
+    if (val != null && val.inspect) {
+      return val.inspect();
+    } else {
+      try {
+        return JSON.stringify(val) || val + "";
+      } catch (e) {
+        return util.inspect(val);
+      }
+    }
+  });
+};

lib/6to5/patch.js

@@ -1,9 +1,7 @@
 "use strict";
 
-var t      = require("./types");
 var extend = require("lodash/object/extend");
-
-require("./types/node");
+var t      = require("./types");
 
 // estraverse
 

lib/6to5/transformation/file.js

@@ -5,16 +5,17 @@ module.exports = File;
 var SHEBANG_REGEX = /^\#\!.*/;
 
 var isFunction = require("lodash/lang/isFunction");
-var transform  = require("./transformation");
-var generate   = require("./generation");
+var transform  = require("./index");
+var generate   = require("../generation");
 var defaults   = require("lodash/object/defaults");
-var contains   = require("lodash/collection/contains");
-var clone      = require("./helpers/clone");
-var Scope      = require("./traverse/scope");
-var util       = require("./util");
+var includes   = require("lodash/collection/includes");
+var clone      = require("../helpers/clone");
+var parse      = require("../helpers/parse");
+var Scope      = require("../traversal/scope");
+var util       = require("../util");
 var path       = require("path");
 var each       = require("lodash/collection/each");
-var t          = require("./types");
+var t          = require("../types");
 
 function File(opts) {
   this.dynamicImportIds = {};
@@ -40,6 +41,7 @@ File.helpers = [
   "tagged-template-literal-loose",
   "interop-require",
   "to-array",
+  "to-consumable-array",
   "sliced-to-array",
   "object-without-properties",
   "has-own",
@@ -53,7 +55,10 @@ File.helpers = [
   "get",
   "set",
   "class-call-check",
-  "object-destructuring-empty"
+  "object-destructuring-empty",
+  "temporal-undefined",
+  "temporal-assert-defined",
+  "tail-call"
 ];
 
 File.validOptions = [
@@ -119,7 +124,10 @@ File.prototype.normalizeOptions = function (opts) {
   });
 
   // normalize windows path separators to unix
-  opts.filename = opts.filename.replace(/\\/g, "/");
+  opts.filename = util.normalisePathSeparator(opts.filename);
+  if (opts.sourceRoot) {
+    opts.sourceRoot = util.normalisePathSeparator(opts.sourceRoot);
+  }
 
   opts.basename = path.basename(opts.filename, path.extname(opts.filename));
 
@@ -128,7 +136,7 @@ File.prototype.normalizeOptions = function (opts) {
   opts.optional  = util.arrayify(opts.optional);
   opts.loose     = util.arrayify(opts.loose);
 
-  if (contains(opts.loose, "all")) {
+  if (includes(opts.loose, "all") || includes(opts.loose, true)) {
     opts.loose = Object.keys(transform.transformers);
   }
 
@@ -159,14 +167,29 @@ File.prototype.normalizeOptions = function (opts) {
 
   opts.blacklist = transform._ensureTransformerNames("blacklist", opts.blacklist);
   opts.whitelist = transform._ensureTransformerNames("whitelist", opts.whitelist);
-  opts.optional = transform._ensureTransformerNames("optional", opts.optional);
-  opts.loose = transform._ensureTransformerNames("loose", opts.loose);
+  opts.optional  = transform._ensureTransformerNames("optional", opts.optional);
+  opts.loose     = transform._ensureTransformerNames("loose", opts.loose);
+
+  if (opts.reactCompat) {
+    opts.optional.push("reactCompat");
+    console.error("The reactCompat option has been moved into the optional transformer " +
+                  "`reactCompat` - backwards compatibility will be removed in v4.0.0");
+  }
+
+  var ensureEnabled = function (key) {
+    var namespace = transform.transformerNamespaces[key];
+    if (namespace === "es7") opts.experimental = true;
+    if (namespace === "playground") opts.playground = true;
+  };
+
+  each(opts.whitelist, ensureEnabled);
+  each(opts.optional, ensureEnabled);
 
   return opts;
 };
 
 File.prototype.isLoose = function (key) {
-  return contains(this.opts.loose, key);
+  return includes(this.opts.loose, key);
 };
 
 File.prototype.buildTransformers = function () {
@@ -197,20 +220,10 @@ File.prototype.buildTransformers = function () {
   this.transformers = transformers;
 };
 
-File.prototype.toArray = function (node, i) {
-  if (t.isArrayExpression(node)) {
-    return node;
-  } else if (t.isIdentifier(node) && node.name === "arguments") {
-    return t.callExpression(t.memberExpression(this.addHelper("slice"), t.identifier("call")), [node]);
-  } else {
-    var declarationName = "to-array";
-    var args = [node];
-    if (i) {
-      args.push(t.literal(i));
-      declarationName = "sliced-to-array";
-    }
-    return t.callExpression(this.addHelper(declarationName), args);
-  }
+File.prototype.debug = function (msg) {
+  var parts = this.opts.filename;
+  if (msg) parts += ": " + msg;
+  util.debug(parts);
 };
 
 File.prototype.getModuleFormatter = function (type) {
@@ -265,7 +278,7 @@ File.prototype.addImport = function (source, name) {
   var id = this.dynamicImportIds[name];
 
   if (!id) {
-    id = this.dynamicImportIds[name] = this.generateUidIdentifier(name);
+    id = this.dynamicImportIds[name] = this.scope.generateUidIdentifier(name);
 
     var specifiers = [t.importSpecifier(t.identifier("default"), id)];
     var declar = t.importDeclaration(specifiers, t.literal(source));
@@ -283,8 +296,8 @@ File.prototype.isConsequenceExpressionStatement = function (node) {
 };
 
 File.prototype.addHelper = function (name) {
-  if (!contains(File.helpers, name)) {
-    throw new ReferenceError("unknown declaration " + name);
+  if (!includes(File.helpers, name)) {
+    throw new ReferenceError("Unknown helper " + name);
   }
 
   var program = this.ast.program;
@@ -299,7 +312,7 @@ File.prototype.addHelper = function (name) {
   } else {
     var ref = util.template(name);
     ref._compact = true;
-    var uid = this.generateUidIdentifier(name);
+    var uid = this.scope.generateUidIdentifier(name);
     this.scope.push({
       key: name,
       id: uid,
@@ -309,6 +322,10 @@ File.prototype.addHelper = function (name) {
   }
 };
 
+File.prototype.logDeopt = function () {
+  // todo, (node, msg)
+};
+
 File.prototype.errorWithNode = function (node, msg, Error) {
   Error = Error || SyntaxError;
 
@@ -334,16 +351,14 @@ File.prototype.parse = function (code) {
   opts.allowImportExportEverywhere = this.isLoose("es6.modules");
   //opts.strictMode = this.transformers.useStrict.canRun();
 
-  return util.parse(opts, code, function (tree) {
+  return parse(opts, code, function (tree) {
     self.transform(tree);
     return self.generate();
   });
 };
 
 File.prototype.transform = function (ast) {
-  var self = this;
-
-  util.debug(this.opts.filename);
+  this.debug();
 
   this.ast = ast;
   this.lastStatements = t.getLastStatements(ast.program);
@@ -356,42 +371,46 @@ File.prototype.transform = function (ast) {
 
   this.checkNode(ast);
 
-  var astRun = function (key) {
-    each(self.transformerStack, function (pass) {
-      pass.astRun(key);
-    });
-  };
-
-  astRun("enter");
+  this.call("pre");
 
   each(this.transformerStack, function (pass) {
     pass.transform();
   });
 
-  astRun("exit");
+  this.call("post");
 };
 
-var checkTransformerVisitor = {
-  enter: function (node, parent, scope, context, state) {
-    state.check(node, scope);
+File.prototype.call = function (key) {
+  var stack = this.transformerStack;
+  for (var i = 0; i < stack.length; i++) {
+    var transformer = stack[i].transformer;
+    if (transformer[key]) {
+      transformer[key](this);
+    }
   }
 };
 
+var checkTransformerVisitor = {
+  enter: function (node, parent, scope, state) {
+    checkNode(state.stack, node, scope);
+  }
+};
+
+var checkNode = function (stack, node, scope) {
+  each(stack, function (pass) {
+    if (pass.shouldRun) return;
+    pass.checkNode(node, scope);
+  });
+};
+
 File.prototype.checkNode = function (node, scope) {
-  var self = this;
+  var stack = this.transformerStack;
   scope = scope || this.scope;
 
-  var check = function (node, scope) {
-    each(self.transformerStack, function (pass) {
-      if (pass.shouldRun) return;
-      pass.checkNode(node, scope);
-    });
-  };
-
-  check(node, scope);
+  checkNode(stack, node, scope);
 
   scope.traverse(node, checkTransformerVisitor, {
-    check: check
+    stack: stack
   });
 };
 
@@ -419,34 +438,8 @@ File.prototype.generate = function () {
 
   if (opts.sourceMap === "inline") {
     result.code += "\n" + util.sourceMapToComment(result.map);
+    result.map = null;
   }
 
   return result;
 };
-
-File.prototype.generateUid = function (name, scope) {
-  name = t.toIdentifier(name).replace(/^_+/, "");
-
-  scope = scope || this.scope;
-
-  var uid;
-  var i = 0;
-  do {
-    uid = this._generateUid(name, i);
-    i++;
-  } while (scope.hasReference(uid));
-  return uid;
-};
-
-File.prototype.generateUidIdentifier = function (name, scope) {
-  scope = scope || this.scope;
-  var id = t.identifier(this.generateUid(name, scope));
-  scope.addDeclarationToFunctionScope("var", id);
-  return id;
-};
-
-File.prototype._generateUid = function (name, i) {
-  var id = name;
-  if (i > 1) id += i;
-  return "_" + id;
-};

lib/6to5/transformation/helpers/build-binary-assignment-operator-transformer.js

@@ -12,7 +12,7 @@ module.exports = function (exports, opts) {
     return t.assignmentExpression("=", left, right);
   };
 
-  exports.ExpressionStatement = function (node, parent, scope, context, file) {
+  exports.ExpressionStatement = function (node, parent, scope, file) {
     // hit the `AssignmentExpression` one below
     if (file.isConsequenceExpressionStatement(node)) return;
 
@@ -29,7 +29,7 @@ module.exports = function (exports, opts) {
     return nodes;
   };
 
-  exports.AssignmentExpression = function (node, parent, scope, context, file) {
+  exports.AssignmentExpression = function (node, parent, scope, file) {
     if (!isAssignment(node)) return;
 
     var nodes    = [];

lib/6to5/transformation/helpers/build-conditional-assignment-operator-transformer.js

@@ -8,7 +8,7 @@ module.exports = function (exports, opts) {
     return t.assignmentExpression("=", left, right);
   };
 
-  exports.ExpressionStatement = function (node, parent, scope, context, file) {
+  exports.ExpressionStatement = function (node, parent, scope, file) {
     // hit the `AssignmentExpression` one below
     if (file.isConsequenceExpressionStatement(node)) return;
 
@@ -27,7 +27,7 @@ module.exports = function (exports, opts) {
     return nodes;
   };
 
-  exports.AssignmentExpression = function (node, parent, scope, context, file) {
+  exports.AssignmentExpression = function (node, parent, scope, file) {
     if (!opts.is(node, file)) return;
 
     var nodes    = [];

lib/6to5/transformation/helpers/build-react-transformer.js

@@ -0,0 +1,284 @@
+"use strict";
+
+// Based upon the excellent jsx-transpiler by Ingvar Stepanyan (RReverser)
+// https://github.com/RReverser/jsx-transpiler
+
+// jsx
+
+var isString = require("lodash/lang/isString");
+var messages = require("../../messages");
+var esutils  = require("esutils");
+var react    = require("./react");
+var t        = require("../../types");
+
+module.exports = function (exports, opts) {
+  exports.check = function (node) {
+    if (t.isJSX(node)) return true;
+    if (react.isCreateClass(node)) return true;
+    return false;
+  };
+
+  exports.JSXIdentifier = function (node, parent) {
+    if (node.name === "this" && t.isReferenced(node, parent)) {
+      return t.thisExpression();
+    } else if (esutils.keyword.isIdentifierName(node.name)) {
+      node.type = "Identifier";
+    } else {
+      return t.literal(node.name);
+    }
+  };
+
+  exports.JSXNamespacedName = function (node, parent, scope, file) {
+    throw file.errorWithNode(node, messages.get("JSXNamespacedTags"));
+  };
+
+  exports.JSXMemberExpression = {
+    exit: function (node) {
+      node.computed = t.isLiteral(node.property);
+      node.type = "MemberExpression";
+    }
+  };
+
+  exports.JSXExpressionContainer = function (node) {
+    return node.expression;
+  };
+
+  exports.JSXAttribute = {
+    exit: function (node) {
+      var value = node.value || t.literal(true);
+
+      if (t.isLiteral(value) && isString(value.value)) {
+        value.value = value.value.replace(/\n\s+/g, " ");
+      }
+
+      return t.inherits(t.property("init", node.name, value), node);
+    }
+  };
+  exports.JSXOpeningElement = {
+    exit: function (node, parent, scope, file) {
+      var tagExpr = node.name;
+      var args = [];
+
+      var tagName;
+      if (t.isIdentifier(tagExpr)) {
+        tagName = tagExpr.name;
+      } else if (t.isLiteral(tagExpr)) {
+        tagName = tagExpr.value;
+      }
+
+      var state = {
+        tagExpr: tagExpr,
+        tagName: tagName,
+        args:    args
+      };
+
+      if (opts.pre) {
+        opts.pre(state);
+      }
+
+      var attribs = node.attributes;
+      if (attribs.length) {
+        attribs = buildJSXOpeningElementAttributes(attribs, file);
+      } else {
+        attribs = t.literal(null);
+      }
+
+      args.push(attribs);
+
+      if (opts.post) {
+        opts.post(state);
+      }
+
+      return state.call || t.callExpression(state.callee, args);
+    }
+  };
+
+  /**
+   * The logic for this is quite terse. It's because we need to
+   * support spread elements. We loop over all attributes,
+   * breaking on spreads, we then push a new object containg
+   * all prior attributes to an array for later processing.
+   */
+
+  var buildJSXOpeningElementAttributes = function (attribs, file) {
+    var _props = [];
+    var objs = [];
+
+    var pushProps = function () {
+      if (!_props.length) return;
+
+      objs.push(t.objectExpression(_props));
+      _props = [];
+    };
+
+    while (attribs.length) {
+      var prop = attribs.shift();
+      if (t.isJSXSpreadAttribute(prop)) {
+        pushProps();
+        objs.push(prop.argument);
+      } else {
+        _props.push(prop);
+      }
+    }
+
+    pushProps();
+
+    if (objs.length === 1) {
+      // only one object
+      attribs = objs[0];
+    } else {
+      // looks like we have multiple objects
+      if (!t.isObjectExpression(objs[0])) {
+        objs.unshift(t.objectExpression([]));
+      }
+
+      // spread it
+      attribs = t.callExpression(
+        file.addHelper("extends"),
+        objs
+      );
+    }
+
+    return attribs;
+  };
+
+  exports.JSXElement = {
+    exit: function (node) {
+      var callExpr = node.openingElement;
+
+      for (var i = 0; i < node.children.length; i++) {
+        var child = node.children[i];
+
+        if (t.isLiteral(child) && typeof child.value === "string") {
+          cleanJSXElementLiteralChild(child, callExpr.arguments);
+          continue;
+        } else if (t.isJSXEmptyExpression(child)) {
+          continue;
+        }
+
+        callExpr.arguments.push(child);
+      }
+
+      callExpr.arguments = flatten(callExpr.arguments);
+
+      if (callExpr.arguments.length >= 3) {
+        callExpr._prettyCall = true;
+      }
+
+      return t.inherits(callExpr, node);
+    }
+  };
+
+  var isStringLiteral = function (node) {
+    return t.isLiteral(node) && isString(node.value);
+  };
+
+  var flatten = function (args) {
+    var flattened = [];
+    var last;
+
+    for (var i = 0; i < args.length; i++) {
+      var arg = args[i];
+      if (isStringLiteral(arg) && isStringLiteral(last)) {
+        last.value += arg.value;
+      } else {
+        last = arg;
+        flattened.push(arg);
+      }
+    }
+
+    return flattened;
+  };
+
+  var cleanJSXElementLiteralChild = function (child, args) {
+    var lines = child.value.split(/\r\n|\n|\r/);
+
+    var lastNonEmptyLine = 0;
+    var i;
+
+    for (i = 0; i < lines.length; i++) {
+      if (lines[i].match(/[^ \t]/)) {
+        lastNonEmptyLine = i;
+      }
+    }
+
+    for (i = 0; i < lines.length; i++) {
+      var line = lines[i];
+
+      var isFirstLine = i === 0;
+      var isLastLine = i === lines.length - 1;
+      var isLastNonEmptyLine = i === lastNonEmptyLine;
+
+      // replace rendered whitespace tabs with spaces
+      var trimmedLine = line.replace(/\t/g, " ");
+
+      // trim whitespace touching a newline
+      if (!isFirstLine) {
+        trimmedLine = trimmedLine.replace(/^[ ]+/, "");
+      }
+
+      // trim whitespace touching an endline
+      if (!isLastLine) {
+        trimmedLine = trimmedLine.replace(/[ ]+$/, "");
+      }
+
+      if (trimmedLine) {
+        if (!isLastNonEmptyLine) {
+          trimmedLine += " ";
+        }
+
+        args.push(t.literal(trimmedLine));
+      }
+    }
+  };
+
+  // display names
+
+  var addDisplayName = function (id, call) {
+    var props = call.arguments[0].properties;
+    var safe = true;
+
+    for (var i = 0; i < props.length; i++) {
+      var prop = props[i];
+      if (t.isIdentifier(prop.key, { name: "displayName" })) {
+        safe = false;
+        break;
+      }
+    }
+
+    if (safe) {
+      props.unshift(t.property("init", t.identifier("displayName"), t.literal(id)));
+    }
+  };
+
+  exports.ExportDeclaration = function (node, parent, scope, file) {
+    if (node.default && react.isCreateClass(node.declaration)) {
+      addDisplayName(file.opts.basename, node.declaration);
+    }
+  };
+
+  exports.AssignmentExpression =
+  exports.Property =
+  exports.VariableDeclarator = function (node) {
+    var left, right;
+
+    if (t.isAssignmentExpression(node)) {
+      left = node.left;
+      right = node.right;
+    } else if (t.isProperty(node)) {
+      left = node.key;
+      right = node.value;
+    } else if (t.isVariableDeclarator(node)) {
+      left = node.id;
+      right = node.init;
+    }
+
+    if (t.isMemberExpression(left)) {
+      left = left.property;
+    }
+
+    if (t.isIdentifier(left) && react.isCreateClass(right)) {
+      addDisplayName(left.name, right);
+    }
+  };
+};

lib/6to5/transformation/helpers/define-map.js

@@ -1,6 +1,6 @@
 var cloneDeep = require("lodash/lang/cloneDeep");
-var traverse  = require("../../traverse");
-var clone      = require("lodash/lang/clone");
+var traverse  = require("../../traversal");
+var clone     = require("lodash/lang/clone");
 var each      = require("lodash/collection/each");
 var has       = require("lodash/object/has");
 var t         = require("../../types");

lib/6to5/transformation/helpers/explode-assignable-expression.js

@@ -18,7 +18,7 @@ var getObjRef = function (node, nodes, file, scope) {
   } else if (t.isMemberExpression(node)) {
     ref = node.object;
 
-    if (t.isIdentifier(ref) && scope.hasReference(ref.name)) {
+    if (t.isIdentifier(ref) && scope.hasGlobal(ref.name)) {
       // the object reference that we need to save is locally declared
       // so as per the previous comment we can be 100% sure evaluating
       // it multiple times will be safe

lib/6to5/transformation/helpers/name-method.js

@@ -4,7 +4,7 @@ var util = require("../../util");
 var t    = require("../../types");
 
 var visitor = {
-  enter: function (node, parent, scope, context, state) {
+  enter: function (node, parent, scope, state) {
     // check if this node is an identifier that matches the same as our function id
     if (!t.isIdentifier(node, { name: state.id })) return;
 
@@ -13,11 +13,11 @@ var visitor = {
 
     // check that we don't have a local variable declared as that removes the need
     // for the wrapper
-    var localDeclar = scope.getBinding(state.id);
+    var localDeclar = scope.getBindingIdentifier(state.id);
     if (localDeclar !== state.outerDeclar) return;
 
     state.selfReference = true;
-    context.stop();
+    this.stop();
   }
 };
 
@@ -31,20 +31,23 @@ exports.property = function (node, file, scope) {
   var state = {
     id: id,
     selfReference: false,
-    outerDeclar: scope.getBinding(id),
+    outerDeclar: scope.getBindingIdentifier(id),
   };
 
   scope.traverse(node, visitor, state);
 
+  var method = node.value;
+
   if (state.selfReference) {
-    // todo: support generators
-    node.value = util.template("property-method-assignment-wrapper", {
-      FUNCTION: node.value,
+    var templateName = "property-method-assignment-wrapper";
+    if (method.generator) templateName += "-generator";
+    node.value = util.template(templateName, {
+      FUNCTION: method,
       FUNCTION_ID: key,
       FUNCTION_KEY: scope.generateUidIdentifier(id),
       WRAPPER_KEY: scope.generateUidIdentifier(id + "Wrapper")
     });
   } else {
-    node.value.id = key;
+    method.id = key;
   }
 };

lib/6to5/transformation/helpers/react.js

@@ -20,3 +20,7 @@ exports.isCreateClass = function (node) {
 };
 
 exports.isReactComponent = t.buildMatchMemberExpression("React.Component");
+
+exports.isCompatTag = function (tagName) {
+  return tagName && /^[a-z]|\-/.test(tagName);
+};

lib/6to5/transformation/helpers/remap-async-to-generator.js

@@ -3,8 +3,8 @@
 var t = require("../../types");
 
 var visitor = {
-  enter: function (node, parent, scope, context) {
-    if (t.isFunction(node)) context.skip();
+  enter: function (node) {
+    if (t.isFunction(node)) this.skip();
 
     if (t.isAwaitExpression(node)) {
       node.type = "YieldExpression";

lib/6to5/transformation/helpers/replace-supers.js

@@ -2,19 +2,24 @@
 
 module.exports = ReplaceSupers;
 
-var t = require("../../types");
+var messages = require("../../messages");
+var t        = require("../../types");
 
 /**
  * Description
  *
  * @param {Object} opts
+ * @param {Boolean} [inClass]
  */
 
-function ReplaceSupers(opts) {
-  this.topLevelThisReference = null;
+function ReplaceSupers(opts, inClass) {
+  this.topLevelThisReference = opts.topLevelThisReference;
   this.methodNode            = opts.methodNode;
   this.className             = opts.className;
   this.superName             = opts.superName;
+  this.isStatic              = opts.isStatic;
+  this.hasSuper              = false;
+  this.inClass               = inClass;
   this.isLoose               = opts.isLoose;
   this.scope                 = opts.scope;
   this.file                  = opts.file;
@@ -28,16 +33,23 @@ function ReplaceSupers(opts) {
  *   _set(Object.getPrototypeOf(CLASS.prototype), "METHOD", "VALUE", this)
  *
  * @param {Node} property
- * @param {boolean} isStatic
- * @param {boolean} isComputed
+ * @param {Node} value
+ * @param {Boolean} isComputed
+ * @param {Node} thisExpression
  *
  * @returns {Node}
  */
-ReplaceSupers.prototype.setSuperProperty = function (property, value, isStatic, isComputed, thisExpression) {
+
+ReplaceSupers.prototype.setSuperProperty = function (property, value, isComputed, thisExpression) {
   return t.callExpression(
     this.file.addHelper("set"),
     [
-      isStatic ? this.superName : t.memberExpression(this.superName, t.identifier("prototype")),
+      t.callExpression(
+        t.memberExpression(t.identifier("Object"), t.identifier("getPrototypeOf")),
+        [
+          this.isStatic ? this.className : t.memberExpression(this.className, t.identifier("prototype"))
+        ]
+      ),
       isComputed ? property : t.literal(property.name),
       value,
       thisExpression
@@ -53,17 +65,22 @@ ReplaceSupers.prototype.setSuperProperty = function (property, value, isStatic,
  *   _get(Object.getPrototypeOf(CLASS.prototype), "METHOD", this)
  *
  * @param {Node} property
- * @param {boolean} isStatic
- * @param {boolean} isComputed
+ * @param {Boolean} isComputed
+ * @param {Node} thisExpression
  *
  * @returns {Node}
  */
 
-ReplaceSupers.prototype.getSuperProperty = function (property, isStatic, isComputed, thisExpression) {
+ReplaceSupers.prototype.getSuperProperty = function (property, isComputed, thisExpression) {
   return t.callExpression(
     this.file.addHelper("get"),
     [
-      isStatic ? this.superName : t.memberExpression(this.superName, t.identifier("prototype")),
+      t.callExpression(
+        t.memberExpression(t.identifier("Object"), t.identifier("getPrototypeOf")),
+        [
+          this.isStatic ? this.className : t.memberExpression(this.className, t.identifier("prototype"))
+        ]
+      ),
       isComputed ? property : t.literal(property.name),
       thisExpression
     ]
@@ -79,19 +96,19 @@ ReplaceSupers.prototype.replace = function () {
 };
 
 var visitor = {
-  enter: function (node, parent, scope, context, state) {
+  enter: function (node, parent, scope, state) {
     var topLevel = state.topLevel;
     var self = state.self;
 
     if (t.isFunction(node) && !t.isArrowFunctionExpression(node)) {
       // we need to call traverseLevel again so we're context aware
       self.traverseLevel(node, false);
-      return context.skip();
+      return this.skip();
     }
 
     if (t.isProperty(node, { method: true }) || t.isMethodDefinition(node)) {
       // break on object methods
-      return context.skip();
+      return this.skip();
     }
 
     var getThisReference = topLevel ?
@@ -126,7 +143,7 @@ ReplaceSupers.prototype.getThisReference = function () {
   if (this.topLevelThisReference) {
     return this.topLevelThisReference;
   } else {
-    var ref = this.topLevelThisReference = this.file.generateUidIdentifier("this");
+    var ref = this.topLevelThisReference = this.scope.generateUidIdentifier("this");
     this.methodNode.value.body.body.unshift(t.variableDeclaration("var", [
       t.variableDeclarator(this.topLevelThisReference, t.thisExpression())
     ]));
@@ -143,7 +160,8 @@ ReplaceSupers.prototype.getThisReference = function () {
  * @returns {Object}
  */
 
-ReplaceSupers.prototype.getLooseSuperProperty = function (methodNode, id, parent) {
+ReplaceSupers.prototype.getLooseSuperProperty = function (id, parent) {
+  var methodNode = this.methodNode;
   var methodName = methodNode.key;
   var superName  = this.superName || t.identifier("Function");
 
@@ -185,13 +203,15 @@ ReplaceSupers.prototype.getLooseSuperProperty = function (methodNode, id, parent
 
 ReplaceSupers.prototype.looseHandle = function (getThisReference, node, parent) {
   if (t.isIdentifier(node, { name: "super" })) {
-    return this.getLooseSuperProperty(this.methodNode, node, parent);
+    this.hasSuper = true;
+    return this.getLooseSuperProperty(node, parent);
   } else if (t.isCallExpression(node)) {
     var callee = node.callee;
     if (!t.isMemberExpression(callee)) return;
     if (callee.object.name !== "super") return;
 
     // super.test(); -> ClassName.prototype.MethodName.call(this);
+    this.hasSuper = true;
     t.appendToMemberExpression(callee, t.identifier("call"));
     node.arguments.unshift(getThisReference());
   }
@@ -212,13 +232,13 @@ ReplaceSupers.prototype.specHandle = function (getThisReference, node, parent) {
   var args;
   var thisReference;
 
-  if (t.isIdentifier(node, { name: "super" })) {
-    if (!(t.isMemberExpression(parent) && !parent.computed && parent.property === node)) {
-      throw this.file.errorWithNode(node, "illegal use of bare super");
-    }
-  } else if (t.isCallExpression(node)) {
+  if (isIllegalBareSuper(node, parent)) {
+    throw this.file.errorWithNode(node, messages.get("classesIllegalBareSuper"));
+  }
+
+  if (t.isCallExpression(node)) {
     var callee = node.callee;
-    if (t.isIdentifier(callee, { name: "super" })) {
+    if (isSuper(callee, node)) {
       // super(); -> _get(Object.getPrototypeOf(ClassName), "MethodName", this).call(this);
       property = methodNode.key;
       computed = methodNode.computed;
@@ -227,38 +247,32 @@ ReplaceSupers.prototype.specHandle = function (getThisReference, node, parent) {
       // bare `super` call is illegal inside non-constructors
       //  - https://esdiscuss.org/topic/super-call-in-methods
       //  - https://twitter.com/wycats/status/544553184396836864
-      if (methodNode.key.name !== "constructor") {
+      if (methodNode.key.name !== "constructor" || !this.inClass) {
         var methodName = methodNode.key.name || "METHOD_NAME";
-        throw this.file.errorWithNode(node, "Direct super call is illegal in non-constructor, use super." + methodName + "() instead");
+        throw this.file.errorWithNode(node, messages.get("classesIllegalSuperCall", methodName));
       }
-    } else {
-      if (!t.isMemberExpression(callee)) return;
-      if (callee.object.name !== "super") return;
-
+    } else if (t.isMemberExpression(callee) && isSuper(callee.object, callee)) {
       // super.test(); -> _get(Object.getPrototypeOf(ClassName.prototype), "test", this).call(this);
       property = callee.property;
       computed = callee.computed;
       args = node.arguments;
     }
-  } else if (t.isMemberExpression(node)) {
-    if (!t.isIdentifier(node.object, { name: "super" })) return;
-
+  } else if (t.isMemberExpression(node) && isSuper(node.object, node)) {
     // super.name; -> _get(Object.getPrototypeOf(ClassName.prototype), "name", this);
     property = node.property;
     computed = node.computed;
-  } else if (t.isAssignmentExpression(node)) {
-    if (!t.isIdentifier(node.left.object, { name: "super" })) return;
-    if (methodNode.kind !== "set") return;
-
-    thisReference = getThisReference();
+  } else if (t.isAssignmentExpression(node) && isSuper(node.left.object, node.left) && methodNode.kind === "set") {
     // super.name = "val"; -> _set(Object.getPrototypeOf(ClassName.prototype), "name", this);
-    return this.setSuperProperty(node.left.property, node.right, methodNode.static, node.left.computed, thisReference);
+    this.hasSuper = true;
+    return this.setSuperProperty(node.left.property, node.right, node.left.computed, getThisReference());
   }
 
   if (!property) return;
 
+  this.hasSuper = true;
+
   thisReference = getThisReference();
-  var superProperty = this.getSuperProperty(property, methodNode.static, computed, thisReference);
+  var superProperty = this.getSuperProperty(property, computed, thisReference);
   if (args) {
     if (args.length === 1 && t.isSpreadElement(args[0])) {
       // super(...arguments);
@@ -276,3 +290,14 @@ ReplaceSupers.prototype.specHandle = function (getThisReference, node, parent) {
     return superProperty;
   }
 };
+
+var isIllegalBareSuper = function (node, parent) {
+  if (!isSuper(node, parent)) return false;
+  if (t.isMemberExpression(parent, { computed: false })) return false;
+  if (t.isCallExpression(parent, { callee: node })) return false;
+  return true;
+};
+
+var isSuper = function (node, parent) {
+  return t.isIdentifier(node, { name: "super" }) && t.isReferenced(node, parent);
+};

lib/6to5/transformation/index.js

@@ -2,11 +2,11 @@
 
 module.exports = transform;
 
-var Transformer = require("./transformer");
-var object      = require("../helpers/object");
-var File        = require("../file");
-var util        = require("../util");
-var each        = require("lodash/collection/each");
+var normalizeAst = require("../helpers/normalize-ast");
+var Transformer  = require("./transformer");
+var object       = require("../helpers/object");
+var File         = require("./file");
+var each         = require("lodash/collection/each");
 
 function transform(code, opts) {
   var file = new File(opts);
@@ -14,7 +14,7 @@ function transform(code, opts) {
 }
 
 transform.fromAst = function (ast, code, opts) {
-  ast = util.normalizeAst(ast);
+  ast = normalizeAst(ast);
 
   var file = new File(opts);
   file.addCode(code);
@@ -56,8 +56,9 @@ transform._ensureTransformerNames = function (type, rawKeys) {
   return keys;
 };
 
-transform.transformers = object();
-transform.namespaces   = object();
+transform.transformerNamespaces = object();
+transform.transformers          = object();
+transform.namespaces            = object();
 
 transform.deprecatedTransformerMap = require("./transformers/deprecated");
 transform.moduleFormatters = require("./modules");
@@ -66,8 +67,10 @@ var rawTransformers = require("./transformers");
 
 each(rawTransformers, function (transformer, key) {
   var namespace = key.split(".")[0];
+
   transform.namespaces[namespace] = transform.namespaces[namespace] || [];
   transform.namespaces[namespace].push(key);
+  transform.transformerNamespaces[key] = namespace;
 
   transform.transformers[key] = new Transformer(key, transformer);
 });

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

@@ -2,14 +2,16 @@
 
 module.exports = DefaultFormatter;
 
+var messages = require("../../messages");
+var extend   = require("lodash/object/extend");
 var object   = require("../../helpers/object");
 var util     = require("../../util");
 var t        = require("../../types");
-var extend   = require("lodash/object/extend");
 
 function DefaultFormatter(file) {
-  this.file = file;
-  this.ids  = object();
+  this.scope = file.scope;
+  this.file  = file;
+  this.ids   = object();
 
   this.hasNonDefaultExports = false;
 
@@ -27,7 +29,7 @@ function DefaultFormatter(file) {
 }
 
 DefaultFormatter.prototype.doDefaultExportInterop = function (node) {
-  return node.default && !this.noInteropRequire && !this.hasNonDefaultExports;
+  return node.default && !this.noInteropRequireExport && !this.hasNonDefaultExports;
 };
 
 DefaultFormatter.prototype.bumpImportOccurences = function (node) {
@@ -38,7 +40,7 @@ DefaultFormatter.prototype.bumpImportOccurences = function (node) {
 };
 
 var exportsVisitor = {
-  enter: function (node, parent, scope, context, formatter) {
+  enter: function (node, parent, scope, formatter) {
     var declar = node && node.declaration;
     if (t.isExportDeclaration(node)) {
       formatter.hasLocalImports = true;
@@ -63,7 +65,7 @@ DefaultFormatter.prototype.getLocalExports = function () {
 };
 
 var importsVisitor = {
-  enter: function (node, parent, scope, context, formatter) {
+  enter: function (node, parent, scope, formatter) {
     if (t.isImportDeclaration(node)) {
       formatter.hasLocalImports = true;
       extend(formatter.localImports, t.getBindingIdentifiers(node));
@@ -77,9 +79,9 @@ DefaultFormatter.prototype.getLocalImports = function () {
 };
 
 var remapVisitor = {
-  enter: function (node, parent, scope, context, formatter) {
+  enter: function (node, parent, scope, formatter) {
     if (t.isUpdateExpression(node) && formatter.isLocalReference(node.argument, scope)) {
-      context.skip();
+      this.skip();
 
       // expand to long file assignment expression
       var assign = t.assignmentExpression(node.operator[0] + "=", node.argument, t.literal(1));
@@ -107,7 +109,7 @@ var remapVisitor = {
     }
 
     if (t.isAssignmentExpression(node) && formatter.isLocalReference(node.left, scope)) {
-      context.skip();
+      this.skip();
       return formatter.remapExportAssignment(node);
     }
   }
@@ -124,13 +126,6 @@ DefaultFormatter.prototype.isLocalReference = function (node) {
   return t.isIdentifier(node) && localImports[node.name] && localImports[node.name] !== node;
 };
 
-DefaultFormatter.prototype.checkLocalReference = function (node) {
-  var file = this.file;
-  if (this.isLocalReference(node)) {
-    throw file.errorWithNode(node, "Illegal assignment of module import");
-  }
-};
-
 DefaultFormatter.prototype.remapExportAssignment = function (node) {
   return t.assignmentExpression(
     "=",
@@ -146,7 +141,7 @@ DefaultFormatter.prototype.remapExportAssignment = function (node) {
 DefaultFormatter.prototype.isLocalReference = function (node, scope) {
   var localExports = this.localExports;
   var name = node.name;
-  return t.isIdentifier(node) && localExports[name] && localExports[name] === scope.getBinding(name);
+  return t.isIdentifier(node) && localExports[name] && localExports[name] === scope.getBindingIdentifier(name);
 };
 
 DefaultFormatter.prototype.getModuleName = function () {
@@ -213,14 +208,11 @@ DefaultFormatter.prototype.getExternalReference = function (node, nodes) {
 
 DefaultFormatter.prototype.checkExportIdentifier = function (node) {
   if (t.isIdentifier(node, { name: "__esModule" })) {
-    throw this.file.errorWithNode(node, "Illegal export __esModule - this is used internally for CommonJS interop");
+    throw this.file.errorWithNode(node, messages.get("modulesIllegalExportName", node.name));
   }
 };
 
 DefaultFormatter.prototype.exportSpecifier = function (specifier, node, nodes) {
-  var inherits = false;
-  if (node.specifiers.length === 1) inherits = node;
-
   if (node.source) {
     var ref = this.getExternalReference(node, nodes);
 
@@ -228,7 +220,7 @@ DefaultFormatter.prototype.exportSpecifier = function (specifier, node, nodes) {
       // export * from "foo";
       nodes.push(this.buildExportsWildcard(ref, node));
     } else {
-      if (t.isSpecifierDefault(specifier) && !this.noInteropRequire) {
+      if (t.isSpecifierDefault(specifier) && !this.noInteropRequireExport) {
         // importing a default so we need to normalize it
         ref = t.callExpression(this.file.addHelper("interop-require"), [ref]);
       } else {

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

@@ -4,7 +4,7 @@ var util = require("../../util");
 
 module.exports = function (Parent) {
   var Constructor = function () {
-    this.noInteropRequire = true;
+    this.noInteropRequireExport = true;
     Parent.apply(this, arguments);
   };
 

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

@@ -6,7 +6,7 @@ var DefaultFormatter = require("./_default");
 var CommonFormatter  = require("./common");
 var util             = require("../../util");
 var t                = require("../../types");
-var contains         = require("lodash/collection/contains");
+var includes         = require("lodash/collection/includes");
 var values           = require("lodash/object/values");
 
 function AMDFormatter() {
@@ -29,9 +29,8 @@ AMDFormatter.prototype.buildDependencyLiterals = function () {
  * Wrap the entire body in a `define` wrapper.
  */
 
-AMDFormatter.prototype.transform = function (ast) {
-  var program = ast.program;
-  var body    = program.body;
+AMDFormatter.prototype.transform = function (program) {
+  var body = program.body;
 
   // build an array of module names
 
@@ -71,7 +70,7 @@ AMDFormatter.prototype.getModuleName = function () {
 };
 
 AMDFormatter.prototype._getExternalReference = function (node) {
-  return this.file.generateUidIdentifier(node.source.value);
+  return this.scope.generateUidIdentifier(node.source.value);
 };
 
 AMDFormatter.prototype.importDeclaration = function (node) {
@@ -82,12 +81,12 @@ AMDFormatter.prototype.importSpecifier = function (specifier, node, nodes) {
   var key = t.getSpecifierName(specifier);
   var ref = this.getExternalReference(node);
 
-  if (contains(this.file.dynamicImported, node)) {
+  if (includes(this.file.dynamicImported, node)) {
     // Prevent unnecessary renaming of dynamic imports.
     this.ids[node.source.value] = ref;
   } else if (t.isImportBatchSpecifier(specifier)) {
     // import * as bar from "foo";
-  } else if (t.isSpecifierDefault(specifier) && !this.noInteropRequire) {
+  } else if (t.isSpecifierDefault(specifier) && !this.noInteropRequireImport) {
     // import foo from "foo";
     ref = t.callExpression(this.file.addHelper("interop-require"), [ref]);
   } else {

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

@@ -0,0 +1,13 @@
+"use strict";
+
+module.exports = CommonStandardFormatter;
+
+var CommonStrictFormatter = require("./common-strict");
+var util = require("../../util");
+
+function CommonStandardFormatter() {
+  this.noInteropRequireImport = true;
+  CommonStrictFormatter.apply(this, arguments);
+}
+
+util.inherits(CommonStandardFormatter, CommonStrictFormatter);

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

@@ -3,7 +3,7 @@
 module.exports = CommonJSFormatter;
 
 var DefaultFormatter = require("./_default");
-var contains         = require("lodash/collection/contains");
+var includes         = require("lodash/collection/includes");
 var util             = require("../../util");
 var t                = require("../../types");
 
@@ -14,8 +14,13 @@ function CommonJSFormatter() {
 util.inherits(CommonJSFormatter, DefaultFormatter);
 
 CommonJSFormatter.prototype.init = function () {
-  if (this.hasNonDefaultExports) {
-    this.file.ast.program.body.push(util.template("exports-module-declaration", true));
+  var file  = this.file;
+  var scope = file.scope;
+
+  scope.rename("module");
+
+  if (!this.noInteropRequireImport && this.hasNonDefaultExports) {
+    file.ast.program.body.push(util.template("exports-module-declaration", true));
   }
 };
 
@@ -26,20 +31,24 @@ CommonJSFormatter.prototype.importSpecifier = function (specifier, node, nodes)
 
   // import foo from "foo";
   if (t.isSpecifierDefault(specifier)) {
-    if (!contains(this.file.dynamicImported, node)) {
-      ref = t.callExpression(this.file.addHelper("interop-require"), [ref]);
+    if (!includes(this.file.dynamicImported, node)) {
+      if (this.noInteropRequireImport) {
+        ref = t.memberExpression(ref, t.identifier("default"));
+      } else {
+        ref = t.callExpression(this.file.addHelper("interop-require"), [ref]);
+      }
     }
     nodes.push(t.variableDeclaration("var", [t.variableDeclarator(variableName, ref)]));
   } else {
     if (specifier.type === "ImportBatchSpecifier") {
+
+      if (!this.noInteropRequireImport) {
+        ref = t.callExpression(this.file.addHelper("interop-require-wildcard"), [ref]);
+      }
+
       // import * as bar from "foo";
       nodes.push(t.variableDeclaration("var", [
-        t.variableDeclarator(
-          variableName,
-          t.callExpression(this.file.addHelper("interop-require-wildcard"), [
-            ref
-          ])
-        )
+        t.variableDeclarator(variableName, ref)
       ]));
     } else {
       // import { foo } from "foo";
@@ -84,7 +93,7 @@ CommonJSFormatter.prototype._getExternalReference = function (node, nodes) {
   var call = t.callExpression(t.identifier("require"), [node.source]);
 
   if (this.localImportOccurences[source] > 1) {
-    var uid = this.file.generateUidIdentifier(source);
+    var uid = this.scope.generateUidIdentifier(source);
     nodes.push(t.variableDeclaration("var", [
       t.variableDeclarator(uid, call)
     ]));

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

@@ -1,10 +1,11 @@
 module.exports = {
-  commonStrict: require("./common-strict"),
-  amdStrict:    require("./amd-strict"),
-  umdStrict:    require("./umd-strict"),
-  common:       require("./common"),
-  system:       require("./system"),
-  ignore:       require("./ignore"),
-  amd:          require("./amd"),
-  umd:          require("./umd")
+  commonStandard: require("./common-standard"),
+  commonStrict:   require("./common-strict"),
+  amdStrict:      require("./amd-strict"),
+  umdStrict:      require("./umd-strict"),
+  common:         require("./common"),
+  system:         require("./system"),
+  ignore:         require("./ignore"),
+  amd:            require("./amd"),
+  umd:            require("./umd")
 };

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

@@ -12,8 +12,9 @@ var each             = require("lodash/collection/each");
 var map              = require("lodash/collection/map");
 
 function SystemFormatter(file) {
-  this.exportIdentifier = file.generateUidIdentifier("export");
-  this.noInteropRequire = true;
+  this.exportIdentifier = file.scope.generateUidIdentifier("export");
+  this.noInteropRequireExport = true;
+  this.noInteropRequireImport = true;
 
   DefaultFormatter.apply(this, arguments);
 }
@@ -28,7 +29,7 @@ SystemFormatter.prototype._addImportSource = function (node, exportNode) {
 };
 
 SystemFormatter.prototype.buildExportsWildcard = function (objectIdentifier, node) {
-  var leftIdentifier = this.file.generateUidIdentifier("key");
+  var leftIdentifier = this.scope.generateUidIdentifier("key");
   var valIdentifier  = t.memberExpression(objectIdentifier, leftIdentifier, true);
 
   var left = t.variableDeclaration("var", [
@@ -68,7 +69,7 @@ SystemFormatter.prototype.importSpecifier = function (specifier, node, nodes) {
 };
 
 var runnerSettersVisitor = {
-  enter: function (node, parent, scope, context, state) {
+  enter: function (node, parent, scope, state) {
     if (node._importSource === state.source) {
       if (t.isVariableDeclaration(node)) {
         each(node.declarations, function (declar) {
@@ -81,7 +82,7 @@ var runnerSettersVisitor = {
         state.nodes.push(node);
       }
 
-      context.remove();
+      this.remove();
     }
   }
 };
@@ -103,10 +104,10 @@ SystemFormatter.prototype.buildRunnerSetters = function (block, hoistDeclarators
 };
 
 var hoistVariablesVisitor = {
-  enter: function (node, parent, scope, context, hoistDeclarators) {
+  enter: function (node, parent, scope, hoistDeclarators) {
     if (t.isFunction(node)) {
       // nothing inside is accessible
-      return context.skip();
+      return this.skip();
     }
 
     if (t.isVariableDeclaration(node)) {
@@ -148,19 +149,17 @@ var hoistVariablesVisitor = {
 };
 
 var hoistFunctionsVisitor = {
-  enter: function (node, parent, scope, context, handlerBody) {
-    if (t.isFunction(node)) context.skip();
+  enter: function (node, parent, scope, handlerBody) {
+    if (t.isFunction(node)) this.skip();
 
     if (t.isFunctionDeclaration(node) || node._blockHoist) {
       handlerBody.push(node);
-      context.remove();
+      this.remove();
     }
   }
 };
 
-SystemFormatter.prototype.transform = function (ast) {
-  var program = ast.program;
-
+SystemFormatter.prototype.transform = function (program) {
   var hoistDeclarators = [];
   var moduleName = this.getModuleName();
   var moduleNameLiteral = t.literal(moduleName);

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

@@ -13,9 +13,8 @@ function UMDFormatter() {
 
 util.inherits(UMDFormatter, AMDFormatter);
 
-UMDFormatter.prototype.transform = function (ast) {
-  var program = ast.program;
-  var body    = program.body;
+UMDFormatter.prototype.transform = function (program) {
+  var body = program.body;
 
   // build an array of module names
 

lib/6to5/transformation/templates/.6to5rc

@@ -0,0 +1,3 @@
+{
+  "blacklist": ["useStrict"]
+}

lib/6to5/transformation/templates/corejs-is-iterator.js

@@ -0,0 +1 @@
+CORE_ID.$for.isIterable(VALUE);

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

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

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

@@ -1,7 +1,10 @@
 (function (obj, defaults) {
-  for (var key in defaults) {
-    if (obj[key] === undefined) {
-      obj[key] = defaults[key];
+  var keys = Object.getOwnPropertyNames(defaults);
+  for (var i = 0; i < keys.length; i++) {
+    var key = keys[i];
+    var value = Object.getOwnPropertyDescriptor(defaults, key);
+    if (value && value.configurable && obj[key] === undefined) {
+      Object.defineProperty(obj, key, value);
     }
   }
   return obj;

lib/6to5/transformation/templates/exports-module-declaration.js

@@ -1 +1,3 @@
-exports.__esModule = true;
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});

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

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

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

@@ -4,21 +4,16 @@
   if (desc === undefined) {
     var parent = Object.getPrototypeOf(object);
 
-    if (parent === null) {
-      return;
-    } else {
+    if (parent !== null) {
       return set(parent, property, value, receiver);
     }
   } else if ("value" in desc && desc.writable) {
-    desc.value = value;
-    return;
+    return desc.value = value;
   } else {
     var setter = desc.set;
 
-    if (setter === undefined) {
-      return;
+    if (setter !== undefined) {
+      return setter.call(receiver, value);
     }
-
-    return setter.call(receiver, value);
   }
 });

lib/6to5/transformation/templates/sliced-to-array.js

@@ -1,12 +1,14 @@
 (function (arr, i) {
   if (Array.isArray(arr)) {
     return arr;
-  } else {
+  } else if (Symbol.iterator in Object(arr)) {
     var _arr = [];
     for (var _iterator = arr[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
       _arr.push(_step.value);
       if (i && _arr.length === i) break;
     }
     return _arr;
+  } else {
+    throw new TypeError("Invalid attempt to destructure non-iterable instance");
   }
 });

lib/6to5/transformation/templates/tail-call-body.js

@@ -0,0 +1,3 @@
+{
+  FUNCTION_ID:while (true) BLOCK
+}

lib/6to5/transformation/templates/tail-call.js

@@ -0,0 +1,23 @@
+(function () {
+  function Tail(func, args, context) {
+    this.func = func;
+    this.args = args;
+    this.context = context;
+  }
+
+  Tail.prototype._isTailDescriptor = true;
+
+  var isRunning = false;
+
+  return function (func, args, context) {
+    var result = new Tail(func, args, context);
+    if (!isRunning) {
+      isRunning = true;
+      do {
+        result = result.func.apply(result.context, result.args);
+      } while (result instanceof Tail || (result && result._isTailDescriptor));
+      isRunning = false;
+    }
+    return result;
+  };
+})()

lib/6to5/transformation/templates/temporal-assert-defined.js

@@ -0,0 +1,6 @@
+(function (val, name, undef) {
+  if (val === undef) {
+    throw new ReferenceError(name + " is not defined - temporal dead zone");
+  }
+  return true;
+})

lib/6to5/transformation/templates/temporal-undefined.js

@@ -0,0 +1 @@
+({})

lib/6to5/transformation/templates/to-consumable-array.js

@@ -0,0 +1,8 @@
+(function (arr) {
+  if (Array.isArray(arr)) {
+    for (var i = 0, arr2 = Array(arr.length); i < arr.length; i++) arr2[i] = arr[i];
+    return arr2;
+  } else {
+    return Array.from(arr);
+  }
+});

lib/6to5/transformation/transformer-pass.js

@@ -1,7 +1,6 @@
 module.exports = TransformerPass;
 
-var util     = require("../util");
-var contains = require("lodash/collection/contains");
+var includes = require("lodash/collection/includes");
 
 /**
  * This class is responsible for traversing over the provided `File`s
@@ -15,17 +14,6 @@ function TransformerPass(file, transformer) {
   this.file        = file;
 }
 
-TransformerPass.prototype.astRun = function (key) {
-  if (!this.shouldRun) return;
-
-  var handlers = this.handlers;
-  var file = this.file;
-
-  if (handlers.ast && handlers.ast[key]) {
-    handlers.ast[key](file.ast, file);
-  }
-};
-
 TransformerPass.prototype.canRun = function () {
   var transformer = this.transformer;
 
@@ -37,14 +25,14 @@ TransformerPass.prototype.canRun = function () {
 
   // blacklist
   var blacklist = opts.blacklist;
-  if (blacklist.length && contains(blacklist, key)) return false;
+  if (blacklist.length && includes(blacklist, key)) return false;
 
   // whitelist
   var whitelist = opts.whitelist;
-  if (whitelist.length && !contains(whitelist, key)) return false;
+  if (whitelist.length) return includes(whitelist, key);
 
   // optional
-  if (transformer.optional && !contains(opts.optional, key)) return false;
+  if (transformer.optional && !includes(opts.optional, key)) return false;
 
   // experimental
   if (transformer.experimental && !opts.experimental) return false;
@@ -64,31 +52,12 @@ TransformerPass.prototype.checkNode = function (node) {
   }
 };
 
-var transformVisitor = {
-  enter: function (node, parent, scope, context, state) {
-    var fns = state.handlers[node.type];
-    if (!fns) return;
-    return fns.enter(node, parent, scope, context, state.file, state.pass);
-  },
-
-  exit: function (node, parent, scope, context, state) {
-    var fns = state.handlers[node.type];
-    if (!fns) return;
-    return fns.exit(node, parent, scope, context, state.file, state.pass);
-  }
-};
-
 TransformerPass.prototype.transform = function () {
   if (!this.shouldRun) return;
 
   var file = this.file;
 
-  util.debug(file.opts.filename + ": Running transformer " + this.transformer.key);
+  file.debug("Running transformer " + this.transformer.key);
 
-  this.astRun("before");
-
-  var state = { file: file, handlers: this.handlers, pass: this };
-  file.scope.traverse(file.ast, transformVisitor, state);
-
-  this.astRun("after");
+  file.scope.traverse(file.ast, this.handlers, file);
 };

lib/6to5/transformation/transformer.js

@@ -4,8 +4,9 @@ module.exports = Transformer;
 
 var TransformerPass = require("./transformer-pass");
 var isFunction      = require("lodash/lang/isFunction");
-var traverse        = require("../traverse");
+var traverse        = require("../traversal");
 var isObject        = require("lodash/lang/isObject");
+var clone           = require("../helpers/clone");
 var each            = require("lodash/collection/each");
 
 /**
@@ -15,13 +16,23 @@ var each            = require("lodash/collection/each");
  */
 
 function Transformer(key, transformer, opts) {
-  this.manipulateOptions = transformer.manipulateOptions;
-  this.check             = transformer.check;
+  transformer = clone(transformer);
 
-  this.experimental = !!transformer.experimental;
-  this.playground   = !!transformer.playground;
-  this.secondPass   = !!transformer.secondPass;
-  this.optional     = !!transformer.optional;
+  var take = function (key) {
+    var val = transformer[key];
+    delete transformer[key];
+    return val;
+  };
+
+  this.manipulateOptions = take("manipulateOptions");
+  this.check             = take("check");
+  this.post              = take("post");
+  this.pre               = take("pre");
+
+  this.experimental = !!take("experimental");
+  this.playground   = !!take("playground");
+  this.secondPass   = !!take("secondPass");
+  this.optional     = !!take("optional");
 
   this.handlers = this.normalize(transformer);
   this.opts     = opts || {};

lib/6to5/transformation/transformers/deprecated.json

@@ -34,6 +34,8 @@
   "coreAliasing": "selfContained",
   "undefinedToVoid": "spec.undefinedToVoid",
   "undeclaredVariableCheck": "validation.undeclaredVariableCheck",
-  "specPropertyLiterals": "minification.propertyLiterals",
-  "specMemberExpressionLiterals": "minification.memberExpressionLiterals"
+  "specPropertyLiterals": "es3.propertyLiterals",
+  "specMemberExpressionLiterals": "es3.memberExpressionLiterals",
+  "minification.propertyLiterals": "es3.propertyLiterals",
+  "minification.memberExpressionLiterals": "es3.memberExpressionLiterals"
 }

lib/6to5/transformation/transformers/es6/block-scoping-tdz.js

@@ -3,31 +3,27 @@
 var t = require("../../../types");
 
 var visitor = {
-  enter: function (node, parent, scope, context, state) {
+  enter: function (node, parent, scope, state) {
     if (!t.isReferencedIdentifier(node, parent)) return;
 
     var declared = state.letRefs[node.name];
     if (!declared) return;
 
     // declared node is different in this scope
-    if (scope.getBinding(node.name) !== declared) return;
+    if (scope.getBindingIdentifier(node.name) !== declared) return;
 
-    var declaredLoc  = declared.loc;
-    var referenceLoc = node.loc;
+    var assert = t.callExpression(
+      state.file.addHelper("temporal-assert-defined"),
+      [node, t.literal(node.name), state.file.addHelper("temporal-undefined")]
+    );
 
-    if (!declaredLoc || !referenceLoc) return;
+    this.skip();
 
-    // does this reference appear on a line before the declaration?
-    var before = referenceLoc.start.line < declaredLoc.start.line;
-
-    if (referenceLoc.start.line === declaredLoc.start.line) {
-      // this reference appears on the same line
-      // check it appears before the declaration
-      before = referenceLoc.start.col < declaredLoc.start.col;
-    }
-
-    if (before) {
-      throw state.file.errorWithNode(node, "Temporal dead zone - accessing a variable before it's initialized");
+    if (t.isAssignmentExpression(parent) || t.isUpdateExpression(parent)) {
+      if (parent._ignoreBlockScopingTDZ) return;
+      this.parentPath.replaceNode(t.sequenceExpression([assert, parent]));
+    } else {
+      return t.logicalExpression("&&", assert, node);
     }
   }
 };
@@ -36,7 +32,7 @@ exports.optional = true;
 
 exports.Loop =
 exports.Program =
-exports.BlockStatement = function (node, parent, scope, context, file) {
+exports.BlockStatement = function (node, parent, scope, file) {
   var letRefs = node._letReferences;
   if (!letRefs) return;
 

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

@@ -1,6 +1,6 @@
 "use strict";
 
-var traverse = require("../../../traverse");
+var traverse = require("../../../traversal");
 var object   = require("../../../helpers/object");
 var util     = require("../../../util");
 var t        = require("../../../types");
@@ -17,7 +17,7 @@ var isLet = function (node, parent) {
   if (node.kind !== "let") return false;
 
   // https://github.com/6to5/6to5/issues/255
-  if (!t.isFor(parent) || t.isFor(parent) && parent.left !== node) {
+  if (isLetInitable(node, parent)) {
     for (var i = 0; i < node.declarations.length; i++) {
       var declar = node.declarations[i];
       declar.init = declar.init || t.identifier("undefined");
@@ -29,6 +29,10 @@ var isLet = function (node, parent) {
   return true;
 };
 
+var isLetInitable = function (node, parent) {
+  return !t.isFor(parent) || t.isFor(parent) && parent.left !== node;
+};
+
 var isVar = function (node, parent) {
   return t.isVariableDeclaration(node, { kind: "var" }) && !isLet(node, parent);
 };
@@ -39,11 +43,29 @@ var standardizeLets = function (declars) {
   }
 };
 
-exports.VariableDeclaration = function (node, parent) {
-  isLet(node, parent);
+exports.VariableDeclaration = function (node, parent, scope, file) {
+  if (!isLet(node, parent)) return;
+
+  if (isLetInitable(node) && file.transformers["es6.blockScopingTDZ"].canRun()) {
+    var nodes = [node];
+
+    for (var i = 0; i < node.declarations.length; i++) {
+      var decl = node.declarations[i];
+      if (decl.init) {
+        var assign = t.assignmentExpression("=", decl.id, decl.init);
+        assign._ignoreBlockScopingTDZ = true;
+        nodes.push(t.expressionStatement(assign));
+      }
+      decl.init = file.addHelper("temporal-undefined");
+    }
+
+    node._blockHoist = 2;
+
+    return nodes;
+  }
 };
 
-exports.Loop = function (node, parent, scope, context, file) {
+exports.Loop = function (node, parent, scope, file) {
   var init = node.left || node.init;
   if (isLet(init, node)) {
     t.ensureBlock(node);
@@ -54,7 +76,7 @@ exports.Loop = function (node, parent, scope, context, file) {
 };
 
 exports.Program =
-exports.BlockStatement = function (block, parent, scope, context, file) {
+exports.BlockStatement = function (block, parent, scope, file) {
   if (!t.isLoop(parent)) {
     var blockScoping = new BlockScoping(false, block, parent, scope, file);
     blockScoping.run();
@@ -108,19 +130,19 @@ BlockScoping.prototype.run = function () {
   }
 };
 
-function replace(node, parent, scope, context, remaps) {
+function replace(node, parent, scope, remaps) {
   if (!t.isReferencedIdentifier(node, parent)) return;
 
   var remap = remaps[node.name];
   if (!remap) return;
 
-  var ownBinding = scope.getBinding(node.name);
+  var ownBinding = scope.getBindingIdentifier(node.name);
   if (ownBinding === remap.binding) {
     node.name = remap.uid;
   } else {
     // scope already has it's own binding that doesn't
     // match the one we have a stored replacement for
-    if (context) context.skip();
+    if (this) this.skip();
   }
 }
 
@@ -129,7 +151,7 @@ var replaceVisitor = {
 };
 
 function traverseReplace(node, parent, scope, remaps) {
-  replace(node, parent, scope, null, remaps);
+  replace(node, parent, scope, remaps);
   scope.traverse(node, replaceVisitor, remaps);
 }
 
@@ -153,7 +175,7 @@ BlockScoping.prototype.remap = function () {
     // this is the defining identifier of a declaration
     var ref = letRefs[key];
 
-    if (scope.parentHasReference(key)) {
+    if (scope.parentHasBinding(key) || scope.hasGlobal(key)) {
       var uid = scope.generateUidIdentifier(ref.name).name;
       ref.name = uid;
 
@@ -225,7 +247,7 @@ BlockScoping.prototype.needsClosure = function () {
 };
 
 var letReferenceFunctionVisitor = {
-  enter: function (node, parent, scope, context, state) {
+  enter: function (node, parent, scope, state) {
     // not a direct reference
     if (!t.isReferencedIdentifier(node, parent)) return;
 
@@ -241,10 +263,10 @@ var letReferenceFunctionVisitor = {
 };
 
 var letReferenceBlockVisitor = {
-  enter: function (node, parent, scope, context, state) {
+  enter: function (node, parent, scope, state) {
     if (t.isFunction(node)) {
       scope.traverse(node, letReferenceFunctionVisitor, state);
-      return context.skip();
+      return this.skip();
     }
   }
 };
@@ -310,7 +332,7 @@ var loopNodeTo = function (node) {
 };
 
 var loopVisitor = {
-  enter: function (node, parent, scope, context, state) {
+  enter: function (node, parent, scope, state) {
     var replace;
 
     if (t.isLoop(node)) {
@@ -320,7 +342,7 @@ var loopVisitor = {
     }
 
     if (t.isFunction(node) || t.isLoop(node)) {
-      return context.skip();
+      return this.skip();
     }
 
     var loopText = loopNodeTo(node);
@@ -362,7 +384,7 @@ var loopVisitor = {
 };
 
 var loopLabelVisitor = {
-  enter: function (node, parent, scope, context, state) {
+  enter: function (node, parent, scope, state) {
     if (t.isLabeledStatement(node)) {
       state.innerLabels.push(node.label.name);
     }
@@ -395,7 +417,7 @@ BlockScoping.prototype.checkLoop = function () {
 };
 
 var hoistVarDeclarationsVisitor = {
-  enter: function (node, parent, scope, context, self) {
+  enter: function (node, parent, scope, self) {
     if (t.isForStatement(node)) {
       if (isVar(node.init, node)) {
         node.init = t.sequenceExpression(self.pushDeclar(node.init));
@@ -407,7 +429,7 @@ var hoistVarDeclarationsVisitor = {
     } else if (isVar(node, parent)) {
       return self.pushDeclar(node).map(t.expressionStatement);
     } else if (t.isFunction(node)) {
-      return context.skip();
+      return this.skip();
     }
   }
 };

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

@@ -3,16 +3,17 @@
 var ReplaceSupers = require("../../helpers/replace-supers");
 var nameMethod    = require("../../helpers/name-method");
 var defineMap     = require("../../helpers/define-map");
+var messages      = require("../../../messages");
 var util          = require("../../../util");
 var t             = require("../../../types");
 
 exports.check = t.isClass;
 
-exports.ClassDeclaration = function (node, parent, scope, context, file) {
-  return new Class(node, file, scope, true).run();
+exports.ClassDeclaration = function (node, parent, scope, file) {
+  return new ClassTransformer(node, file, scope, true).run();
 };
 
-exports.ClassExpression = function (node, parent, scope, context, file) {
+exports.ClassExpression = function (node, parent, scope, file) {
   if (!node.id) {
     if (t.isProperty(parent) && parent.value === node && !parent.computed && t.isIdentifier(parent.key)) {
       // var o = { foo: class {} };
@@ -25,7 +26,7 @@ exports.ClassExpression = function (node, parent, scope, context, file) {
     }
   }
 
-  return new Class(node, file, scope, false).run();
+  return new ClassTransformer(node, file, scope, false).run();
 };
 
 /**
@@ -34,10 +35,10 @@ exports.ClassExpression = function (node, parent, scope, context, file) {
  * @param {Node} node
  * @param {File} file
  * @param {Scope} scope
- * @param {Boolean} closure
+ * @param {Boolean} isStatement
  */
 
-function Class(node, file, scope, isStatement) {
+function ClassTransformer(node, file, scope, isStatement) {
   this.isStatement = isStatement;
   this.scope       = scope;
   this.node        = node;
@@ -61,7 +62,7 @@ function Class(node, file, scope, isStatement) {
  * @returns {Array}
  */
 
-Class.prototype.run = function () {
+ClassTransformer.prototype.run = function () {
   var superName = this.superName;
   var className = this.className;
   var file      = this.file;
@@ -98,8 +99,7 @@ Class.prototype.run = function () {
     closureArgs.push(superName);
 
     if (!t.isIdentifier(superName)) {
-      var superRef = this.scope.generateUidBasedOnNode(superName, this.file);
-      superName = superRef;
+      superName = this.scope.generateUidBasedOnNode(superName, this.file);
     }
 
     closureParams.push(superName);
@@ -138,7 +138,7 @@ Class.prototype.run = function () {
  * Description
  */
 
-Class.prototype.buildBody = function () {
+ClassTransformer.prototype.buildBody = function () {
   var constructor = this.constructor;
   var className   = this.className;
   var superName   = this.superName;
@@ -152,10 +152,11 @@ Class.prototype.buildBody = function () {
         methodNode: node,
         className:  this.className,
         superName:  this.superName,
+        isStatic:   node.static,
         isLoose:    this.isLoose,
         scope:      this.scope,
         file:       this.file
-      });
+      }, true);
       replaceSupers.replace();
 
       if (node.key.name === "constructor") {
@@ -166,6 +167,8 @@ Class.prototype.buildBody = function () {
     } else if (t.isPrivateDeclaration(node)) {
       this.closure = true;
       body.unshift(node);
+    } else if (t.isClassProperty(node)) {
+      this.pushProperty(node);
     }
   }
 
@@ -203,12 +206,12 @@ Class.prototype.buildBody = function () {
 };
 
 /**
- * Push a method to it's respective mutatorMap.
+ * Push a method to its respective mutatorMap.
  *
  * @param {Node} node MethodDefinition
  */
 
-Class.prototype.pushMethod = function (node) {
+ClassTransformer.prototype.pushMethod = function (node) {
   var methodName = node.key;
 
   var kind = node.kind;
@@ -244,15 +247,39 @@ Class.prototype.pushMethod = function (node) {
   defineMap.push(mutatorMap, methodName, "enumerable", node.computed, false);
 };
 
+/**
+ * Description
+ *
+ * @param {Node} node
+ */
+
+ClassTransformer.prototype.pushProperty = function (node) {
+  if (!node.value) return;
+
+  var key;
+
+  if (node.static) {
+    key = t.memberExpression(this.className, node.key);
+    this.body.push(
+      t.expressionStatement(t.assignmentExpression("=", key, node.value))
+    );
+  } else {
+    key = t.memberExpression(t.thisExpression(), node.key);
+    this.constructor.body.body.unshift(
+      t.expressionStatement(t.assignmentExpression("=", key, node.value))
+    );
+  }
+};
+
 /**
  * Replace the constructor body of our class.
  *
  * @param {Node} method MethodDefinition
  */
 
-Class.prototype.pushConstructor = function (method) {
+ClassTransformer.prototype.pushConstructor = function (method) {
   if (method.kind) {
-    throw this.file.errorWithNode(method, "illegal kind for constructor method");
+    throw this.file.errorWithNode(method, messages.get("classesIllegalConstructorKind"));
   }
 
   var construct = this.constructor;

lib/6to5/transformation/transformers/es6/constants.js

@@ -1,43 +1,48 @@
 "use strict";
 
-var t = require("../../../types");
+var messages = require("../../../messages");
+var t        = require("../../../types");
 
 exports.check = function (node) {
   return t.isVariableDeclaration(node, { kind: "const" });
 };
 
 var visitor = {
-  enter: function (node, parent, scope, context, state) {
+  enter: function (node, parent, scope, state) {
     if (t.isAssignmentExpression(node) || t.isUpdateExpression(node)) {
+      if (t.isMemberExpression(node.left || node.argument)) return;
+
       var ids = t.getBindingIdentifiers(node);
 
-      for (var key in ids) {
-        var id = ids[key];
+      for (var name in ids) {
+        var id = ids[name];
 
-        var constant = state.constants[key];
+        var constant = state.constants[name];
 
         // no constant exists
         if (!constant) continue;
 
+        var constantIdentifier = constant.identifier;
+
         // check if the assignment id matches the constant declaration id
         // if it does then it was the id used to initially declare the
         // constant so we can just ignore it
-        if (id === constant) continue;
+        if (id === constantIdentifier) continue;
 
-        var localBinding = scope.getBinding(key);
-        if (localBinding !== constant) continue;
+        // check if there's been a local binding that shadows this constant
+        if (!scope.bindingIdentifierEquals(name, constantIdentifier)) continue;
 
-        throw state.file.errorWithNode(id, key + " is read-only");
+        throw state.file.errorWithNode(id, messages.get("readOnly", name));
       }
-    } else if (t.isScope(node)) {
-      context.skip();
+    } else if (t.isScope(node, parent)) {
+      this.skip();
     }
   }
 };
 
-exports.Scope = function (node, parent, scope, context, file) {
+exports.Scopable = function (node, parent, scope, file) {
   scope.traverse(node, visitor, {
-    constants: scope.getAllDeclarationsOfKind("const"),
+    constants: scope.getAllBindingsOfKind("const"),
     file:      file
   });
 };

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

@@ -1,10 +1,11 @@
 "use strict";
 
-var t = require("../../../types");
+var messages = require("../../../messages");
+var t        = require("../../../types");
 
 exports.check = t.isPattern;
 
-function Destructuring(opts) {
+function DestructuringTransformer(opts) {
   this.blockHoist = opts.blockHoist;
   this.operator   = opts.operator;
   this.nodes      = opts.nodes;
@@ -13,7 +14,7 @@ function Destructuring(opts) {
   this.kind       = opts.kind;
 }
 
-Destructuring.prototype.buildVariableAssignment = function (id, init) {
+DestructuringTransformer.prototype.buildVariableAssignment = function (id, init) {
   var op = this.operator;
   if (t.isMemberExpression(id)) op = "=";
 
@@ -32,7 +33,7 @@ Destructuring.prototype.buildVariableAssignment = function (id, init) {
   return node;
 };
 
-Destructuring.prototype.buildVariableDeclaration = function (id, init) {
+DestructuringTransformer.prototype.buildVariableDeclaration = function (id, init) {
   var declar = t.variableDeclaration("var", [
     t.variableDeclarator(id, init)
   ]);
@@ -40,7 +41,7 @@ Destructuring.prototype.buildVariableDeclaration = function (id, init) {
   return declar;
 };
 
-Destructuring.prototype.push = function (elem, parentId) {
+DestructuringTransformer.prototype.push = function (elem, parentId) {
   if (t.isObjectPattern(elem)) {
     this.pushObjectPattern(elem, parentId);
   } else if (t.isArrayPattern(elem)) {
@@ -52,7 +53,7 @@ Destructuring.prototype.push = function (elem, parentId) {
   }
 };
 
-Destructuring.prototype.pushAssignmentPattern = function (pattern, parentId) {
+DestructuringTransformer.prototype.pushAssignmentPattern = function (pattern, parentId) {
   var tempParentId = this.scope.generateUidBasedOnNode(parentId);
 
   var declar = t.variableDeclaration("var", [
@@ -71,7 +72,7 @@ Destructuring.prototype.pushAssignmentPattern = function (pattern, parentId) {
   ));
 };
 
-Destructuring.prototype.pushObjectSpread = function (pattern, parentId, prop, i) {
+DestructuringTransformer.prototype.pushObjectSpread = function (pattern, parentId, prop, i) {
   // get all the keys that appear in this object before the current spread
   var keys = [];
   for (var i2 = 0; i2 < pattern.properties.length; i2++) {
@@ -92,7 +93,7 @@ Destructuring.prototype.pushObjectSpread = function (pattern, parentId, prop, i)
   this.nodes.push(this.buildVariableAssignment(prop.argument, value));
 };
 
-Destructuring.prototype.pushObjectProperty = function (prop, parentId) {
+DestructuringTransformer.prototype.pushObjectProperty = function (prop, parentId) {
   if (t.isLiteral(prop.key)) prop.computed = true;
 
   var pattern2   = prop.value;
@@ -105,13 +106,19 @@ Destructuring.prototype.pushObjectProperty = function (prop, parentId) {
   }
 };
 
-Destructuring.prototype.pushObjectPattern = function (pattern, parentId) {
+DestructuringTransformer.prototype.pushObjectPattern = function (pattern, parentId) {
   if (!pattern.properties.length) {
     this.nodes.push(t.expressionStatement(
       t.callExpression(this.file.addHelper("object-destructuring-empty"), [parentId])
     ));
   }
 
+  if (pattern.properties.length > 1 && t.isMemberExpression(parentId)) {
+    var temp = this.scope.generateUidBasedOnNode(parentId, this.file);
+    this.nodes.push(this.buildVariableDeclaration(temp, parentId));
+    parentId = temp;
+  }
+
   for (var i = 0; i < pattern.properties.length; i++) {
     var prop = pattern.properties[i];
     if (t.isSpreadProperty(prop)) {
@@ -131,18 +138,20 @@ var hasRest = function (pattern) {
   return false;
 };
 
-Destructuring.prototype.pushArrayPattern = function (pattern, parentId) {
+DestructuringTransformer.prototype.pushArrayPattern = function (pattern, parentId) {
   if (!pattern.elements) return;
 
   // if we have a rest then we need all the elements
   var count = !hasRest(pattern) && pattern.elements.length;
 
-  var toArray = this.file.toArray(parentId, count);
+  var toArray = this.scope.toArray(parentId, count);
 
-  var _parentId = this.scope.generateUidBasedOnNode(parentId, this.file);
+  var _parentId = this.scope.generateUidBasedOnNode(parentId);
   this.nodes.push(this.buildVariableDeclaration(_parentId, toArray));
   parentId = _parentId;
 
+  this.scope.assignTypeGeneric(parentId.name, "Array");
+
   for (var i = 0; i < pattern.elements.length; i++) {
     var elem = pattern.elements[i];
 
@@ -152,7 +161,7 @@ Destructuring.prototype.pushArrayPattern = function (pattern, parentId) {
     var newPatternId;
 
     if (t.isRestElement(elem)) {
-      newPatternId = this.file.toArray(parentId);
+      newPatternId = this.scope.toArray(parentId);
 
       if (i > 0) {
         newPatternId = t.callExpression(t.memberExpression(newPatternId, t.identifier("slice")), [t.literal(i)]);
@@ -167,7 +176,7 @@ Destructuring.prototype.pushArrayPattern = function (pattern, parentId) {
   }
 };
 
-Destructuring.prototype.init = function (pattern, parentId) {
+DestructuringTransformer.prototype.init = function (pattern, parentId) {
   if (!t.isArrayExpression(parentId) && !t.isMemberExpression(parentId) && !t.isIdentifier(parentId)) {
     var key = this.scope.generateUidBasedOnNode(parentId);
     this.nodes.push(this.buildVariableDeclaration(key, parentId));
@@ -178,22 +187,41 @@ Destructuring.prototype.init = function (pattern, parentId) {
 };
 
 exports.ForInStatement =
-exports.ForOfStatement = function (node, parent, scope, context, file) {
-  var declar = node.left;
-  if (!t.isVariableDeclaration(declar)) return;
+exports.ForOfStatement = function (node, parent, scope, file) {
+  var left = node.left;
 
-  var pattern = declar.declarations[0].id;
+  if (t.isPattern(left)) {
+    // for ({ length: k } in { abc: 3 });
+
+    var temp = scope.generateUidIdentifier("ref");
+
+    node.left = t.variableDeclaration("var", [
+      t.variableDeclarator(temp)
+    ]);
+
+    t.ensureBlock(node);
+
+    node.body.body.unshift(t.variableDeclaration("var", [
+      t.variableDeclarator(left, temp)
+    ]));
+
+    return;
+  }
+
+  if (!t.isVariableDeclaration(left)) return;
+
+  var pattern = left.declarations[0].id;
   if (!t.isPattern(pattern)) return;
 
   var key = scope.generateUidIdentifier("ref");
-  node.left = t.variableDeclaration(declar.kind, [
+  node.left = t.variableDeclaration(left.kind, [
     t.variableDeclarator(key, null)
   ]);
 
   var nodes = [];
 
-  var destructuring = new Destructuring({
-    kind: declar.kind,
+  var destructuring = new DestructuringTransformer({
+    kind: left.kind,
     file: file,
     scope: scope,
     nodes: nodes
@@ -207,18 +235,18 @@ exports.ForOfStatement = function (node, parent, scope, context, file) {
   block.body = nodes.concat(block.body);
 };
 
-exports.Function = function (node, parent, scope, context, file) {
+exports.Function = function (node, parent, scope, file) {
   var nodes = [];
 
-  var hasDestructuring = false;
+  var hasDestructuringTransformer = false;
 
   node.params = node.params.map(function (pattern, i) {
     if (!t.isPattern(pattern)) return pattern;
 
-    hasDestructuring = true;
+    hasDestructuringTransformer = true;
     var parentId = scope.generateUidIdentifier("ref");
 
-    var destructuring = new Destructuring({
+    var destructuring = new DestructuringTransformer({
       blockHoist: node.params.length - i,
       nodes:      nodes,
       scope:      scope,
@@ -230,7 +258,7 @@ exports.Function = function (node, parent, scope, context, file) {
     return parentId;
   });
 
-  if (!hasDestructuring) return;
+  if (!hasDestructuringTransformer) return;
 
   t.ensureBlock(node);
 
@@ -238,7 +266,7 @@ exports.Function = function (node, parent, scope, context, file) {
   block.body = nodes.concat(block.body);
 };
 
-exports.CatchClause = function (node, parent, scope, context, file) {
+exports.CatchClause = function (node, parent, scope, file) {
   var pattern = node.param;
   if (!t.isPattern(pattern)) return;
 
@@ -247,8 +275,8 @@ exports.CatchClause = function (node, parent, scope, context, file) {
 
   var nodes = [];
 
-  var destructuring = new Destructuring({
-    kind: "var",
+  var destructuring = new DestructuringTransformer({
+    kind: "let",
     file: file,
     scope: scope,
     nodes: nodes
@@ -256,9 +284,11 @@ exports.CatchClause = function (node, parent, scope, context, file) {
   destructuring.init(pattern, ref);
 
   node.body.body = nodes.concat(node.body.body);
+
+  return node;
 };
 
-exports.ExpressionStatement = function (node, parent, scope, context, file) {
+exports.ExpressionStatement = function (node, parent, scope, file) {
   var expr = node.expression;
   if (expr.type !== "AssignmentExpression") return;
   if (!t.isPattern(expr.left)) return;
@@ -271,7 +301,7 @@ exports.ExpressionStatement = function (node, parent, scope, context, file) {
     t.variableDeclarator(ref, expr.right)
   ]));
 
-  var destructuring = new Destructuring({
+  var destructuring = new DestructuringTransformer({
     operator: expr.operator,
     file: file,
     scope: scope,
@@ -282,7 +312,7 @@ exports.ExpressionStatement = function (node, parent, scope, context, file) {
   return nodes;
 };
 
-exports.AssignmentExpression = function (node, parent, scope, context, file) {
+exports.AssignmentExpression = function (node, parent, scope, file) {
   if (!t.isPattern(node.left)) return;
 
   var ref = scope.generateUidIdentifier("temp");
@@ -294,7 +324,7 @@ exports.AssignmentExpression = function (node, parent, scope, context, file) {
   var nodes = [];
   nodes.push(t.assignmentExpression("=", ref, node.right));
 
-  var destructuring = new Destructuring({
+  var destructuring = new DestructuringTransformer({
     operator: node.operator,
     file: file,
     scope: scope,
@@ -316,7 +346,7 @@ var variableDeclarationhasPattern = function (node) {
   return false;
 };
 
-exports.VariableDeclaration = function (node, parent, scope, context, file) {
+exports.VariableDeclaration = function (node, parent, scope, file) {
   if (t.isForInStatement(parent) || t.isForOfStatement(parent)) return;
   if (!variableDeclarationhasPattern(node)) return;
 
@@ -329,7 +359,7 @@ exports.VariableDeclaration = function (node, parent, scope, context, file) {
     var patternId = declar.init;
     var pattern   = declar.id;
 
-    var destructuring = new Destructuring({
+    var destructuring = new DestructuringTransformer({
       nodes: nodes,
       scope: scope,
       kind:  node.kind,
@@ -360,7 +390,7 @@ exports.VariableDeclaration = function (node, parent, scope, context, file) {
       declar = declar || t.variableDeclaration(node.kind, []);
 
       if (!t.isVariableDeclaration(node) && declar.kind !== node.kind) {
-        throw file.errorWithNode(node, "Cannot use this node within the current parent");
+        throw file.errorWithNode(node, messages.get("invalidParentForThisNode"));
       }
 
       declar.declarations = declar.declarations.concat(node.declarations);

lib/6to5/transformation/transformers/es6/for-of.js

@@ -1,15 +1,16 @@
 "use strict";
 
-var util = require("../../../util");
-var t    = require("../../../types");
+var messages = require("../../../messages");
+var util     = require("../../../util");
+var t        = require("../../../types");
 
 exports.check = t.isForOfStatement;
 
-exports.ForOfStatement = function (node, parent, scope, context, file) {
+exports.ForOfStatement = function (node, parent, scope, file) {
   var callback = spec;
   if (file.isLoose("es6.forOf")) callback = loose;
 
-  var build  = callback(node, parent, scope, context, file);
+  var build  = callback(node, parent, scope, file);
   var declar = build.declar;
   var loop   = build.loop;
   var block  = loop.body;
@@ -17,7 +18,7 @@ exports.ForOfStatement = function (node, parent, scope, context, file) {
   // inherit comments from the original loop
   t.inheritsComments(loop, node);
 
-  // ensure that it's a block so we can take all it's statemetns
+  // ensure that it's a block so we can take all its statements
   t.ensureBlock(node);
 
   // add the value declaration to the new loop body
@@ -28,13 +29,15 @@ exports.ForOfStatement = function (node, parent, scope, context, file) {
   // push the rest of the original loop body onto our new body
   block.body = block.body.concat(node.body.body);
 
+  t.inherits(loop, node);
+
   // todo: find out why this is necessary? #538
   loop._scopeInfo = node._scopeInfo;
 
   return loop;
 };
 
-var loose = function (node, parent, scope, context, file) {
+var loose = function (node, parent, scope, file) {
   var left = node.left;
   var declar, id;
 
@@ -48,7 +51,7 @@ var loose = function (node, parent, scope, context, file) {
       t.variableDeclarator(left.declarations[0].id, id)
     ]);
   } else {
-    throw file.errorWithNode(left, "Unknown node type " + left.type + " in ForOfStatement");
+    throw file.errorWithNode(left, messages.get("unknownForHead", left.type));
   }
 
   var loop = util.template("for-of-loose", {
@@ -71,7 +74,7 @@ var loose = function (node, parent, scope, context, file) {
   };
 };
 
-var spec = function (node, parent, scope, context, file) {
+var spec = function (node, parent, scope, file) {
   var left = node.left;
   var declar;
 
@@ -87,7 +90,7 @@ var spec = function (node, parent, scope, context, file) {
       t.variableDeclarator(left.declarations[0].id, stepValue)
     ]);
   } else {
-    throw file.errorWithNode(left, "Unknown node type " + left.type + " in ForOfStatement");
+    throw file.errorWithNode(left, messages.get("unknownForHead", left.type));
   }
 
   var loop = util.template("for-of", {

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

@@ -4,7 +4,7 @@ var t = require("../../../types");
 
 exports.check = require("../internal/modules").check;
 
-exports.ImportDeclaration = function (node, parent, scope, context, file) {
+exports.ImportDeclaration = function (node, parent, scope, file) {
   var nodes = [];
 
   if (node.specifiers.length) {
@@ -23,7 +23,7 @@ exports.ImportDeclaration = function (node, parent, scope, context, file) {
   return nodes;
 };
 
-exports.ExportDeclaration = function (node, parent, scope, context, file) {
+exports.ExportDeclaration = function (node, parent, scope, file) {
   var nodes = [];
   var i;
 

lib/6to5/transformation/transformers/es6/object-super.js

@@ -0,0 +1,34 @@
+"use strict";
+
+var ReplaceSupers = require("../../helpers/replace-supers");
+var t             = require("../../../types");
+
+exports.check = function (node) {
+  return t.isIdentifier(node, { name: "super" });
+};
+
+exports.Property = function (node, parent, scope, file) {
+  if (!node.method) return;
+
+  var value = node.value;
+  var thisExpr = scope.generateUidIdentifier("this");
+
+  var replaceSupers = new ReplaceSupers({
+    topLevelThisReference: thisExpr,
+    methodNode:            node,
+    className:             thisExpr,
+    isStatic:              true,
+    scope:                 scope,
+    file:                  file
+  });
+
+  replaceSupers.replace();
+
+  if (replaceSupers.hasSuper) {
+    value.body.body.unshift(
+      t.variableDeclaration("var", [
+        t.variableDeclarator(thisExpr, t.thisExpression())
+      ])
+    );
+  }
+};

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

@@ -9,21 +9,23 @@ exports.check = function (node) {
 
 var hasDefaults = function (node) {
   for (var i = 0; i < node.params.length; i++) {
-    if (t.isAssignmentPattern(node.params[i])) return true;
+    if (!t.isIdentifier(node.params[i])) return true;
   }
   return false;
 };
 
 var iifeVisitor = {
-  enter: function (node, parent, scope, context, state) {
-    if (t.isReferencedIdentifier(node, parent) && state.scope.hasOwnReference(node.name)) {
-      state.iife = true;
-      context.stop();
-    }
+  enter: function (node, parent, scope, state) {
+    if (!t.isReferencedIdentifier(node, parent)) return;
+    if (!state.scope.hasOwnBinding(node.name)) return;
+    if (state.scope.bindingIdentifierEquals(node.name, node)) return;
+
+    state.iife = true;
+    this.stop();
   }
 };
 
-exports.Function = function (node, parent, scope) {
+exports.Function = function (node, parent, scope, file) {
   if (!hasDefaults(node)) return;
 
   t.ensureBlock(node);
@@ -37,35 +39,53 @@ exports.Function = function (node, parent, scope) {
 
   var state = { iife: false, scope: scope };
 
+  var pushDefNode = function (left, right, i) {
+    var defNode = util.template("default-parameter", {
+      VARIABLE_NAME: left,
+      DEFAULT_VALUE: right,
+      ARGUMENT_KEY:  t.literal(i),
+      ARGUMENTS:     argsIdentifier
+    }, true);
+    file.checkNode(defNode);
+    defNode._blockHoist = node.params.length - i;
+    body.push(defNode);
+  };
+
   for (var i = 0; i < node.params.length; i++) {
     var param = node.params[i];
 
     if (!t.isAssignmentPattern(param)) {
-      lastNonDefaultParam = +i + 1;
+      if (!t.isRestElement(param)) {
+        lastNonDefaultParam = i + 1;
+      }
+
+      if (!t.isIdentifier(param)) {
+        scope.traverse(param, iifeVisitor, state);
+      }
+
+      if (file.transformers["es6.blockScopingTDZ"].canRun()) {
+        pushDefNode(param, t.identifier("undefined"), i);
+      }
+
       continue;
     }
 
     var left  = param.left;
     var right = param.right;
 
-    node.params[i] = scope.generateUidIdentifier("x");
+    var placeholder = scope.generateUidIdentifier("x");
+    placeholder._isDefaultPlaceholder = true;
+    node.params[i] = placeholder;
 
     if (!state.iife) {
-      if (t.isIdentifier(right) && scope.hasOwnReference(right.name)) {
+      if (t.isIdentifier(right) && scope.hasOwnBinding(right.name)) {
         state.iife = true;
       } else {
         scope.traverse(right, iifeVisitor, state);
       }
     }
 
-    var defNode = util.template("default-parameter", {
-      VARIABLE_NAME: left,
-      DEFAULT_VALUE: right,
-      ARGUMENT_KEY:  t.literal(+i),
-      ARGUMENTS:     argsIdentifier
-    }, true);
-    defNode._blockHoist = node.params.length - i;
-    body.push(defNode);
+    pushDefNode(left, right, i);
   }
 
   // we need to cut off all trailing default parameters

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

@@ -60,6 +60,8 @@ exports.Function = function (node, parent, scope) {
     node.body.body.unshift(restDeclar);
   }
 
+  scope.assignTypeGeneric(rest.name, "Array");
+
   var loop = util.template("rest", {
     ARGUMENTS: argsId,
     ARRAY_KEY: arrKey,

lib/6to5/transformation/transformers/es6/properties.computed.js

@@ -6,7 +6,7 @@ exports.check = function (node) {
   return t.isProperty(node) && node.computed;
 };
 
-exports.ObjectExpression = function (node, parent, scope, context, file) {
+exports.ObjectExpression = function (node, parent, scope, file) {
   var hasComputed = false;
 
   for (var i = 0; i < node.properties.length; i++) {

lib/6to5/transformation/transformers/es6/properties.shorthand.js

@@ -8,7 +8,7 @@ exports.check = function (node) {
   return t.isProperty(node) && (node.method || node.shorthand);
 };
 
-exports.Property = function (node, parent, scope, context, file) {
+exports.Property = function (node, parent, scope, file) {
   if (node.method) {
     node.method = false;
     nameMethod.property(node, file, scope);

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

@@ -1,12 +1,12 @@
 "use strict";
 
-var contains = require("lodash/collection/contains");
+var includes = require("lodash/collection/includes");
 var t        = require("../../../types");
 
 exports.check = t.isSpreadElement;
 
-var getSpreadLiteral = function (spread, file) {
-  return file.toArray(spread.argument);
+var getSpreadLiteral = function (spread, scope) {
+  return scope.toArray(spread.argument, true);
 };
 
 var hasSpread = function (nodes) {
@@ -18,7 +18,7 @@ var hasSpread = function (nodes) {
   return false;
 };
 
-var build = function (props, file) {
+var build = function (props, scope) {
   var nodes = [];
 
   var _props = [];
@@ -33,7 +33,7 @@ var build = function (props, file) {
     var prop = props[i];
     if (t.isSpreadElement(prop)) {
       push();
-      nodes.push(getSpreadLiteral(prop, file));
+      nodes.push(getSpreadLiteral(prop, scope));
     } else {
       _props.push(prop);
     }
@@ -44,11 +44,11 @@ var build = function (props, file) {
   return nodes;
 };
 
-exports.ArrayExpression = function (node, parent, scope, context, file) {
+exports.ArrayExpression = function (node, parent, scope) {
   var elements = node.elements;
   if (!hasSpread(elements)) return;
 
-  var nodes = build(elements, file);
+  var nodes = build(elements, scope);
   var first = nodes.shift();
 
   if (!t.isArrayExpression(first)) {
@@ -59,7 +59,7 @@ exports.ArrayExpression = function (node, parent, scope, context, file) {
   return t.callExpression(t.memberExpression(first, t.identifier("concat")), nodes);
 };
 
-exports.CallExpression = function (node, parent, scope, context, file) {
+exports.CallExpression = function (node, parent, scope) {
   var args = node.arguments;
   if (!hasSpread(args)) return;
 
@@ -71,10 +71,10 @@ exports.CallExpression = function (node, parent, scope, context, file) {
   if (args.length === 1 && args[0].argument.name === "arguments") {
     nodes = [args[0].argument];
   } else {
-    nodes = build(args, file);
+    nodes = build(args, scope);
   }
-  var first = nodes.shift();
 
+  var first = nodes.shift();
   if (nodes.length) {
     node.arguments.push(t.callExpression(t.memberExpression(first, t.identifier("concat")), nodes));
   } else {
@@ -99,13 +99,13 @@ exports.CallExpression = function (node, parent, scope, context, file) {
   node.arguments.unshift(contextLiteral);
 };
 
-exports.NewExpression = function (node, parent, scope, context, file) {
+exports.NewExpression = function (node, parent, scope, file) {
   var args = node.arguments;
   if (!hasSpread(args)) return;
 
-  var nativeType = t.isIdentifier(node.callee) && contains(t.NATIVE_TYPE_NAMES, node.callee.name);
+  var nativeType = t.isIdentifier(node.callee) && includes(t.NATIVE_TYPE_NAMES, node.callee.name);
 
-  var nodes = build(args, file);
+  var nodes = build(args, scope);
 
   if (nativeType) {
     nodes.unshift(t.arrayExpression([t.literal(null)]));

lib/6to5/transformation/transformers/es6/tail-call.js

@@ -0,0 +1,359 @@
+"use strict";
+
+var reduceRight = require("lodash/collection/reduceRight");
+var messages    = require("../../../messages");
+var flatten     = require("lodash/array/flatten");
+var util        = require("../../../util");
+var map         = require("lodash/collection/map");
+var t           = require("../../../types");
+
+function returnBlock(expr) {
+  return t.blockStatement([t.returnStatement(expr)]);
+}
+
+function TailCallTransformer(node, scope, file) {
+  this.hasTailRecursion = false;
+  this.needsArguments   = false;
+  this.setsArguments    = false;
+  this.needsThis        = false;
+  this.ownerId          = node.id;
+  this.vars             = [];
+
+  this.scope = scope;
+  this.file  = file;
+  this.node  = node;
+}
+
+TailCallTransformer.prototype.getArgumentsId = function () {
+  return this.argumentsId = this.argumentsId || this.scope.generateUidIdentifier("arguments");
+};
+
+TailCallTransformer.prototype.getThisId = function () {
+  return this.thisId = this.thisId || this.scope.generateUidIdentifier("this");
+};
+
+TailCallTransformer.prototype.getLeftId = function () {
+  return this.leftId = this.leftId || this.scope.generateUidIdentifier("left");
+};
+
+TailCallTransformer.prototype.getFunctionId = function () {
+  return this.functionId = this.functionId || this.scope.generateUidIdentifier("function");
+};
+
+TailCallTransformer.prototype.getParams = function () {
+  var params = this.params;
+
+  if (!params) {
+    params = this.node.params;
+    this.paramDecls = [];
+
+    for (var i = 0; i < params.length; i++) {
+      var param = params[i];
+      if (!param._isDefaultPlaceholder) {
+        this.paramDecls.push(t.variableDeclarator(
+          param,
+          params[i] = this.scope.generateUidIdentifier("x")
+        ));
+      }
+    }
+  }
+
+  return this.params = params;
+};
+
+TailCallTransformer.prototype.hasDeopt = function () {
+  // check if the ownerId has been reassigned, if it has then it's not safe to
+  // perform optimisations
+  var ownerIdInfo = this.scope.getBindingInfo(this.ownerId.name);
+  return ownerIdInfo && ownerIdInfo.reassigned;
+};
+
+TailCallTransformer.prototype.run = function () {
+  var scope = this.scope;
+  var node  = this.node;
+
+  // only tail recursion can be optimized as for now, so we can skip anonymous
+  // functions entirely
+  var ownerId = this.ownerId;
+  if (!ownerId) return;
+
+  // traverse the function and look for tail recursion
+  scope.traverse(node, firstPass, this);
+
+  if (!this.hasTailRecursion) return;
+
+  if (this.hasDeopt()) {
+    this.file.logDeopt(node, messages.get("tailCallReassignmentDeopt"));
+    return;
+  }
+
+  //
+
+  scope.traverse(node, secondPass, this);
+
+  if (!this.needsThis || !this.needsArguments) {
+    scope.traverse(node, thirdPass, this);
+  }
+
+  var body = t.ensureBlock(node).body;
+
+  if (this.vars.length > 0) {
+    var declarations = flatten(map(this.vars, function (decl) {
+      return decl.declarations;
+    }, this));
+    var statement = reduceRight(declarations, function (expr, decl) {
+      return t.assignmentExpression("=", decl.id, expr);
+    }, t.identifier("undefined"));
+    body.unshift(t.expressionStatement(statement));
+  }
+
+  var paramDecls = this.paramDecls;
+  if (paramDecls.length > 0) {
+    body.unshift(t.variableDeclaration("var", paramDecls));
+  }
+
+  node.body = util.template("tail-call-body", {
+    THIS_ID:       this.thisId,
+    ARGUMENTS_ID:  this.argumentsId,
+    FUNCTION_ID:   this.getFunctionId(),
+    BLOCK:         node.body
+  });
+
+  var topVars = [];
+
+  if (this.needsThis) {
+    topVars.push(t.variableDeclarator(this.getThisId(), t.thisExpression()));
+  }
+
+  if (this.needsArguments || this.setsArguments) {
+    var decl = t.variableDeclarator(this.getArgumentsId());
+    if (this.needsArguments) {
+      decl.init = t.identifier("arguments");
+    }
+    topVars.push(decl);
+  }
+
+  var leftId = this.leftId;
+  if (leftId) {
+    topVars.push(t.variableDeclarator(leftId));
+  }
+
+  if (topVars.length > 0) {
+    node.body.body.unshift(t.variableDeclaration("var", topVars));
+  }
+};
+
+TailCallTransformer.prototype.subTransform = function (node) {
+  if (!node) return;
+
+  var handler = this["subTransform" + node.type];
+  if (handler) return handler.call(this, node);
+};
+
+TailCallTransformer.prototype.subTransformConditionalExpression = function (node) {
+  var callConsequent = this.subTransform(node.consequent);
+  var callAlternate = this.subTransform(node.alternate);
+  if (!callConsequent && !callAlternate) {
+    return;
+  }
+
+  // if ternary operator had tail recursion in value, convert to optimized if-statement
+  node.type = "IfStatement";
+  node.consequent = callConsequent ? t.toBlock(callConsequent) : returnBlock(node.consequent);
+
+  if (callAlternate) {
+    node.alternate = t.isIfStatement(callAlternate) ? callAlternate : t.toBlock(callAlternate);
+  } else {
+    node.alternate = returnBlock(node.alternate);
+  }
+
+  return [node];
+};
+
+TailCallTransformer.prototype.subTransformLogicalExpression = function (node) {
+  // only call in right-value of can be optimized
+  var callRight = this.subTransform(node.right);
+  if (!callRight) return;
+
+  // cache left value as it might have side-effects
+  var leftId = this.getLeftId();
+  var testExpr = t.assignmentExpression(
+    "=",
+    leftId,
+    node.left
+  );
+
+  if (node.operator === "&&") {
+    testExpr = t.unaryExpression("!", testExpr);
+  }
+
+  return [t.ifStatement(testExpr, returnBlock(leftId))].concat(callRight);
+};
+
+TailCallTransformer.prototype.subTransformSequenceExpression = function (node) {
+  var seq = node.expressions;
+
+  // only last element can be optimized
+  var lastCall = this.subTransform(seq[seq.length - 1]);
+  if (!lastCall) {
+    return;
+  }
+
+  // remove converted expression from sequence
+  // and convert to regular expression if needed
+  if (--seq.length === 1) {
+    node = seq[0];
+  }
+
+  return [t.expressionStatement(node)].concat(lastCall);
+};
+
+TailCallTransformer.prototype.subTransformCallExpression = function (node) {
+  var callee = node.callee, thisBinding, args;
+
+  if (t.isMemberExpression(callee, { computed: false }) && t.isIdentifier(callee.property)) {
+    switch (callee.property.name) {
+      case "call":
+        args = t.arrayExpression(node.arguments.slice(1));
+        break;
+
+      case "apply":
+        args = node.arguments[1] || t.identifier("undefined");
+        break;
+
+      default:
+        return;
+    }
+
+    thisBinding = node.arguments[0];
+    callee = callee.object;
+  }
+
+  // only tail recursion can be optimized as for now
+  if (!t.isIdentifier(callee) || !this.scope.bindingIdentifierEquals(callee.name, this.ownerId)) {
+    return;
+  }
+
+  this.hasTailRecursion = true;
+
+  if (this.hasDeopt()) return;
+
+  var body = [];
+
+  if (!t.isThisExpression(thisBinding)) {
+    body.push(t.expressionStatement(t.assignmentExpression(
+      "=",
+      this.getThisId(),
+      thisBinding || t.identifier("undefined")
+    )));
+  }
+
+  if (!args) {
+    args = t.arrayExpression(node.arguments);
+  }
+
+  var argumentsId = this.getArgumentsId();
+  var params = this.getParams();
+
+  body.push(t.expressionStatement(t.assignmentExpression(
+    "=",
+    argumentsId,
+    args
+  )));
+
+  var i, param;
+
+  if (t.isArrayExpression(args)) {
+    var elems = args.elements;
+    for (i = 0; i < elems.length && i < params.length; i++) {
+      param = params[i];
+      var elem = elems[i] || (elems[i] = t.identifier("undefined"));
+      if (!param._isDefaultPlaceholder) {
+        elems[i] = t.assignmentExpression("=", param, elem);
+      }
+    }
+  } else {
+    this.setsArguments = true;
+    for (i = 0; i < params.length; i++) {
+      param = params[i];
+      if (!param._isDefaultPlaceholder) {
+        body.push(t.expressionStatement(t.assignmentExpression(
+          "=",
+          param,
+          t.memberExpression(argumentsId, t.literal(i), true)
+        )));
+      }
+    }
+  }
+
+  body.push(t.continueStatement(this.getFunctionId()));
+
+  return body;
+};
+
+// looks for and replaces tail recursion calls
+var firstPass = {
+  enter: function (node, parent, scope, state) {
+    if (t.isReturnStatement(node)) {
+      this.skip();
+      return state.subTransform(node.argument);
+    } else if (t.isTryStatement(parent)) {
+      if (node === parent.block) {
+        this.skip();
+      } else if (parent.finalizer && node !== parent.finalizer) {
+        this.skip();
+      }
+    } else if (t.isFunction(node)) {
+      this.skip();
+    } else if (t.isVariableDeclaration(node)) {
+      this.skip();
+      state.vars.push(node);
+    }
+  }
+};
+
+// hoists up function declarations, replaces `this` and `arguments` and marks
+// them as needed
+var secondPass = {
+  enter: function (node, parent, scope, state) {
+    if (t.isThisExpression(node)) {
+      state.needsThis = true;
+      return state.getThisId();
+    } else if (t.isReferencedIdentifier(node, parent, { name: "arguments" })) {
+      state.needsArguments = true;
+      return state.getArgumentsId();
+    } else if (t.isFunction(node)) {
+      this.skip();
+      if (t.isFunctionDeclaration(node)) {
+        node = t.variableDeclaration("var", [
+          t.variableDeclarator(node.id, t.toExpression(node))
+        ]);
+        node._blockHoist = 2;
+        return node;
+      }
+    }
+  }
+};
+
+// optimizes recursion by removing `this` and `arguments` if they aren't used
+var thirdPass = {
+  enter: function (node, parent, scope, state) {
+    if (!t.isExpressionStatement(node)) return;
+
+    var expr = node.expression;
+    if (!t.isAssignmentExpression(expr)) return;
+
+    if (!state.needsThis && expr.left === state.getThisId()) {
+      this.remove();
+    } else if (!state.needsArguments && expr.left === state.getArgumentsId() && t.isArrayExpression(expr.right)) {
+      return map(expr.right.elements, function (elem) {
+        return t.expressionStatement(elem);
+      });
+    }
+  }
+};
+
+exports.Function = function (node, parent, scope, file) {
+  var tailCall = new TailCallTransformer(node, scope, file);
+  tailCall.run();
+};

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

@@ -10,7 +10,7 @@ exports.check = function (node) {
   return t.isTemplateLiteral(node) || t.isTaggedTemplateExpression(node);
 };
 
-exports.TaggedTemplateExpression = function (node, parent, scope, context, file) {
+exports.TaggedTemplateExpression = function (node, parent, scope, file) {
   var args = [];
   var quasi = node.quasi;
 

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

@@ -23,7 +23,7 @@ var container = function (parent, call, ret, file) {
   }
 };
 
-exports.AssignmentExpression = function (node, parent, scope, context, file) {
+exports.AssignmentExpression = function (node, parent, scope, file) {
   var left = node.left;
   if (!t.isVirtualPropertyExpression(left)) return;
 
@@ -63,7 +63,7 @@ exports.AssignmentExpression = function (node, parent, scope, context, file) {
   return container(parent, call, value, file);
 };
 
-exports.UnaryExpression = function (node, parent, scope, context, file) {
+exports.UnaryExpression = function (node, parent, scope, file) {
   var arg = node.argument;
   if (!t.isVirtualPropertyExpression(arg)) return;
   if (node.operator !== "delete") return;

lib/6to5/transformation/transformers/es7/comprehensions.js

@@ -1,13 +1,13 @@
 "use strict";
 
 var buildComprehension = require("../../helpers/build-comprehension");
-var traverse           = require("../../../traverse");
+var traverse           = require("../../../traversal");
 var util               = require("../../../util");
 var t                  = require("../../../types");
 
 exports.experimental = true;
 
-exports.ComprehensionExpression = function (node, parent, scope, context, file) {
+exports.ComprehensionExpression = function (node, parent, scope, file) {
   var callback = array;
   if (node.generator) callback = generator;
   return callback(node, parent, scope, file);

lib/6to5/transformation/transformers/es7/object-rest-spread.js

@@ -19,7 +19,7 @@ var hasSpread = function (node) {
   return false;
 };
 
-exports.ObjectExpression = function (node, parent, scope, context, file) {
+exports.ObjectExpression = function (node, parent, scope, file) {
   if (!hasSpread(node)) return;
 
   var args = [];

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

@@ -11,6 +11,7 @@ module.exports = {
   "playground.memoizationOperator":        require("./playground/memoization-operator"),
   "playground.objectGetterMemoization":    require("./playground/object-getter-memoization"),
 
+  reactCompat:                             require("./other/react-compat"),
   react:                                   require("./other/react"),
 
   _modules:                                require("./internal/modules"),
@@ -27,9 +28,9 @@ module.exports = {
   asyncToGenerator:                        require("./other/async-to-generator"),
   bluebirdCoroutines:                      require("./other/bluebird-coroutines"),
 
+  "es6.objectSuper":                       require("./es6/object-super"),
   "es7.objectRestSpread":                  require("./es7/object-rest-spread"),
   "es7.exponentiationOperator":            require("./es7/exponentiation-operator"),
-  "es6.spread":                            require("./es6/spread"),
   "es6.templateLiterals":                  require("./es6/template-literals"),
 
   "es5.properties.mutators":               require("./es5/properties.mutators"),
@@ -45,6 +46,18 @@ module.exports = {
 
   "es6.constants":                         require("./es6/constants"),
 
+  // needs to be before `es6.parameters.default` as default parameters will destroy the rest param
+  "es6.parameters.rest":                   require("./es6/parameters.rest"),
+
+  // needs to be after `es6.parameters.rest` as we use `toArray` and avoid turning an already known array into one
+  "es6.spread":                            require("./es6/spread"),
+
+  // needs to be before `es6.blockScoping` as default parameters have a TDZ
+  "es6.parameters.default":                require("./es6/parameters.default"),
+
+  // needs to be before `es6.blockScoping` as let variables may be produced
+  "es6.destructuring":                     require("./es6/destructuring"),
+
   // needs to be before `_aliasFunction` due to block scopes sometimes being wrapped in a
   // closure
   "es6.blockScoping":                      require("./es6/block-scoping"),
@@ -52,10 +65,9 @@ module.exports = {
   // needs to be after `es6.blockScoping` due to needing `letReferences` set on blocks
   "es6.blockScopingTDZ":                   require("./es6/block-scoping-tdz"),
 
-  "es6.parameters.default":                require("./es6/parameters.default"),
-  "es6.parameters.rest":                   require("./es6/parameters.rest"),
-
-  "es6.destructuring":                     require("./es6/destructuring"),
+  // needs to be after `es6.parameters.*` and `es6.blockScoping` due to needing pure
+  // identifiers in parameters and variable declarators
+  "es6.tailCall":                          require("./es6/tail-call"),
 
   regenerator:                             require("./other/regenerator"),
 
@@ -79,11 +91,13 @@ module.exports = {
   "spec.typeofSymbol":                     require("./spec/typeof-symbol"),
   "spec.undefinedToVoid":                  require("./spec/undefined-to-void"),
 
-  "minification.propertyLiterals":         require("./minification/property-literals"),
-  "minification.memberExpressionLiterals": require("./minification/member-expression-literals"),
+  "es3.propertyLiterals":                  require("./es3/property-literals"),
+  "es3.memberExpressionLiterals":          require("./es3/member-expression-literals"),
 
   "minification.removeDebugger":           require("./minification/remove-debugger"),
   "minification.removeConsoleCalls":       require("./minification/remove-console-calls"),
   "minification.deadCodeElimination":      require("./minification/dead-code-elimination"),
-  "minification.renameLocalVariables":     require("./minification/rename-local-variables")
+  "minification.renameLocalVariables":     require("./minification/rename-local-variables"),
+
+  _cleanUp:                                require("./internal/cleanup")
 };

lib/6to5/transformation/transformers/internal/alias-functions.js

@@ -3,12 +3,12 @@
 var t = require("../../../types");
 
 var functionChildrenVisitor = {
-  enter: function (node, parent, scope, context, state) {
+  enter: function (node, parent, scope, state) {
     if (t.isFunction(node) && !node._aliasFunction) {
-      return context.skip();
+      return this.skip();
     }
 
-    if (node._ignoreAliasFunctions) return context.skip();
+    if (node._ignoreAliasFunctions) return this.skip();
 
     var getId;
 
@@ -25,11 +25,11 @@ var functionChildrenVisitor = {
 };
 
 var functionVisitor = {
-  enter: function (node, parent, scope, context, state) {
+  enter: function (node, parent, scope, state) {
     if (!node._aliasFunction) {
       if (t.isFunction(node)) {
         // stop traversal of this node as it'll be hit again by this transformer
-        return context.skip();
+        return this.skip();
       } else {
         return;
       }
@@ -38,7 +38,7 @@ var functionVisitor = {
     // traverse all child nodes of this function and find `arguments` and `this`
     scope.traverse(node, functionChildrenVisitor, state);
 
-    return context.skip();
+    return this.skip();
   }
 };
 

lib/6to5/transformation/transformers/internal/cleanup.js

@@ -0,0 +1,5 @@
+exports.SequenceExpression = function (node) {
+  if (node.expressions.length === 1) {
+    return node.expressions[0];
+  }
+};

lib/6to5/transformation/transformers/internal/module-formatter.js

@@ -2,16 +2,16 @@
 
 var useStrict = require("../../helpers/use-strict");
 
-exports.ast = {
-  exit: function (ast, file) {
-    if (!file.transformers["es6.modules"].canRun()) return;
+exports.post = function (file) {
+  if (!file.transformers["es6.modules"].canRun()) return;
 
-    useStrict.wrap(ast.program, function () {
-      ast.program.body = file.dynamicImports.concat(ast.program.body);
-    });
+  var program = file.ast.program;
 
-    if (file.moduleFormatter.transform) {
-      file.moduleFormatter.transform(ast);
-    }
+  useStrict.wrap(program, function () {
+    program.body = file.dynamicImports.concat(program.body);
+  });
+
+  if (file.moduleFormatter.transform) {
+    file.moduleFormatter.transform(program);
   }
 };

lib/6to5/transformation/transformers/internal/modules.js

@@ -8,7 +8,7 @@
 
 var t = require("../../../types");
 
-var resolveModuleSource = function (node, parent, scope, context, file) {
+var resolveModuleSource = function (node, parent, scope, file) {
   var resolveModuleSource = file.opts.resolveModuleSource;
   if (node.source && resolveModuleSource) {
     node.source.value = resolveModuleSource(node.source.value);

lib/6to5/transformation/transformers/minification/dead-code-elimination.js

@@ -2,8 +2,9 @@ var t = require("../../../types");
 
 exports.optional = true;
 
-exports.ExpressionStatement = function (node, parent, scope, context) {
-  // remove consequenceless expressions such as local variables and literals
+exports.ExpressionStatement = function (node) {
+  // remove consequence-less expressions such as local variables and literals
+  // note: will remove directives
   //
   //   var foo = true; foo; -> var foo = true;
   //   "foo"; ->
@@ -11,12 +12,12 @@ exports.ExpressionStatement = function (node, parent, scope, context) {
 
   var expr = node.expression;
   if (t.isLiteral(expr) || (t.isIdentifier(node) && t.hasBinding(node.name))) {
-    context.remove();
+    this.remove();
   }
 };
 
 exports.IfStatement = {
-  exit: function (node, parent, scope, context) {
+  exit: function (node) {
     // todo: in scenarios where we can just return the consequent or
     // alternate we should drop the block statement if it contains no
     // block scoped variables
@@ -25,7 +26,7 @@ exports.IfStatement = {
     var alternate  = node.alternate;
     var test       = node.test;
 
-    // we can check if a test will be truthy 100% and if so we can inline
+    // we can check if a test will be truthy 100% and if so then we can inline
     // the consequent and completely ignore the alternate
     //
     //   if (true) { foo; } -> { foo; }
@@ -33,11 +34,11 @@ exports.IfStatement = {
     //
 
     if (t.isLiteral(test) && test.value) {
-      return alternate;
+      return consequent;
     }
 
-    // we can check if a test will be falsy 100% and if so we can inline
-    // the alternate if there is one and completely remove the consequent
+    // we can check if a test will be falsy 100% and if so we can inline the
+    // alternate if there is one and completely remove the consequent
     //
     //   if ("") { bar; } else { foo; } -> { foo; }
     //   if ("") { bar; } ->
@@ -47,7 +48,7 @@ exports.IfStatement = {
       if (alternate) {
         return alternate;
       } else {
-        return context.remove();
+        return this.remove();
       }
     }
 
@@ -60,15 +61,13 @@ exports.IfStatement = {
       alternate = node.alternate = null;
     }
 
-    // turn alternate blocks into a consequent and flip the test if the
-    // consequent block is empty
+    // if the consequent block is empty turn alternate blocks into a consequent
+    // and flip the test
     //
-    //   if (foo) {} else { bar; }
-    //   if (!foo) { bar; }
+    //   if (foo) {} else { bar; } -> if (!foo) { bar; }
     //
 
-    if (t.blockStatement(consequent) && !consequent.body.length &&
-        t.isBlockStatement(alternate) && alternate.body.length) {
+    if (t.blockStatement(consequent) && !consequent.body.length && t.isBlockStatement(alternate) && alternate.body.length) {
       node.consequent = node.alternate;
       node.alternate  = null;
       node.test       = t.unaryExpression("!", test, true);

lib/6to5/transformation/transformers/minification/remove-console-calls.js

@@ -6,8 +6,12 @@ var isConsole = t.buildMatchMemberExpression("console", true);
 
 exports.optional = true;
 
-exports.CallExpression = function (node, parent, scope, context) {
+exports.CallExpression = function (node, parent) {
   if (isConsole(node.callee)) {
-    context.remove();
+    if (t.isExpressionStatement(parent)) {
+      this.parentPath.remove();
+    } else {
+      this.remove();
+    }
   }
 };

lib/6to5/transformation/transformers/minification/remove-debugger.js

@@ -2,8 +2,8 @@ var t = require("../../../types");
 
 exports.optional = true;
 
-exports.ExpressionStatement = function (node, parent, scope, context) {
+exports.ExpressionStatement = function (node) {
   if (t.isIdentifier(node.expression, { name: "debugger" })) {
-    context.remove();
+    this.remove();
   }
 };

lib/6to5/transformation/transformers/minification/rename-local-variables.js

@@ -2,9 +2,8 @@
 
 exports.optional = true;
 
-exports.Scope = function () {
-  // todo: get all binding identifiers, generate compact names
-  // that wont collide and then call the remap identifier helper
-  // this transformer **has** to be ran last as it will absolutley
-  // destroy the scope tree
+exports.Scopable = function () {
+  //for (var name in scope.bindings) {
+  //  scope.rename(name, scope.generateUidIdentifier("a").name);
+  //}
 };

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

@@ -7,7 +7,7 @@ exports.optional = true;
 
 exports.manipulateOptions = bluebirdCoroutines.manipulateOptions;
 
-exports.Function = function (node, parent, scope, context, file) {
+exports.Function = function (node, parent, scope, file) {
   if (!node.async || node.generator) return;
 
   return remapAsyncToGenerator(node, file.addHelper("async-to-generator"), scope);

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

@@ -10,7 +10,7 @@ exports.manipulateOptions = function (opts) {
 
 exports.optional = true;
 
-exports.Function = function (node, parent, scope, context, file) {
+exports.Function = function (node, parent, scope, file) {
   if (!node.async || node.generator) return;
 
   return remapAsyncToGenerator(

lib/6to5/transformation/transformers/other/react-compat.js

@@ -0,0 +1,29 @@
+"use strict";
+
+var react = require("../../helpers/react");
+var t     = require("../../../types");
+
+exports.manipulateOptions = function (opts) {
+  opts.blacklist.push("react");
+};
+
+exports.optional = true;
+
+require("../../helpers/build-react-transformer")(exports, {
+  pre: function (state) {
+    state.callee = state.tagExpr;
+  },
+
+  post: function (state) {
+    if (react.isCompatTag(state.tagName)) {
+      state.call = t.callExpression(
+        t.memberExpression(
+          t.memberExpression(t.identifier("React"), t.identifier("DOM")),
+          state.tagExpr,
+          t.isLiteral(state.tagExpr)
+        ),
+        state.args
+      );
+    }
+  }
+});

lib/6to5/transformation/transformers/other/react.js

@@ -1,291 +1,20 @@
 "use strict";
 
-// Based upon the excellent jsx-transpiler by Ingvar Stepanyan (RReverser)
-// https://github.com/RReverser/jsx-transpiler
+var react = require("../../helpers/react");
+var t     = require("../../../types");
 
-// jsx
-
-var isString = require("lodash/lang/isString");
-var esutils  = require("esutils");
-var react    = require("../../helpers/react");
-var t        = require("../../../types");
-
-exports.check = function (node) {
-  if (t.isJSX(node)) return true;
-  if (react.isCreateClass(node)) return true;
-  return false;
-};
-
-exports.JSXIdentifier = function (node, parent) {
-  if (node.name === "this" && t.isReferenced(node, parent)) {
-    return t.thisExpression();
-  } else if (esutils.keyword.isIdentifierName(node.name)) {
-    node.type = "Identifier";
-  } else {
-    return t.literal(node.name);
-  }
-};
-
-exports.JSXNamespacedName = function (node, parent, scope, context, file) {
-  throw file.errorWithNode(node, "Namespace tags are not supported. ReactJSX is not XML.");
-};
-
-exports.JSXMemberExpression = {
-  exit: function (node) {
-    node.computed = t.isLiteral(node.property);
-    node.type = "MemberExpression";
-  }
-};
-
-exports.JSXExpressionContainer = function (node) {
-  return node.expression;
-};
-
-exports.JSXAttribute = {
-  exit: function (node) {
-    var value = node.value || t.literal(true);
-    return t.inherits(t.property("init", node.name, value), node);
-  }
-};
-
-var isCompatTag = function (tagName) {
-  return /^[a-z]|\-/.test(tagName);
-};
-
-exports.JSXOpeningElement = {
-  exit: function (node, parent, scope, context, file) {
-    var reactCompat = file.opts.reactCompat;
-    var tagExpr = node.name;
-    var args = [];
-
-    var tagName;
-    if (t.isIdentifier(tagExpr)) {
-      tagName = tagExpr.name;
-    } else if (t.isLiteral(tagExpr)) {
-      tagName = tagExpr.value;
-    }
-
-    if (!reactCompat) {
-      if (tagName && isCompatTag(tagName)) {
-        args.push(t.literal(tagName));
-      } else {
-        args.push(tagExpr);
-      }
-    }
-
-    var attribs = node.attributes;
-    if (attribs.length) {
-      attribs = buildJSXOpeningElementAttributes(attribs, file);
+require("../../helpers/build-react-transformer")(exports, {
+  pre: function (state) {
+    var tagName = state.tagName;
+    var args    = state.args;
+    if (react.isCompatTag(tagName)) {
+      args.push(t.literal(tagName));
     } else {
-      attribs = t.literal(null);
+      args.push(state.tagExpr);
     }
+  },
 
-    args.push(attribs);
-
-    if (reactCompat) {
-      if (tagName && isCompatTag(tagName)) {
-        return t.callExpression(
-          t.memberExpression(
-            t.memberExpression(t.identifier("React"), t.identifier("DOM")),
-            tagExpr,
-            t.isLiteral(tagExpr)
-          ),
-          args
-        );
-      }
-    } else {
-      tagExpr = t.memberExpression(t.identifier("React"), t.identifier("createElement"));
-    }
-
-    return t.callExpression(tagExpr, args);
+  post: function (state) {
+    state.callee = t.memberExpression(t.identifier("React"), t.identifier("createElement"));
   }
-};
-
-/**
- * The logic for this is quite terse. It's because we need to
- * support spread elements. We loop over all attributes,
- * breaking on spreads, we then push a new object containg
- * all prior attributes to an array for later processing.
- */
-
-var buildJSXOpeningElementAttributes = function (attribs, file) {
-  var _props = [];
-  var objs = [];
-
-  var pushProps = function () {
-    if (!_props.length) return;
-
-    objs.push(t.objectExpression(_props));
-    _props = [];
-  };
-
-  while (attribs.length) {
-    var prop = attribs.shift();
-    if (t.isJSXSpreadAttribute(prop)) {
-      pushProps();
-      objs.push(prop.argument);
-    } else {
-      _props.push(prop);
-    }
-  }
-
-  pushProps();
-
-  if (objs.length === 1) {
-    // only one object
-    attribs = objs[0];
-  } else {
-    // looks like we have multiple objects
-    if (!t.isObjectExpression(objs[0])) {
-      objs.unshift(t.objectExpression([]));
-    }
-
-    // spread it
-    attribs = t.callExpression(
-      file.addHelper("extends"),
-      objs
-    );
-  }
-
-  return attribs;
-};
-
-exports.JSXElement = {
-  exit: function (node) {
-    var callExpr = node.openingElement;
-
-    for (var i = 0; i < node.children.length; i++) {
-      var child = node.children[i];
-
-      if (t.isLiteral(child) && typeof child.value === "string") {
-        cleanJSXElementLiteralChild(child, callExpr.arguments);
-        continue;
-      } else if (t.isJSXEmptyExpression(child)) {
-        continue;
-      }
-
-      callExpr.arguments.push(child);
-    }
-
-    callExpr.arguments = flatten(callExpr.arguments);
-
-    if (callExpr.arguments.length >= 3) {
-      callExpr._prettyCall = true;
-    }
-
-    return t.inherits(callExpr, node);
-  }
-};
-
-var isStringLiteral = function (node) {
-  return t.isLiteral(node) && isString(node.value);
-};
-
-var flatten = function (args) {
-  var flattened = [];
-  var last;
-
-  for (var i = 0; i < args.length; i++) {
-    var arg = args[i];
-    if (isStringLiteral(arg) && isStringLiteral(last)) {
-      last.value += arg.value;
-    } else {
-      last = arg;
-      flattened.push(arg);
-    }
-  }
-
-  return flattened;
-};
-
-var cleanJSXElementLiteralChild = function (child, args) {
-  var lines = child.value.split(/\r\n|\n|\r/);
-
-  var lastNonEmptyLine = 0;
-  var i;
-
-  for (i = 0; i < lines.length; i++) {
-    if (lines[i].match(/[^ \t]/)) {
-      lastNonEmptyLine = i;
-    }
-  }
-
-  for (i = 0; i < lines.length; i++) {
-    var line = lines[i];
-
-    var isFirstLine = i === 0;
-    var isLastLine = i === lines.length - 1;
-    var isLastNonEmptyLine = i === lastNonEmptyLine;
-
-    // replace rendered whitespace tabs with spaces
-    var trimmedLine = line.replace(/\t/g, " ");
-
-    // trim whitespace touching a newline
-    if (!isFirstLine) {
-      trimmedLine = trimmedLine.replace(/^[ ]+/, "");
-    }
-
-    // trim whitespace touching an endline
-    if (!isLastLine) {
-      trimmedLine = trimmedLine.replace(/[ ]+$/, "");
-    }
-
-    if (trimmedLine) {
-      if (!isLastNonEmptyLine) {
-        trimmedLine += " ";
-      }
-
-      args.push(t.literal(trimmedLine));
-    }
-  }
-};
-
-// display names
-
-var addDisplayName = function (id, call) {
-  var props = call.arguments[0].properties;
-  var safe = true;
-
-  for (var i = 0; i < props.length; i++) {
-    var prop = props[i];
-    if (t.isIdentifier(prop.key, { name: "displayName" })) {
-      safe = false;
-      break;
-    }
-  }
-
-  if (safe) {
-    props.unshift(t.property("init", t.identifier("displayName"), t.literal(id)));
-  }
-};
-
-exports.ExportDeclaration = function (node, parent, scope, context, file) {
-  if (node.default && react.isCreateClass(node.declaration)) {
-    addDisplayName(file.opts.basename, node.declaration);
-  }
-};
-
-exports.AssignmentExpression =
-exports.Property =
-exports.VariableDeclarator = function (node) {
-  var left, right;
-
-  if (t.isAssignmentExpression(node)) {
-    left = node.left;
-    right = node.right;
-  } else if (t.isProperty(node)) {
-    left = node.key;
-    right = node.value;
-  } else if (t.isVariableDeclarator(node)) {
-    left = node.id;
-    right = node.init;
-  }
-
-  if (t.isMemberExpression(left)) {
-    left = left.property;
-  }
-
-  if (t.isIdentifier(left) && react.isCreateClass(right)) {
-    addDisplayName(left.name, right);
-  }
-};
+});

lib/6to5/transformation/transformers/other/regenerator.js

@@ -7,10 +7,9 @@ exports.check = function (node) {
   return t.isFunction(node) && (node.async || node.generator);
 };
 
-exports.ast = {
-  before: function (ast, file) {
-    regenerator.transform(ast, {
-      includeRuntime: file.opts.includeRegenerator && "if used"
-    });
+exports.Program = {
+  enter: function (ast) {
+    regenerator.transform(ast);
+    this.stop();
   }
 };

lib/6to5/transformation/transformers/other/self-contained.js

@@ -4,7 +4,7 @@ var util     = require("../../../util");
 var core     = require("core-js/library");
 var t        = require("../../../types");
 var has      = require("lodash/object/has");
-var contains = require("lodash/collection/contains");
+var includes = require("lodash/collection/includes");
 
 var coreHas = function (node) {
   return node.name !== "_" && has(core, node.name);
@@ -20,7 +20,7 @@ var ALIASABLE_CONSTRUCTORS = [
 ];
 
 var astVisitor = {
-  enter: function (node, parent, scope, context, file) {
+  enter: function (node, parent, scope, file) {
     var prop;
 
     if (t.isMemberExpression(node) && t.isReferenced(node, parent)) {
@@ -30,30 +30,44 @@ var astVisitor = {
 
       if (!t.isReferenced(obj, node)) return;
 
-      if (!node.computed && coreHas(obj) && has(core[obj.name], prop.name)) {
-        context.skip();
+      if (!node.computed && coreHas(obj) && has(core[obj.name], prop.name) && !scope.getBindingIdentifier(obj.name)) {
+        this.skip();
         return t.prependToMemberExpression(node, file.get("coreIdentifier"));
       }
-    } else if (t.isReferencedIdentifier(node, parent) && !t.isMemberExpression(parent) && contains(ALIASABLE_CONSTRUCTORS, node.name) && !scope.getBinding(node.name)) {
+    } else if (t.isReferencedIdentifier(node, parent) && !t.isMemberExpression(parent) && includes(ALIASABLE_CONSTRUCTORS, node.name) && !scope.getBindingIdentifier(node.name)) {
       // Symbol() -> _core.Symbol(); new Promise -> new _core.Promise
       return t.memberExpression(file.get("coreIdentifier"), 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;
+      if (node.arguments.length) return false;
+
+      if (!t.isMemberExpression(callee)) return false;
+      if (!callee.computed) return false;
 
       prop = callee.property;
-      if (!t.isIdentifier(prop.object, { name: "Symbol" })) return;
-      if (!t.isIdentifier(prop.property, { name: "iterator" })) return;
+      if (!t.isIdentifier(prop.object, { name: "Symbol" })) return false;
+      if (!t.isIdentifier(prop.property, { name: "iterator" })) return false;
 
       return util.template("corejs-iterator", {
         CORE_ID: file.get("coreIdentifier"),
         VALUE:   callee.object
       });
+    } else if (t.isBinaryExpression(node)) {
+      // Symbol.iterator in arr -> core.$for.isIterable(arr)
+
+      if (node.operator !== "in") return;
+
+      var left = node.left;
+      if (!t.isMemberExpression(left)) return;
+      if (!t.isIdentifier(left.object, { name: "Symbol" })) return;
+      if (!t.isIdentifier(left.property, { name: "iterator" })) return;
+
+      return util.template("corejs-is-iterator", {
+        CORE_ID: file.get("coreIdentifier"),
+        VALUE:   node.right
+      });
     }
   }
 };
@@ -64,28 +78,26 @@ exports.manipulateOptions = function (opts) {
   if (opts.whitelist.length) opts.whitelist.push("es6.modules");
 };
 
-exports.ast = {
-  enter: function (ast, file) {
-    file.setDynamic("runtimeIdentifier", function () {
-      return file.addImport("6to5-runtime/helpers", "to5Helpers");
-    });
-
-    file.setDynamic("coreIdentifier", function () {
-      return file.addImport("6to5-runtime/core-js", "core");
-    });
-
-    file.setDynamic("regeneratorIdentifier", function () {
-      return file.addImport("6to5-runtime/regenerator", "regeneratorRuntime");
-    });
-  },
-
-  after: function (ast, file) {
-    file.scope.traverse(ast, astVisitor, file);
-  }
+exports.post = function (file) {
+  file.scope.traverse(file.ast, astVisitor, file);
 };
 
-exports.Identifier = function (node, parent, scope, context, file) {
-  if (node.name === "regeneratorRuntime" && t.isReferenced(node, parent)) {
+exports.pre = function (file) {
+  file.setDynamic("runtimeIdentifier", function () {
+    return file.addImport("6to5-runtime/helpers", "to5Helpers");
+  });
+
+  file.setDynamic("coreIdentifier", function () {
+    return file.addImport("6to5-runtime/core-js", "core");
+  });
+
+  file.setDynamic("regeneratorIdentifier", function () {
+    return file.addImport("6to5-runtime/regenerator", "regeneratorRuntime");
+  });
+};
+
+exports.Identifier = function (node, parent, scope, file) {
+  if (t.isReferencedIdentifier(node, parent, { name: "regeneratorRuntime" })) {
     return file.get("regeneratorIdentifier");
   }
 };

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

@@ -3,17 +3,16 @@
 var useStrict = require("../../helpers/use-strict");
 var t         = require("../../../types");
 
-exports.ast = {
-  exit: function (ast) {
-    if (!useStrict.has(ast.program)) {
-      ast.program.body.unshift(t.expressionStatement(t.literal("use strict")));
-    }
+exports.post = function (file) {
+  var program = file.ast.program;
+  if (!useStrict.has(program)) {
+    program.body.unshift(t.expressionStatement(t.literal("use strict")));
   }
 };
 
 exports.FunctionDeclaration =
-exports.FunctionExpression = function (node, parent, scope, context) {
-  context.skip();
+exports.FunctionExpression = function () {
+  this.skip();
 };
 
 exports.ThisExpression = function () {

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

@@ -1,7 +1,8 @@
 "use strict";
 
-var build = require("../../helpers/build-conditional-assignment-operator-transformer");
-var t     = require("../../../types");
+var messages = require("../../../messages");
+var build    = require("../../helpers/build-conditional-assignment-operator-transformer");
+var t        = require("../../../types");
 
 exports.playground = true;
 
@@ -11,7 +12,7 @@ build(exports, {
     if (is) {
       var left = node.left;
       if (!t.isMemberExpression(left) && !t.isIdentifier(left)) {
-        throw file.errorWithNode(left, "Expected type MemeberExpression or Identifier");
+        throw file.errorWithNode(left, messages.get("expectedMemberExpressionOrIdentifier"));
       }
       return true;
     }

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

@@ -26,7 +26,7 @@ exports.BindMemberExpression = function (node, parent, scope) {
   }
 };
 
-exports.BindFunctionExpression = function (node, parent, scope, context, file) {
+exports.BindFunctionExpression = function (node, parent, scope) {
   var buildCall = function (args) {
     var param = scope.generateUidIdentifier("val");
     return t.functionExpression(null, [param], t.blockStatement([
@@ -34,7 +34,7 @@ exports.BindFunctionExpression = function (node, parent, scope, context, file) {
     ]));
   };
 
-  var temp = scope.generateTemp(file, "args");
+  var temp = scope.generateTemp("args");
 
   return t.sequenceExpression([
     t.assignmentExpression("=", temp, t.arrayExpression(node.arguments)),