v3.6.5

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

.6to5rc

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

.travis.yml

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

CHANGELOG.md

@@ -11,6 +11,55 @@
 
 _Note: Gaps between patch versions are faulty/broken releases._
 
+## 3.6.5
+
+ * **Internal**
+  * Upgrade `core-js`.
+ * **Bug Fix**
+  * Fix block scoping leaking variables in IIFE mode.
+  * Fix tail call transformer exploding on return statements as the consequent of an if statement.
+ * **New Feature**
+  * Add `validation.react` transformer.
+
+## 3.6.4
+
+ * **New Feature**
+  * Add support for flow type casts and module types.
+
+## 3.6.3
+
+ * **Internal**
+  * Upgrade `acorn-6to5`.
+  * Use `default` property on `6to5-runtime`.
+
+## 3.6.2
+
+ * **Polish**
+  * Use better iterator detection in `slicedToArray` helper and add support for it to the `selfContained` transformer.
+
+## 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.

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
@@ -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
 

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

@@ -16,7 +16,9 @@ module.exports = function (commander, filenames, opts) {
 
     var dest = path.join(commander.outDir, relative);
 
-    var data = util.compile(src, { sourceMapName: dest });
+    var data = util.compile(src, {
+      sourceFileName: path.relative(dest + "/..", src)
+    });
 
     if (commander.sourceMaps) {
       var mapLoc = dest + ".map";
@@ -37,8 +39,13 @@ 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

@@ -26,6 +26,7 @@ commander.option("-c, --remove-comments", "Remove comments from the compiled cod
 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);
+commander.option("-a, --auxilary-comment [comment]", "Comment text to prepend to all auxilary code");
 
 commander.on("--help", function () {
   var outKeys = function (title, obj) {
@@ -99,6 +100,7 @@ if (errors.length) {
 
 exports.opts = {
   keepModuleIdExtensions: commander.keepModuleIdExtensions,
+  auxilaryComment:        commander.auxilaryComment,
   sourceMapName:          commander.outFile,
   experimental:           commander.experimental,
   reactCompat:            commander.reactCompat,

bin/6to5/util.js

@@ -12,12 +12,16 @@ exports.readdirFilter = function (filename) {
   });
 };
 
+exports.readdir = readdir;
+
+exports.canCompile = util.canCompile;
+
 exports.addSourceMappingUrl = function (code, loc) {
   return code + "\n//# sourceMappingURL=" + path.basename(loc);
 };
 
 exports.transform = function (filename, code, opts) {
-  opts = _.extend(opts || {}, index.opts);
+  opts = _.defaults(opts || {}, index.opts);
   opts.filename = filename;
 
   var result;

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

@@ -3,7 +3,7 @@
 module.exports = Buffer;
 
 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");
 
@@ -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/flow.js

@@ -30,6 +30,7 @@ exports.ObjectTypeIndexer =
 exports.ObjectTypeProperty =
 exports.QualifiedTypeIdentifier =
 exports.UnionTypeAnnotation =
+exports.TypeCastExpression =
 exports.VoidTypeAnnotation = function () {
   // todo: implement these once we have a `--keep-types` option
 };

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/whitespace.js

@@ -82,7 +82,7 @@ Whitespace.prototype.getNewlinesAfter = function (node) {
     }
   }
 
-  if (endToken.type.type === "eof") {
+  if (endToken && endToken.type.type === "eof") {
     return 1;
   } else {
     var lines = this.getNewlinesBetween(startToken, endToken);
@@ -96,6 +96,8 @@ Whitespace.prototype.getNewlinesAfter = function (node) {
 };
 
 Whitespace.prototype.getNewlinesBetween = function (startToken, endToken) {
+  if (!endToken || !endToken.loc) return 0;
+
   var start = startToken ? startToken.loc.end.line : 1;
   var end   = endToken.loc.start.line;
   var lines = 0;

lib/6to5/messages.js

@@ -0,0 +1,49 @@
+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",
+  didYouMean: "Did you mean $1?"
+};
+
+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

@@ -3,8 +3,6 @@
 var extend = require("lodash/object/extend");
 var t      = require("./types");
 
-require("./types/node");
-
 // estraverse
 
 var estraverse = require("estraverse");

lib/6to5/transformation/file.js

@@ -8,7 +8,7 @@ var isFunction = require("lodash/lang/isFunction");
 var transform  = require("./index");
 var generate   = require("../generation");
 var defaults   = require("lodash/object/defaults");
-var contains   = require("lodash/collection/contains");
+var includes   = require("lodash/collection/includes");
 var clone      = require("../helpers/clone");
 var parse      = require("../helpers/parse");
 var Scope      = require("../traversal/scope");
@@ -18,9 +18,10 @@ var each       = require("lodash/collection/each");
 var t          = require("../types");
 
 function File(opts) {
-  this.dynamicImportIds = {};
-  this.dynamicImported  = [];
-  this.dynamicImports   = [];
+  this.dynamicImportedNoDefault = [];
+  this.dynamicImportIds         = {};
+  this.dynamicImported          = [];
+  this.dynamicImports           = [];
 
   this.dynamicData      = {};
   this.data             = {};
@@ -41,6 +42,7 @@ File.helpers = [
   "tagged-template-literal-loose",
   "interop-require",
   "to-array",
+  "to-consumable-array",
   "sliced-to-array",
   "object-without-properties",
   "has-own",
@@ -84,6 +86,7 @@ File.validOptions = [
   "experimental",
   "resolveModuleSource",
   "runtime",
+  "auxilaryComment",
 
   // these are used by plugins
   "ignore",
@@ -104,6 +107,7 @@ File.prototype.normalizeOptions = function (opts) {
   defaults(opts, {
     keepModuleIdExtensions: false,
     resolveModuleSource:    null,
+    auxilaryComment:        "",
     experimental:           false,
     reactCompat:            false,
     playground:             false,
@@ -123,7 +127,10 @@ 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));
 
@@ -132,7 +139,7 @@ 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);
   }
 
@@ -172,11 +179,20 @@ File.prototype.normalizeOptions = function (opts) {
                   "`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 () {
@@ -213,22 +229,6 @@ File.prototype.debug = function (msg) {
   util.debug(parts);
 };
 
-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.getModuleFormatter = function (type) {
   var ModuleFormatter = isFunction(type) ? type : transform.moduleFormatters[type];
 
@@ -276,17 +276,19 @@ File.prototype.get = function (key) {
   }
 };
 
-File.prototype.addImport = function (source, name) {
+File.prototype.addImport = function (source, name, noDefault) {
   name = name || source;
   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));
     declar._blockHoist = 3;
+
     this.dynamicImported.push(declar);
+    if (noDefault) this.dynamicImportedNoDefault.push(declar);
 
     this.moduleFormatter.importSpecifier(specifiers[0], declar, this.dynamicImports);
   }
@@ -298,8 +300,20 @@ File.prototype.isConsequenceExpressionStatement = function (node) {
   return t.isExpressionStatement(node) && this.lastStatements.indexOf(node) >= 0;
 };
 
+File.prototype.attachAuxilaryComment = function (node) {
+  var comment = this.opts.auxilaryComment;
+  if (comment) {
+    node.leadingComments = node.leadingComments || [];
+    node.leadingComments.push({
+      type: "Line",
+      value: " " + comment
+    });
+  }
+  return node;
+};
+
 File.prototype.addHelper = function (name) {
-  if (!contains(File.helpers, name)) {
+  if (!includes(File.helpers, name)) {
     throw new ReferenceError("Unknown helper " + name);
   }
 
@@ -315,7 +329,7 @@ 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,
@@ -325,6 +339,10 @@ File.prototype.addHelper = function (name) {
   }
 };
 
+File.prototype.logDeopt = function () {
+  // todo, (node, msg)
+};
+
 File.prototype.errorWithNode = function (node, msg, Error) {
   Error = Error || SyntaxError;
 
@@ -442,30 +460,3 @@ File.prototype.generate = function () {
 
   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-react-transformer.js

@@ -6,6 +6,7 @@
 // jsx
 
 var isString = require("lodash/lang/isString");
+var messages = require("../../messages");
 var esutils  = require("esutils");
 var react    = require("./react");
 var t        = require("../../types");
@@ -28,7 +29,7 @@ module.exports = function (exports, opts) {
   };
 
   exports.JSXNamespacedName = function (node, parent, scope, file) {
-    throw file.errorWithNode(node, "Namespace tags are not supported. ReactJSX is not XML.");
+    throw file.errorWithNode(node, messages.get("JSXNamespacedTags"));
   };
 
   exports.JSXMemberExpression = {
@@ -45,6 +46,11 @@ module.exports = function (exports, opts) {
   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);
     }
   };

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

@@ -13,7 +13,7 @@ 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;
@@ -31,7 +31,7 @@ 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);

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

@@ -2,7 +2,8 @@
 
 module.exports = ReplaceSupers;
 
-var t = require("../../types");
+var messages = require("../../messages");
+var t        = require("../../types");
 
 /**
  * Description
@@ -142,7 +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())
     ]));
@@ -232,7 +233,7 @@ ReplaceSupers.prototype.specHandle = function (getThisReference, node, parent) {
   var thisReference;
 
   if (isIllegalBareSuper(node, parent)) {
-    throw this.file.errorWithNode(node, "Illegal use of bare super");
+    throw this.file.errorWithNode(node, messages.get("classesIllegalBareSuper"));
   }
 
   if (t.isCallExpression(node)) {
@@ -248,7 +249,7 @@ ReplaceSupers.prototype.specHandle = function (getThisReference, node, parent) {
       //  - https://twitter.com/wycats/status/544553184396836864
       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) && isSuper(callee.object, callee)) {
       // super.test(); -> _get(Object.getPrototypeOf(ClassName.prototype), "test", this).call(this);

lib/6to5/transformation/index.js

@@ -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;
 
@@ -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);
 

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

@@ -4,10 +4,10 @@ module.exports = AMDFormatter;
 
 var DefaultFormatter = require("./_default");
 var CommonFormatter  = require("./common");
+var includes         = require("lodash/collection/includes");
+var values           = require("lodash/object/values");
 var util             = require("../../util");
 var t                = require("../../types");
-var contains         = require("lodash/collection/contains");
-var values           = require("lodash/object/values");
 
 function AMDFormatter() {
   CommonFormatter.apply(this, arguments);
@@ -70,7 +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) {
@@ -81,12 +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.dynamicImportedNoDefault, 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.noInteropRequireImport) {
+  } else if (!includes(this.file.dynamicImported, node) && t.isSpecifierDefault(specifier) && !this.noInteropRequireImport) {
     // import foo from "foo";
     ref = t.callExpression(this.file.addHelper("interop-require"), [ref]);
   } else {

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 () {
+  var file  = this.file;
+  var scope = file.scope;
+
+  scope.rename("module");
+
   if (!this.noInteropRequireImport && this.hasNonDefaultExports) {
-    this.file.ast.program.body.push(util.template("exports-module-declaration", true));
+    file.ast.program.body.push(util.template("exports-module-declaration", true));
   }
 };
 
@@ -26,8 +31,8 @@ CommonJSFormatter.prototype.importSpecifier = function (specifier, node, nodes)
 
   // import foo from "foo";
   if (t.isSpecifierDefault(specifier)) {
-    if (!contains(this.file.dynamicImported, node)) {
-      if (this.noInteropRequireImport) {
+    if (!includes(this.file.dynamicImportedNoDefault, node)) {
+      if (this.noInteropRequireImport || includes(this.file.dynamicImported, node)) {
         ref = t.memberExpression(ref, t.identifier("default"));
       } else {
         ref = t.callExpression(this.file.addHelper("interop-require"), [ref]);
@@ -88,7 +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/system.js

@@ -12,7 +12,7 @@ var each             = require("lodash/collection/each");
 var map              = require("lodash/collection/map");
 
 function SystemFormatter(file) {
-  this.exportIdentifier = file.generateUidIdentifier("export");
+  this.exportIdentifier = file.scope.generateUidIdentifier("export");
   this.noInteropRequireExport = true;
   this.noInteropRequireImport = true;
 
@@ -29,7 +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", [

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/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/self-contained-helpers-head.js

@@ -0,0 +1,2 @@
+var helpers = exports.default = {};
+exports.__esModule = true;

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

@@ -1,13 +1,3 @@
 {
-  var ARGUMENTS_ID = arguments,
-      THIS_ID = this,
-      SHOULD_CONTINUE_ID,
-      RESULT_ID;
-
-  do {
-    SHOULD_CONTINUE_ID = false;
-    RESULT_ID = FUNCTION.apply(THIS_ID, ARGUMENTS_ID);
-  } while(SHOULD_CONTINUE_ID);
-
-  return RESULT_ID;
+  FUNCTION_ID:while (true) BLOCK
 }

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

@@ -1,6 +1,6 @@
 module.exports = TransformerPass;
 
-var contains = require("lodash/collection/contains");
+var includes = require("lodash/collection/includes");
 
 /**
  * This class is responsible for traversing over the provided `File`s
@@ -25,14 +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) return contains(whitelist, key);
+  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;

lib/6to5/transformation/transformer.js

@@ -55,6 +55,8 @@ Transformer.prototype.normalize = function (transformer) {
       return;
     }
 
+    if (type === "enter" || type === "exit") return;
+
     if (isFunction(fns)) fns = { enter: fns };
 
     if (!isObject(fns)) return;

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

@@ -1,116 +0,0 @@
-"use strict";
-
-var t = require("../../../types");
-
-function transformExpression(node, scope, state) {
-  if (!node) return;
-
-  return (function subTransform(node) {
-    switch (node.type) {
-      case "ConditionalExpression":
-        // any value of ternary operator can be final one
-        subTransform(node.consequent);
-        subTransform(node.alternate);
-        break;
-
-      case "LogicalExpression":
-        // only right expression can be final and so optimized
-        subTransform(node.right);
-        break;
-
-      case "SequenceExpression":
-        // only last element of sequence can be optimized
-        var seq = node.expressions;
-        subTransform(seq[seq.length - 1]);
-        break;
-
-      case "CallExpression":
-        var callee = node.callee, thisBinding;
-        var args = [callee];
-
-        // bind `this` to object in member expressions
-        if (t.isMemberExpression(callee)) {
-          var object = state.wrapSideEffect(callee.object);
-          callee.object = object.expr;
-          thisBinding = object.ref;
-        }
-
-        if (node.arguments.length > 0 || thisBinding) {
-          args.push(t.arrayExpression(node.arguments));
-        }
-
-        if (thisBinding) {
-          args.push(thisBinding);
-        }
-
-        node.callee = state.getHelperRef();
-        node.arguments = args;
-        break;
-    }
-  })(node);
-}
-
-var functionChildrenVisitor = {
-  enter: function (node, parent, scope, state) {
-    if (t.isReturnStatement(node)) {
-      // prevent entrance by current visitor
-      this.skip();
-      // transform return argument into statement if
-      // it contains tail recursion
-      transformExpression(node.argument, scope, state);
-    } else if (t.isFunction(node)) {
-      // inner function's bodies are irrelevant
-      this.skip();
-    } else if (t.isTryStatement(parent)) {
-      if (node === parent.block) {
-        // `try`-blocks can't be optimized
-        this.skip();
-      } else if (parent.finalizer && node !== parent.finalizer) {
-        // `catch` clause followed by `finally` can't be optimized
-        this.skip();
-      }
-    }
-  }
-};
-
-var functionVisitor = {
-  enter: function (node, parent, scope, state) {
-    // traverse all child nodes of this function and find `arguments` and `this`
-    scope.traverse(node, functionChildrenVisitor, state);
-
-    return this.skip();
-  }
-};
-
-exports.FunctionDeclaration =
-exports.FunctionExpression = function (node, parent, scope, file) {
-  var tempId, helperRef;
-
-  var state = {
-    ownerId: node.id,
-
-    getHelperRef: function () {
-      return helperRef = helperRef || file.addHelper("tail-call");
-    },
-
-    wrapSideEffect: function (node) {
-      if (t.isIdentifier(node) || t.isLiteral(node)) {
-        return {expr: node, ref: node};
-      }
-      tempId = tempId || scope.generateUidIdentifier("temp");
-      return {
-        expr: t.assignmentExpression("=", tempId, node),
-        ref: tempId
-      };
-    }
-  };
-
-  // traverse the function and look for tail recursion
-  scope.traverse(node, functionVisitor, state);
-
-  if (tempId) {
-    t.ensureBlock(node).body.unshift(t.variableDeclaration("var", [
-      t.variableDeclarator(tempId)
-    ]));
-  }
-};

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

@@ -10,7 +10,7 @@ var visitor = {
     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 assert = t.callExpression(
       state.file.addHelper("temporal-assert-defined"),

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

@@ -124,7 +124,7 @@ BlockScoping.prototype.run = function () {
   if (!this.hasLetReferences) return;
 
   if (needsClosure) {
-    this.needsClosure();
+    this.wrapClosure();
   } else {
     this.remap();
   }
@@ -136,7 +136,7 @@ function replace(node, parent, scope, remaps) {
   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 {
@@ -175,7 +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;
 
@@ -205,9 +205,28 @@ BlockScoping.prototype.remap = function () {
  * Description
  */
 
-BlockScoping.prototype.needsClosure = function () {
+BlockScoping.prototype.wrapClosure = function () {
   var block = this.block;
 
+  var outsideRefs = this.outsideLetReferences;
+
+  // remap loop heads with colliding variables
+  if (this.loopParent) {
+    for (var name in outsideRefs) {
+      var id = outsideRefs[name];
+
+      if (this.scope.hasGlobal(id.name)) {
+        delete outsideRefs[id.name];
+        delete this.letReferences[id.name];
+
+        this.scope.rename(id.name);
+
+        this.letReferences[id.name] = id;
+        outsideRefs[id.name] = id;
+      }
+    }
+  }
+
   // if we're inside of a for loop then we search to see if there are any
   // `break`s, `continue`s, `return`s etc
   this.has = this.checkLoop();
@@ -216,7 +235,7 @@ BlockScoping.prototype.needsClosure = function () {
   this.hoistVarDeclarations();
 
   // turn outsideLetReferences into an array
-  var params = values(this.outsideLetReferences);
+  var params = values(outsideRefs);
 
   // build the closure that we're going to wrap the block with
   var fn = t.functionExpression(null, params, t.blockStatement(block.body));

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

@@ -3,13 +3,14 @@
 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, file) {
-  return new Class(node, file, scope, true).run();
+  return new ClassTransformer(node, file, scope, true).run();
 };
 
 exports.ClassExpression = function (node, parent, scope, file) {
@@ -25,7 +26,7 @@ exports.ClassExpression = function (node, parent, scope, 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, 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;
@@ -167,6 +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);
     }
   }
 
@@ -204,12 +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;
@@ -245,15 +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

@@ -1,6 +1,7 @@
 "use strict";
 
-var t = require("../../../types");
+var messages = require("../../../messages");
+var t        = require("../../../types");
 
 exports.check = function (node) {
   return t.isVariableDeclaration(node, { kind: "const" });
@@ -11,33 +12,35 @@ var visitor = {
     if (t.isAssignmentExpression(node) || t.isUpdateExpression(node)) {
       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;
 
         // check if there's been a local binding that shadows this constant
-        if (!scope.bindingEquals(key, constant)) continue;
+        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)) {
+    } else if (t.isScope(node, parent)) {
       this.skip();
     }
   }
 };
 
-exports.Scope = function (node, parent, scope, 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;
@@ -105,7 +106,7 @@ 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])
@@ -137,18 +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];
 
@@ -158,7 +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)]);
@@ -173,7 +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));
@@ -217,7 +220,7 @@ exports.ForOfStatement = function (node, parent, scope, file) {
 
   var nodes = [];
 
-  var destructuring = new Destructuring({
+  var destructuring = new DestructuringTransformer({
     kind: left.kind,
     file: file,
     scope: scope,
@@ -235,15 +238,15 @@ exports.ForOfStatement = function (node, parent, scope, 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,
@@ -255,7 +258,7 @@ exports.Function = function (node, parent, scope, file) {
     return parentId;
   });
 
-  if (!hasDestructuring) return;
+  if (!hasDestructuringTransformer) return;
 
   t.ensureBlock(node);
 
@@ -272,7 +275,7 @@ exports.CatchClause = function (node, parent, scope, file) {
 
   var nodes = [];
 
-  var destructuring = new Destructuring({
+  var destructuring = new DestructuringTransformer({
     kind: "let",
     file: file,
     scope: scope,
@@ -298,7 +301,7 @@ exports.ExpressionStatement = function (node, parent, scope, file) {
     t.variableDeclarator(ref, expr.right)
   ]));
 
-  var destructuring = new Destructuring({
+  var destructuring = new DestructuringTransformer({
     operator: expr.operator,
     file: file,
     scope: scope,
@@ -321,7 +324,7 @@ exports.AssignmentExpression = function (node, parent, scope, 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,
@@ -356,7 +359,7 @@ exports.VariableDeclaration = function (node, parent, scope, file) {
     var patternId = declar.init;
     var pattern   = declar.id;
 
-    var destructuring = new Destructuring({
+    var destructuring = new DestructuringTransformer({
       nodes: nodes,
       scope: scope,
       kind:  node.kind,
@@ -387,7 +390,7 @@ exports.VariableDeclaration = function (node, parent, scope, 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

@@ -1,7 +1,8 @@
 "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;
 
@@ -17,7 +18,7 @@ exports.ForOfStatement = function (node, parent, scope, 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
@@ -50,7 +51,7 @@ var loose = function (node, parent, scope, 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", {
@@ -89,7 +90,7 @@ var spec = function (node, parent, scope, 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/parameters.default.js

@@ -18,7 +18,7 @@ var iifeVisitor = {
   enter: function (node, parent, scope, state) {
     if (!t.isReferencedIdentifier(node, parent)) return;
     if (!state.scope.hasOwnBinding(node.name)) return;
-    if (state.scope.bindingEquals(node.name, node)) return;
+    if (state.scope.bindingIdentifierEquals(node.name, node)) return;
 
     state.iife = true;
     this.stop();
@@ -55,7 +55,9 @@ exports.Function = function (node, parent, scope, file) {
     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);
@@ -71,10 +73,12 @@ exports.Function = function (node, parent, scope, file) {
     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);

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/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, 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, file) {
   return t.callExpression(t.memberExpression(first, t.identifier("concat")), nodes);
 };
 
-exports.CallExpression = function (node, parent, scope, file) {
+exports.CallExpression = function (node, parent, scope) {
   var args = node.arguments;
   if (!hasSpread(args)) return;
 
@@ -71,7 +71,7 @@ exports.CallExpression = function (node, parent, scope, 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();
@@ -103,9 +103,9 @@ 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

@@ -1,207 +1,367 @@
 "use strict";
 
-var util = require("../../../util");
-var t    = require("../../../types");
+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 transformExpression(node, scope, state) {
-  if (!node) return;
+function TailCallTransformer(node, scope, file) {
+  this.hasTailRecursion = false;
+  this.needsArguments   = false;
+  this.setsArguments    = false;
+  this.needsThis        = false;
+  this.ownerId          = node.id;
+  this.vars             = [];
 
-  return (function subTransform(node) {
-    switch (node.type) {
-      case "ConditionalExpression":
-        var callConsequent = subTransform(node.consequent);
-        var callAlternate = 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;
-
-      case "LogicalExpression":
-        // only call in right-value of can be optimized
-        var callRight = subTransform(node.right);
-        if (!callRight) {
-          return;
-        }
-
-        // cache left value as it might have side-effects
-        var leftId = state.getLeftId();
-        var testExpr = t.assignmentExpression(
-          "=",
-          leftId,
-          node.left
-        );
-        if (node.operator === "&&") {
-          testExpr = t.unaryExpression("!", testExpr);
-        }
-        return [t.ifStatement(testExpr, returnBlock(leftId))].concat(callRight);
-
-      case "SequenceExpression":
-        var seq = node.expressions;
-
-        // only last element can be optimized
-        var lastCall = 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);
-
-      case "CallExpression":
-        var callee = node.callee, prop, thisBinding, args;
-
-        if (t.isMemberExpression(callee, { computed: false }) &&
-            t.isIdentifier(prop = callee.property)) {
-          switch (prop.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) || !scope.bindingEquals(callee.name, state.ownerId)) {
-          return;
-        }
-
-        state.hasTailRecursion = true;
-
-        return [
-          t.expressionStatement(t.assignmentExpression(
-            "=",
-            state.getArgumentsId(),
-            args || t.arrayExpression(node.arguments)
-          )),
-
-          t.expressionStatement(t.assignmentExpression(
-            "=",
-            state.getThisId(),
-            thisBinding || t.identifier("undefined")
-          )),
-
-          t.returnStatement(t.assignmentExpression(
-            "=",
-            state.getShouldContinueId(),
-            t.literal(true)
-          ))
-        ];
-    }
-  })(node);
+  this.scope = scope;
+  this.file  = file;
+  this.node  = node;
 }
 
-var functionChildrenVisitor = {
+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)) {
-      // prevent entrance by current visitor
+    if (t.isIfStatement(node)) {
+      if (t.isReturnStatement(node.alternate)) {
+        t.ensureBlock(node, "alternate");
+      }
+
+      if (t.isReturnStatement(node.consequent)) {
+        t.ensureBlock(node, "consequent");
+      }
+    } else if (t.isReturnStatement(node)) {
       this.skip();
-      // transform return argument into statement if
-      // it contains tail recursion
-      return transformExpression(node.argument, scope, state);
-    } else if (t.isFunction(node)) {
-      return this.skip();
+      return state.subTransform(node.argument);
     } else if (t.isTryStatement(parent)) {
       if (node === parent.block) {
-        return this.skip();
-      } else if (node === parent.finalizer) {
-        return;
-      } else {
-        if (parent.finalizer) {
-          this.skip();
-        }
-        return;
+        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;
       }
     }
   }
 };
 
-var functionVisitor = {
+// optimizes recursion by removing `this` and `arguments` if they aren't used
+var thirdPass = {
   enter: function (node, parent, scope, state) {
-    // traverse all child nodes of this function and find `arguments` and `this`
-    scope.traverse(node, functionChildrenVisitor, state);
+    if (!t.isExpressionStatement(node)) return;
 
-    return this.skip();
-  }
-};
+    var expr = node.expression;
+    if (!t.isAssignmentExpression(expr)) return;
 
-exports.FunctionDeclaration =
-exports.FunctionExpression = function (node, parent, scope) {
-  // only tail recursion can be optimized as for now,
-  // so we can skip anonymous functions entirely
-  var ownerId = node.id;
-  if (!ownerId) return;
-
-  var argumentsId, thisId, shouldContinueId, leftId;
-
-  var state = {
-    hasTailRecursion: false,
-    ownerId: ownerId,
-
-    getArgumentsId: function () {
-      return argumentsId = argumentsId || scope.generateUidIdentifier("arguments");
-    },
-
-    getThisId: function () {
-      return thisId = thisId || scope.generateUidIdentifier("this");
-    },
-
-    getShouldContinueId: function () {
-      return shouldContinueId = shouldContinueId || scope.generateUidIdentifier("shouldContinue");
-    },
-
-    getLeftId: function () {
-      return leftId = leftId || scope.generateUidIdentifier("left");
+    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);
+      });
     }
-  };
-
-  // traverse the function and look for tail recursion
-  scope.traverse(node, functionVisitor, state);
-
-  if (!state.hasTailRecursion) return;
-
-  var block = t.ensureBlock(node);
-
-  if (leftId) {
-    block.body.unshift(t.variableDeclaration("var", [
-      t.variableDeclarator(leftId)
-    ]));
   }
-
-  var resultId = scope.generateUidIdentifier("result");
-  state.getShouldContinueId();
-
-  node.body = util.template("tail-call-body", {
-    SHOULD_CONTINUE_ID: shouldContinueId,
-    ARGUMENTS_ID:       argumentsId,
-    RESULT_ID:          resultId,
-    FUNCTION:           t.functionExpression(null, node.params, block),
-    THIS_ID:            thisId,
-  });
+};
+
+exports.Function = function (node, parent, scope, file) {
+  var tailCall = new TailCallTransformer(node, scope, file);
+  tailCall.run();
 };

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

@@ -4,6 +4,7 @@ module.exports = {
   "validation.undeclaredVariableCheck":    require("./validation/undeclared-variable-check"),
   "validation.noForInOfAssignment":        require("./validation/no-for-in-of-assignment"),
   "validation.setters":                    require("./validation/setters"),
+  "validation.react":                      require("./validation/react"),
   "spec.blockScopedFunctions":             require("./spec/block-scoped-functions"),
 
   "playground.malletOperator":             require("./playground/mallet-operator"),
@@ -12,6 +13,7 @@ module.exports = {
   "playground.objectGetterMemoization":    require("./playground/object-getter-memoization"),
 
   reactCompat:                             require("./other/react-compat"),
+  flow:                                    require("./other/flow"),
   react:                                   require("./other/react"),
 
   _modules:                                require("./internal/modules"),
@@ -31,7 +33,6 @@ module.exports = {
   "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"),
@@ -47,11 +48,15 @@ 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"),
 
-  "es6.parameters.rest":                   require("./es6/parameters.rest"),
-
   // needs to be before `es6.blockScoping` as let variables may be produced
   "es6.destructuring":                     require("./es6/destructuring"),
 
@@ -62,6 +67,8 @@ module.exports = {
   // needs to be after `es6.blockScoping` due to needing `letReferences` set on blocks
   "es6.blockScopingTDZ":                   require("./es6/block-scoping-tdz"),
 
+  // 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"),
@@ -81,11 +88,12 @@ module.exports = {
   _declarations:                           require("./internal/declarations"),
 
   _aliasFunctions:                         require("./internal/alias-functions"),
-  _moduleFormatter:                        require("./internal/module-formatter"),
 
   "spec.typeofSymbol":                     require("./spec/typeof-symbol"),
   "spec.undefinedToVoid":                  require("./spec/undefined-to-void"),
 
+  _moduleFormatter:                        require("./internal/module-formatter"),
+
   "es3.propertyLiterals":                  require("./es3/property-literals"),
   "es3.memberExpressionLiterals":          require("./es3/member-expression-literals"),
 

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

@@ -6,7 +6,7 @@ var t         = require("../../../types");
 exports.secondPass = true;
 
 exports.BlockStatement =
-exports.Program = function (node) {
+exports.Program = function (node, parent, scope, file) {
   if (!node._declarations) return;
 
   var kinds = {};
@@ -19,16 +19,16 @@ exports.Program = function (node) {
       kind = declar.kind || "var";
       var declarNode = t.variableDeclarator(declar.id, declar.init);
 
-      if (!declar.init) {
+      if (declar.init) {
+        node.body.unshift(file.attachAuxilaryComment(t.variableDeclaration(kind, [declarNode])));
+      } else {
         kinds[kind] = kinds[kind] || [];
         kinds[kind].push(declarNode);
-      } else {
-        node.body.unshift(t.variableDeclaration(kind, [declarNode]));
       }
     }
 
     for (kind in kinds) {
-      node.body.unshift(t.variableDeclaration(kind, kinds[kind]));
+      node.body.unshift(file.attachAuxilaryComment(t.variableDeclaration(kind, kinds[kind])));
     }
   });
 

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

@@ -2,11 +2,9 @@
 
 var useStrict = require("../../helpers/use-strict");
 
-exports.post = function (file) {
+exports.Program = function (program, parent, scope, file) {
   if (!file.transformers["es6.modules"].canRun()) return;
 
-  var program = file.ast.program;
-
   useStrict.wrap(program, function () {
     program.body = file.dynamicImports.concat(program.body);
   });

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

@@ -3,7 +3,8 @@ var t = require("../../../types");
 exports.optional = true;
 
 exports.ExpressionStatement = function (node) {
-  // remove consequenceless expressions such as local variables and literals
+  // remove consequence-less expressions such as local variables and literals
+  // note: will remove directives
   //
   //   var foo = true; foo; -> var foo = true;
   //   "foo"; ->
@@ -33,7 +34,7 @@ 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
@@ -66,8 +67,7 @@ exports.IfStatement = {
     //   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) {
+exports.CallExpression = function (node, parent) {
   if (isConsole(node.callee)) {
-    this.remove();
+    if (t.isExpressionStatement(parent)) {
+      this.parentPath.remove();
+    } else {
+      this.remove();
+    }
   }
 };

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

@@ -2,10 +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/bluebird-coroutines.js

@@ -15,7 +15,7 @@ exports.Function = function (node, parent, scope, file) {
 
   return remapAsyncToGenerator(
     node,
-    t.memberExpression(file.addImport("bluebird"), t.identifier("coroutine")),
+    t.memberExpression(file.addImport("bluebird", null, true), t.identifier("coroutine")),
     scope
   );
 };

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

@@ -0,0 +1,13 @@
+var t = require("../../../types");
+
+exports.TypeCastExpression = function (node) {
+  return node.expression;
+};
+
+exports.ImportDeclaration = function (node) {
+  if (node.isType) this.remove();
+};
+
+exports.ExportDeclaration = function (node) {
+  if (t.isTypeAlias(node.declaration)) this.remove();
+};

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

@@ -1,10 +1,12 @@
 "use strict";
 
+var includes = require("lodash/collection/includes");
 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 t        = require("../../../types");
+
+var isSymboliterator = t.buildMatchMemberExpression("Symbol.iterator");
 
 var coreHas = function (node) {
   return node.name !== "_" && has(core, node.name);
@@ -30,30 +32,41 @@ var astVisitor = {
 
       if (!t.isReferenced(obj, node)) return;
 
-      if (!node.computed && coreHas(obj) && has(core[obj.name], prop.name) && !scope.getBinding(obj.name)) {
+      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 (!isSymboliterator(prop)) 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 (!isSymboliterator(left)) return;
+
+      return util.template("corejs-is-iterator", {
+        CORE_ID: file.get("coreIdentifier"),
+        VALUE:   node.right
+      });
     }
   }
 };
@@ -64,8 +77,8 @@ exports.manipulateOptions = function (opts) {
   if (opts.whitelist.length) opts.whitelist.push("es6.modules");
 };
 
-exports.post = function (file) {
-  file.scope.traverse(file.ast, astVisitor, file);
+exports.Program = function (node, parent, scope, file) {
+  scope.traverse(node, astVisitor, file);
 };
 
 exports.pre = function (file) {
@@ -83,7 +96,7 @@ exports.pre = function (file) {
 };
 
 exports.Identifier = function (node, parent, scope, file) {
-  if (node.name === "regeneratorRuntime" && t.isReferenced(node, parent)) {
+  if (t.isReferencedIdentifier(node, parent, { name: "regeneratorRuntime" })) {
     return file.get("regeneratorIdentifier");
   }
 };

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

@@ -3,8 +3,7 @@
 var useStrict = require("../../helpers/use-strict");
 var t         = require("../../../types");
 
-exports.post = function (file) {
-  var program = file.ast.program;
+exports.Program = function (program) {
   if (!useStrict.has(program)) {
     program.body.unshift(t.expressionStatement(t.literal("use strict")));
   }

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, 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, file) {
     ]));
   };
 
-  var temp = scope.generateTemp(file, "args");
+  var temp = scope.generateTemp("args");
 
   return t.sequenceExpression([
     t.assignmentExpression("=", temp, t.arrayExpression(node.arguments)),

lib/6to5/transformation/transformers/validation/no-for-in-of-assignment.js

@@ -1,6 +1,7 @@
 "use strict";
 
-var t = require("../../../types");
+var messages = require("../../../messages");
+var t        = require("../../../types");
 
 exports.check = t.isFor;
 
@@ -9,6 +10,6 @@ exports.ForOfStatement = function (node, parent, scope, file) {
   var left = node.left;
   if (t.isVariableDeclaration(left)) {
     var declar = left.declarations[0];
-    if (declar.init) throw file.errorWithNode(declar, "No assignments allowed in for-in/of head");
+    if (declar.init) throw file.errorWithNode(declar, messages.get("noAssignmentsInForHead"));
   }
 };

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

@@ -0,0 +1,25 @@
+var messages = require("../../../messages");
+var t        = require("../../../types");
+
+// check if the input Literal `source` is an alternate casing of "react"
+var check = function (source, file) {
+  if (t.isLiteral(source)) {
+    var name  = source.value;
+    var lower = name.toLowerCase();
+
+    if (lower === "react" && name !== lower) {
+      throw file.errorWithNode(source, messages.get("didYouMean", "react"));
+    }
+  }
+};
+
+exports.CallExpression = function (node, parent, scope, file) {
+  if (t.isIdentifier(node.callee, { name: "require" }) && node.arguments.length === 1) {
+    check(node.arguments[0], file);
+  }
+};
+
+exports.ImportDeclaration =
+exports.ExportDeclaration = function (node, parent, scope, file) {
+  check(node.source, file);
+};

lib/6to5/transformation/transformers/validation/setters.js

@@ -1,5 +1,7 @@
 "use strict";
 
+var messages = require("../../../messages");
+
 exports.check = function (node) {
   return node.kind === "set";
 };
@@ -7,6 +9,6 @@ exports.check = function (node) {
 exports.MethodDefinition =
 exports.Property = function (node, parent, scope, file) {
   if (node.kind === "set" && node.value.params.length !== 1) {
-    throw file.errorWithNode(node.value, "Setters must have only one parameter");
+    throw file.errorWithNode(node.value, messages.get("settersInvalidParamLength"));
   }
 };

lib/6to5/transformation/transformers/validation/undeclared-variable-check.js

@@ -1,6 +1,7 @@
 "use strict";
 
 var levenshtein = require("../../../helpers/levenshtein");
+var messages    = require("../../../messages");
 var t           = require("../../../types");
 
 exports.optional = true;
@@ -9,8 +10,6 @@ exports.Identifier = function (node, parent, scope, file) {
   if (!t.isReferenced(node, parent)) return;
   if (scope.hasBinding(node.name)) return;
 
-  var msg = "Reference to undeclared variable";
-
   // get the closest declaration to offer as a suggestion
   // the variable name may have just been mistyped
 
@@ -28,8 +27,11 @@ exports.Identifier = function (node, parent, scope, file) {
     shortest = distance;
   }
 
+  var msg;
   if (closest) {
-    msg += " - Did you mean " + closest + "?";
+    msg = messages.get("undeclaredVariableSuggestion", node.name, closest);
+  } else {
+    msg = messages.get("undeclaredVariable", node.name);
   }
 
   //

lib/6to5/traversal/context.js

@@ -1,7 +1,5 @@
 "use strict";
 
-/* jshint maxparams:7 */
-
 module.exports = TraversalContext;
 
 var TraversalPath = require("./path");

lib/6to5/traversal/index.js

@@ -3,7 +3,7 @@
 module.exports = traverse;
 
 var TraversalContext = require("./context");
-var contains         = require("lodash/collection/contains");
+var includes         = require("lodash/collection/includes");
 var t                = require("../types");
 
 function traverse(parent, opts, scope, state) {
@@ -102,7 +102,7 @@ function hasBlacklistedType(node, parent, scope, state) {
 
 traverse.hasType = function (tree, scope, type, blacklistTypes) {
   // the node we're searching in is blacklisted
-  if (contains(blacklistTypes, tree.type)) return false;
+  if (includes(blacklistTypes, tree.type)) return false;
 
   // the type we're looking for is the same as the passed node
   if (tree.type === type) return true;

lib/6to5/traversal/path.js

@@ -5,7 +5,7 @@ module.exports = TraversalPath;
 /* jshint maxparams:7 */
 
 var traverse = require("./index");
-var contains = require("lodash/collection/contains");
+var includes = require("lodash/collection/includes");
 var Scope    = require("./scope");
 var t        = require("../types");
 
@@ -49,7 +49,7 @@ TraversalPath.getScope = function (node, parent, scope) {
   var ourScope = scope;
 
   // we're entering a new scope so let's construct it!
-  if (t.isScope(node)) {
+  if (t.isScope(node, parent)) {
     ourScope = new Scope(node, parent, scope);
   }
 
@@ -96,7 +96,7 @@ TraversalPath.prototype.replaceNode = function (replacement) {
   // we're replacing a statement or block node with an array of statements so we better
   // ensure that it's a block
   if (isArray) {
-    if (contains(t.STATEMENT_OR_BLOCK_KEYS, this.key) && !t.isBlockStatement(this.obj)) {
+    if (includes(t.STATEMENT_OR_BLOCK_KEYS, this.key) && !t.isBlockStatement(this.obj)) {
       t.ensureBlock(this.obj, this.key);
     }
 
@@ -109,7 +109,7 @@ TraversalPath.prototype.call = function (key) {
   if (!node) return;
 
   var opts = this.opts;
-  var fn   = opts[key];
+  var fn   = opts[key] || opts;
   if (opts[node.type]) fn = opts[node.type][key] || fn;
 
   var replacement = fn.call(this, node, this.parent, this.scope, this.state);

lib/6to5/traversal/scope.js

@@ -2,15 +2,15 @@
 
 module.exports = Scope;
 
-var contains = require("lodash/collection/contains");
+var includes = require("lodash/collection/includes");
 var traverse = require("./index");
 var defaults = require("lodash/object/defaults");
+var messages = require("../messages");
 var globals  = require("globals");
 var flatten  = require("lodash/array/flatten");
 var extend   = require("lodash/object/extend");
 var object   = require("../helpers/object");
 var each     = require("lodash/collection/each");
-var has      = require("lodash/object/has");
 var t        = require("../types");
 
 /**
@@ -33,7 +33,7 @@ function Scope(block, parentBlock, parent, file) {
   this.crawl();
 }
 
-Scope.defaultDeclarations = flatten([globals.builtin, globals.browser, globals.node].map(Object.keys));
+Scope.globals = flatten([globals.builtin, globals.browser, globals.node].map(Object.keys));
 
 /**
  * Description
@@ -50,12 +50,11 @@ Scope.prototype.traverse = function (node, opts, state) {
 /**
  * Description
  *
- * @param {File} file
  * @param {String} [name="temp"]
  */
 
-Scope.prototype.generateTemp = function (file, name) {
-  var id = file.generateUidIdentifier(name || "temp", this);
+Scope.prototype.generateTemp = function (name) {
+  var id = this.generateUidIdentifier(name || "temp");
   this.push({
     key: id.name,
     id: id
@@ -70,7 +69,33 @@ Scope.prototype.generateTemp = function (file, name) {
  */
 
 Scope.prototype.generateUidIdentifier = function (name) {
-  return this.file.generateUidIdentifier(name, this);
+  var id = t.identifier(this.generateUid(name));
+  this.getFunctionParent().registerBinding("uid", id);
+  return id;
+};
+
+/**
+ * Description
+ *
+ * @param {String} name
+ */
+
+Scope.prototype.generateUid = function (name) {
+  name = t.toIdentifier(name).replace(/^_+/, "");
+
+  var uid;
+  var i = 0;
+  do {
+    uid = this._generateUid(name, i);
+    i++;
+  } while (this.hasBinding(uid) || this.hasGlobal(uid));
+  return uid;
+};
+
+Scope.prototype._generateUid = function (name, i) {
+  var id = name;
+  if (i > 1) id += i;
+  return "_" + id;
 };
 
 /*
@@ -111,7 +136,7 @@ Scope.prototype.generateUidBasedOnNode = function (parent) {
   var id = parts.join("$");
   id = id.replace(/^_/, "") || "ref";
 
-  return this.file.generateUidIdentifier(id, this);
+  return this.generateUidIdentifier(id);
 };
 
 /**
@@ -134,12 +159,50 @@ Scope.prototype.generateTempBasedOnNode = function (node) {
   return id;
 };
 
-Scope.prototype.checkBlockScopedCollisions = function (key, id) {
-  if (this.declarationKinds["let"][key] || this.declarationKinds["const"][key]) {
-    throw this.file.errorWithNode(id, "Duplicate declaration " + key, TypeError);
+Scope.prototype.checkBlockScopedCollisions = function (kind, name, id) {
+  var local = this.getOwnBindingInfo(name);
+  if (!local) return;
+
+  if (kind === "param") return;
+  if (kind === "hoisted" && local.kind === "let") return;
+
+  if (local.kind === "let" || local.kind === "const" || local.kind === "module") {
+    throw this.file.errorWithNode(id, messages.get("scopeDuplicateDeclaration", name), TypeError);
   }
 };
 
+Scope.prototype.rename = function (oldName, newName) {
+  newName = newName || this.generateUidIdentifier(oldName).name;
+
+  var info = this.getBindingInfo(oldName);
+  if (!info) return;
+
+  var binding = info.identifier;
+  var scope = info.scope;
+
+  scope.traverse(scope.block, {
+    enter: function (node, parent, scope) {
+      if (t.isReferencedIdentifier(node, parent) && node.name === oldName) {
+        node.name = newName;
+      } else if (t.isDeclaration(node)) {
+        var ids = t.getBindingIdentifiers(node);
+        for (var name in ids) {
+          if (name === oldName) ids[name].name = newName;
+        }
+      } else if (t.isScope(node, parent)) {
+        if (!scope.bindingIdentifierEquals(oldName, binding)) {
+          this.skip();
+        }
+      }
+    }
+  });
+
+  this.clearOwnBinding(oldName);
+  scope.bindings[newName] = info;
+
+  binding.name = newName;
+};
+
 Scope.prototype.inferType = function (node) {
   var target;
 
@@ -147,24 +210,56 @@ Scope.prototype.inferType = function (node) {
     target = node.init;
   }
 
-  if (t.isLiteral(target) || t.isArrayExpression(target) || t.isObjectExpression(target)) {
-    // todo: possibly call some helper that will resolve these to a flow type annotation
+  if (t.isArrayExpression(target)) {
+    return t.genericTypeAnnotation(t.identifier("Array"));
   }
 
-  if (t.isCallExpression(target)) {
-    // todo: resolve this to a return type
+  if (t.isObjectExpression(target)) {
+    return;
   }
 
-  if (t.isMemberExpression(target)) {
-    // todo: crawl this and find the correct type, bail on anything that we cannot possibly be 100% confident on
+  if (t.isLiteral(target)) {
+    return;
+  }
+
+  if (t.isCallExpression(target) && t.isIdentifier(target.callee)) {
+    var funcInfo = this.getBindingInfo(target.callee.name);
+    if (funcInfo) {
+      var funcNode = funcInfo.node;
+      return !funcInfo.reassigned && t.isFunction(funcNode) && node.returnType;
+    }
   }
 
   if (t.isIdentifier(target)) {
-    return this.getType(target.name);
+    return;
   }
 };
 
-Scope.prototype.registerType = function (key, id, node) {
+Scope.prototype.isTypeGeneric = function (name, genericName) {
+  var info = this.getBindingInfo(name);
+  if (!info) return false;
+
+  var type = info.typeAnnotation;
+  return t.isGenericTypeAnnotation(type) && t.isIdentifier(type.id, { name: genericName });
+};
+
+Scope.prototype.assignTypeGeneric = function (name, type) {
+  this.assignType(name, t.genericTypeAnnotation(t.identifier(type)));
+};
+
+Scope.prototype.assignType = function (name, type) {
+  var info = this.getBindingInfo(name);
+  if (!info) return;
+
+  info.identifier.typeAnnotation = info.typeAnnotation = type;
+};
+
+Scope.prototype.getTypeAnnotation = function (name, id, node) {
+  var info = {
+    annotation: null,
+    inferred: false
+  };
+
   var type;
 
   if (id.typeAnnotation) {
@@ -172,43 +267,107 @@ Scope.prototype.registerType = function (key, id, node) {
   }
 
   if (!type) {
+    info.inferred = true;
     type = this.inferType(node);
   }
 
   if (type) {
     if (t.isTypeAnnotation(type)) type = type.typeAnnotation;
-    this.types[key] = type;
+    info.annotation = type;
+  }
+
+  return info;
+};
+
+Scope.prototype.toArray = function (node, i) {
+  var file = this.file;
+
+  if (t.isIdentifier(node) && this.isTypeGeneric(node.name, "Array")) {
+    return node;
+  }
+
+  if (t.isArrayExpression(node)) {
+    return node;
+  }
+
+  if (t.isIdentifier(node, { name: "arguments" })) {
+    return t.callExpression(t.memberExpression(file.addHelper("slice"), t.identifier("call")), [node]);
+  }
+
+  var helperName = "to-array";
+  var args = [node];
+  if (i === true) {
+    helperName = "to-consumable-array";
+  } else if (i) {
+    args.push(t.literal(i));
+    helperName = "sliced-to-array";
+  }
+  return t.callExpression(file.addHelper(helperName), args);
+};
+
+Scope.prototype.clearOwnBinding = function (name) {
+  delete this.bindings[name];
+};
+
+Scope.prototype.registerDeclaration = function (node) {
+  if (t.isFunctionDeclaration(node)) {
+    this.registerBinding("hoisted", node);
+  } else if (t.isVariableDeclaration(node)) {
+    for (var i = 0; i < node.declarations.length; i++) {
+      this.registerBinding(node.kind, node.declarations[i]);
+    }
+  } else if (t.isClassDeclaration(node)) {
+    this.registerBinding("let", node);
+  } else if (t.isImportDeclaration(node) || t.isExportDeclaration(node)) {
+    this.registerBinding("module", node);
+  } else {
+    this.registerBinding("unknown", node);
   }
 };
 
-Scope.prototype.register = function (node, reference, kind) {
-  if (t.isVariableDeclaration(node)) {
-    return this.registerVariableDeclaration(node);
+Scope.prototype.registerBindingReassignment = function (node) {
+  var ids = t.getBindingIdentifiers(node);
+  for (var name in ids) {
+    var info = this.getBindingInfo(name);
+    if (info) {
+      info.reassigned = true;
+
+      if (info.typeAnnotationInferred) {
+        // destroy the inferred typeAnnotation
+        info.typeAnnotation = null;
+      }
+    }
   }
+};
+
+Scope.prototype.registerBinding = function (kind, node) {
+  if (!kind) throw new ReferenceError("no `kind`");
 
   var ids = t.getBindingIdentifiers(node);
 
-  extend(this.references, ids);
+  for (var name in ids) {
+    var id = ids[name];
 
-  if (reference) return;
+    this.checkBlockScopedCollisions(kind, name, id);
 
-  for (var key in ids) {
-    var id = ids[key];
+    var typeInfo = this.getTypeAnnotation(name, id, node);
 
-    this.checkBlockScopedCollisions(key, id);
-
-    this.registerType(key, id, node);
-    this.bindings[key] = id;
+    this.bindings[name] = {
+      typeAnnotationInferred: typeInfo.inferred,
+      typeAnnotation:         typeInfo.annotation,
+      reassigned:             false,
+      identifier:             id,
+      scope:                  this,
+      node:                   node,
+      kind:                   kind
+    };
   }
-
-  var kinds = this.declarationKinds[kind];
-  if (kinds) extend(kinds, ids);
 };
 
 Scope.prototype.registerVariableDeclaration = function (declar) {
   var declars = declar.declarations;
   for (var i = 0; i < declars.length; i++) {
-    this.register(declars[i], false, declar.kind);
+    this.registerBinding(declars[i], declar.kind);
   }
 };
 
@@ -217,7 +376,7 @@ var functionVariableVisitor = {
     if (t.isFor(node)) {
       each(t.FOR_INIT_KEYS, function (key) {
         var declar = node[key];
-        if (t.isVar(declar)) state.scope.register(declar);
+        if (t.isVar(declar)) state.scope.registerBinding("var", declar);
       });
     }
 
@@ -235,30 +394,47 @@ var functionVariableVisitor = {
     if (t.isExportDeclaration(node) && t.isDeclaration(node.declaration)) return;
 
     // we've ran into a declaration!
-    if (t.isDeclaration(node)) state.scope.register(node);
+    if (t.isDeclaration(node)) state.scope.registerDeclaration(node);
   }
 };
 
+Scope.prototype.addGlobal = function (node) {
+  this.globals[node.name] = node;
+};
+
+Scope.prototype.hasGlobal = function (name) {
+  var scope = this;
+
+  do {
+    if (scope.globals[name]) return true;
+  } while (scope = scope.parent);
+
+  return false;
+};
+
 var programReferenceVisitor = {
   enter: function (node, parent, scope, state) {
-    if (t.isReferencedIdentifier(node, parent) && !scope.hasReference(node.name)) {
-      state.register(node, true);
+    if (t.isReferencedIdentifier(node, parent) && !scope.hasBinding(node.name)) {
+      state.addGlobal(node);
+    } else if (t.isLabeledStatement(node)) {
+      state.addGlobal(node);
+    } else if (t.isAssignmentExpression(node) || t.isUpdateExpression(node) || (t.isUnaryExpression(node) && node.operator === "delete")) {
+      scope.registerBindingReassignment(node);
     }
   }
 };
 
 var blockVariableVisitor = {
   enter: function (node, parent, scope, state) {
-    if (t.isBlockScoped(node)) {
-      state.register(node);
-    } else if (t.isScope(node)) {
+    if (t.isFunctionDeclaration(node) || t.isBlockScoped(node)) {
+      state.registerDeclaration(node);
+    } else if (t.isScope(node, parent)) {
       this.skip();
     }
   }
 };
 
 Scope.prototype.crawl = function () {
-  var parent = this.parent;
   var block  = this.block;
   var i;
 
@@ -271,34 +447,18 @@ Scope.prototype.crawl = function () {
   }
 
   info = block._scopeInfo = {
-    declarationKinds: {
-      "const": object(),
-      "var":   object(),
-      "let":   object()
-    },
-
-    references: object(),
-    bindings:   object(),
-    types:      object(),
+    bindings: object(),
+    globals:  object()
   };
 
   extend(this, info);
 
-  //
-
-  if (parent && t.isBlockStatement(block)) {
-    if (t.isLoop(parent.block, { body: block }) ||
-        t.isFunction(parent.block, { body: block })) {
-      return;
-    }
-  }
-
   // ForStatement - left, init
 
   if (t.isLoop(block)) {
     for (i = 0; i < t.FOR_INIT_KEYS.length; i++) {
       var node = block[t.FOR_INIT_KEYS[i]];
-      if (t.isBlockScoped(node)) this.register(node, false, true);
+      if (t.isBlockScoped(node)) this.registerBinding("let", node);
     }
 
     if (t.isBlockStatement(block.body)) {
@@ -310,7 +470,7 @@ Scope.prototype.crawl = function () {
 
   if (t.isFunctionExpression(block) && block.id) {
     if (!t.isProperty(this.parentBlock, { method: true })) {
-      this.register(block.id);
+      this.registerBinding("var", block.id);
     }
   }
 
@@ -318,7 +478,7 @@ Scope.prototype.crawl = function () {
 
   if (t.isFunction(block)) {
     for (i = 0; i < block.params.length; i++) {
-      this.register(block.params[i]);
+      this.registerBinding("param", block.params[i]);
     }
     this.traverse(block.body, blockVariableVisitor, this);
   }
@@ -332,13 +492,13 @@ Scope.prototype.crawl = function () {
   // CatchClause - param
 
   if (t.isCatchClause(block)) {
-    this.register(block.param);
+    this.registerBinding("let", block.param);
   }
 
   // ComprehensionExpression - blocks
 
   if (t.isComprehensionExpression(block)) {
-    this.register(block);
+    this.registerBinding("let", block);
   }
 
   // Program, Function - var variables
@@ -383,26 +543,6 @@ Scope.prototype.push = function (opts) {
   }
 };
 
-/**
- * Walk up the scope tree until we hit a `Function` and then
- * push our `node` to it's references.
- *
- * @param {String} kind
- * @param {Object} node
- */
-
-Scope.prototype.addDeclarationToFunctionScope = function (kind, node) {
-  var scope = this.getFunctionParent();
-  var ids   = t.getBindingIdentifiers(node);
-
-  extend(scope.bindings, ids);
-  extend(scope.references, ids);
-
-  // this ignores the duplicate declaration logic specified in `getInfo`
-  // but it doesn't really matter
-  extend(scope.declarationKinds[kind], ids);
-};
-
 /**
  * Walk up the scope tree until we hit either a Function or reach the
  * very top and hit Program.
@@ -441,72 +581,66 @@ Scope.prototype.getAllBindings = function () {
  * @returns {Object}
  */
 
-Scope.prototype.getAllDeclarationsOfKind = function (kind) {
+Scope.prototype.getAllBindingsOfKind = function (kind) {
   var ids = object();
 
   var scope = this;
   do {
-    defaults(ids, scope.declarationKinds[kind]);
+    for (var name in scope.bindings) {
+      var binding = scope.bindings[name];
+      if (binding.kind === kind) ids[name] = binding;
+    }
     scope = scope.parent;
   } while (scope);
 
   return ids;
 };
 
-//
+// misc
 
-Scope.prototype.get = function (id, type) {
-  return id && (this.getOwn(id, type) || this.parentGet(id, type));
+Scope.prototype.bindingIdentifierEquals = function (name, node) {
+  return this.getBindingIdentifier(name) === node;
 };
 
-Scope.prototype.getOwn = function (id, type) {
-  var refs = {
-    reference: this.references,
-    binding:   this.bindings,
-    type:      this.types
-  }[type];
-  return refs && has(refs, id) && refs[id];
+// get
+
+Scope.prototype.getBindingInfo = function (name) {
+  var scope = this;
+
+  do {
+    var binding = scope.getOwnBindingInfo(name);
+    if (binding) return binding;
+  } while (scope = scope.parent);
 };
 
-Scope.prototype.parentGet = function (id, type) {
-  return this.parent && this.parent.get(id, type);
+Scope.prototype.getOwnBindingInfo = function (name) {
+  return this.bindings[name];
 };
 
-Scope.prototype.has = function (id, type) {
-  if (!id) return false;
-  if (this.hasOwn(id, type)) return true;
-  if (this.parentHas(id, type)) return true;
-  if (contains(Scope.defaultDeclarations, id)) return true;
+Scope.prototype.getBindingIdentifier = function (name) {
+  var info = this.getBindingInfo(name);
+  return info && info.identifier;
+};
+
+Scope.prototype.getOwnBindingIdentifier = function (name) {
+  var binding = this.bindings[name];
+  return binding && binding.identifier;
+};
+
+// has
+
+Scope.prototype.hasOwnBinding = function (name) {
+  return !!this.getOwnBindingInfo(name);
+};
+
+Scope.prototype.hasBinding = function (name) {
+  if (!name) return false;
+  if (this.hasOwnBinding(name)) return true;
+  if (this.parentHasBinding(name)) return true;
+  if (includes(Scope.globals, name)) return true;
   return false;
 };
 
-Scope.prototype.hasOwn = function (id, type) {
-  return !!this.getOwn(id, type);
+Scope.prototype.parentHasBinding = function (name) {
+  return this.parent && this.parent.hasBinding(name);
 };
-
-Scope.prototype.parentHas = function (id, type) {
-  return this.parent && this.parent.has(id, type);
-};
-
-each({
-  reference: "Reference",
-  binding: "Binding",
-  type: "Type"
-}, function (title, type) {
-  Scope.prototype[type + "Equals"] = function (id, node) {
-    return this["get" + title](id) === node;
-  };
-
-  each([
-    "get",
-    "has",
-    "getOwn",
-    "hasOwn",
-    "parentGet",
-    "parentHas",
-  ], function (methodName) {
-    Scope.prototype[methodName + title] = function (id) {
-      return this[methodName](id, type);
-    };
-  });
-});

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

@@ -3,13 +3,13 @@
   "BreakStatement":      ["Statement"],
   "ContinueStatement":   ["Statement"],
   "DebuggerStatement":   ["Statement"],
-  "DoWhileStatement":    ["Statement", "Loop", "While", "Scope"],
+  "DoWhileStatement":    ["Statement", "Loop", "While", "Scopable"],
   "IfStatement":         ["Statement"],
   "ReturnStatement":     ["Statement"],
   "SwitchStatement":     ["Statement"],
   "ThrowStatement":      ["Statement"],
   "TryStatement":        ["Statement"],
-  "WhileStatement":      ["Statement", "Loop", "While", "Scope"],
+  "WhileStatement":      ["Statement", "Loop", "While", "Scopable"],
   "WithStatement":       ["Statement"],
   "EmptyStatement":      ["Statement"],
   "LabeledStatement":    ["Statement"],
@@ -18,13 +18,16 @@
   "ImportDeclaration":   ["Statement", "Declaration"],
   "PrivateDeclaration":  ["Statement", "Declaration"],
 
-  "ArrowFunctionExpression": ["Scope", "Function", "Expression"],
-  "FunctionDeclaration":     ["Statement", "Declaration", "Scope", "Function"],
-  "FunctionExpression":      ["Scope", "Function", "Expression"],
+  "ArrowFunctionExpression": ["Scopable", "Function", "Expression"],
+  "FunctionDeclaration":     ["Statement", "Declaration", "Scopable", "Function"],
+  "FunctionExpression":      ["Scopable", "Function", "Expression"],
 
-  "BlockStatement": ["Statement", "Scope"],
-  "Program":        ["Scope"],
-  "CatchClause":    ["Scope"],
+  "ImportSpecifier": ["ModuleSpecifier"],
+  "ExportSpecifier": ["ModuleSpecifier"],
+
+  "BlockStatement": ["Statement", "Scopable"],
+  "Program":        ["Scopable"],
+  "CatchClause":    ["Scopable"],
 
   "LogicalExpression": ["Binary", "Expression"],
   "BinaryExpression":  ["Binary", "Expression"],
@@ -36,9 +39,9 @@
   "ClassDeclaration": ["Statement", "Declaration", "Class"],
   "ClassExpression":  ["Class", "Expression"],
 
-  "ForOfStatement": ["Statement", "For", "Scope", "Loop"],
-  "ForInStatement": ["Statement", "For", "Scope", "Loop"],
-  "ForStatement":   ["Statement", "For", "Scope", "Loop"],
+  "ForOfStatement": ["Statement", "For", "Scopable", "Loop"],
+  "ForInStatement": ["Statement", "For", "Scopable", "Loop"],
+  "ForStatement":   ["Statement", "For", "Scopable", "Loop"],
 
   "ObjectPattern":     ["Pattern"],
   "ArrayPattern":      ["Pattern"],
@@ -53,7 +56,7 @@
   "BindFunctionExpression":    ["Expression"],
   "BindMemberExpression":      ["Expression"],
   "CallExpression":            ["Expression"],
-  "ComprehensionExpression":   ["Expression", "Scope"],
+  "ComprehensionExpression":   ["Expression", "Scopable"],
   "ConditionalExpression":     ["Expression"],
   "Identifier":                ["Expression"],
   "Literal":                   ["Expression"],

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

@@ -1,33 +1,168 @@
 {
-  "ArrayExpression":         ["elements"],
-  "ArrowFunctionExpression": ["params", "body"],
-  "AssignmentExpression":    ["operator", "left", "right"],
-  "BinaryExpression":        ["operator", "left", "right"],
-  "BlockStatement":          ["body"],
-  "CallExpression":          ["callee", "arguments"],
-  "ConditionalExpression":   ["test", "consequent", "alternate"],
-  "ExpressionStatement":     ["expression"],
-  "File":                    ["program", "comments", "tokens"],
-  "FunctionExpression":      ["id", "params", "body", "generator"],
-  "FunctionDeclaration":     ["id", "params", "body", "generator"],
-  "Identifier":              ["name"],
-  "IfStatement":             ["test", "consequent", "alternate"],
-  "ImportDeclaration":       ["specifiers", "source"],
-  "ImportSpecifier":         ["id", "name"],
-  "Literal":                 ["value"],
-  "LogicalExpression":       ["operator", "left", "right"],
-  "MemberExpression":        ["object", "property", "computed"],
-  "MethodDefinition":        ["key", "value", "computed", "kind"],
-  "NewExpression":           ["callee", "arguments"],
-  "ObjectExpression":        ["properties"],
-  "Program":                 ["body"],
-  "Property":                ["kind", "key", "value", "computed"],
-  "ReturnStatement":         ["argument"],
-  "SequenceExpression":      ["expressions"],
-  "ThrowExpression":         ["argument"],
-  "UnaryExpression":         ["operator", "argument", "prefix"],
-  "VariableDeclaration":     ["kind", "declarations"],
-  "VariableDeclarator":      ["id", "init"],
-  "WithStatement":           ["object", "body"],
-  "YieldExpression":         ["argument", "delegate"]
+  "ArrayExpression": {
+    "elements": null
+  },
+
+  "ArrowFunctionExpression": {
+    "params": null,
+    "body": null
+  },
+
+  "AssignmentExpression": {
+    "operator": null,
+    "left": null,
+    "right": null
+  },
+
+  "BinaryExpression": {
+    "operator": null,
+    "left": null,
+    "right": null
+  },
+
+  "BlockStatement": {
+    "body": null
+  },
+
+  "CallExpression": {
+    "callee": null,
+    "arguments": null
+  },
+
+  "ConditionalExpression": {
+    "test": null,
+    "consequent": null,
+    "alternate": null
+  },
+
+  "ExpressionStatement": {
+    "expression": null
+  },
+
+  "File": {
+    "program": null,
+    "comments": null,
+    "tokens": null
+  },
+
+  "FunctionExpression": {
+    "id": null,
+    "params": null,
+    "body": null,
+    "generator": false
+  },
+
+  "FunctionDeclaration": {
+    "id": null,
+    "params": null,
+    "body": null,
+    "generator": false
+  },
+
+  "GenericTypeAnnotation": {
+    "id": null,
+    "typeParameters": null
+  },
+
+  "Identifier": {
+    "name": null
+  },
+
+  "IfStatement": {
+    "test": null,
+    "consequent": null,
+    "alternate": null
+  },
+
+  "ImportDeclaration": {
+    "specifiers": null,
+    "source": null
+  },
+
+  "ImportSpecifier": {
+    "id": null,
+    "name": null
+  },
+
+  "Literal": {
+    "value": null
+  },
+
+  "LogicalExpression": {
+    "operator": null,
+    "left": null,
+    "right": null
+  },
+
+  "MemberExpression": {
+    "object": null,
+    "property": null,
+    "computed": false
+  },
+
+  "MethodDefinition": {
+    "key": null,
+    "value": null,
+    "computed": false,
+    "static": false,
+    "kind": null
+  },
+
+  "NewExpression": {
+    "callee": null,
+    "arguments": null
+  },
+
+  "ObjectExpression": {
+    "properties": null
+  },
+
+  "Program": {
+    "body": null
+  },
+
+  "Property": {
+    "kind": null,
+    "key": null,
+    "value": null,
+    "computed": false
+  },
+
+  "ReturnStatement": {
+    "argument": null
+  },
+
+  "SequenceExpression": {
+    "expressions": null
+  },
+
+  "ThrowExpression": {
+    "argument": null
+  },
+
+  "UnaryExpression": {
+    "operator": null,
+    "argument": null,
+    "prefix": null
+  },
+
+  "VariableDeclaration": {
+    "kind": null,
+    "declarations": null
+  },
+
+  "VariableDeclarator": {
+    "id": null,
+    "init": null
+  },
+
+  "WithStatement": {
+    "object": null,
+    "body": null
+  },
+
+  "YieldExpression": {
+    "argument": null,
+    "delegate": null
+  }
 }

lib/6to5/types/index.js

@@ -1,12 +1,10 @@
 "use strict";
 
 var toFastProperties = require("../helpers/to-fast-properties");
-var defaults         = require("lodash/object/defaults");
 var isString         = require("lodash/lang/isString");
 var compact          = require("lodash/array/compact");
 var esutils          = require("esutils");
 var object           = require("../helpers/object");
-var Node             = require("./node");
 var each             = require("lodash/collection/each");
 var uniq             = require("lodash/array/uniq");
 
@@ -72,9 +70,9 @@ each(t.FLIPPED_ALIAS_KEYS, function (types, type) {
  */
 
 t.is = function (type, node, opts, skipAliasCheck) {
-  if (!node) return;
+  if (!node) return false;
 
-  var typeMatches = (type === node.type);
+  var typeMatches = type === node.type;
 
   if (!typeMatches && !skipAliasCheck) {
     var aliases = t.FLIPPED_ALIAS_KEYS[type];
@@ -97,17 +95,32 @@ t.is = function (type, node, opts, skipAliasCheck) {
 
 //
 
-t.BUILDER_KEYS = defaults(require("./builder-keys"), t.VISITOR_KEYS);
+t.BUILDER_KEYS = require("./builder-keys");
+
+each(t.VISITOR_KEYS, function (keys, type) {
+  if (t.BUILDER_KEYS[type]) return;
+
+  var defs = {};
+  each(keys, function (key) {
+    defs[key] = null;
+  });
+  t.BUILDER_KEYS[type] = defs;
+});
 
 each(t.BUILDER_KEYS, function (keys, type) {
   t[type[0].toLowerCase() + type.slice(1)] = function () {
-    var args = arguments;
-    var node = new Node;
+    var node = {};
     node.start = null;
     node.type = type;
-    each(keys, function (key, i) {
-      node[key] = args[i];
-    });
+
+    var i = 0;
+
+    for (var key in keys) {
+      var arg = arguments[i++];
+      if (arg === undefined) arg = keys[key];
+      node[key] = arg;
+    }
+
     return node;
   };
 });
@@ -305,7 +318,7 @@ t.isReferenced = function (node, parent) {
   // no: [NODE = foo] = [];
   // yes: [foo = NODE] = [];
   if (t.isAssignmentPattern(parent)) {
-    return parent.right !== node;
+    return parent.right === node;
   }
 
   // no: [NODE] = [];
@@ -335,8 +348,8 @@ t.isReferenced = function (node, parent) {
 /**
  * Check if the input `node` is an `Identifier` and `isReferenced`.
  *
- * @param {Object} node
- * @param {Object} parent
+ * @param {Node} node
+ * @parma {Node} parent
  * @returns {Boolean}
  */
 
@@ -390,7 +403,7 @@ t.toIdentifier = function (name) {
  * Description
  *
  * @param {Object} node
- * @param {String} key
+ * @param {String=} key
  */
 
 t.ensureBlock = function (node, key) {
@@ -405,7 +418,7 @@ t.ensureBlock = function (node, key) {
  * For example, given the match `React.createClass` it would match the
  * parsed nodes of `React.createClass` and `React["createClass"]`.
  *
- * @param {String} match Dot delimetered string
+ * @param {String} match Dot-delimited string
  * @param {Boolean} [allowPartial] Allow a partial match
  * @returns {Function}
  */
@@ -423,6 +436,10 @@ t.buildMatchMemberExpression = function (match, allowPartial) {
     while (search.length) {
       var node = search.shift();
 
+      if (allowPartial && i === parts.length) {
+        return true;
+      }
+
       if (t.isIdentifier(node)) {
         // this part doesn't match
         if (parts[i] !== node.name) return false;
@@ -445,11 +462,7 @@ t.buildMatchMemberExpression = function (match, allowPartial) {
 
       // too many parts
       if (++i > parts.length) {
-        if (allowPartial) {
-          return true;
-        } else {
-          return false;
-        }
+        return false;
       }
     }
 
@@ -577,6 +590,8 @@ t.getBindingIdentifiers = function (node) {
 
     if (t.isIdentifier(id)) {
       ids[id.name] = id;
+    } else if (t.isImportSpecifier(id)) {
+      search.push(id.name || id.id);
     } else if (t.isExportDeclaration(id)) {
       if (t.isDeclaration(node.declaration)) {
         search.push(node.declaration);
@@ -593,17 +608,16 @@ t.getBindingIdentifiers = function (node) {
 };
 
 t.getBindingIdentifiers.keys = {
+  UnaryExpression: ["argument"],
   AssignmentExpression: ["left"],
   ImportBatchSpecifier: ["name"],
-  ImportSpecifier: ["name", "id"],
-  ExportSpecifier: ["name", "id"],
   VariableDeclarator: ["id"],
   FunctionDeclaration: ["id"],
   ClassDeclaration: ["id"],
-  MemeberExpression: ["object"],
   SpreadElement: ["argument"],
   RestElement: ["argument"],
   UpdateExpression: ["argument"],
+  SpreadProperty: ["argument"],
   Property: ["value"],
   ComprehensionBlock: ["left"],
   AssignmentPattern: ["left"],
@@ -765,5 +779,27 @@ t.isSpecifierDefault = function (specifier) {
   return specifier.default || t.isIdentifier(specifier.id) && specifier.id.name === "default";
 };
 
+/**
+ * Description
+ *
+ * @param {Node} node
+ * @param {Node} parent
+ * @returns {Boolean}
+ */
+
+t.isScope = function (node, parent) {
+  if (t.isBlockStatement(node)) {
+    if (t.isLoop(parent.block, { body: node })) {
+      return false;
+    }
+
+    if (t.isFunction(parent.block, { body: node })) {
+      return false;
+    }
+  }
+
+  return t.isScopable(node);
+};
+
 toFastProperties(t);
 toFastProperties(t.VISITOR_KEYS);

lib/6to5/types/node.js

@@ -1,12 +0,0 @@
-"use strict";
-
-module.exports = Node;
-
-var acorn = require("acorn-6to5");
-
-var oldNode = acorn.Node;
-acorn.Node = Node;
-
-function Node() {
-  oldNode.apply(this);
-}

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

@@ -73,7 +73,7 @@
   "AnyTypeAnnotation":           [],
   "ArrayTypeAnnotation":         [],
   "BooleanTypeAnnotation":       [],
-  "ClassProperty":               ["key"],
+  "ClassProperty":               ["key", "value"],
   "DeclareClass":                [],
   "DeclareFunction":             [],
   "DeclareModule":               [],
@@ -92,6 +92,7 @@
   "TypeofTypeAnnotation":        [],
   "TypeAlias":                   [],
   "TypeAnnotation":              [],
+  "TypeCastExpression":          ["expression"],
   "TypeParameterDeclaration":    [],
   "TypeParameterInstantiation":  [],
   "ObjectTypeAnnotation":        [],

lib/6to5/util.js

@@ -30,6 +30,10 @@ exports.canCompile = function (filename, altExts) {
 
 exports.canCompile.EXTENSIONS = [".js", ".jsx", ".es6", ".es"];
 
+exports.normalisePathSeparator = function (filename) {
+  return filename.replace(/\\/g, "/");
+};
+
 exports.isInteger = function (i) {
   return isNumber(i) && i % 1 === 0;
 };
@@ -80,7 +84,11 @@ exports.sourceMapToComment = function (map) {
 
 var templateVisitor = {
   enter: function (node, parent, scope, nodes) {
+    if (t.isExpressionStatement(node)) {
+      node = node.expression;
+    }
     if (t.isIdentifier(node) && has(nodes, node.name)) {
+      this.skip();
       return nodes[node.name];
     }
   }
@@ -101,6 +109,8 @@ exports.template = function (name, nodes, keepExpression) {
     traverse(template, templateVisitor, null, nodes);
   }
 
+  if (template.body.length > 1) return template.body;
+
   var node = template.body[0];
 
   if (!keepExpression && t.isExpressionStatement(node)) {

package.json

@@ -1,7 +1,7 @@
 {
   "name": "6to5",
   "description": "Turn ES6 code into readable vanilla ES5 with source maps",
-  "version": "3.5.3",
+  "version": "3.6.5",
   "author": "Sebastian McKenzie <sebmck@gmail.com>",
   "homepage": "https://6to5.org/",
   "repository": "6to5/6to5",
@@ -33,12 +33,12 @@
     "test": "make test"
   },
   "dependencies": {
-    "acorn-6to5": "0.11.1-28",
+    "acorn-6to5": "0.11.1-31",
     "ast-types": "~0.6.1",
     "chalk": "^0.5.1",
     "chokidar": "0.12.6",
     "commander": "2.6.0",
-    "core-js": "^0.4.9",
+    "core-js": "^0.5.3",
     "debug": "^2.1.1",
     "detect-indent": "3.0.0",
     "estraverse": "1.9.1",
@@ -49,7 +49,7 @@
     "lodash": "3.0.0",
     "output-file-sync": "1.1.0",
     "private": "0.1.6",
-    "regenerator-6to5": "0.8.9-8",
+    "regenerator-6to5": "0.8.10-1",
     "regexpu": "1.1.0",
     "roadrunner": "1.0.4",
     "source-map": "0.1.43",
@@ -58,6 +58,7 @@
     "useragent": "^2.1.5"
   },
   "devDependencies": {
+    "6to5": "3.6.0",
     "browserify": "8.1.1",
     "chai": "1.10.0",
     "esvalid": "1.1.0",
@@ -69,8 +70,5 @@
     "mocha": "2.1.0",
     "rimraf": "2.2.8",
     "uglify-js": "2.4.16"
-  },
-  "optionalDependencies": {
-    "kexec": "1.0.0"
   }
 }

packages/6to5-runtime/package.json

@@ -1,7 +1,7 @@
 {
   "name": "6to5-runtime",
   "description": "6to5 selfContained runtime",
-  "version": "3.5.2",
+  "version": "3.6.4",
   "repository": "6to5/6to5",
   "author": "Sebastian McKenzie <sebmck@gmail.com>"
 }

packages/build-runtime.js

@@ -2,6 +2,7 @@
 
 var buildHelpers = require("../lib/6to5/build-helpers");
 var transform    = require("../lib/6to5/transformation");
+var util         = require("../lib/6to5/util");
 var fs           = require("fs");
 var t            = require("../lib/6to5/types");
 var _            = require("lodash");
@@ -16,8 +17,14 @@ var writeFile = function (filename, content) {
   fs.writeFileSync(filename, content);
 };
 
-var readFile = function (filename) {
-  return fs.readFileSync(require.resolve(filename), "utf8");
+var readFile = function (filename, defaultify) {
+  var file = fs.readFileSync(require.resolve(filename), "utf8");
+
+  if (defaultify) {
+    file += '\nmodule.exports = { "default": module.exports, __esModule: true };\n';
+  }
+
+  return file;
 };
 
 var updatePackage = function () {
@@ -37,10 +44,10 @@ var selfContainify = function (code) {
 };
 
 var buildHelpers2 = function () {
-  var body = [];
+  var body = util.template("self-contained-helpers-head");
   var tree = t.program(body);
 
-  buildHelpers(body, t.identifier("exports"));
+  buildHelpers(body, t.identifier("helpers"));
 
   return transform.fromAst(tree, null, {
     optional: ["selfContained"]
@@ -48,7 +55,7 @@ var buildHelpers2 = function () {
 };
 
 writeFile("helpers.js", buildHelpers2());
-writeFile("core-js.js", readFile("core-js/library"));
-writeFile("regenerator/index.js", readFile("regenerator-6to5/runtime-module"));
+writeFile("core-js.js", readFile("core-js/library", true));
+writeFile("regenerator/index.js", readFile("regenerator-6to5/runtime-module", true));
 writeFile("regenerator/runtime.js", selfContainify(readFile("regenerator-6to5/runtime")));
 updatePackage();

test/fixtures/bin/6to5-node/filename/options.json

@@ -1,3 +1,3 @@
 {
-  "args": ["foo"]
+  "args": ["bar"]
 }

test/fixtures/bin/6to5-node/require/in-files/foo2.js

@@ -1,4 +1,4 @@
 var foo = () => console.log("foo");
 foo();
 
-import "./bar";
+import "./bar2";

test/fixtures/bin/6to5-node/require/options.json

@@ -1,3 +1,3 @@
 {
-  "args": ["foo"]
+  "args": ["foo2"]
 }

test/fixtures/bin/6to5/dir --out-dir --source-maps-inline/out-files/lib/bar/bar.js

@@ -5,4 +5,4 @@ var _classCallCheck = function (instance, Constructor) { if (!(instance instance
 var Test = function Test() {
   _classCallCheck(this, Test);
 };
-//# sourceMappingURL=data:application/json;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbInNyYy9iYXIvYmFyLmpzIl0sIm5hbWVzIjpbXSwibWFwcGluZ3MiOiI7Ozs7SUFBTSxJQUFJLFlBQUosSUFBSTt3QkFBSixJQUFJIiwiZmlsZSI6InNyYy9iYXIvYmFyLmpzIiwic291cmNlc0NvbnRlbnQiOlsiY2xhc3MgVGVzdCB7XG5cbn0iXX0=
+//# sourceMappingURL=data:application/json;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbIi4uLy4uL3NyYy9iYXIvYmFyLmpzIl0sIm5hbWVzIjpbXSwibWFwcGluZ3MiOiI7Ozs7SUFBTSxJQUFJLFlBQUosSUFBSTt3QkFBSixJQUFJIiwiZmlsZSI6InNyYy9iYXIvYmFyLmpzIiwic291cmNlc0NvbnRlbnQiOlsiY2xhc3MgVGVzdCB7XG5cbn0iXX0=

test/fixtures/bin/6to5/dir --out-dir --source-maps-inline/out-files/lib/foo.js

@@ -3,4 +3,4 @@
 arr.map(function (x) {
   return x * MULTIPLIER;
 });
-//# sourceMappingURL=data:application/json;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbInNyYy9mb28uanMiXSwibmFtZXMiOltdLCJtYXBwaW5ncyI6Ijs7QUFBQSxHQUFHLENBQUMsR0FBRyxDQUFDLFVBQUEsQ0FBQztTQUFJLENBQUMsR0FBRyxVQUFVO0NBQUEsQ0FBQyxDQUFDIiwiZmlsZSI6InNyYy9mb28uanMiLCJzb3VyY2VzQ29udGVudCI6WyJhcnIubWFwKHggPT4geCAqIE1VTFRJUExJRVIpOyJdfQ==
+//# sourceMappingURL=data:application/json;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbIi4uL3NyYy9mb28uanMiXSwibmFtZXMiOltdLCJtYXBwaW5ncyI6Ijs7QUFBQSxHQUFHLENBQUMsR0FBRyxDQUFDLFVBQUEsQ0FBQztTQUFJLENBQUMsR0FBRyxVQUFVO0NBQUEsQ0FBQyxDQUFDIiwiZmlsZSI6InNyYy9mb28uanMiLCJzb3VyY2VzQ29udGVudCI6WyJhcnIubWFwKHggPT4geCAqIE1VTFRJUExJRVIpOyJdfQ==

test/fixtures/bin/6to5/dir --out-dir --source-maps/out-files/lib/bar/bar.js.map

@@ -1 +1 @@
-{"version":3,"sources":["src/bar/bar.js"],"names":[],"mappings":";;;;IAAM,IAAI,YAAJ,IAAI;wBAAJ,IAAI","file":"src/bar/bar.js","sourcesContent":["class Test {\n\n}"]}
+{"version":3,"sources":["../../src/bar/bar.js"],"names":[],"mappings":";;;;IAAM,IAAI,YAAJ,IAAI;wBAAJ,IAAI","file":"src/bar/bar.js","sourcesContent":["class Test {\n\n}"]}

test/fixtures/bin/6to5/dir --out-dir --source-maps/out-files/lib/foo.js.map

@@ -1 +1 @@
-{"version":3,"sources":["src/foo.js"],"names":[],"mappings":";;AAAA,GAAG,CAAC,GAAG,CAAC,UAAA,CAAC;SAAI,CAAC,GAAG,UAAU;CAAA,CAAC,CAAC","file":"src/foo.js","sourcesContent":["arr.map(x => x * MULTIPLIER);"]}
+{"version":3,"sources":["../src/foo.js"],"names":[],"mappings":";;AAAA,GAAG,CAAC,GAAG,CAAC,UAAA,CAAC;SAAI,CAAC,GAAG,UAAU;CAAA,CAAC,CAAC","file":"src/foo.js","sourcesContent":["arr.map(x => x * MULTIPLIER);"]}

test/fixtures/transformation/.es6-tail-call/call-apply/actual.js

@@ -1,7 +0,0 @@
-(function f(n) {
-  if (n <= 0) {
-    console.log(this, arguments);
-    return "foo";
-  }
-  return Math.random() > 0.5 ? f.call(this, n - 1) : f.apply(this, [n - 1]);
-})(1e6) === "foo";

test/fixtures/transformation/.es6-tail-call/call-apply/expected.js

@@ -1,9 +0,0 @@
-"use strict";
-
-(function f(n) {
-  if (n <= 0) {
-    console.log(this, arguments);
-    return "foo";
-  }
-  return Math.random() > 0.5 ? to5Runtime.tailCall(f.call, [this, n - 1], f) : to5Runtime.tailCall(f.apply, [this, [n - 1]], f);
-})(1000000) === "foo";

test/fixtures/transformation/.es6-tail-call/cross-function/actual.js

@@ -1,7 +0,0 @@
-function f(n) {
-  return n <= 0 ? "foo" : g(n - 1);
-}
-
-function g(n) {
-  return n <= 0 ? "goo" : f(n - 1);
-}

test/fixtures/transformation/.es6-tail-call/cross-function/expected.js

@@ -1,9 +0,0 @@
-"use strict";
-
-function f(n) {
-  return n <= 0 ? "foo" : to5Runtime.tailCall(g, [n - 1]);
-}
-
-function g(n) {
-  return n <= 0 ? "goo" : to5Runtime.tailCall(f, [n - 1]);
-}

test/fixtures/transformation/.es6-tail-call/expressions/actual.js

@@ -1,3 +0,0 @@
-(function f(n) {
-  return n <= 0 ? "foo" : (doSmth(), getTrueValue() && (getFalseValue() || f(n - 1)));
-})(1e6, true) === "foo";

test/fixtures/transformation/.es6-tail-call/expressions/expected.js

@@ -1,5 +0,0 @@
-"use strict";
-
-(function f(n) {
-  return n <= 0 ? "foo" : (doSmth(), getTrueValue() && (getFalseValue() || to5Runtime.tailCall(f, [n - 1])));
-})(1000000, true) === "foo";

test/fixtures/transformation/.es6-tail-call/options.json

@@ -1,4 +0,0 @@
-{
-  "runtime": true,
-  "blacklist": []
-}

test/fixtures/transformation/.es6-tail-call/recursion/actual.js

@@ -1,8 +0,0 @@
-(function f(n = getDefaultValue(), /* should be undefined after first pass */ m) {
-  if (n <= 0) {
-    return "foo";
-  }
-  // Should be clean (undefined) on each pass
-  var local;
-  return f(n - 1);
-})(1e6, true) === "foo";

test/fixtures/transformation/.es6-tail-call/recursion/expected.js

@@ -1,11 +0,0 @@
-"use strict";
-
-(function f(_x, /* should be undefined after first pass */m) {
-  var n = arguments[0] === undefined ? getDefaultValue() : arguments[0];
-  if (n <= 0) {
-    return "foo";
-  }
-  // Should be clean (undefined) on each pass
-  var local;
-  return to5Runtime.tailCall(f, [n - 1]);
-})(1000000, true) === "foo";

test/fixtures/transformation/.es6-tail-call/side-effect/actual.js

@@ -1,7 +0,0 @@
-function f() {
-  return getObj().method();
-}
-
-function g() {
-  return getFalseValue() || getValue();
-}

test/fixtures/transformation/.es6-tail-call/side-effect/expected.js

@@ -1,10 +0,0 @@
-"use strict";
-
-function f() {
-  var _temp;
-  return to5Runtime.tailCall((_temp = getObj()).method, [], _temp);
-}
-
-function g() {
-  return getFalseValue() || to5Runtime.tailCall(getValue);
-}

test/fixtures/transformation/.es6-tail-call/try-catch/actual.js

@@ -1,39 +0,0 @@
-(function f(n) {
-  if (n <= 0) {
-    return "foo";
-  }
-  try {
-    return f(n - 1);
-  } catch (e) {}
-})(1e6) === "foo";
-
-(function f(n) {
-  if (n <= 0) {
-    return "foo";
-  }
-  try {
-    throw new Error();
-  } catch (e) {
-    return f(n - 1);
-  }
-})(1e6) === "foo";
-
-(function f(n) {
-  if (n <= 0) {
-    return "foo";
-  }
-  try {
-    throw new Error();
-  } catch (e) {
-    return f(n - 1);
-  } finally {}
-})(1e6) === "foo";
-
-(function f(n) {
-  if (n <= 0) {
-    return "foo";
-  }
-  try {} finally {
-    return f(n - 1);
-  }
-})(1e6) === "foo";

test/fixtures/transformation/.es6-tail-call/try-catch/expected.js

@@ -1,41 +0,0 @@
-"use strict";
-
-(function f(n) {
-  if (n <= 0) {
-    return "foo";
-  }
-  try {
-    return f(n - 1);
-  } catch (e) {}
-})(1000000) === "foo";
-
-(function f(n) {
-  if (n <= 0) {
-    return "foo";
-  }
-  try {
-    throw new Error();
-  } catch (e) {
-    return to5Runtime.tailCall(f, [n - 1]);
-  }
-})(1000000) === "foo";
-
-(function f(n) {
-  if (n <= 0) {
-    return "foo";
-  }
-  try {
-    throw new Error();
-  } catch (e) {
-    return f(n - 1);
-  } finally {}
-})(1000000) === "foo";
-
-(function f(n) {
-  if (n <= 0) {
-    return "foo";
-  }
-  try {} finally {
-    return to5Runtime.tailCall(f, [n - 1]);
-  }
-})(1000000) === "foo";

test/fixtures/transformation/errors/constants/options.json

@@ -1,3 +1,3 @@
 {
-  "throws": "Line 2: MULTIPLIER is read-only"
+  "throws": "Line 2: \"MULTIPLIER\" is read-only"
 }

test/fixtures/transformation/es6-block-scoping-exec/closure-wrap-collision.js

@@ -0,0 +1,9 @@
+for (let i = 1; i < 3; i += 1) {
+  (function () {
+    i;
+  })();
+}
+
+assert.throws(function () {
+  i;
+}, ReferenceError);

test/fixtures/transformation/es6-classes-playground-property-initializers/instance/exec.js

@@ -0,0 +1,7 @@
+class MyClass {
+  myProp = { someValue: 42 };
+}
+
+var myClass = new MyClass;
+assert.ok(myClass.myProp !== MyClass.prototype.myProp);
+assert.equal(myClass.myProp.someValue, 42);