v4.5.2

Test full `make build` on Travis

.babelrc

@@ -1,5 +1,6 @@
 {
   "experimental": true,
   "playground": true,
-  "loose": true
+  "loose": true,
+  "blacklist": ["es6.tailCall"]
 }

.gitignore

@@ -13,3 +13,4 @@ dist
 .package.json
 packages/babel-runtime/*.js
 packages/babel-runtime/regenerator/*.js
+lib

.jscsrc

@@ -1,58 +0,0 @@
-{
-  "excludeFiles": ["lib/babel/transformation/templates"],
-  "disallowSpacesInNamedFunctionExpression": {
-    "beforeOpeningRoundBrace": true
-  },
-  "requireSpacesInAnonymousFunctionExpression": {
-    "beforeOpeningRoundBrace": true
-  },
-  "requireSpacesInAnonymousFunctionExpression": {
-    "beforeOpeningRoundBrace": true
-  },
-  "disallowSpacesInFunctionDeclaration": {
-    "beforeOpeningRoundBrace": true
-  },
-  "disallowSpacesInsideArrayBrackets": true,
-  "disallowSpacesInsideParentheses": true,
-  "disallowSpaceAfterObjectKeys": true,
-  "disallowSpaceAfterPrefixUnaryOperators": true,
-  "disallowSpaceBeforePostfixUnaryOperators": true,
-  "disallowSpaceBeforeBinaryOperators": [
-    ","
-  ],
-  "disallowMixedSpacesAndTabs": true,
-  "disallowTrailingWhitespace": true,
-  "disallowYodaConditions": true,
-  "disallowKeywords": [ "with" ],
-  "disallowMultipleLineBreaks": true,
-  "requireSpaceBeforeBlockStatements": true,
-  "requireParenthesesAroundIIFE": true,
-  "requireSpacesInConditionalExpression": true,
-  "requireBlocksOnNewline": 1,
-  "requireCommaBeforeLineBreak": true,
-  "requireSpaceBeforeBinaryOperators": true,
-  "requireSpaceAfterBinaryOperators": true,
-  "requireLineFeedAtFileEnd": true,
-  "requireCapitalizedConstructors": true,
-  "requireSpacesInForStatement": true,
-  "requireCurlyBraces": [
-    "do"
-  ],
-  "requireSpaceAfterKeywords": [
-    "if",
-    "else",
-    "for",
-    "while",
-    "do",
-    "switch",
-    "case",
-    "return",
-    "try",
-    "catch",
-    "typeof",
-    "function"
-  ],
-  "validateLineBreaks": "LF",
-  "validateQuoteMarks": "\"",
-  "validateIndentation": 2
-}

.jshintignore

@@ -1 +0,0 @@
-lib/babel/transformation/templates

.jshintrc

@@ -1,27 +0,0 @@
-{
-  "esnext": true,
-  "indent": 2,
-  "freeze": true,
-  "validthis": true,
-  "camelcase": true,
-  "unused": true,
-  "eqnull": true,
-  "newcap": true,
-  "supernew": true,
-  "noyield": true,
-  "evil": true,
-  "node": true,
-  "boss": true,
-  "expr": true,
-  "undef": true,
-  "maxparams": 5,
-  "maxdepth": 4,
-
-  "globals": {
-    "window": true,
-    "suite": true,
-    "set": true,
-    "before": true,
-    "bench": true
-  }
-}

.npmignore

@@ -13,3 +13,4 @@ CHANGELOG.md
 coverage
 vendor
 packages
+src

CHANGELOG.md

@@ -13,6 +13,48 @@ _Note: Gaps between patch versions are faulty/broken releases._
 
 See [CHANGELOG - 6to5](CHANGELOG-6to5.md) for the pre-4.0.0 version changelog.
 
+## 4.5.2
+
+ * **New Feature**
+  * `returnUsedHelpers` option and add whitelist to `buildHelpers`.
+ * **Bug Fix**
+  * Fix function arity on self referencing inferred named functions.
+ * **Internal**
+  * Bump `acorn-babel`.
+  * Start converting source to ES6...
+
+## 4.5.1
+
+**Babel now compiles itself!**
+
+![holy shit](http://gifsec.com/wp-content/uploads/GIF/2014/03/OMG-GIF_2.gif)
+
+## 4.5.0
+
+ * **New Feature**
+  * Add `.babelrc` support.
+ * **Bug Fix**
+  * Move use strict directives to the module formatter bodies.
+ * **Internal**
+  * Make default `bin/babel` behaviour to ignore non-compilable files and add a `--copy-files` flag to revert to the old behaviour.
+
+## 4.4.6
+
+ * **Bug Fix**
+  * Fix extending a class expression with no methods/only constructor. Thanks [@neVERberleRfellerER](https://github.com/neVERberleRfellerER)!
+  * Allow `MemberExpression` as a valid `left` of `ForOfStatement`.
+ * **Polish**
+  * Throw an error when people try and transpile code with the `@jsx React.DOM` pragma as it conflicts with the custom jsx constructo method detection.
+  * Crawl all comments for `@jsx` pragma.
+ * **Internal**
+  * Upgrade `chalk`.
+  * Upgrade `core-js`.
+
+## 4.4.5
+
+ * **Internal**
+  * Remove function self reference optimisation.
+
 ## 4.4.4
 
  * **Bug Fix**

CONTRIBUTING.md

@@ -10,6 +10,49 @@ pollutes the git tree.
 
 ## Developing
 
+#### Setup
+
+```sh
+$ git clone https://github.com/babel/babel
+$ cd babel
+$ make bootstrap
+```
+
+Then you need to run:
+
+```sh
+$ make watch-core
+```
+
+This will compile babel and then sit in the background and on file modification
+recompile the necessary files.
+
+#### Running tests
+
+You can run tests via:
+
+```sh
+$ make test
+```
+
+This will usually take around two minutes as it's compiling the entire
+[test262](https://github.com/tc39/test262) test suite and validating it's AST.
+This is mostly overkill and you can limit the tests to a select few by directly
+running them with `mocha`:
+
+```sh
+$ mocha test/transformation.js
+```
+
+#### Linting
+
+Please follow the correct code style, this ensures that the code is consistent
+and increases maintainability.
+
+```sh
+$ make lint
+```
+
 #### Workflow
 
 * Fork the repository
@@ -18,8 +61,7 @@ pollutes the git tree.
 * 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
 
@@ -43,11 +85,3 @@ pollutes the git tree.
  * **Declaration**
    * No unused variables
    * No pollution of global variables and prototypes
-
-## Testing
-
-    $ make test
-
-## Linting
-
-    $ make lint

Makefile

@@ -4,21 +4,21 @@ UGLIFY_CMD = node_modules/uglify-js/bin/uglifyjs
 #UGLIFY_CMD = node_modules/uglify-js/bin/uglifyjs --mangle sort
 JSHINT_CMD = node_modules/jshint/bin/jshint
 MOCHA_CMD = node_modules/mocha/bin/_mocha
-JSCS_CMD = node_modules/jscs/bin/jscs
 BABEL_CMD = node_modules/babel/bin/babel
 
 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 build-core watch-core
+.PHONY: clean test test-cov test-clean test-travis test-simple test-all test-browser publish build bootstrap publish-core publish-runtime build-core watch-core
 
 build-core:
-	#node $(BABEL_CMD) src --out-dir lib
+	node $(BABEL_CMD) src --out-dir lib --copy-files
 
 watch-core:
-	#node $(BABEL_CMD) src --out-dir lib --watch
+	node $(BABEL_CMD) src --out-dir lib --watch --copy-files
 
 build:
 	mkdir -p dist
+	make build-core
 
 	node tools/cache-templates
 
@@ -36,14 +36,10 @@ build:
 clean:
 	rm -rf coverage templates.json test/tmp dist
 
-lint:
-	$(JSHINT_CMD) --reporter node_modules/jshint-stylish/stylish.js lib bin
-	$(JSCS_CMD) lib bin
-
 test-clean:
 	rm -rf test/tmp
 
-test: lint
+test:
 	$(MOCHA_CMD)
 	make test-clean
 
@@ -61,7 +57,7 @@ test-cov:
 	export SIMPLE_BABEL_TESTS=1; \
 	node $(ISTANBUL_CMD) $(MOCHA_CMD) --
 
-test-travis: build-core bootstrap
+test-travis: bootstrap build
 	node $(ISTANBUL_CMD) $(MOCHA_CMD) --
 	if test -n "$$CODECLIMATE_REPO_TOKEN"; then codeclimate < coverage/lcov.info; fi
 

README.md

@@ -9,9 +9,7 @@
 </p>
 
 <p align="center">
-  For more information view the <a href="https://babeljs.io/">documentation</a>. For questions
-  and support please visit the <a href="https://gitter.im/babel/babel">gitter room</a> before
-  creating an issue.
+  For questions and support please visit the <a href="https://gitter.im/babel/babel">gitter room</a> before creating an issue.
 </p>
 
 <p align="center">

bin/babel/dir.js

@@ -43,7 +43,7 @@ module.exports = function (commander, filenames, opts) {
         var src = path.join(dirname, filename);
         if (util.canCompile(filename)) {
           write(src, filename);
-        } else {
+        } else if (commander.copyFiles) {
           outputFileSync(path.join(commander.outDir, filename), fs.readFileSync(src));
         }
       });
@@ -64,7 +64,7 @@ module.exports = function (commander, filenames, opts) {
       _.each(["add", "change"], function (type) {
         watcher.on(type, function (filename) {
           var relative = path.relative(dirname, filename) || filename;
-          write(filename, relative);
+          if (util.canCompile(filename)) write(filename, relative);
         });
       });
     });

bin/babel/index.js

@@ -28,6 +28,7 @@ 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, --auxiliary-comment [comment]", "Comment text to prepend to all auxiliary code");
+commander.option("-D, --copy-files", "When compiling a directory copy over non-compilable files");
 
 commander.on("--help", function () {
   var outKeys = function (title, obj) {

bin/babel/util.js

@@ -1,10 +1,11 @@
-var readdir = require("fs-readdir-recursive");
-var index   = require("./index");
-var babel   = require("../../lib/babel/api/node");
-var util    = require("../../lib/babel/util");
-var path    = require("path");
-var fs      = require("fs");
-var _       = require("lodash");
+var resolveRc = require("../../lib/babel/api/register/resolve-rc");
+var readdir   = require("fs-readdir-recursive");
+var index     = require("./index");
+var babel     = require("../../lib/babel/api/node");
+var util      = require("../../lib/babel/util");
+var path      = require("path");
+var fs        = require("fs");
+var _         = require("lodash");
 
 exports.readdirFilter = function (filename) {
   return readdir(filename).filter(function (filename) {
@@ -23,6 +24,7 @@ exports.addSourceMappingUrl = function (code, loc) {
 exports.transform = function (filename, code, opts) {
   opts = _.defaults(opts || {}, index.opts);
   opts.filename = filename;
+  resolveRc(filename, opts);
 
   var result;
   try {

doc/index.md

@@ -1 +0,0 @@
-See [babel.github.io/docs](https://github.com/babel/babel.github.io/tree/master/docs).

lib/babel/transformation/templates/.babelrc

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

lib/babel/transformation/transformers/es6/block-scoping.js

@@ -1,561 +0,0 @@
-"use strict";
-
-var traverse = require("../../../traversal");
-var object   = require("../../../helpers/object");
-var util     = require("../../../util");
-var t        = require("../../../types");
-var values   = require("lodash/object/values");
-var extend   = require("lodash/object/extend");
-
-exports.check = function (node) {
-  return t.isVariableDeclaration(node) && (node.kind === "let" || node.kind === "const");
-};
-
-var isLet = function (node, parent) {
-  if (!t.isVariableDeclaration(node)) return false;
-  if (node._let) return true;
-  if (node.kind !== "let") return false;
-
-  // https://github.com/babel/babel/issues/255
-  if (isLetInitable(node, parent)) {
-    for (var i = 0; i < node.declarations.length; i++) {
-      var declar = node.declarations[i];
-      declar.init = declar.init || t.identifier("undefined");
-    }
-  }
-
-  node._let = true;
-  node.kind = "var";
-  return true;
-};
-
-var isLetInitable = function (node, parent) {
-  return !t.isFor(parent) || !t.isFor(parent, { left: node });
-};
-
-var isVar = function (node, parent) {
-  return t.isVariableDeclaration(node, { kind: "var" }) && !isLet(node, parent);
-};
-
-var standardizeLets = function (declars) {
-  for (var i = 0; i < declars.length; i++) {
-    delete declars[i]._let;
-  }
-};
-
-exports.VariableDeclaration = function (node, parent, scope, file) {
-  if (!isLet(node, parent)) return;
-
-  if (isLetInitable(node) && file.transformers["es6.blockScopingTDZ"].canRun()) {
-    var nodes = [node];
-
-    for (var i = 0; i < node.declarations.length; i++) {
-      var decl = node.declarations[i];
-      if (decl.init) {
-        var assign = t.assignmentExpression("=", decl.id, decl.init);
-        assign._ignoreBlockScopingTDZ = true;
-        nodes.push(t.expressionStatement(assign));
-      }
-      decl.init = file.addHelper("temporal-undefined");
-    }
-
-    node._blockHoist = 2;
-
-    return nodes;
-  }
-};
-
-exports.Loop = function (node, parent, scope, file) {
-  var init = node.left || node.init;
-  if (isLet(init, node)) {
-    t.ensureBlock(node);
-    node.body._letDeclarators = [init];
-  }
-  var blockScoping = new BlockScoping(node, node.body, parent, scope, file);
-  blockScoping.run();
-};
-
-exports.Program =
-exports.BlockStatement = function (block, parent, scope, file) {
-  if (!t.isLoop(parent)) {
-    var blockScoping = new BlockScoping(false, block, parent, scope, file);
-    blockScoping.run();
-  }
-};
-
-/**
- * Description
- *
- * @param {Boolean|Node} loopParent
- * @param {Node} block
- * @param {Node} parent
- * @param {Scope} scope
- * @param {File} file
- */
-
-function BlockScoping(loopParent, block, parent, scope, file) {
-  this.loopParent = loopParent;
-  this.parent     = parent;
-  this.scope      = scope;
-  this.block      = block;
-  this.file       = file;
-
-  this.outsideLetReferences = object();
-  this.hasLetReferences     = false;
-  this.letReferences        = block._letReferences = object();
-  this.body                 = [];
-}
-
-/**
- * Start the ball rolling.
- */
-
-BlockScoping.prototype.run = function () {
-  var block = this.block;
-  if (block._letDone) return;
-  block._letDone = true;
-
-  var needsClosure = this.getLetReferences();
-
-  // this is a block within a `Function/Program` so we can safely leave it be
-  if (t.isFunction(this.parent) || t.isProgram(this.block)) return;
-
-  // we can skip everything
-  if (!this.hasLetReferences) return;
-
-  if (needsClosure) {
-    this.wrapClosure();
-  } else {
-    this.remap();
-  }
-};
-
-function replace(node, parent, scope, remaps) {
-  if (!t.isReferencedIdentifier(node, parent)) return;
-
-  var remap = remaps[node.name];
-  if (!remap) return;
-
-  var ownBinding = scope.getBindingIdentifier(node.name);
-  if (ownBinding === remap.binding) {
-    node.name = remap.uid;
-  } else {
-    // scope already has it's own binding that doesn't
-    // match the one we have a stored replacement for
-    if (this) this.skip();
-  }
-}
-
-var replaceVisitor = {
-  enter: replace
-};
-
-function traverseReplace(node, parent, scope, remaps) {
-  replace(node, parent, scope, remaps);
-  scope.traverse(node, replaceVisitor, remaps);
-}
-
-/**
- * Description
- */
-
-BlockScoping.prototype.remap = function () {
-  var hasRemaps = false;
-  var letRefs   = this.letReferences;
-  var scope     = this.scope;
-
-  // alright, so since we aren't wrapping this block in a closure
-  // we have to check if any of our let variables collide with
-  // those in upper scopes and then if they do, generate a uid
-  // for them and replace all references with it
-  var remaps = object();
-
-  for (var key in letRefs) {
-    // just an Identifier node we collected in `getLetReferences`
-    // this is the defining identifier of a declaration
-    var ref = letRefs[key];
-
-    if (scope.parentHasBinding(key) || scope.hasGlobal(key)) {
-      var uid = scope.generateUidIdentifier(ref.name).name;
-      ref.name = uid;
-
-      hasRemaps = true;
-      remaps[key] = remaps[uid] = {
-        binding: ref,
-        uid: uid
-      };
-    }
-  }
-
-  if (!hasRemaps) return;
-
-  //
-
-  var loopParent = this.loopParent;
-  if (loopParent) {
-    traverseReplace(loopParent.right, loopParent, scope, remaps);
-    traverseReplace(loopParent.test, loopParent, scope, remaps);
-    traverseReplace(loopParent.update, loopParent, scope, remaps);
-  }
-
-  scope.traverse(this.block, replaceVisitor, remaps);
-};
-
-/**
- * Description
- */
-
-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();
-
-  // hoist var references to retain scope
-  this.hoistVarDeclarations();
-
-  // turn outsideLetReferences into an array
-  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));
-  fn._aliasFunction = true;
-
-  // replace the current block body with the one we're going to build
-  block.body = this.body;
-
-  // build a call and a unique id that we can assign the return value to
-  var call = t.callExpression(fn, params);
-  var ret  = this.scope.generateUidIdentifier("ret");
-
-  // handle generators
-  var hasYield = traverse.hasType(fn.body, this.scope, "YieldExpression", t.FUNCTION_TYPES);
-  if (hasYield) {
-    fn.generator = true;
-    call = t.yieldExpression(call, true);
-  }
-
-  // handlers async functions
-  var hasAsync = traverse.hasType(fn.body, this.scope, "AwaitExpression", t.FUNCTION_TYPES);
-  if (hasAsync) {
-    fn.async = true;
-    call = t.awaitExpression(call, true);
-  }
-
-  this.build(ret, call);
-};
-
-var letReferenceFunctionVisitor = {
-  enter: function (node, parent, scope, state) {
-    // not a direct reference
-    if (!t.isReferencedIdentifier(node, parent)) return;
-
-    // this scope has a variable with the same name so it couldn't belong
-    // to our let scope
-    if (scope.hasOwnBinding(node.name)) return;
-
-    // not a part of our scope
-    if (!state.letReferences[node.name]) return;
-
-    state.closurify = true;
-  }
-};
-
-var letReferenceBlockVisitor = {
-  enter: function (node, parent, scope, state) {
-    if (t.isFunction(node)) {
-      scope.traverse(node, letReferenceFunctionVisitor, state);
-      return this.skip();
-    }
-  }
-};
-
-/**
- * Description
- */
-
-BlockScoping.prototype.getLetReferences = function () {
-  var block = this.block;
-
-  var declarators = block._letDeclarators || [];
-  var declar;
-
-  //
-  for (var i = 0; i < declarators.length; i++) {
-    declar = declarators[i];
-    extend(this.outsideLetReferences, t.getBindingIdentifiers(declar));
-  }
-
-  //
-  if (block.body) {
-    for (i = 0; i < block.body.length; i++) {
-      declar = block.body[i];
-      if (isLet(declar, block)) {
-        declarators = declarators.concat(declar.declarations);
-      }
-    }
-  }
-
-  //
-  for (i = 0; i < declarators.length; i++) {
-    declar = declarators[i];
-    var keys = t.getBindingIdentifiers(declar);
-    extend(this.letReferences, keys);
-    this.hasLetReferences = true;
-  }
-
-  // no let references so we can just quit
-  if (!this.hasLetReferences) return;
-
-  // set let references to plain var references
-  standardizeLets(declarators);
-
-  var state = {
-    letReferences: this.letReferences,
-    closurify:     false
-  };
-
-  // traverse through this block, stopping on functions and checking if they
-  // contain any local let references
-  this.scope.traverse(this.block, letReferenceBlockVisitor, state);
-
-  return state.closurify;
-};
-
-var loopNodeTo = function (node) {
-  if (t.isBreakStatement(node)) {
-    return "break";
-  } else if (t.isContinueStatement(node)) {
-    return "continue";
-  }
-};
-
-var loopVisitor = {
-  enter: function (node, parent, scope, state) {
-    var replace;
-
-    if (t.isLoop(node)) {
-      state.ignoreLabeless = true;
-      scope.traverse(node, loopVisitor, state);
-      state.ignoreLabeless = false;
-    }
-
-    if (t.isFunction(node) || t.isLoop(node)) {
-      return this.skip();
-    }
-
-    var loopText = loopNodeTo(node);
-
-    if (loopText) {
-      if (node.label) {
-        // we shouldn't be transforming this because it exists somewhere inside
-        if (state.innerLabels.indexOf(node.label.name) >= 0) {
-          return;
-        }
-
-        loopText = loopText + "|" + node.label.name;
-      } else {
-        // we shouldn't be transforming these statements because
-        // they don't refer to the actual loop we're scopifying
-        if (state.ignoreLabeless) return;
-
-        // break statements mean something different in this context
-        if (t.isBreakStatement(node) && t.isSwitchCase(parent)) return;
-      }
-
-      state.hasBreakContinue = true;
-      state.map[loopText] = node;
-      replace = t.literal(loopText);
-    }
-
-    if (t.isReturnStatement(node)) {
-      state.hasReturn = true;
-      replace = t.objectExpression([
-        t.property("init", t.identifier("v"), node.argument || t.identifier("undefined"))
-      ]);
-    }
-
-    if (replace) {
-      replace = t.returnStatement(replace);
-      return t.inherits(replace, node);
-    }
-  }
-};
-
-var loopLabelVisitor = {
-  enter: function (node, parent, scope, state) {
-    if (t.isLabeledStatement(node)) {
-      state.innerLabels.push(node.label.name);
-    }
-  }
-};
-
-/**
- * If we're inside of a loop then traverse it and check if it has one of
- * the following node types `ReturnStatement`, `BreakStatement`,
- * `ContinueStatement` and replace it with a return value that we can track
- * later on.
- *
- * @returns {Object}
- */
-
-BlockScoping.prototype.checkLoop = function () {
-  var state = {
-    hasBreakContinue: false,
-    ignoreLabeless:   false,
-    innerLabels:      [],
-    hasReturn:        false,
-    isLoop:           !!this.loopParent,
-    map:              {}
-  };
-
-  this.scope.traverse(this.block, loopLabelVisitor, state);
-  this.scope.traverse(this.block, loopVisitor, state);
-
-  return state;
-};
-
-var hoistVarDeclarationsVisitor = {
-  enter: function (node, parent, scope, self) {
-    if (t.isForStatement(node)) {
-      if (isVar(node.init, node)) {
-        node.init = t.sequenceExpression(self.pushDeclar(node.init));
-      }
-    } else if (t.isFor(node)) {
-      if (isVar(node.left, node)) {
-        node.left = node.left.declarations[0].id;
-      }
-    } else if (isVar(node, parent)) {
-      return self.pushDeclar(node).map(t.expressionStatement);
-    } else if (t.isFunction(node)) {
-      return this.skip();
-    }
-  }
-};
-
-/**
- * Hoist all var declarations in this block to before it so they retain scope
- * once we wrap everything in a closure.
- */
-
-BlockScoping.prototype.hoistVarDeclarations = function () {
-  traverse(this.block, hoistVarDeclarationsVisitor, this.scope, this);
-};
-
-/**
- * Turn a `VariableDeclaration` into an array of `AssignmentExpressions` with
- * their declarations hoisted to before the closure wrapper.
- *
- * @param {Node} node VariableDeclaration
- * @returns {Array}
- */
-
-BlockScoping.prototype.pushDeclar = function (node) {
-  this.body.push(t.variableDeclaration(node.kind, node.declarations.map(function (declar) {
-    return t.variableDeclarator(declar.id);
-  })));
-
-  var replace = [];
-
-  for (var i = 0; i < node.declarations.length; i++) {
-    var declar = node.declarations[i];
-    if (!declar.init) continue;
-
-    var expr = t.assignmentExpression("=", declar.id, declar.init);
-    replace.push(t.inherits(expr, declar));
-  }
-
-  return replace;
-};
-
-/**
- * Push the closure to the body.
- *
- * @param {Node} ret Identifier
- * @param {Node} call CallExpression
- */
-
-BlockScoping.prototype.build = function (ret, call) {
-  var has = this.has;
-  if (has.hasReturn || has.hasBreakContinue) {
-    this.buildHas(ret, call);
-  } else {
-    this.body.push(t.expressionStatement(call));
-  }
-};
-
-/**
- * Description
- *
- * @param {Node} ret Identifier
- * @param {Node} call CallExpression
- */
-
-BlockScoping.prototype.buildHas = function (ret, call) {
-  var body = this.body;
-
-  body.push(t.variableDeclaration("var", [
-    t.variableDeclarator(ret, call)
-  ]));
-
-  var loopParent = this.loopParent;
-  var retCheck;
-  var has = this.has;
-  var cases = [];
-
-  if (has.hasReturn) {
-    // typeof ret === "object"
-    retCheck = util.template("let-scoping-return", {
-      RETURN: ret
-    });
-  }
-
-  if (has.hasBreakContinue) {
-    if (!loopParent) {
-      throw new Error("Has no loop parent but we're trying to reassign breaks " +
-                      "and continues, something is going wrong here.");
-    }
-
-    for (var key in has.map) {
-      cases.push(t.switchCase(t.literal(key), [has.map[key]]));
-    }
-
-    if (has.hasReturn) {
-      cases.push(t.switchCase(null, [retCheck]));
-    }
-
-    if (cases.length === 1) {
-      var single = cases[0];
-      body.push(this.file.attachAuxiliaryComment(t.ifStatement(
-        t.binaryExpression("===", ret, single.test),
-        single.consequent[0]
-      )));
-    } else {
-      body.push(this.file.attachAuxiliaryComment(t.switchStatement(ret, cases)));
-    }
-  } else {
-    if (has.hasReturn) {
-      body.push(this.file.attachAuxiliaryComment(retCheck));
-    }
-  }
-};

lib/babel/transformation/transformers/es6/classes.js

@@ -1,296 +0,0 @@
-"use strict";
-
-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 ClassTransformer(node, file, scope, true).run();
-};
-
-exports.ClassExpression = function (node, parent, scope, file) {
-  if (!node.id) {
-    if (t.isProperty(parent) && parent.value === node && !parent.computed && t.isIdentifier(parent.key)) {
-      // var o = { foo: class {} };
-      node.id = parent.key;
-    }
-
-    if (t.isVariableDeclarator(parent) && t.isIdentifier(parent.id)) {
-      // var foo = class {};
-      node.id = parent.id;
-    }
-  }
-
-  return new ClassTransformer(node, file, scope, false).run();
-};
-
-/**
- * Description
- *
- * @param {Node} node
- * @param {File} file
- * @param {Scope} scope
- * @param {Boolean} isStatement
- */
-
-function ClassTransformer(node, file, scope, isStatement) {
-  this.isStatement = isStatement;
-  this.scope       = scope;
-  this.node        = node;
-  this.file        = file;
-
-  this.hasInstanceMutators = false;
-  this.hasStaticMutators   = false;
-
-  this.instanceMutatorMap = {};
-  this.staticMutatorMap   = {};
-  this.hasConstructor     = false;
-  this.className          = node.id || scope.generateUidIdentifier("class");
-  this.superName          = node.superClass || t.identifier("Function");
-  this.hasSuper           = !!node.superClass;
-  this.isLoose            = file.isLoose("es6.classes");
-}
-
-/**
- * Description
- *
- * @returns {Array}
- */
-
-ClassTransformer.prototype.run = function () {
-  var superName = this.superName;
-  var className = this.className;
-  var file      = this.file;
-
-  //
-
-  var body = this.body = [];
-
-  var constructorBody = t.blockStatement([
-    t.expressionStatement(t.callExpression(file.addHelper("class-call-check"), [
-      t.thisExpression(),
-      className
-    ]))
-  ]);
-  var constructor;
-
-  if (this.node.id) {
-    constructor = t.functionDeclaration(className, [], constructorBody);
-    body.push(constructor);
-  } else {
-    constructor = t.functionExpression(null, [], constructorBody);
-    body.push(t.variableDeclaration("var", [
-      t.variableDeclarator(className, constructor)
-    ]));
-  }
-  this.constructor = constructor;
-
-  var closureParams = [];
-  var closureArgs = [];
-
-  //
-
-  if (this.hasSuper) {
-    closureArgs.push(superName);
-
-    if (!t.isIdentifier(superName)) {
-      superName = this.scope.generateUidBasedOnNode(superName, this.file);
-    }
-
-    closureParams.push(superName);
-
-    this.superName = superName;
-    body.push(t.expressionStatement(t.callExpression(file.addHelper("inherits"), [className, superName])));
-  }
-
-  this.buildBody();
-
-  t.inheritsComments(body[0], this.node);
-
-  var init;
-
-  if (body.length === 1) {
-    // only a constructor so no need for a closure container
-    init = t.toExpression(constructor);
-  } else {
-    body.push(t.returnStatement(className));
-    init = t.callExpression(
-      t.functionExpression(null, closureParams, t.blockStatement(body)),
-      closureArgs
-    );
-  }
-
-  if (this.isStatement) {
-    return t.variableDeclaration("let", [
-      t.variableDeclarator(className, init)
-    ]);
-  } else {
-    return init;
-  }
-};
-
-/**
- * Description
- */
-
-ClassTransformer.prototype.buildBody = function () {
-  var constructor = this.constructor;
-  var className   = this.className;
-  var superName   = this.superName;
-  var classBody   = this.node.body.body;
-  var body        = this.body;
-
-  for (var i = 0; i < classBody.length; i++) {
-    var node = classBody[i];
-    if (t.isMethodDefinition(node)) {
-      var replaceSupers = new ReplaceSupers({
-        methodNode: node,
-        className:  this.className,
-        superName:  this.superName,
-        isStatic:   node.static,
-        isLoose:    this.isLoose,
-        scope:      this.scope,
-        file:       this.file
-      }, true);
-      replaceSupers.replace();
-
-      if ((!node.computed && t.isIdentifier(node.key, { name: "constructor" })) || t.isLiteral(node.key, { value: "constructor" })) {
-        this.pushConstructor(node);
-      } else {
-        this.pushMethod(node);
-      }
-    } else if (t.isPrivateDeclaration(node)) {
-      this.closure = true;
-      body.unshift(node);
-    } else if (t.isClassProperty(node)) {
-      this.pushProperty(node);
-    }
-  }
-
-  // we have no constructor, we have a super, and the super doesn't appear to be falsy
-  if (!this.hasConstructor && this.hasSuper && !t.isFalsyExpression(superName)) {
-    var helperName = "class-super-constructor-call";
-    if (this.isLoose) helperName += "-loose";
-    constructor.body.body.push(util.template(helperName, {
-      CLASS_NAME: className,
-      SUPER_NAME: this.superName
-    }, true));
-  }
-
-  var instanceProps;
-  var staticProps;
-
-  if (this.hasInstanceMutators) {
-    instanceProps = defineMap.build(this.instanceMutatorMap);
-  }
-
-  if (this.hasStaticMutators) {
-    staticProps = defineMap.build(this.staticMutatorMap);
-  }
-
-  if (instanceProps || staticProps) {
-    staticProps = staticProps || t.literal(null);
-
-    var args = [className, staticProps];
-    if (instanceProps) args.push(instanceProps);
-
-    body.push(t.expressionStatement(
-      t.callExpression(this.file.addHelper("prototype-properties"), args)
-    ));
-  }
-};
-
-/**
- * Push a method to its respective mutatorMap.
- *
- * @param {Node} node MethodDefinition
- */
-
-ClassTransformer.prototype.pushMethod = function (node) {
-  var methodName = node.key;
-
-  var kind = node.kind;
-
-  if (kind === "") {
-    nameMethod.property(node, this.file, this.scope);
-
-    if (this.isLoose) {
-      // use assignments instead of define properties for loose classes
-
-      var className = this.className;
-      if (!node.static) className = t.memberExpression(className, t.identifier("prototype"));
-      methodName = t.memberExpression(className, methodName, node.computed);
-
-      var expr = t.expressionStatement(t.assignmentExpression("=", methodName, node.value));
-      t.inheritsComments(expr, node);
-      this.body.push(expr);
-      return;
-    }
-
-    kind = "value";
-  }
-
-  var mutatorMap = this.instanceMutatorMap;
-  if (node.static) {
-    this.hasStaticMutators = true;
-    mutatorMap = this.staticMutatorMap;
-  } else {
-    this.hasInstanceMutators = true;
-  }
-
-  defineMap.push(mutatorMap, methodName, kind, node.computed, 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
- */
-
-ClassTransformer.prototype.pushConstructor = function (method) {
-  if (method.kind) {
-    throw this.file.errorWithNode(method, messages.get("classesIllegalConstructorKind"));
-  }
-
-  var construct = this.constructor;
-  var fn        = method.value;
-
-  this.hasConstructor = true;
-
-  t.inherits(construct, fn);
-  t.inheritsComments(construct, method);
-
-  construct._ignoreUserWhitespace = true;
-  construct.params                = fn.params;
-  construct.body.body             = construct.body.body.concat(fn.body.body);
-};

lib/babel/transformation/transformers/es6/destructuring.js

@@ -1,485 +0,0 @@
-"use strict";
-
-var messages = require("../../../messages");
-var t        = require("../../../types");
-
-exports.check = t.isPattern;
-
-function DestructuringTransformer(opts) {
-  this.blockHoist = opts.blockHoist;
-  this.operator   = opts.operator;
-  this.nodes      = opts.nodes;
-  this.scope      = opts.scope;
-  this.file       = opts.file;
-  this.kind       = opts.kind;
-}
-
-DestructuringTransformer.prototype.buildVariableAssignment = function (id, init) {
-  var op = this.operator;
-  if (t.isMemberExpression(id)) op = "=";
-
-  var node;
-
-  if (op) {
-    node = t.expressionStatement(t.assignmentExpression(op, id, init));
-  } else {
-    node = t.variableDeclaration(this.kind, [
-      t.variableDeclarator(id, init)
-    ]);
-  }
-
-  node._blockHoist = this.blockHoist;
-
-  return node;
-};
-
-DestructuringTransformer.prototype.buildVariableDeclaration = function (id, init) {
-  var declar = t.variableDeclaration("var", [
-    t.variableDeclarator(id, init)
-  ]);
-  declar._blockHoist = this.blockHoist;
-  return declar;
-};
-
-DestructuringTransformer.prototype.push = function (id, init) {
-  if (t.isObjectPattern(id)) {
-    this.pushObjectPattern(id, init);
-  } else if (t.isArrayPattern(id)) {
-    this.pushArrayPattern(id, init);
-  } else if (t.isAssignmentPattern(id)) {
-    this.pushAssignmentPattern(id, init);
-  } else {
-    this.nodes.push(this.buildVariableAssignment(id, init));
-  }
-};
-
-DestructuringTransformer.prototype.get = function () {
-
-};
-
-DestructuringTransformer.prototype.pushAssignmentPattern = function (pattern, valueRef) {
-  // we need to assign the current value of the assignment to avoid evaluating
-  // it more than once
-
-  var tempValueRef = this.scope.generateUidBasedOnNode(valueRef);
-
-  var declar = t.variableDeclaration("var", [
-    t.variableDeclarator(tempValueRef, valueRef)
-  ]);
-  declar._blockHoist = this.blockHoist;
-  this.nodes.push(declar);
-
-  //
-
-  this.nodes.push(this.buildVariableAssignment(
-    pattern.left,
-    t.conditionalExpression(
-      t.binaryExpression("===", tempValueRef, t.identifier("undefined")),
-      pattern.right,
-      tempValueRef
-    )
-  ));
-};
-
-DestructuringTransformer.prototype.pushObjectSpread = function (pattern, objRef, spreadProp, spreadPropIndex) {
-  // get all the keys that appear in this object before the current spread
-
-  var keys = [];
-
-  for (var i = 0; i < pattern.properties.length; i++) {
-    var prop = pattern.properties[i];
-
-    // we've exceeded the index of the spread property to all properties to the
-    // right need to be ignored
-    if (i >= spreadPropIndex) break;
-
-    // ignore other spread properties
-    if (t.isSpreadProperty(prop)) continue;
-
-    var key = prop.key;
-    if (t.isIdentifier(key)) key = t.literal(prop.key.name);
-    keys.push(key);
-  }
-
-  keys = t.arrayExpression(keys);
-
-  //
-
-  var value = t.callExpression(this.file.addHelper("object-without-properties"), [objRef, keys]);
-  this.nodes.push(this.buildVariableAssignment(spreadProp.argument, value));
-};
-
-DestructuringTransformer.prototype.pushObjectProperty = function (prop, propRef) {
-  if (t.isLiteral(prop.key)) prop.computed = true;
-
-  var pattern = prop.value;
-  var objRef  = t.memberExpression(propRef, prop.key, prop.computed);
-
-  if (t.isPattern(pattern)) {
-    this.push(pattern, objRef);
-  } else {
-    this.nodes.push(this.buildVariableAssignment(pattern, objRef));
-  }
-};
-
-DestructuringTransformer.prototype.pushObjectPattern = function (pattern, objRef) {
-  // https://github.com/babel/babel/issues/681
-
-  if (!pattern.properties.length) {
-    this.nodes.push(t.expressionStatement(
-      t.callExpression(this.file.addHelper("object-destructuring-empty"), [objRef])
-    ));
-  }
-
-  // if we have more than one properties in this pattern and the objectRef is a
-  // member expression then we need to assign it to a temporary variable so it's
-  // only evaluated once
-
-  if (pattern.properties.length > 1 && t.isMemberExpression(objRef)) {
-    var temp = this.scope.generateUidBasedOnNode(objRef, this.file);
-    this.nodes.push(this.buildVariableDeclaration(temp, objRef));
-    objRef = temp;
-  }
-
-  //
-
-  for (var i = 0; i < pattern.properties.length; i++) {
-    var prop = pattern.properties[i];
-    if (t.isSpreadProperty(prop)) {
-      this.pushObjectSpread(pattern, objRef, prop, i);
-    } else {
-      this.pushObjectProperty(prop, objRef);
-    }
-  }
-};
-
-var hasRest = function (pattern) {
-  for (var i = 0; i < pattern.elements.length; i++) {
-    if (t.isRestElement(pattern.elements[i])) {
-      return true;
-    }
-  }
-  return false;
-};
-
-DestructuringTransformer.prototype.canUnpackArrayPattern = function (pattern, arr) {
-  // not an array so there's no way we can deal with this
-  if (!t.isArrayExpression(arr)) return false;
-
-  // pattern has less elements than the array and doesn't have a rest so some
-  // elements wont be evaluated
-  if (pattern.elements.length > arr.elements.length) return;
-  if (pattern.elements.length < arr.elements.length && !hasRest(pattern)) return false;
-
-  // deopt on holes
-  for (var i = 0; i < pattern.elements.length; i++) {
-    if (!pattern.elements[i]) return false;
-  }
-
-  return true;
-};
-
-DestructuringTransformer.prototype.pushUnpackedArrayPattern = function (pattern, arr) {
-  for (var i = 0; i < pattern.elements.length; i++) {
-    var elem = pattern.elements[i];
-    if (t.isRestElement(elem)) {
-      this.push(elem.argument, t.arrayExpression(arr.elements.slice(i)));
-    } else {
-      this.push(elem, arr.elements[i]);
-    }
-  }
-};
-
-DestructuringTransformer.prototype.pushArrayPattern = function (pattern, arrayRef) {
-  if (!pattern.elements) return;
-
-  // optimise basic array destructuring of an array expression
-  //
-  // we can't do this to a pattern of unequal size to it's right hand
-  // array expression as then there will be values that wont be evaluated
-  //
-  // eg: var [a, b] = [1, 2];
-
-  if (this.canUnpackArrayPattern(pattern, arrayRef)) {
-    return this.pushUnpackedArrayPattern(pattern, arrayRef);
-  }
-
-  // if we have a rest then we need all the elements so don't tell
-  // `scope.toArray` to only get a certain amount
-
-  var count = !hasRest(pattern) && pattern.elements.length;
-
-  // so we need to ensure that the `arrayRef` is an array, `scope.toArray` will
-  // return a locally bound identifier if it's been inferred to be an array,
-  // otherwise it'll be a call to a helper that will ensure it's one
-
-  var toArray = this.scope.toArray(arrayRef, count);
-
-  if (t.isIdentifier(toArray)) {
-    // we've been given an identifier so it must have been inferred to be an
-    // array
-    arrayRef = toArray;
-  } else {
-    arrayRef = this.scope.generateUidBasedOnNode(arrayRef);
-    this.nodes.push(this.buildVariableDeclaration(arrayRef, toArray));
-    this.scope.assignTypeGeneric(arrayRef.name, "Array");
-  }
-
-  //
-
-  for (var i = 0; i < pattern.elements.length; i++) {
-    var elem = pattern.elements[i];
-
-    // hole
-    if (!elem) continue;
-
-    var elemRef;
-
-    if (t.isRestElement(elem)) {
-      elemRef = this.scope.toArray(arrayRef);
-
-      if (i > 0) {
-        elemRef = t.callExpression(t.memberExpression(elemRef, t.identifier("slice")), [t.literal(i)]);
-      }
-
-      // set the element to the rest element argument since we've dealt with it
-      // being a rest already
-      elem = elem.argument;
-    } else {
-      elemRef = t.memberExpression(arrayRef, t.literal(i), true);
-    }
-
-    this.push(elem, elemRef);
-  }
-};
-
-DestructuringTransformer.prototype.init = function (pattern, ref) {
-  // trying to destructure a value that we can't evaluate more than once so we
-  // need to save it to a variable
-
-  if (!t.isArrayExpression(ref) && !t.isMemberExpression(ref) && !t.isIdentifier(ref)) {
-    var key = this.scope.generateUidBasedOnNode(ref);
-    this.nodes.push(this.buildVariableDeclaration(key, ref));
-    ref = key;
-  }
-
-  //
-
-  this.push(pattern, ref);
-};
-
-exports.ForInStatement =
-exports.ForOfStatement = function (node, parent, scope, file) {
-  var left = node.left;
-
-  if (t.isPattern(left)) {
-    // for ({ length: k } in { abc: 3 });
-
-    var temp = scope.generateUidIdentifier("ref");
-
-    node.left = t.variableDeclaration("var", [
-      t.variableDeclarator(temp)
-    ]);
-
-    t.ensureBlock(node);
-
-    node.body.body.unshift(t.variableDeclaration("var", [
-      t.variableDeclarator(left, temp)
-    ]));
-
-    return;
-  }
-
-  if (!t.isVariableDeclaration(left)) return;
-
-  var pattern = left.declarations[0].id;
-  if (!t.isPattern(pattern)) return;
-
-  var key = scope.generateUidIdentifier("ref");
-  node.left = t.variableDeclaration(left.kind, [
-    t.variableDeclarator(key, null)
-  ]);
-
-  var nodes = [];
-
-  var destructuring = new DestructuringTransformer({
-    kind: left.kind,
-    file: file,
-    scope: scope,
-    nodes: nodes
-  });
-
-  destructuring.init(pattern, key);
-
-  t.ensureBlock(node);
-
-  var block = node.body;
-  block.body = nodes.concat(block.body);
-};
-
-exports.Function = function (node, parent, scope, file) {
-  var nodes = [];
-
-  var hasDestructuringTransformer = false;
-
-  node.params = node.params.map(function (pattern, i) {
-    if (!t.isPattern(pattern)) return pattern;
-
-    hasDestructuringTransformer = true;
-    var ref = scope.generateUidIdentifier("ref");
-
-    var destructuring = new DestructuringTransformer({
-      blockHoist: node.params.length - i,
-      nodes:      nodes,
-      scope:      scope,
-      file:       file,
-      kind:       "var",
-    });
-    destructuring.init(pattern, ref);
-
-    return ref;
-  });
-
-  if (!hasDestructuringTransformer) return;
-
-  t.ensureBlock(node);
-
-  var block = node.body;
-  block.body = nodes.concat(block.body);
-};
-
-exports.CatchClause = function (node, parent, scope, file) {
-  var pattern = node.param;
-  if (!t.isPattern(pattern)) return;
-
-  var ref = scope.generateUidIdentifier("ref");
-  node.param = ref;
-
-  var nodes = [];
-
-  var destructuring = new DestructuringTransformer({
-    kind: "let",
-    file: file,
-    scope: scope,
-    nodes: nodes
-  });
-  destructuring.init(pattern, ref);
-
-  node.body.body = nodes.concat(node.body.body);
-
-  return node;
-};
-
-exports.ExpressionStatement = function (node, parent, scope, file) {
-  var expr = node.expression;
-  if (expr.type !== "AssignmentExpression") return;
-  if (!t.isPattern(expr.left)) return;
-  if (file.isConsequenceExpressionStatement(node)) return;
-
-  var nodes = [];
-
-  var ref = scope.generateUidIdentifier("ref");
-  nodes.push(t.variableDeclaration("var", [
-    t.variableDeclarator(ref, expr.right)
-  ]));
-
-  var destructuring = new DestructuringTransformer({
-    operator: expr.operator,
-    file: file,
-    scope: scope,
-    nodes: nodes
-  });
-  destructuring.init(expr.left, ref);
-
-  return nodes;
-};
-
-exports.AssignmentExpression = function (node, parent, scope, file) {
-  if (!t.isPattern(node.left)) return;
-
-  var ref = scope.generateUidIdentifier("temp");
-  scope.push({
-    key: ref.name,
-    id: ref
-  });
-
-  var nodes = [];
-  nodes.push(t.assignmentExpression("=", ref, node.right));
-
-  var destructuring = new DestructuringTransformer({
-    operator: node.operator,
-    file: file,
-    scope: scope,
-    nodes: nodes
-  });
-  destructuring.init(node.left, ref);
-
-  nodes.push(ref);
-
-  return t.toSequenceExpression(nodes, scope);
-};
-
-var variableDeclarationHasPattern = function (node) {
-  for (var i = 0; i < node.declarations.length; i++) {
-    if (t.isPattern(node.declarations[i].id)) {
-      return true;
-    }
-  }
-  return false;
-};
-
-exports.VariableDeclaration = function (node, parent, scope, file) {
-  if (t.isForInStatement(parent) || t.isForOfStatement(parent)) return;
-  if (!variableDeclarationHasPattern(node)) return;
-
-  var nodes = [];
-  var declar;
-
-  for (var i = 0; i < node.declarations.length; i++) {
-    declar = node.declarations[i];
-
-    var patternId = declar.init;
-    var pattern   = declar.id;
-
-    var destructuring = new DestructuringTransformer({
-      nodes: nodes,
-      scope: scope,
-      kind:  node.kind,
-      file:  file
-    });
-
-    if (t.isPattern(pattern) && patternId) {
-      destructuring.init(pattern, patternId);
-
-      if (+i !== node.declarations.length - 1) {
-        // we aren't the last declarator so let's just make the
-        // last transformed node inherit from us
-        t.inherits(nodes[nodes.length - 1], declar);
-      }
-    } else {
-      nodes.push(t.inherits(destructuring.buildVariableAssignment(declar.id, declar.init), declar));
-    }
-  }
-
-  if (!t.isProgram(parent) && !t.isBlockStatement(parent)) {
-    // https://github.com/babel/babel/issues/113
-    // for (let [x] = [0]; false;) {}
-
-    declar = null;
-
-    for (i = 0; i < nodes.length; i++) {
-      node = nodes[i];
-      declar = declar || t.variableDeclaration(node.kind, []);
-
-      if (!t.isVariableDeclaration(node) && declar.kind !== node.kind) {
-        throw file.errorWithNode(node, messages.get("invalidParentForThisNode"));
-      }
-
-      declar.declarations = declar.declarations.concat(node.declarations);
-    }
-
-    return declar;
-  }
-
-  return nodes;
-};

lib/babel/transformation/transformers/es6/tail-call.js

@@ -1,379 +0,0 @@
-"use strict";
-
-var reduceRight = require("lodash/collection/reduceRight");
-var messages    = require("../../../messages");
-var flatten     = require("lodash/array/flatten");
-var util        = require("../../../util");
-var map         = require("lodash/collection/map");
-var t           = require("../../../types");
-
-function returnBlock(expr) {
-  return t.blockStatement([t.returnStatement(expr)]);
-}
-
-function TailCallTransformer(node, scope, file) {
-  this.hasTailRecursion = false;
-  this.needsArguments   = false;
-  this.setsArguments    = false;
-  this.needsThis        = false;
-  this.ownerId          = node.id;
-  this.vars             = [];
-
-  this.scope = scope;
-  this.file  = file;
-  this.node  = node;
-}
-
-TailCallTransformer.prototype.getArgumentsId = function () {
-  return this.argumentsId = this.argumentsId || this.scope.generateUidIdentifier("arguments");
-};
-
-TailCallTransformer.prototype.getThisId = function () {
-  return this.thisId = this.thisId || this.scope.generateUidIdentifier("this");
-};
-
-TailCallTransformer.prototype.getLeftId = function () {
-  return this.leftId = this.leftId || this.scope.generateUidIdentifier("left");
-};
-
-TailCallTransformer.prototype.getFunctionId = function () {
-  return this.functionId = this.functionId || this.scope.generateUidIdentifier("function");
-};
-
-TailCallTransformer.prototype.getAgainId = function () {
-  return this.againId = this.againId || this.scope.generateUidIdentifier("again");
-};
-
-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));
-  }
-
-  body.unshift(t.expressionStatement(
-    t.assignmentExpression("=", this.getAgainId(), t.literal(false)))
-  );
-
-  node.body = util.template("tail-call-body", {
-    AGAIN_ID:      this.getAgainId(),
-    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.expressionStatement(
-    t.assignmentExpression("=", this.getAgainId(), t.literal(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.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();
-      return state.subTransform(node.argument);
-    } else if (t.isTryStatement(parent)) {
-      if (node === parent.block) {
-        this.skip();
-      } else if (parent.finalizer && node !== parent.finalizer) {
-        this.skip();
-      }
-    } else if (t.isFunction(node)) {
-      this.skip();
-    } else if (t.isVariableDeclaration(node)) {
-      this.skip();
-      state.vars.push(node);
-    }
-  }
-};
-
-// hoists up function declarations, replaces `this` and `arguments` and marks
-// them as needed
-var secondPass = {
-  enter: function (node, parent, scope, state) {
-    if (t.isThisExpression(node)) {
-      state.needsThis = true;
-      return state.getThisId();
-    } else if (t.isReferencedIdentifier(node, parent, { name: "arguments" })) {
-      state.needsArguments = true;
-      return state.getArgumentsId();
-    } else if (t.isFunction(node)) {
-      this.skip();
-      if (t.isFunctionDeclaration(node)) {
-        node = t.variableDeclaration("var", [
-          t.variableDeclarator(node.id, t.toExpression(node))
-        ]);
-        node._blockHoist = 2;
-        return node;
-      }
-    }
-  }
-};
-
-// optimizes recursion by removing `this` and `arguments` if they aren't used
-var thirdPass = {
-  enter: function (node, parent, scope, state) {
-    if (!t.isExpressionStatement(node)) return;
-
-    var expr = node.expression;
-    if (!t.isAssignmentExpression(expr)) return;
-
-    if (!state.needsThis && expr.left === state.getThisId()) {
-      this.remove();
-    } else if (!state.needsArguments && expr.left === state.getArgumentsId() && t.isArrayExpression(expr.right)) {
-      return map(expr.right.elements, function (elem) {
-        return t.expressionStatement(elem);
-      });
-    }
-  }
-};
-
-exports.Function = function (node, parent, scope, file) {
-  var tailCall = new TailCallTransformer(node, scope, file);
-  tailCall.run();
-};

lib/babel/transformation/transformers/internal/declarations.js

@@ -1,33 +0,0 @@
-"use strict";
-
-var t = require("../../../types");
-
-exports.secondPass = true;
-
-exports.BlockStatement =
-exports.Program = function (node, parent, scope, file) {
-  if (!node._declarations) return;
-
-  var kinds = {};
-  var kind;
-
-  for (var i in node._declarations) {
-    var declar = node._declarations[i];
-
-    kind = declar.kind || "var";
-    var declarNode = t.variableDeclarator(declar.id, declar.init);
-
-    if (declar.init) {
-      node.body.unshift(file.attachAuxiliaryComment(t.variableDeclaration(kind, [declarNode])));
-    } else {
-      kinds[kind] = kinds[kind] || [];
-      kinds[kind].push(declarNode);
-    }
-  }
-
-  for (kind in kinds) {
-    node.body.unshift(file.attachAuxiliaryComment(t.variableDeclaration(kind, kinds[kind])));
-  }
-
-  node._declarations = null;
-};

package.json

@@ -1,7 +1,7 @@
 {
   "name": "babel",
   "description": "Turn ES6 code into readable vanilla ES5 with source maps",
-  "version": "4.4.4",
+  "version": "4.5.2",
   "author": "Sebastian McKenzie <sebmck@gmail.com>",
   "homepage": "https://babeljs.io/",
   "repository": "babel/babel",
@@ -36,12 +36,12 @@
     "test": "make test"
   },
   "dependencies": {
-    "acorn-babel": "0.11.1-34",
+    "acorn-babel": "0.11.1-35",
     "ast-types": "~0.6.1",
-    "chalk": "^0.5.1",
+    "chalk": "^1.0.0",
     "chokidar": "^0.12.6",
     "commander": "^2.6.0",
-    "core-js": "^0.5.4",
+    "core-js": "^0.6.1",
     "debug": "^2.1.1",
     "detect-indent": "^3.0.0",
     "estraverse": "^1.9.1",
@@ -56,7 +56,7 @@
     "output-file-sync": "^1.1.0",
     "path-is-absolute": "^1.0.0",
     "private": "^0.1.6",
-    "regenerator-babel": "0.8.10-2",
+    "regenerator-babel": "0.8.13-1",
     "regexpu": "^1.1.1",
     "repeating": "^1.1.2",
     "shebang-regex": "^1.0.0",
@@ -67,13 +67,11 @@
     "trim-right": "^1.0.0"
   },
   "devDependencies": {
+    "babel": "4.5.1",
     "browserify": "^8.1.3",
     "chai": "^2.0.0",
     "esvalid": "^1.1.0",
     "istanbul": "^0.3.5",
-    "jscs": "^1.11.3",
-    "jshint": "^2.6.0",
-    "jshint-stylish": "^1.0.0",
     "matcha": "^0.6.0",
     "mocha": "^2.1.0",
     "rimraf": "^2.2.8",

packages/babel-runtime/package.json

@@ -1,7 +1,7 @@
 {
   "name": "babel-runtime",
   "description": "babel selfContained runtime",
-  "version": "4.4.3",
+  "version": "4.5.1",
   "repository": "babel/babel",
   "author": "Sebastian McKenzie <sebmck@gmail.com>"
 }

src/babel/api/browser.js

@@ -1,5 +1,3 @@
-"use strict";
-
 var transform = module.exports = require("../transformation");
 
 transform.version = require("../../../package").version;
@@ -7,14 +5,14 @@ transform.version = require("../../../package").version;
 transform.transform = transform;
 
 transform.run = function (code, opts) {
-  opts = opts || {};
+  opts ||= {};
   opts.sourceMap = "inline";
   return new Function(transform(code, opts).code)();
 };
 
 transform.load = function (url, callback, opts, hold) {
-  opts = opts || {};
-  opts.filename = opts.filename || url;
+  opts ||= {};
+  opts.filename ||= url;
 
   var xhr = global.ActiveXObject ? new global.ActiveXObject("Microsoft.XMLHTTP") : new global.XMLHttpRequest();
   xhr.open("GET", url, true);

src/babel/api/node.js

@@ -1,5 +1,3 @@
-"use strict";
-
 var isFunction = require("lodash/lang/isFunction");
 var transform  = require("../transformation");
 var util       = require("../util");
@@ -52,7 +50,7 @@ exports.transformFile = function (filename, opts, callback) {
 };
 
 exports.transformFileSync = function (filename, opts) {
-  opts = opts || {};
+  opts ||= {};
   opts.filename = filename;
   return transform(fs.readFileSync(filename), opts);
 };

src/babel/api/register/browser.js

@@ -1,5 +1,3 @@
-"use strict";
-
 // required to safely use babel/register within a browserify codebase
 
 module.exports = function () {};

src/babel/api/register/cache.js

@@ -1,5 +1,3 @@
-"use strict";
-
 var path = require("path");
 var os   = require("os");
 var fs   = require("fs");

src/babel/api/register/node.js

@@ -1,9 +1,8 @@
-"use strict";
-
 require("../../polyfill");
 
 var sourceMapSupport = require("source-map-support");
 var registerCache    = require("./cache");
+var resolveRc        = require("./resolve-rc");
 var extend           = require("lodash/object/extend");
 var babel            = require("../node");
 var each             = require("lodash/collection/each");
@@ -11,7 +10,7 @@ var util             = require("../../util");
 var fs               = require("fs");
 
 sourceMapSupport.install({
-  retrieveSourceMap: function (source) {
+  retrieveSourceMap(source) {
     var map = maps && maps[source];
     if (map) {
       return {
@@ -44,7 +43,10 @@ var mtime = function (filename) {
 var compile = function (filename) {
   var result;
 
-  var cacheKey = filename + ":" + JSON.stringify(transformOpts);
+  var opts = extend({}, transformOpts);
+  resolveRc(filename, opts);
+
+  var cacheKey = filename + ":" + JSON.stringify(opts);
 
   if (cache) {
     var cached = cache[cacheKey];
@@ -54,10 +56,10 @@ var compile = function (filename) {
   }
 
   if (!result) {
-    result = babel.transformFileSync(filename, extend({
+    result = babel.transformFileSync(filename, extend(opts, {
       sourceMap: true,
       ast:       false
-    }, transformOpts));
+    }));
   }
 
   if (cache) {
@@ -134,7 +136,7 @@ hookExtensions(util.canCompile.EXTENSIONS);
 
 module.exports = function (opts) {
   // normalize options
-  opts = opts || {};
+  opts ||= {};
 
   if (opts.only != null) onlyRegex = util.regexify(opts.only);
   if (opts.ignore != null) ignoreRegex = util.regexify(opts.ignore);

src/babel/api/register/resolve-rc.js

@@ -0,0 +1,48 @@
+var merge = require("lodash/object/merge");
+var path  = require("path");
+var fs    = require("fs");
+
+var cache = {};
+
+function exists(filename) {
+  var cached = cache[filename];
+  if (cached != null) return cached;
+  return cache[filename] = fs.existsSync(filename);
+}
+
+module.exports = function (loc, opts) {
+  var rel = ".babelrc";
+  opts ||= {};
+
+  function find(start, rel) {
+    var file = path.join(start, rel);
+
+    if (exists(file)) {
+      var content = fs.readFileSync(file, "utf8");
+      var json;
+
+      try {
+        json = JSON.parse(content);
+      } catch (err) {
+        err.message = file + ": " + err.message;
+        throw err;
+      }
+
+      if (json.breakConfig) return;
+      merge(opts, json, function(a, b) {
+        if (Array.isArray(a)) {
+          return a.concat(b);
+        }
+      });
+    }
+
+    var up = path.dirname(start);
+    if (up !== start) { // root
+      find(up, rel);
+    }
+  }
+
+  find(loc, rel);
+
+  return opts;
+};

src/babel/build-external-helpers.js

@@ -1,11 +1,9 @@
-"use strict";
-
 var buildHelpers = require("./build-helpers");
 var generator    = require("./generation");
 var util         = require("./util");
 var t            = require("./types");
 
-module.exports = function () {
+module.exports = function (whitelist) {
   var namespace = t.identifier("babelHelpers");
 
   var body      = [];
@@ -19,7 +17,7 @@ module.exports = function () {
     )
   ]));
 
-  buildHelpers(body, namespace);
+  buildHelpers(body, namespace, whitelist);
 
   return generator(tree).code;
 };

src/babel/build-helpers.js

@@ -3,9 +3,11 @@ var util = require("./util");
 var each = require("lodash/collection/each");
 var t    = require("./types");
 
-module.exports = function (body, namespace) {
+module.exports = function (body, namespace, whitelist = []) {
   each(File.helpers, function (name) {
     var key = t.identifier(t.toIdentifier(name));
+    if (whitelist.length && whitelist.indexOf(key) >= 0) return;
+
     body.push(t.expressionStatement(
       t.assignmentExpression("=", t.memberExpression(namespace, key), util.template(name))
     ));

src/babel/detection/index.js

@@ -15,7 +15,7 @@ function detect(ast) {
   };
 
   traverse(ast, {
-    enter: function (node, parent) {
+    enter(node, parent) {
       if (SYNTAX_KEYS[node.type]) {
         detectedSyntax(SYNTAX_KEYS[node.type]);
       }

src/babel/generation/buffer.js

@@ -1,5 +1,3 @@
-"use strict";
-
 module.exports = Buffer;
 
 var repeating = require("repeating");
@@ -80,7 +78,7 @@ Buffer.prototype.newline = function (i, removeLast) {
     return;
   }
 
-  removeLast = removeLast || false;
+  removeLast ||= false;
 
   if (isNumber(i)) {
     i = Math.min(2, i);

src/babel/generation/generators/base.js

@@ -1,5 +1,3 @@
-"use strict";
-
 exports.File = function (node, print) {
   print(node.program);
 };

src/babel/generation/generators/classes.js

@@ -1,5 +1,3 @@
-"use strict";
-
 exports.ClassExpression =
 exports.ClassDeclaration = function (node, print) {
   this.push("class");

src/babel/generation/generators/comprehensions.js

@@ -1,5 +1,3 @@
-"use strict";
-
 exports.ComprehensionBlock = function (node, print) {
   this.keyword("for");
   this.push("(");

src/babel/generation/generators/expressions.js

@@ -1,5 +1,3 @@
-"use strict";
-
 var isInteger = require("is-integer");
 var isNumber  = require("lodash/lang/isNumber");
 var t         = require("../../types");

src/babel/generation/generators/flow.js

@@ -1,5 +1,3 @@
-"use strict";
-
 exports.AnyTypeAnnotation =
 exports.ArrayTypeAnnotation =
 exports.BooleanTypeAnnotation =

src/babel/generation/generators/jsx.js

@@ -1,5 +1,3 @@
-"use strict";
-
 var t    = require("../../types");
 var each = require("lodash/collection/each");
 
@@ -40,16 +38,14 @@ exports.JSXExpressionContainer = function (node, print) {
 };
 
 exports.JSXElement = function (node, print) {
-  var self = this;
-
   var open = node.openingElement;
   print(open);
   if (open.selfClosing) return;
 
   this.indent();
-  each(node.children, function (child) {
+  each(node.children, (child) => {
     if (t.isLiteral(child)) {
-      self.push(child.value);
+      this.push(child.value);
     } else {
       print(child);
     }

src/babel/generation/generators/methods.js

@@ -1,5 +1,3 @@
-"use strict";
-
 var t = require("../../types");
 
 exports._params = function (node, print) {

src/babel/generation/generators/modules.js

@@ -1,5 +1,3 @@
-"use strict";
-
 var t    = require("../../types");
 var each = require("lodash/collection/each");
 
@@ -58,8 +56,6 @@ exports.ExportDeclaration = function (node, print) {
 };
 
 exports.ImportDeclaration = function (node, print) {
-  var self = this;
-
   this.push("import ");
 
   if (node.isType) {
@@ -70,16 +66,16 @@ exports.ImportDeclaration = function (node, print) {
   if (specfiers && specfiers.length) {
     var foundImportSpecifier = false;
 
-    each(node.specifiers, function (spec, i) {
+    each(node.specifiers, (spec, i) => {
       if (+i > 0) {
-        self.push(", ");
+        this.push(", ");
       }
 
       var isDefault = t.isSpecifierDefault(spec);
 
       if (!isDefault && spec.type !== "ImportBatchSpecifier" && !foundImportSpecifier) {
         foundImportSpecifier = true;
-        self.push("{ ");
+        this.push("{ ");
       }
 
       print(spec);

src/babel/generation/generators/playground.js

@@ -1,5 +1,3 @@
-"use strict";
-
 var each = require("lodash/collection/each");
 
 each(["BindMemberExpression", "BindFunctionExpression"], function (type) {

src/babel/generation/generators/statements.js

@@ -1,5 +1,3 @@
-"use strict";
-
 var repeating = require("repeating");
 var t         = require("../../types");
 
@@ -151,7 +149,7 @@ exports.SwitchStatement = function (node, print) {
 
   print.sequence(node.cases, {
     indent: true,
-    addNewlines: function (leading, cas) {
+    addNewlines(leading, cas) {
       if (!leading && node.cases[node.cases.length - 1] === cas) return -1;
     }
   });

src/babel/generation/generators/template-literals.js

@@ -1,5 +1,3 @@
-"use strict";
-
 var each = require("lodash/collection/each");
 
 exports.TaggedTemplateExpression = function (node, print) {
@@ -15,16 +13,15 @@ exports.TemplateLiteral = function (node, print) {
   this.push("`");
 
   var quasis = node.quasis;
-  var self   = this;
   var len    = quasis.length;
 
-  each(quasis, function (quasi, i) {
+  each(quasis, (quasi, i) => {
     print(quasi);
 
     if (i + 1 < len) {
-      self.push("${ ");
+      this.push("${ ");
       print(node.expressions[i]);
-      self.push(" }");
+      this.push(" }");
     }
   });
 

src/babel/generation/generators/types.js

@@ -1,5 +1,3 @@
-"use strict";
-
 var each = require("lodash/collection/each");
 
 exports.Identifier = function (node) {
@@ -58,23 +56,22 @@ exports.Property = function (node, print) {
 exports.ArrayExpression =
 exports.ArrayPattern = function (node, print) {
   var elems = node.elements;
-  var self  = this;
   var len   = elems.length;
 
   this.push("[");
 
-  each(elems, function (elem, i) {
+  each(elems, (elem, i) => {
     if (!elem) {
       // If the array expression ends with a hole, that hole
       // will be ignored by the interpreter, but if it ends with
       // two (or more) holes, we need to write out two (or more)
       // commas so that the resulting code is interpreted with
       // both (all) of the holes.
-      self.push(",");
+      this.push(",");
     } else {
-      if (i > 0) self.push(" ");
+      if (i > 0) this.push(" ");
       print(elem);
-      if (i < len - 1) self.push(",");
+      if (i < len - 1) this.push(",");
     }
   });
 

src/babel/generation/index.js

@@ -1,5 +1,3 @@
-"use strict";
-
 module.exports = function (ast, opts, code) {
   var gen = new CodeGenerator(ast, opts, code);
   return gen.generate();
@@ -20,7 +18,7 @@ var n            = require("./node");
 var t            = require("../types");
 
 function CodeGenerator(ast, opts, code) {
-  opts = opts || {};
+  opts ||= {};
 
   this.comments = ast.comments || [];
   this.tokens   = ast.tokens || [];
@@ -105,34 +103,32 @@ CodeGenerator.prototype.generate = function () {
 };
 
 CodeGenerator.prototype.buildPrint = function (parent) {
-  var self = this;
-
-  var print = function (node, opts) {
-    return self.print(node, parent, opts);
+  var print = (node, opts) => {
+    return this.print(node, parent, opts);
   };
 
-  print.sequence = function (nodes, opts) {
-    opts = opts || {};
+  print.sequence = (nodes, opts) => {
+    opts ||= {};
     opts.statement = true;
-    return self.printJoin(print, nodes, opts);
+    return this.printJoin(print, nodes, opts);
   };
 
-  print.join = function (nodes, opts) {
-    return self.printJoin(print, nodes, opts);
+  print.join = (nodes, opts) => {
+    return this.printJoin(print, nodes, opts);
   };
 
   print.list = function (items, opts) {
-    opts = opts || {};
-    opts.separator = opts.separator || ", ";
+    opts ||= {};
+    opts.separator ||= ", ";
     print.join(items, opts);
   };
 
-  print.block = function (node) {
-    return self.printBlock(print, node);
+  print.block = (node) => {
+    return this.printBlock(print, node);
   };
 
-  print.indentOnComments = function (node) {
-    return self.printAndIndentOnComments(print, node);
+  print.indentOnComments = (node) => {
+    return this.printAndIndentOnComments(print, node);
   };
 
   return print;
@@ -150,11 +146,9 @@ CodeGenerator.prototype.print = function (node, parent, opts) {
     this.format.concise = true;
   }
 
-  var self = this;
+  opts ||= {};
 
-  opts = opts || {};
-
-  var newline = function (leading) {
+  var newline = (leading) => {
     if (!opts.statement && !n.isUserWhitespacable(node, parent)) {
       return;
     }
@@ -164,9 +158,9 @@ CodeGenerator.prototype.print = function (node, parent, opts) {
     if (node.start != null && !node._ignoreUserWhitespace) {
       // user node
       if (leading) {
-        lines = self.whitespace.getNewlinesBefore(node);
+        lines = this.whitespace.getNewlinesBefore(node);
       } else {
-        lines = self.whitespace.getNewlinesAfter(node);
+        lines = this.whitespace.getNewlinesAfter(node);
       }
     } else {
       // generated node
@@ -178,10 +172,10 @@ CodeGenerator.prototype.print = function (node, parent, opts) {
       if (needs(node, parent)) lines++;
 
       // generated nodes can't add starting file whitespace
-      if (!self.buffer.buf) lines = 0;
+      if (!this.buffer.buf) lines = 0;
     }
 
-    self.newline(lines);
+    this.newline(lines);
   };
 
   if (this[node.type]) {
@@ -222,30 +216,29 @@ CodeGenerator.prototype.print = function (node, parent, opts) {
 CodeGenerator.prototype.printJoin = function (print, nodes, opts) {
   if (!nodes || !nodes.length) return;
 
-  opts = opts || {};
+  opts ||= {};
 
-  var self = this;
-  var len  = nodes.length;
+  var len = nodes.length;
 
-  if (opts.indent) self.indent();
+  if (opts.indent) this.indent();
 
-  each(nodes, function (node, i) {
+  each(nodes, (node, i) => {
     print(node, {
       statement: opts.statement,
       addNewlines: opts.addNewlines,
-      after: function () {
+      after: () => {
         if (opts.iterator) {
           opts.iterator(node, i);
         }
 
         if (opts.separator && i < len - 1) {
-          self.push(opts.separator);
+          this.push(opts.separator);
         }
       }
     });
   });
 
-  if (opts.indent) self.dedent();
+  if (opts.indent) this.dedent();
 };
 
 CodeGenerator.prototype.printAndIndentOnComments = function (print, node) {
@@ -289,14 +282,13 @@ CodeGenerator.prototype.getComments = function (key, node, parent) {
 
   var comments = [];
   var nodes    = [node];
-  var self     = this;
 
   if (t.isExpressionStatement(node)) {
     nodes.push(node.argument);
   }
 
-  each(nodes, function (node) {
-    comments = comments.concat(self._getComments(key, node));
+  each(nodes, (node) => {
+    comments = comments.concat(this._getComments(key, node));
   });
 
   return comments;
@@ -312,13 +304,11 @@ CodeGenerator.prototype._printComments = function (comments) {
   if (!this.format.comments) return;
   if (!comments || !comments.length) return;
 
-  var self = this;
-
-  each(comments, function (comment) {
+  each(comments, (comment) => {
     var skip = false;
 
     // find the original comment in the ast and set it as displayed
-    each(self.ast.comments, function (origComment) {
+    each(this.ast.comments, function (origComment) {
       if (origComment.start === comment.start) {
         // comment has already been output
         if (origComment._displayed) skip = true;
@@ -331,38 +321,38 @@ CodeGenerator.prototype._printComments = function (comments) {
     if (skip) return;
 
     // whitespace before
-    self.newline(self.whitespace.getNewlinesBefore(comment));
+    this.newline(this.whitespace.getNewlinesBefore(comment));
 
-    var column = self.position.column;
-    var val    = self.generateComment(comment);
+    var column = this.position.column;
+    var val    = this.generateComment(comment);
 
-    if (column && !self.isLast(["\n", " ", "[", "{"])) {
-      self._push(" ");
+    if (column && !this.isLast(["\n", " ", "[", "{"])) {
+      this._push(" ");
       column++;
     }
 
     //
 
-    if (comment.type === "Block" && self.format.indent.adjustMultilineComment) {
+    if (comment.type === "Block" && this.format.indent.adjustMultilineComment) {
       var offset = comment.loc.start.column;
       if (offset) {
         var newlineRegex = new RegExp("\\n\\s{1," + offset + "}", "g");
         val = val.replace(newlineRegex, "\n");
       }
 
-      var indent = Math.max(self.indentSize(), column);
+      var indent = Math.max(this.indentSize(), column);
       val = val.replace(/\n/g, "\n" + repeating(" ", indent));
     }
 
     if (column === 0) {
-      val = self.getIndent() + val;
+      val = this.getIndent() + val;
     }
 
     //
 
-    self._push(val);
+    this._push(val);
 
     // whitespace after
-    self.newline(self.whitespace.getNewlinesAfter(comment));
+    this.newline(this.whitespace.getNewlinesAfter(comment));
   });
 };

src/babel/generation/node/index.js

@@ -1,5 +1,3 @@
-"use strict";
-
 module.exports = Node;
 
 var whitespace = require("./whitespace");

src/babel/generation/node/parentheses.js

@@ -1,5 +1,3 @@
-"use strict";
-
 var t    = require("../../types");
 var each = require("lodash/collection/each");
 

src/babel/generation/node/whitespace.js

@@ -1,12 +1,10 @@
-"use strict";
-
 var isBoolean = require("lodash/lang/isBoolean");
 var each      = require("lodash/collection/each");
 var map       = require("lodash/collection/map");
 var t         = require("../../types");
 
 var crawl = function (node, state) {
-  state = state || {};
+  state ||= {};
 
   if (t.isMemberExpression(node)) {
     crawl(node.object, state);
@@ -20,7 +18,7 @@ var crawl = function (node, state) {
   } else if (t.isFunction(node)) {
     state.hasFunction = true;
   } else if (t.isIdentifier(node)) {
-    state.hasHelper = state.hasHelper || isHelper(node.callee);
+    state.hasHelper ||= isHelper(node.callee);
   }
 
   return state;
@@ -46,7 +44,7 @@ var isType = function (node) {
 };
 
 exports.nodes = {
-  AssignmentExpression: function (node) {
+  AssignmentExpression(node) {
     var state = crawl(node.right);
     if ((state.hasCall && state.hasHelper) || state.hasFunction) {
       return {
@@ -56,13 +54,13 @@ exports.nodes = {
     }
   },
 
-  SwitchCase: function (node, parent) {
+  SwitchCase(node, parent) {
     return {
       before: node.consequent.length || parent.cases[0] === node
     };
   },
 
-  LogicalExpression: function (node) {
+  LogicalExpression(node) {
     if (t.isFunction(node.left) || t.isFunction(node.right)) {
       return {
         after: true
@@ -70,7 +68,7 @@ exports.nodes = {
     }
   },
 
-  Literal: function (node) {
+  Literal(node) {
     if (node.value === "use strict") {
       return {
         after: true
@@ -78,7 +76,7 @@ exports.nodes = {
     }
   },
 
-  CallExpression: function (node) {
+  CallExpression(node) {
     if (t.isFunction(node.callee) || isHelper(node)) {
       return {
         before: true,
@@ -87,7 +85,7 @@ exports.nodes = {
     }
   },
 
-  VariableDeclaration: function (node) {
+  VariableDeclaration(node) {
     for (var i = 0; i < node.declarations.length; i++) {
       var declar = node.declarations[i];
 
@@ -106,7 +104,7 @@ exports.nodes = {
     }
   },
 
-  IfStatement: function (node) {
+  IfStatement(node) {
     if (t.isBlockStatement(node.consequent)) {
       return {
         before: true,
@@ -126,15 +124,15 @@ exports.nodes.SpreadProperty = function (node, parent) {
 };
 
 exports.list = {
-  VariableDeclaration: function (node) {
+  VariableDeclaration(node) {
     return map(node.declarations, "init");
   },
 
-  ArrayExpression: function (node) {
+  ArrayExpression(node) {
     return node.elements;
   },
 
-  ObjectExpression: function (node) {
+  ObjectExpression(node) {
     return node.properties;
   }
 };

src/babel/generation/position.js

@@ -1,5 +1,3 @@
-"use strict";
-
 module.exports = Position;
 
 function Position() {

src/babel/generation/source-map.js

@@ -1,5 +1,3 @@
-"use strict";
-
 module.exports = SourceMap;
 
 var sourceMap = require("source-map");

src/babel/generation/whitespace.js

@@ -1,5 +1,3 @@
-"use strict";
-
 module.exports = Whitespace;
 
 var sortBy = require("lodash/collection/sortBy");

src/babel/helpers/code-frame.js

@@ -77,7 +77,7 @@ module.exports = function (lines, lineNumber, colNumber) {
     start: start + 1,
     before: "  ",
     after: " | ",
-    transform: function (params) {
+    transform(params) {
       if (params.number !== lineNumber) {
         return;
       }

src/babel/helpers/object.js

@@ -1,5 +1,3 @@
-"use strict";
-
 module.exports = function () {
   return Object.create(null);
 };

src/babel/helpers/to-fast-properties.js

@@ -1,5 +1,3 @@
-"use strict";
-
 /**
  * A trick from Bluebird to force V8 to use fast properties for an object.
  * Read more: http://stackoverflow.com/questions/24987896/

src/babel/patch.js

@@ -1,5 +1,3 @@
-"use strict";
-
 var extend = require("lodash/object/extend");
 var t      = require("./types");
 

src/babel/polyfill.js

@@ -1,5 +1,3 @@
-"use strict";
-
 if (global._babelPolyfill) {
   throw new Error("only one instance of babel/polyfill is allowed");
 }

src/babel/transformation/file.js

@@ -1,5 +1,3 @@
-"use strict";
-
 module.exports = File;
 
 var sourceMapToComment = require("source-map-to-comment");
@@ -24,12 +22,13 @@ function File(opts) {
   this.dynamicImported          = [];
   this.dynamicImports           = [];
 
-  this.dynamicData      = {};
-  this.data             = {};
+  this.usedHelpers = {};
+  this.dynamicData = {};
+  this.data        = {};
 
-  this.lastStatements   = [];
-  this.opts             = this.normalizeOptions(opts);
-  this.ast              = {};
+  this.lastStatements = [];
+  this.opts           = this.normalizeOptions(opts);
+  this.ast            = {};
 
   this.buildTransformers();
 }
@@ -87,6 +86,7 @@ File.validOptions = [
   "externalHelpers",
   "auxiliaryComment",
   "compact",
+  "returnUsedHelpers",
 
   "resolveModuleSource",
   "moduleId",
@@ -113,6 +113,7 @@ File.prototype.normalizeOptions = function (opts) {
   defaults(opts, {
     keepModuleIdExtensions: false,
     resolveModuleSource:    null,
+    returnUsedHelpers:      false,
     externalHelpers:        false,
     auxilaryComment:        "",
     experimental:           false,
@@ -288,7 +289,7 @@ File.prototype.get = function (key) {
 };
 
 File.prototype.addImport = function (source, name, noDefault) {
-  name = name || source;
+  name ||= source;
   var id = this.dynamicImportIds[name];
 
   if (!id) {
@@ -314,7 +315,7 @@ File.prototype.isConsequenceExpressionStatement = function (node) {
 File.prototype.attachAuxiliaryComment = function (node) {
   var comment = this.opts.auxiliaryComment;
   if (comment) {
-    node.leadingComments = node.leadingComments || [];
+    node.leadingComments ||= [];
     node.leadingComments.push({
       type: "Line",
       value: " " + comment
@@ -333,6 +334,8 @@ File.prototype.addHelper = function (name) {
   var declar = program._declarations && program._declarations[name];
   if (declar) return declar.id;
 
+  this.usedHelpers[name] = true;
+
   var runtime = this.get("helpersNamespace");
   if (runtime) {
     name = t.identifier(t.toIdentifier(name));
@@ -355,7 +358,7 @@ File.prototype.logDeopt = function () {
 };
 
 File.prototype.errorWithNode = function (node, msg, Error) {
-  Error = Error || SyntaxError;
+  Error ||= SyntaxError;
 
   var loc = node.loc.start;
   var err = new Error("Line " + loc.line + ": " + msg);
@@ -370,8 +373,6 @@ File.prototype.addCode = function (code) {
 };
 
 File.prototype.parse = function (code) {
-  var self = this;
-
   code = this.addCode(code);
 
   var opts = this.opts;
@@ -379,9 +380,9 @@ File.prototype.parse = function (code) {
   opts.allowImportExportEverywhere = this.isLoose("es6.modules");
   opts.strictMode = this.transformers.useStrict.canRun();
 
-  return parse(opts, code, function (tree) {
-    self.transform(tree);
-    return self.generate();
+  return parse(opts, code, (tree) => {
+    this.transform(tree);
+    return this.generate();
   });
 };
 
@@ -419,7 +420,7 @@ File.prototype.call = function (key) {
 };
 
 var checkTransformerVisitor = {
-  enter: function (node, parent, scope, state) {
+  enter(node, parent, scope, state) {
     checkNode(state.stack, node, scope);
   }
 };
@@ -433,7 +434,7 @@ var checkNode = function (stack, node, scope) {
 
 File.prototype.checkNode = function (node, scope) {
   var stack = this.transformerStack;
-  scope = scope || this.scope;
+  scope ||= this.scope;
 
   checkNode(stack, node, scope);
 
@@ -452,6 +453,10 @@ File.prototype.generate = function () {
     ast: null
   };
 
+  if (this.opts.returnUsedHelpers) {
+    result.usedHelpers = Object.keys(this.usedHelpers);
+  }
+
   if (opts.ast) result.ast = ast;
   if (!opts.code) return result;
 

src/babel/transformation/helpers/build-binary-assignment-operator-transformer.js

@@ -1,5 +1,3 @@
-"use strict";
-
 var explode = require("./explode-assignable-expression");
 var t       = require("../../types");
 

src/babel/transformation/helpers/build-comprehension.js

@@ -1,5 +1,3 @@
-"use strict";
-
 var t = require("../../types");
 
 module.exports = function build(node, buildBody) {

src/babel/transformation/helpers/build-conditional-assignment-operator-transformer.js

@@ -1,5 +1,3 @@
-"use strict";
-
 var explode = require("./explode-assignable-expression");
 var t       = require("../../types");
 

src/babel/transformation/helpers/build-react-transformer.js

@@ -1,5 +1,3 @@
-"use strict";
-
 // Based upon the excellent jsx-transpiler by Ingvar Stepanyan (RReverser)
 // https://github.com/RReverser/jsx-transpiler
 
@@ -33,7 +31,7 @@ module.exports = function (exports, opts) {
   };
 
   exports.JSXMemberExpression = {
-    exit: function (node) {
+    exit(node) {
       node.computed = t.isLiteral(node.property);
       node.type = "MemberExpression";
     }
@@ -44,18 +42,21 @@ module.exports = function (exports, opts) {
   };
 
   exports.JSXAttribute = {
-    exit: function (node) {
-      var value = node.value || t.literal(true);
-
+    enter(node) {
+      var value = node.value;
       if (t.isLiteral(value) && isString(value.value)) {
         value.value = value.value.replace(/\n\s+/g, " ");
       }
+    },
 
+    exit(node) {
+      var value = node.value || t.literal(true);
       return t.inherits(t.property("init", node.name, value), node);
     }
   };
+
   exports.JSXOpeningElement = {
-    exit: function (node, parent, scope, file) {
+    exit(node, parent, scope, file) {
       var tagExpr = node.name;
       var args = [];
 
@@ -143,7 +144,7 @@ module.exports = function (exports, opts) {
   };
 
   exports.JSXElement = {
-    exit: function (node) {
+    exit(node) {
       var callExpr = node.openingElement;
 
       for (var i = 0; i < node.children.length; i++) {

src/babel/transformation/helpers/explode-assignable-expression.js

@@ -1,5 +1,3 @@
-"use strict";
-
 var t = require("../../types");
 
 var getObjRef = function (node, nodes, file, scope) {

src/babel/transformation/helpers/get-function-arity.js

@@ -0,0 +1,9 @@
+var t = require("../../types");
+
+module.exports = function (node) {
+  var lastNonDefault = 0;
+  for (var i = 0; i < node.params.length; i++) {
+    if (!t.isAssignmentPattern(node.params[i])) lastNonDefault = i + 1;
+  }
+  return lastNonDefault;
+};

src/babel/transformation/helpers/name-method.js

@@ -1,10 +1,9 @@
-"use strict";
-
-var util = require("../../util");
-var t    = require("../../types");
+var getFunctionArity = require("./get-function-arity");
+var util             = require("../../util");
+var t                = require("../../types");
 
 var visitor = {
-  enter: function (node, parent, scope, state) {
+  enter(node, parent, scope, state) {
     // check if this node is a referenced identifier that matches the same as our
     // function id
     if (!t.isReferencedIdentifier(node, parent, { name: state.name })) return;
@@ -15,49 +14,29 @@ var visitor = {
     if (localDeclar !== state.outerDeclar) return;
 
     state.selfReference = true;
-    state.references.push(this);
-
-    if (t.isPattern(parent) || t.isAssignmentExpression(parent) || t.isUpdateExpression(parent)) {
-      state.selfAssignment = true;
-    }
+    this.stop();
   }
 };
 
-var wrapIncludesSelfReference = function (state, method, id, scope) {
-  var outerId = scope.generateUidIdentifier("getOuter");
-  var outerIdCall = t.callExpression(outerId, []);
-
-  for (var i = 0; i < state.references.length; i++) {
-    state.references[i].replaceNode(outerIdCall);
-  }
-
-  method.id = id;
-
-  return util.template("named-function", {
-    GET_OUTER_ID: outerId,
-    FUNCTION_ID:  id,
-    FUNCTION:     method
-  });
-};
-
-var wrapIncludesSelfAssignment = function (state, method, id, scope) {
-  var templateName = "property-method-assignment-wrapper";
-  if (method.generator) templateName += "-generator";
-  return util.template(templateName, {
-    FUNCTION: method,
-    FUNCTION_ID: id,
-    FUNCTION_KEY: scope.generateUidIdentifier(id.name),
-    WRAPPER_KEY: scope.generateUidIdentifier(id.name + "Wrapper")
-  });
-};
-
 var wrap = function (state, method, id, scope) {
   if (state.selfReference) {
-    if (state.selfAssignment) {
-      return wrapIncludesSelfAssignment(state, method, id, scope);
-    } else {
-      return wrapIncludesSelfReference(state, method, id, scope);
+    var templateName = "property-method-assignment-wrapper";
+    if (method.generator) templateName += "-generator";
+    var template = util.template(templateName, {
+      FUNCTION: method,
+      FUNCTION_ID: id,
+      FUNCTION_KEY: scope.generateUidIdentifier(id.name),
+      WRAPPER_KEY: scope.generateUidIdentifier(id.name + "Wrapper")
+    });
+
+    // shim in dummy params to retain function arity, if you try to read the
+    // source then you'll get the original since it's proxied so it's all good
+    var params = template.callee.body.body[0].declarations[0].init.params;
+    for (var i = 0, len = getFunctionArity(method); i < len; i++) {
+      params.push(scope.generateUidIdentifier("x"));
     }
+
+    return template;
   } else {
     method.id = id;
     return method;
@@ -76,7 +55,7 @@ var visit = function (node, name, scope) {
   // check to see if we have a local binding of the id we're setting inside of
   // the function, this is important as there are caveats associated
 
-  var bindingInfo = scope.getOwnBindingInfo(name);
+  var bindingInfo = null; // todo: proper scope not being passed in es6/classes // scope.getOwnBindingInfo(name);
 
   if (bindingInfo) {
     if (bindingInfo.kind === "param") {
@@ -92,7 +71,6 @@ var visit = function (node, name, scope) {
       // this isn't to the spec and they've invented this behaviour which is
       // **extremely** annoying so we avoid setting the name if it has a param
       // with the same id
-      state.selfAssignment = true;
       state.selfReference = true;
     } else {
       // otherwise it's defined somewhere in scope like:
@@ -129,7 +107,7 @@ exports.bare = function (node, parent, scope) {
 
   var id;
   if (t.isProperty(parent) && parent.kind === "init" && !parent.computed) {
-    // { foo: function () {} };
+    // { foo() {} };
     id = parent.key;
   } else if (t.isVariableDeclarator(parent)) {
     // var foo = function () {};

src/babel/transformation/helpers/remap-async-to-generator.js

@@ -1,9 +1,7 @@
-"use strict";
-
 var t = require("../../types");
 
 var visitor = {
-  enter: function (node) {
+  enter(node) {
     if (t.isFunction(node)) this.skip();
 
     if (t.isAwaitExpression(node)) {

src/babel/transformation/helpers/replace-supers.js

@@ -1,5 +1,3 @@
-"use strict";
-
 module.exports = ReplaceSupers;
 
 var messages = require("../../messages");
@@ -96,7 +94,7 @@ ReplaceSupers.prototype.replace = function () {
 };
 
 var visitor = {
-  enter: function (node, parent, scope, state) {
+  enter(node, parent, scope, state) {
     var topLevel = state.topLevel;
     var self = state.self;
 

src/babel/transformation/helpers/use-strict.js

@@ -0,0 +1,19 @@
+var t = require("../../types");
+
+exports.has = function (node) {
+  var first = node.body[0];
+  return t.isExpressionStatement(first) && t.isLiteral(first.expression, { value: "use strict" });
+};
+
+exports.wrap = function (node, callback) {
+  var useStrictNode;
+  if (exports.has(node)) {
+    useStrictNode = node.body.shift();
+  }
+
+  callback();
+
+  if (useStrictNode) {
+    node.body.unshift(useStrictNode);
+  }
+};

src/babel/transformation/index.js

@@ -1,5 +1,3 @@
-"use strict";
-
 module.exports = transform;
 
 var normalizeAst = require("../helpers/normalize-ast");
@@ -60,7 +58,7 @@ var rawTransformers = require("./transformers");
 each(rawTransformers, function (transformer, key) {
   var namespace = key.split(".")[0];
 
-  transform.namespaces[namespace] = transform.namespaces[namespace] || [];
+  transform.namespaces[namespace] ||= [];
   transform.namespaces[namespace].push(key);
   transform.transformerNamespaces[key] = namespace;
 

src/babel/transformation/modules/_default.js

@@ -1,5 +1,3 @@
-"use strict";
-
 module.exports = DefaultFormatter;
 
 var messages = require("../../messages");
@@ -35,12 +33,12 @@ DefaultFormatter.prototype.doDefaultExportInterop = function (node) {
 DefaultFormatter.prototype.bumpImportOccurences = function (node) {
   var source = node.source.value;
   var occurs = this.localImportOccurences;
-  occurs[source] = occurs[source] || 0;
+  occurs[source] ||= 0;
   occurs[source] += node.specifiers.length;
 };
 
 var exportsVisitor = {
-  enter: function (node, parent, scope, formatter) {
+  enter(node, parent, scope, formatter) {
     var declar = node && node.declaration;
     if (t.isExportDeclaration(node)) {
       formatter.hasLocalImports = true;
@@ -65,7 +63,7 @@ DefaultFormatter.prototype.getLocalExports = function () {
 };
 
 var importsVisitor = {
-  enter: function (node, parent, scope, formatter) {
+  enter(node, parent, scope, formatter) {
     if (t.isImportDeclaration(node)) {
       formatter.hasLocalImports = true;
       extend(formatter.localImports, t.getBindingIdentifiers(node));
@@ -79,7 +77,7 @@ DefaultFormatter.prototype.getLocalImports = function () {
 };
 
 var remapVisitor = {
-  enter: function (node, parent, scope, formatter) {
+  enter(node, parent, scope, formatter) {
     if (t.isUpdateExpression(node) && formatter.isLocalReference(node.argument, scope)) {
       this.skip();
 

src/babel/transformation/modules/_strict.js

@@ -1,5 +1,3 @@
-"use strict";
-
 var util = require("../../util");
 
 module.exports = function (Parent) {

src/babel/transformation/modules/amd-strict.js

@@ -1,3 +1 @@
-"use strict";
-
 module.exports = require("./_strict")(require("./amd"));

src/babel/transformation/modules/amd.js

@@ -1,5 +1,3 @@
-"use strict";
-
 module.exports = AMDFormatter;
 
 var DefaultFormatter = require("./_default");

src/babel/transformation/modules/common-strict.js

@@ -1,3 +1 @@
-"use strict";
-
 module.exports = require("./_strict")(require("./common"));

src/babel/transformation/modules/common.js

@@ -1,5 +1,3 @@
-"use strict";
-
 module.exports = CommonJSFormatter;
 
 var DefaultFormatter = require("./_default");

src/babel/transformation/modules/ignore.js

@@ -1,5 +1,3 @@
-"use strict";
-
 module.exports = IgnoreFormatter;
 
 var t = require("../../types");

src/babel/transformation/modules/system.js

@@ -1,5 +1,3 @@
-"use strict";
-
 module.exports = SystemFormatter;
 
 var DefaultFormatter = require("./_default");
@@ -68,7 +66,7 @@ SystemFormatter.prototype.importSpecifier = function (specifier, node, nodes) {
 };
 
 var runnerSettersVisitor = {
-  enter: function (node, parent, scope, state) {
+  enter(node, parent, scope, state) {
     if (node._importSource === state.source) {
       if (t.isVariableDeclaration(node)) {
         each(node.declarations, function (declar) {
@@ -103,7 +101,7 @@ SystemFormatter.prototype.buildRunnerSetters = function (block, hoistDeclarators
 };
 
 var hoistVariablesVisitor = {
-  enter: function (node, parent, scope, hoistDeclarators) {
+  enter(node, parent, scope, hoistDeclarators) {
     if (t.isFunction(node)) {
       // nothing inside is accessible
       return this.skip();
@@ -148,7 +146,7 @@ var hoistVariablesVisitor = {
 };
 
 var hoistFunctionsVisitor = {
-  enter: function (node, parent, scope, handlerBody) {
+  enter(node, parent, scope, handlerBody) {
     if (t.isFunction(node)) this.skip();
 
     if (t.isFunctionDeclaration(node) || node._blockHoist) {

src/babel/transformation/modules/umd-strict.js

@@ -1,3 +1 @@
-"use strict";
-
 module.exports = require("./_strict")(require("./umd"));

src/babel/transformation/modules/umd.js

@@ -1,5 +1,3 @@
-"use strict";
-
 module.exports = UMDFormatter;
 
 var AMDFormatter = require("./amd");

src/babel/transformation/templates/.babelrc

@@ -0,0 +1,3 @@
+{
+  "blacklist": ["useStrict", "es6.blockScoping"]
+}