v4.7.2

Add choice of output format to babel-external-helpers

CHANGELOG.md

@@ -13,6 +13,50 @@ _Note: Gaps between patch versions are faulty/broken releases._
 
 See [CHANGELOG - 6to5](CHANGELOG-6to5.md) for the pre-4.0.0 version changelog.
 
+## 4.7.2
+
+ * **New Feature**
+  * `"both"` option for `sourceMap`.
+  * Add output types to external helpers. Thanks [@neVERberleRfellerER](https://github.com/neVERberleRfellerER)!
+ * **Bug Fix**
+  * Fix node duplication sometimes resulting in a recursion error.
+  * Ignore `break`s within cases inside `for...of`.
+ * **Polish**
+  * Split up variable declarations and export declarations to allow easier transformation.
+
+## 4.7.0
+
+ * **Bug Fix**
+  * Add `alternate` to list of `STATEMENT_OR_BLOCK` keys.
+  * Add support for module specifiers to `t.isReferenced`.
+ * **New Feature**
+  * Add `inputSourceMap` option.
+ * **Polish**
+  * Throw an error on different `babel` and `babel-runtime` versions.
+  * Replicate module environment for `babel-node` eval.
+  * Clean up classes output.
+ * **Spec Compliancy**
+  * Make it illegal to use a rest parameter on a setter.
+
+## 4.6.6
+
+ * **Bug Fix**
+  * Fix incorrect method call in `utility.deadCodeElimination` transformer.
+  * Fix `es6.blockScopingTDZ` transformer duplicating binding nodes.
+
+## 4.6.5
+
+ * **Internal**
+  * `useStrict` transformer has been renamed to `strict`.
+
+## 4.6.4
+
+ * **Bug Fix**
+  * Fix `ForOfStatement` not proplery inheriting labels.
+  * When in closure mode in block scoping transformer, properly check for variable shadowing.
+ * **New Feature**
+  * New `utility.inlineEnvironmentVariables` and `utility.inlineExpression` transformers.
+
 ## 4.6.3
 
  * **Bug Fix**

CONTRIBUTING.md

@@ -53,7 +53,6 @@ $ mocha test/transformation.js
 #### Code Standards
 
  * **General**
-   * No ES6 syntax features or methods, exclusively ES5.
    * Max of five arguments for functions
    * Max depth of four nested blocks
    * 2-spaced soft tabs

bin/_babel-node

@@ -60,7 +60,18 @@ if (program.eval || program.print) {
   var code = program.eval;
   if (!code || code === true) code = program.print;
 
-  var result = _eval(code, "eval");
+  global.__filename = "[eval]";
+  global.__dirname = process.cwd();
+
+  var module = new Module(global.__filename);
+  module.filename = global.__filename;
+  module.paths    = Module._nodeModulePaths(global.__dirname);
+
+  global.exports = module.exports;
+  global.module  = module;
+  global.require = module.require.bind(module);
+
+  var result = _eval(code, global.__filename);
   if (program.print) console.log(result);
 } else {
   if (program.args.length) {
@@ -88,7 +99,7 @@ if (program.eval || program.print) {
     args = args.slice(i);
 
     // make the filename absolute
-    var filename = args[0]
+    var filename = args[0];
     if (!pathIsAbsolute(filename)) args[0] = path.join(process.cwd(), filename);
 
     // add back on node and concat the sliced args

bin/babel-external-helpers

@@ -1,4 +1,13 @@
 #!/usr/bin/env node
 
+var commander = require("commander");
+var util      = require("../lib/babel/util");
 var runtime = require("../lib/babel/build-external-helpers");
-console.log(runtime());
+
+commander.option("-l, --whitelist [whitelist]", "Whitelist of helpers to ONLY include", util.list);
+commander.option("-t, --output-type [type]", "Type of output (global|umd|var)", "global");
+
+commander.usage("[options]");
+commander.parse(process.argv);
+
+console.log(runtime(commander.whitelist, commander.outputType));

bin/babel-node

@@ -7,7 +7,17 @@
 
 var args  = [__dirname + "/_babel-node"];
 
-process.argv.slice(2).forEach(function(arg){
+var babelArgs = process.argv.slice(2);
+var userArgs;
+
+// separate node arguments from script arguments
+var argSeparator = babelArgs.indexOf("--");
+if (argSeparator > -1) {
+  userArgs  = babelArgs.slice(argSeparator); // including the  --
+  babelArgs = babelArgs.slice(0, argSeparator);
+}
+
+babelArgs.forEach(function(arg){
   var flag = arg.split("=")[0];
 
   switch (flag) {
@@ -49,6 +59,11 @@ process.argv.slice(2).forEach(function(arg){
   }
 });
 
+// append arguments passed after --
+if (argSeparator > -1) {
+  args = args.concat(userArgs);
+}
+
 try {
   var kexec = require("kexec");
   kexec(process.argv[0], args);

bin/babel/file.js

@@ -1,10 +1,10 @@
-var sourceMapToComment = require("source-map-to-comment");
-var sourceMap          = require("source-map");
-var chokidar           = require("chokidar");
-var path               = require("path");
-var util               = require("./util");
-var fs                 = require("fs");
-var _                  = require("lodash");
+var convertSourceMap = require("convert-source-map");
+var sourceMap        = require("source-map");
+var chokidar         = require("chokidar");
+var path             = require("path");
+var util             = require("./util");
+var fs               = require("fs");
+var _                = require("lodash");
 
 module.exports = function (commander, filenames) {
   var results = [];
@@ -42,7 +42,7 @@ module.exports = function (commander, filenames) {
     });
 
     if (commander.sourceMapsInline || (!commander.outFile && commander.sourceMaps)) {
-      code += "\n" + sourceMapToComment(map);
+      code += "\n" + convertSourceMap.fromObject(map).toComment();
     }
 
     return {

package.json

@@ -1,7 +1,7 @@
 {
   "name": "babel",
   "description": "Turn ES6 code into readable vanilla ES5 with source maps",
-  "version": "4.6.4",
+  "version": "4.7.2",
   "author": "Sebastian McKenzie <sebmck@gmail.com>",
   "homepage": "https://babeljs.io/",
   "repository": "babel/babel",
@@ -37,10 +37,11 @@
   },
   "dependencies": {
     "acorn-babel": "0.11.1-37",
-    "ast-types": "~0.6.1",
+    "ast-types": "~0.7.0",
     "chalk": "^1.0.0",
     "chokidar": "^0.12.6",
     "commander": "^2.6.0",
+    "convert-source-map": "^0.5.0",
     "core-js": "^0.6.1",
     "debug": "^2.1.1",
     "detect-indent": "^3.0.0",
@@ -56,14 +57,14 @@
     "output-file-sync": "^1.1.0",
     "path-is-absolute": "^1.0.0",
     "private": "^0.1.6",
-    "regenerator-babel": "0.8.13-1",
+    "regenerator-babel": "0.8.13-2",
     "regexpu": "^1.1.2",
     "repeating": "^1.1.2",
     "shebang-regex": "^1.0.0",
     "slash": "^1.0.0",
     "source-map": "^0.4.0",
     "source-map-support": "^0.2.9",
-    "source-map-to-comment": "^1.0.0",
+    "to-fast-properties": "^1.0.0",
     "trim-right": "^1.0.0"
   },
   "devDependencies": {

packages/babel-runtime/package.json

@@ -1,7 +1,7 @@
 {
   "name": "babel-runtime",
   "description": "babel selfContained runtime",
-  "version": "4.6.3",
+  "version": "4.7.1",
   "repository": "babel/babel",
   "author": "Sebastian McKenzie <sebmck@gmail.com>"
 }

src/babel/api/browser.js

@@ -25,7 +25,7 @@ transform.load = function (url, callback, opts = {}, hold) {
       if (!hold) transform.run.apply(transform, param);
       if (callback) callback(param);
     } else {
-      throw new Error("Could not load " + url);
+      throw new Error(`Could not load ${url}`);
     }
   };
 

src/babel/api/register/node.js

@@ -46,7 +46,7 @@ var compile = function (filename) {
   var opts = extend({}, transformOpts);
   resolveRc(filename, opts);
 
-  var cacheKey = filename + ":" + JSON.stringify(opts);
+  var cacheKey = `${filename}:${JSON.stringify(opts)}`;
 
   if (cache) {
     var cached = cache[cacheKey];
@@ -57,7 +57,7 @@ var compile = function (filename) {
 
   if (!result) {
     result = babel.transformFileSync(filename, extend(opts, {
-      sourceMap: true,
+      sourceMap: "both",
       ast:       false
     }));
   }
@@ -153,3 +153,16 @@ export default function (opts = {}) {
 
   extend(transformOpts, opts);
 };
+
+//
+
+try {
+  var runtimePackage = require("babel-runtime/package");
+  var version = require("../../package").version;
+  if (runtimePackage.version !== version) {
+    throw new ReferenceError(`The verison of babel-runtime of ${runtimePackage.runtime} that you have installed does not match the babel verison of ${version}`);
+  }
+} catch (err) {
+  if (err.code !== "MODULE_NOT_FOUND") throw err;
+}
+

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

@@ -23,7 +23,7 @@ export default function (loc, opts = {}) {
       try {
         json = JSON.parse(content);
       } catch (err) {
-        err.message = file + ": " + err.message;
+        err.message = `${file}: ${err.message}`;
         throw err;
       }
 

src/babel/build-external-helpers.js

@@ -1,11 +1,10 @@
 import buildHelpers from "./build-helpers";
 import generator from "./generation";
+import * as messages from "./messages";
 import * as util from  "./util";
 import t from "./types";
 
-export default function (whitelist) {
-  var namespace = t.identifier("babelHelpers");
-
+function buildGlobal(namespace, builder) {
   var body      = [];
   var container = t.functionExpression(null, [t.identifier("global")], t.blockStatement(body));
   var tree      = t.program([t.expressionStatement(t.callExpression(container, [util.template("self-global")]))]);
@@ -17,7 +16,58 @@ export default function (whitelist) {
     )
   ]));
 
-  buildHelpers(body, namespace, whitelist);
+  builder(body);
+
+  return tree;
+}
+
+function buildUmd(namespace, builder) {
+  var body = [];
+  body.push(t.variableDeclaration("var", [
+    t.variableDeclarator(namespace, t.identifier("global"))
+  ]));
+
+  builder(body);
+
+  var container = util.template("umd-commonjs-strict", {
+    FACTORY_PARAMETERS: t.identifier("global"),
+    BROWSER_ARGUMENTS:  t.assignmentExpression("=", t.memberExpression(t.identifier("root"), namespace), t.objectExpression({})),
+    COMMON_ARGUMENTS:   t.identifier("exports"),
+    AMD_ARGUMENTS:      t.arrayExpression([t.literal("exports")]),
+    FACTORY_BODY:       body,
+    UMD_ROOT:           t.identifier("this")
+  });
+  return t.program([container]);
+}
+
+function buildVar(namespace, builder) {
+  var body = [];
+  body.push(t.variableDeclaration("var", [
+    t.variableDeclarator(namespace, t.objectExpression({}))
+  ]));
+  builder(body);
+  return t.program(body);
+}
+
+export default function (whitelist, outputType = "global") {
+  var namespace = t.identifier("babelHelpers");
+  var builder = function (body) {
+    return buildHelpers(body, namespace, whitelist);
+  };
+
+  var tree;
+
+  var build = {
+    global: buildGlobal,
+    umd:    buildUmd,
+    var:    buildVar
+  }[outputType];
+
+  if (build) {
+    tree = build(namespace, builder);
+  } else {
+    throw new Error(messages.get("unsupportedOutputType", outputType));
+  }
 
   return generator(tree).code;
 };

src/babel/generation/buffer.js

@@ -140,7 +140,7 @@ export default class Buffer {
       var indent = this.getIndent();
 
       // replace all newlines with newlines with the indentation
-      str = str.replace(/\n/g, "\n" + indent);
+      str = str.replace(/\n/g, `\n${indent}`);
 
       // we've got a newline before us so prepend on the indentation
       if (this.isLast("\n")) this._push(indent);

src/babel/generation/generators/expressions.js

@@ -109,16 +109,19 @@ export function ExpressionStatement(node, print) {
   this.semicolon();
 }
 
-exports.BinaryExpression =
-exports.LogicalExpression =
-exports.AssignmentPattern =
-exports.AssignmentExpression = function (node, print) {
+export function AssignmentExpression(node, print) {
   // todo: add cases where the spaces can be dropped when in compact mode
   print(node.left);
   this.push(" ");
   this.push(node.operator);
   this.push(" ");
   print(node.right);
+}
+
+export {
+  AssignmentExpression as BinaryExpression,
+  AssignmentExpression as LogicalExpression,
+  AssignmentExpression as AssignmentPattern
 };
 
 var SCIENTIFIC_NOTATION = /e/i;

src/babel/generation/generators/methods.js

@@ -44,8 +44,7 @@ export function _method(node, print) {
   print(value.body);
 }
 
-exports.FunctionDeclaration =
-exports.FunctionExpression = function (node, print) {
+export function FunctionExpression(node, print) {
   if (node.async) this.push("async ");
   this.push("function");
   if (node.generator) this.push("*");
@@ -60,7 +59,9 @@ exports.FunctionExpression = function (node, print) {
   this._params(node, print);
   this.space();
   print(node.body);
-};
+}
+
+export { FunctionExpression as FunctionDeclaration };
 
 export function ArrowFunctionExpression(node, print) {
   if (node.async) this.push("async ");

src/babel/generation/generators/modules.js

@@ -5,7 +5,7 @@ export function ImportSpecifier(node, print) {
   if (t.isSpecifierDefault(node)) {
     print(t.getSpecifierName(node));
   } else {
-    return exports.ExportSpecifier.apply(this, arguments);
+    return ExportSpecifier.apply(this, arguments);
   }
 }
 

src/babel/generation/generators/playground.js

@@ -2,6 +2,6 @@ import each from "lodash/collection/each";
 
 each(["BindMemberExpression", "BindFunctionExpression"], function (type) {
   exports[type] = function () {
-    throw new ReferenceError("Trying to render non-standard playground node " + JSON.stringify(type));
+    throw new ReferenceError(`Trying to render non-standard playground node ${JSON.stringify(type)}`);
   };
 });

src/babel/generation/generators/statements.js

@@ -60,7 +60,7 @@ var buildForXStatement = function (op) {
     this.keyword("for");
     this.push("(");
     print(node.left);
-    this.push(" " + op + " ");
+    this.push(` ${op} `);
     print(node.right);
     this.push(")");
     print.block(node.body);
@@ -192,7 +192,7 @@ export function VariableDeclaration(node, print, parent) {
 
   var sep = ",";
   if (!this.format.compact && hasInits) {
-    sep += "\n" + repeating(" ", node.kind.length + 1);
+    sep += `\n${repeating(" ", node.kind.length + 1)}`;
   } else {
     sep += " ";
   }

src/babel/generation/generators/types.js

@@ -4,12 +4,12 @@ export function Identifier(node) {
   this.push(node.name);
 }
 
-exports.RestElement =
-exports.SpreadElement =
-exports.SpreadProperty = function (node, print) {
+export function RestElement(node, print) {
   this.push("...");
   print(node.argument);
-};
+}
+
+export { RestElement as SpreadElement, RestElement as SpreadProperty };
 
 export function VirtualPropertyExpression(node, print) {
   print(node.object);
@@ -17,8 +17,7 @@ export function VirtualPropertyExpression(node, print) {
   print(node.property);
 }
 
-exports.ObjectExpression =
-exports.ObjectPattern = function (node, print) {
+export function ObjectExpression(node, print) {
   var props = node.properties;
 
   if (props.length) {
@@ -32,7 +31,9 @@ exports.ObjectPattern = function (node, print) {
   } else {
     this.push("{}");
   }
-};
+}
+
+export { ObjectExpression as ObjectPattern };
 
 export function Property(node, print) {
   if (node.method || node.kind === "get" || node.kind === "set") {
@@ -53,8 +54,7 @@ export function Property(node, print) {
   }
 }
 
-exports.ArrayExpression =
-exports.ArrayPattern = function (node, print) {
+export function ArrayExpression(node, print) {
   var elems = node.elements;
   var len   = elems.length;
 
@@ -76,7 +76,9 @@ exports.ArrayPattern = function (node, print) {
   });
 
   this.push("]");
-};
+}
+
+export { ArrayExpression as ArrayPattern };
 
 export function Literal(node) {
   var val  = node.value;
@@ -89,7 +91,7 @@ export function Literal(node) {
   } else if (type === "boolean") {
     this.push(val ? "true" : "false");
   } else if (node.regex) {
-    this.push("/" + node.regex.pattern + "/" + node.regex.flags);
+    this.push(`/${node.regex.pattern}/${node.regex.flags}`);
   } else if (val === null) {
     this.push("null");
   }

src/babel/generation/index.js

@@ -187,7 +187,7 @@ class CodeGenerator {
 
       this.printTrailingComments(node, parent);
     } else {
-      throw new ReferenceError("unknown node of type " + JSON.stringify(node.type) + " with constructor " + JSON.stringify(node && node.constructor.name));
+      throw new ReferenceError(`unknown node of type ${JSON.stringify(node.type)} with constructor ${JSON.stringify(node && node.constructor.name)}`);
     }
 
     this.format.concise = oldConcise;
@@ -238,9 +238,9 @@ class CodeGenerator {
   generateComment(comment) {
     var val = comment.value;
     if (comment.type === "Line") {
-      val = "//" + val;
+      val = `//${val}`;
     } else {
-      val = "/*" + val + "*/";
+      val = `/*${val}*/`;
     }
     return val;
   }
@@ -319,7 +319,7 @@ class CodeGenerator {
         }
 
         var indent = Math.max(this.indentSize(), column);
-        val = val.replace(/\n/g, "\n" + repeating(" ", indent));
+        val = val.replace(/\n/g, `\n${repeating(" ", indent)}`);
       }
 
       if (column === 0) {

src/babel/helpers/code-frame.js

@@ -55,7 +55,7 @@ var highlight = function (text) {
   });
 };
 
-module.exports = function (lines, lineNumber, colNumber) {
+export default function (lines, lineNumber, colNumber) {
   colNumber = Math.max(colNumber, 0);
 
   if (chalk.supportsColor) {
@@ -81,8 +81,7 @@ module.exports = function (lines, lineNumber, colNumber) {
         return;
       }
       if (colNumber) {
-        params.line += "\n" + params.before + repeating(" ", params.width) +
-                       params.after + repeating(" ", colNumber - 1) + "^";
+        params.line += `\n${params.before}${repeating(" ", params.width)}${params.after}${repeating(" ", colNumber - 1)}^`;
       }
       params.before = params.before.replace(/^./, ">");
     }

src/babel/helpers/normalize-ast.js

@@ -1,6 +1,6 @@
 import t from "../types";
 
-module.exports = function (ast, comments, tokens) {
+export default function (ast, comments, tokens) {
   if (ast && ast.type === "Program") {
     return t.file(ast, comments || [], tokens || []);
   } else {

src/babel/helpers/object.js

@@ -1,3 +1,3 @@
-module.exports = function () {
+export default function () {
   return Object.create(null);
 };

src/babel/helpers/parse.js

@@ -3,7 +3,7 @@ import estraverse from "estraverse";
 import codeFrame from "./code-frame";
 import acorn from "acorn-babel";
 
-module.exports = function (opts, code, callback) {
+export default function (opts, code, callback) {
   try {
     var comments = [];
     var tokens   = [];
@@ -32,7 +32,7 @@ module.exports = function (opts, code, callback) {
   } catch (err) {
     if (!err._babel) {
       err._babel = true;
-      var message = opts.filename + ": " + err.message;
+      var message = `${opts.filename}: ${err.message}`;
 
       var loc = err.loc;
       if (loc) {

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

@@ -1,15 +0,0 @@
-/**
- * A trick from Bluebird to force V8 to use fast properties for an object.
- * Read more: http://stackoverflow.com/questions/24987896/
- *
- * Use %HasFastProperties(obj) and --allow-natives-syntax to check whether
- * a particular object already has fast properties.
- */
-
-module.exports = function toFastProperties(obj) {
-  /*jshint -W027*/
-  function f() {}
-  f.prototype = obj;
-  return f;
-  eval(obj);
-};

src/babel/messages.js

@@ -10,6 +10,7 @@ export var messages = {
   undeclaredVariable: "Reference to undeclared variable $1",
   undeclaredVariableSuggestion: "Reference to undeclared variable $1 - did you mean $2?",
   settersInvalidParamLength: "Setters must have exactly one parameter",
+  settersNoRest: "Setters aren't allowed to have a rest",
   noAssignmentsInForHead: "No assignments allowed in for-in/of head",
   expectedMemberExpressionOrIdentifier: "Expected type MemeberExpression or Identifier",
   invalidParentForThisNode: "We don't know how to handle this node within the current parent - please open an issue",
@@ -18,18 +19,20 @@ export var messages = {
   unknownForHead: "Unknown node type $1 in ForStatement",
   didYouMean: "Did you mean $1?",
   evalInStrictMode: "eval is not allowed in strict mode",
-  codeGeneratorDeopt: "Note: The code generator has deoptimised the styling of $1 as it exceeds the max of $2."
+  codeGeneratorDeopt: "Note: The code generator has deoptimised the styling of $1 as it exceeds the max of $2.",
+  missingTemplatesDirectory: "no templates directory - this is most likely the result of a broken `npm publish`. Please report to https://github.com/babel/babel/issues",
+  unsupportedOutputType: "Unsupported output type $1"
 };
 
 export function get(key) {
-  var msg = exports.messages[key];
-  if (!msg) throw new ReferenceError("Unknown message `" + key + "`");
+  var msg = messages[key];
+  if (!msg) throw new ReferenceError(`Unknown message ${JSON.stringify(key)}`);
 
   var args = [];
   for (var i = 1; i < arguments.length; i++) {
     args.push(arguments[i]);
   }
-  args = exports.parseArgs(args);
+  args = parseArgs(args);
 
   return msg.replace(/\$(\d+)/g, function (str, i) {
     return args[--i];

src/babel/transformation/file.js

@@ -1,6 +1,7 @@
-import sourceMapToComment from "source-map-to-comment";
+import convertSourceMap from "convert-source-map";
 import shebangRegex from "shebang-regex";
 import isFunction from "lodash/lang/isFunction";
+import sourceMap from "source-map";
 import transform from "./index";
 import generate from "../generation";
 import defaults from "lodash/object/defaults";
@@ -48,7 +49,7 @@ export default class File {
   static helpers = [
     "inherits",
     "defaults",
-    "prototype-properties",
+    "create-class",
     "apply-constructor",
     "tagged-template-literal",
     "tagged-template-literal-loose",
@@ -77,34 +78,41 @@ export default class File {
   static validOptions = [
     "filename",
     "filenameRelative",
+
     "blacklist",
     "whitelist",
-    "loose",
     "optional",
+
+    "loose",
+    "playground",
+    "experimental",
+
     "modules",
+    "moduleIds",
+    "moduleId",
+    "resolveModuleSource",
+    "keepModuleIdExtensions",
+
+    "code",
+    "ast",
+
+    "comments",
+    "compact",
+
+    "auxiliaryComment",
+    "externalHelpers",
+    "returnUsedHelpers",
+
+    "inputSourceMap",
     "sourceMap",
     "sourceMapName",
     "sourceFileName",
     "sourceRoot",
     "moduleRoot",
-    "moduleIds",
-    "comments",
-    "reactCompat",
-    "keepModuleIdExtensions",
-    "code",
-    "ast",
-    "playground",
-    "experimental",
-    "externalHelpers",
-    "auxiliaryComment",
-    "compact",
-    "returnUsedHelpers",
-
-    "resolveModuleSource",
-    "moduleId",
 
     // legacy
     "format",
+    "reactCompat",
 
     // these are used by plugins
     "ignore",
@@ -118,7 +126,7 @@ export default class File {
 
     for (var key in opts) {
       if (key[0] !== "_" && File.validOptions.indexOf(key) < 0) {
-        throw new ReferenceError("Unknown option: " + key);
+        throw new ReferenceError(`Unknown option: ${key}`);
       }
     }
 
@@ -128,6 +136,7 @@ export default class File {
       returnUsedHelpers:      false,
       externalHelpers:        false,
       auxilaryComment:        "",
+      inputSourceMap:         false,
       experimental:           false,
       reactCompat:            false,
       playground:             false,
@@ -145,6 +154,10 @@ export default class File {
       ast:                    true
     });
 
+    if (opts.inputSourceMap) {
+      opts.sourceMap = true;
+    }
+
     // normalize windows path separators to unix
     opts.filename = slash(opts.filename);
     if (opts.sourceRoot) {
@@ -248,7 +261,7 @@ export default class File {
 
   debug(msg) {
     var parts = this.opts.filename;
-    if (msg) parts += ": " + msg;
+    if (msg) parts += `: ${msg}`;
     util.debug(parts);
   }
 
@@ -261,12 +274,24 @@ export default class File {
     }
 
     if (!ModuleFormatter) {
-      throw new ReferenceError("Unknown module formatter type " + JSON.stringify(type));
+      throw new ReferenceError(`Unknown module formatter type ${JSON.stringify(type)}`);
     }
 
     return new ModuleFormatter(this);
   }
 
+  parseInputSourceMap(code) {
+    var opts = this.opts;
+
+    var inputMap = convertSourceMap.fromSource(code);
+    if (inputMap) {
+      opts.inputSourceMap = inputMap.toObject();
+      code = convertSourceMap.removeComments(code);
+    }
+
+    return code;
+  }
+
   parseShebang(code) {
     var shebangMatch = shebangRegex.exec(code);
 
@@ -314,7 +339,11 @@ export default class File {
       this.dynamicImported.push(declar);
       if (noDefault) this.dynamicImportedNoDefault.push(declar);
 
-      this.moduleFormatter.importSpecifier(specifiers[0], declar, this.dynamicImports);
+      if (this.transformers["es6.modules"].canRun()) {
+        this.moduleFormatter.importSpecifier(specifiers[0], declar, this.dynamicImports);
+      } else {
+        this.dynamicImports.push(declar);
+      }
     }
 
     return id;
@@ -338,7 +367,7 @@ export default class File {
 
   addHelper(name) {
     if (!includes(File.helpers, name)) {
-      throw new ReferenceError("Unknown helper " + name);
+      throw new ReferenceError(`Unknown helper ${name}`);
     }
 
     var program = this.ast.program;
@@ -371,13 +400,14 @@ export default class File {
 
   errorWithNode(node, msg, Error = SyntaxError) {
     var loc = node.loc.start;
-    var err = new Error("Line " + loc.line + ": " + msg);
+    var err = new Error(`Line ${loc.line}: ${msg}`);
     err.loc = loc;
     return err;
   }
 
   addCode(code) {
     code = (code || "") + "";
+    code = this.parseInputSourceMap(code);
     this.code = code;
     return this.parseShebang(code);
   }
@@ -388,7 +418,7 @@ export default class File {
     var opts = this.opts;
 
     opts.allowImportExportEverywhere = this.isLoose("es6.modules");
-    opts.strictMode = this.transformers.useStrict.canRun();
+    opts.strictMode = this.transformers.strict.canRun();
 
     return parse(opts, code, (tree) => {
       this.transform(tree);
@@ -430,6 +460,13 @@ export default class File {
   }
 
   checkNode(node, scope) {
+    if (Array.isArray(node)) {
+      for (var i = 0; i < node.length; i++) {
+        this.checkNode(node[i], scope);
+      }
+      return;
+    }
+
     var stack = this.transformerStack;
     scope ||= this.scope;
 
@@ -440,6 +477,28 @@ export default class File {
     });
   }
 
+  mergeSourceMap(map) {
+    var opts = this.opts;
+
+    var inputMap = opts.inputSourceMap;
+
+    if (inputMap) {
+      map.sources[0] = inputMap.file;
+
+      var inputMapConsumer = new sourceMap.SourceMapConsumer(inputMap);
+      var outputMapConsumer = new sourceMap.SourceMapConsumer(map);
+      var outputMapGenerator = sourceMap.SourceMapGenerator.fromSourceMap(outputMapConsumer);
+      outputMapGenerator.applySourceMap(inputMapConsumer);
+
+      var mergedMap = outputMapGenerator.toJSON();
+      mergedMap.sources = inputMap.sources
+      mergedMap.file = inputMap.file;
+      return mergedMap;
+    }
+
+    return map;
+  }
+
   generate() {
     var opts = this.opts;
     var ast  = this.ast;
@@ -463,11 +522,16 @@ export default class File {
 
     if (this.shebang) {
       // add back shebang
-      result.code = this.shebang + "\n" + result.code;
+      result.code = `${this.shebang}\n${result.code}`;
     }
 
-    if (opts.sourceMap === "inline") {
-      result.code += "\n" + sourceMapToComment(result.map);
+    result.map = this.mergeSourceMap(result.map);
+
+    if (opts.sourceMap === "inline" || opts.sourceMap === "both") {
+      result.code += "\n" + convertSourceMap.fromObject(result.map).toComment();
+    }
+
+    if (opts.sourceMap === "both") {
       result.map = null;
     }
 

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

@@ -1,7 +1,7 @@
 import explode from "./explode-assignable-expression";
 import t from "../../types";
 
-module.exports = function (exports, opts) {
+export default function (exports, opts) {
   var isAssignment = function (node) {
     return node.operator === opts.operator + "=";
   };

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

@@ -1,6 +1,6 @@
 import t from "../../types";
 
-module.exports = function build(node, buildBody) {
+export default function build(node, buildBody) {
   var self = node.blocks.shift();
   if (!self) return;
 
@@ -20,4 +20,4 @@ module.exports = function build(node, buildBody) {
     self.right,
     t.blockStatement([child])
   );
-};
+}

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

@@ -1,7 +1,7 @@
 import explode from "./explode-assignable-expression";
 import t from "../../types";
 
-module.exports = function (exports, opts) {
+export default function (exports, opts) {
   var buildAssignment = function (left, right) {
     return t.assignmentExpression("=", left, right);
   };

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

@@ -9,7 +9,7 @@ import esutils from "esutils";
 import * as react from "./react";
 import t from "../../types";
 
-module.exports = function (exports, opts) {
+export default function (exports, opts) {
   exports.check = function (node) {
     if (t.isJSX(node)) return true;
     if (react.isCreateClass(node)) return true;

src/babel/transformation/helpers/define-map.js

@@ -1,6 +1,5 @@
 import cloneDeep from "lodash/lang/cloneDeep";
 import traverse from "../../traversal";
-import clone from "lodash/lang/clone";
 import each from "lodash/collection/each";
 import has from "lodash/object/has";
 import t from "../../types";
@@ -10,11 +9,11 @@ export function push(mutatorMap, key, kind, computed, value) {
 
   if (t.isIdentifier(key)) {
     alias = key.name;
-    if (computed) alias = "computed:" + alias;
+    if (computed) alias = `computed:${alias}`;
   } else if (t.isLiteral(key)) {
     alias = String(key.value);
   } else {
-    alias = JSON.stringify(traverse.removeProperties(cloneDeep(key)));
+    alias = JSON.stringify(traverse.removeProperties(t.cloneDeep(key)));
   }
 
   var map;
@@ -33,7 +32,7 @@ export function push(mutatorMap, key, kind, computed, value) {
   map[kind] = value;
 }
 
-export function build(mutatorMap) {
+export function toClassObject(mutatorMap) {
   var objExpr = t.objectExpression([]);
 
   each(mutatorMap, function (map) {
@@ -41,22 +40,43 @@ export function build(mutatorMap) {
 
     var propNode = t.property("init", map._key, mapNode, map._computed);
 
-    if (!map.get && !map.set) {
-      map.writable = t.literal(true);
-    }
-
-    if (map.enumerable === false) {
-      delete map.enumerable;
-    } else {
-      map.enumerable = t.literal(true);
-    }
-
-    map.configurable = t.literal(true);
-
     each(map, function (node, key) {
       if (key[0] === "_") return;
 
-      node = clone(node);
+      var inheritNode = node;
+      if (t.isMethodDefinition(node)) node = node.value;
+
+      var prop = t.property("init", t.identifier(key), node);
+      t.inheritsComments(prop, inheritNode);
+      t.removeComments(inheritNode);
+      mapNode.properties.push(prop);
+    });
+
+    objExpr.properties.push(propNode);
+  });
+
+  return objExpr;
+}
+
+export function toDefineObject(mutatorMap) {
+  var objExpr = t.objectExpression([]);
+
+  each(mutatorMap, function (map) {
+    var mapNode = t.objectExpression([]);
+
+    var propNode = t.property("init", map._key, mapNode, map._computed);
+
+    if (map.value) {
+      map.writable = t.literal(true);
+    }
+
+    map.configurable = t.literal(true);
+    map.enumerable = t.literal(true);
+
+    each(map, function (node, key) {
+      if (key[0] === "_") return;
+
+      node = t.clone(node);
       var inheritNode = node;
       if (t.isMethodDefinition(node)) node = node.value;
 

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

@@ -23,7 +23,7 @@ var getObjRef = function (node, nodes, file, scope) {
       return ref;
     }
   } else {
-    throw new Error("We can't explode this node type " + node.type);
+    throw new Error(`We can't explode this node type ${node.type}`);
   }
 
   var temp = scope.generateUidBasedOnNode(ref);
@@ -45,7 +45,7 @@ var getPropRef = function (node, nodes, file, scope) {
   return temp;
 };
 
-module.exports = function (node, nodes, file, scope, allowedSingleIdent) {
+export default function (node, nodes, file, scope, allowedSingleIdent) {
   var obj;
   if (t.isIdentifier(node) && allowedSingleIdent) {
     obj = node;

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

@@ -1,6 +1,6 @@
 import t from "../../types";
 
-module.exports = function (node) {
+export default function (node) {
   var lastNonDefault = 0;
   for (var i = 0; i < node.params.length; i++) {
     if (!t.isAssignmentPattern(node.params[i])) lastNonDefault = i + 1;

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

@@ -6,7 +6,7 @@ var visitor = {
   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;
+    if (!this.isReferencedIdentifier({ name: state.name })) return;
 
     // check that we don't have a local variable declared as that removes the need
     // for the wrapper
@@ -89,6 +89,11 @@ var visit = function (node, name, scope) {
   return state;
 };
 
+export function custom(node, id, scope) {
+  var state = visit(node, id.name, scope);
+  return wrap(state, node, id, scope);
+}
+
 export function property(node, file, scope) {
   var key = t.toComputedKey(node, node.key);
   if (!t.isLiteral(key)) return node; // we can't set a function id with this
@@ -103,7 +108,7 @@ export function property(node, file, scope) {
 
 export function bare(node, parent, scope) {
   // has an `id` so we don't need to infer one
-  if (node.id) return;
+  if (node.id) return node;
 
   var id;
   if (t.isProperty(parent) && parent.kind === "init" && !parent.computed) {
@@ -113,10 +118,10 @@ export function bare(node, parent, scope) {
     // var foo = function () {};
     id = parent.id;
   } else {
-    return;
+    return node;
   }
 
-  if (!t.isIdentifier(id)) return;
+  if (!t.isIdentifier(id)) return node;
 
   var name = t.toIdentifier(id.name);
   id = t.identifier(name);

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

@@ -16,7 +16,7 @@ var visitor = {
   }
 };
 
-module.exports = function (node, callId, scope) {
+export default function (node, callId, scope) {
   node.async = false;
   node.generator = true;
 
@@ -24,7 +24,7 @@ module.exports = function (node, callId, scope) {
 
   var call = t.callExpression(callId, [node]);
   var id = node.id;
-  delete node.id;
+  node.id = null;
 
   if (t.isFunctionDeclaration(node)) {
     var declar = t.variableDeclaration("let", [

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

@@ -55,14 +55,18 @@ export default class ReplaceSupers {
   constructor(opts, inClass) {
     this.topLevelThisReference = opts.topLevelThisReference;
     this.methodNode            = opts.methodNode;
-    this.className             = opts.className;
-    this.superName             = opts.superName;
+    this.superRef              = opts.superRef;
     this.isStatic              = opts.isStatic;
     this.hasSuper              = false;
     this.inClass               = inClass;
     this.isLoose               = opts.isLoose;
     this.scope                 = opts.scope;
     this.file                  = opts.file;
+    this.opts                  = opts;
+  }
+
+  getObjectRef() {
+    return this.opts.objectRef || this.opts.getObjectRef();
   }
 
   /**
@@ -87,7 +91,7 @@ export default class ReplaceSupers {
         t.callExpression(
           t.memberExpression(t.identifier("Object"), t.identifier("getPrototypeOf")),
           [
-            this.isStatic ? this.className : t.memberExpression(this.className, t.identifier("prototype"))
+            this.isStatic ? this.getObjectRef() : t.memberExpression(this.getObjectRef(), t.identifier("prototype"))
           ]
         ),
         isComputed ? property : t.literal(property.name),
@@ -118,7 +122,7 @@ export default class ReplaceSupers {
         t.callExpression(
           t.memberExpression(t.identifier("Object"), t.identifier("getPrototypeOf")),
           [
-            this.isStatic ? this.className : t.memberExpression(this.className, t.identifier("prototype"))
+            this.isStatic ? this.getObjectRef() : t.memberExpression(this.getObjectRef(), t.identifier("prototype"))
           ]
         ),
         isComputed ? property : t.literal(property.name),
@@ -175,19 +179,19 @@ export default class ReplaceSupers {
   getLooseSuperProperty(id, parent) {
     var methodNode = this.methodNode;
     var methodName = methodNode.key;
-    var superName  = this.superName || t.identifier("Function");
+    var superRef   = this.superRef || t.identifier("Function");
 
     if (parent.property === id) {
       return;
     } else if (t.isCallExpression(parent, { callee: id })) {
-      // super(); -> ClassName.prototype.MethodName.call(this);
+      // super(); -> objectRef.prototype.MethodName.call(this);
       parent.arguments.unshift(t.thisExpression());
 
       if (methodName.name === "constructor") {
         // constructor() { super(); }
-        return t.memberExpression(superName, t.identifier("call"));
+        return t.memberExpression(superRef, t.identifier("call"));
       } else {
-        id = superName;
+        id = superRef;
 
         // foo() { super(); }
         if (!methodNode.static) {
@@ -198,10 +202,10 @@ export default class ReplaceSupers {
         return t.memberExpression(id, t.identifier("call"));
       }
     } else if (t.isMemberExpression(parent) && !methodNode.static) {
-      // super.test -> ClassName.prototype.test
-      return t.memberExpression(superName, t.identifier("prototype"));
+      // super.test -> objectRef.prototype.test
+      return t.memberExpression(superRef, t.identifier("prototype"));
     } else {
-      return superName;
+      return superRef;
     }
   }
 
@@ -222,7 +226,7 @@ export default class ReplaceSupers {
       if (!t.isMemberExpression(callee)) return;
       if (callee.object.name !== "super") return;
 
-      // super.test(); -> ClassName.prototype.MethodName.call(this);
+      // super.test(); -> objectRef.prototype.MethodName.call(this);
       this.hasSuper = true;
       t.appendToMemberExpression(callee, t.identifier("call"));
       node.arguments.unshift(getThisReference());
@@ -251,7 +255,7 @@ export default class ReplaceSupers {
     if (t.isCallExpression(node)) {
       var callee = node.callee;
       if (isSuper(callee, node)) {
-        // super(); -> _get(Object.getPrototypeOf(ClassName), "MethodName", this).call(this);
+        // super(); -> _get(Object.getPrototypeOf(objectRef), "MethodName", this).call(this);
         property = methodNode.key;
         computed = methodNode.computed;
         args = node.arguments;
@@ -264,17 +268,17 @@ export default class ReplaceSupers {
           throw this.file.errorWithNode(node, messages.get("classesIllegalSuperCall", methodName));
         }
       } else if (t.isMemberExpression(callee) && isSuper(callee.object, callee)) {
-        // super.test(); -> _get(Object.getPrototypeOf(ClassName.prototype), "test", this).call(this);
+        // super.test(); -> _get(Object.getPrototypeOf(objectRef.prototype), "test", this).call(this);
         property = callee.property;
         computed = callee.computed;
         args = node.arguments;
       }
     } else if (t.isMemberExpression(node) && isSuper(node.object, node)) {
-      // super.name; -> _get(Object.getPrototypeOf(ClassName.prototype), "name", this);
+      // super.name; -> _get(Object.getPrototypeOf(objectRef.prototype), "name", this);
       property = node.property;
       computed = node.computed;
     } else if (t.isAssignmentExpression(node) && isSuper(node.left.object, node.left) && methodNode.kind === "set") {
-      // super.name = "val"; -> _set(Object.getPrototypeOf(ClassName.prototype), "name", this);
+      // super.name = "val"; -> _set(Object.getPrototypeOf(objectRef.prototype), "name", this);
       this.hasSuper = true;
       return this.setSuperProperty(node.left.property, node.right, node.left.computed, getThisReference());
     }

src/babel/transformation/helpers/strict.js

@@ -7,7 +7,7 @@ export function has(node) {
 
 export function wrap(node, callback) {
   var useStrictNode;
-  if (exports.has(node)) {
+  if (has(node)) {
     useStrictNode = node.body.shift();
   }
 

src/babel/transformation/index.js

@@ -25,9 +25,12 @@ transform._ensureTransformerNames = function (type, rawKeys) {
     var key = rawKeys[i];
 
     var deprecatedKey = transform.deprecatedTransformerMap[key];
-    if (deprecatedKey) {
+    var aliasKey = transform.aliasTransformerMap[key];
+    if (aliasKey) {
+      keys.push(aliasKey);
+    } else if (deprecatedKey) {
       // deprecated key, remap it to the new one
-      console.error("The transformer " + key + " has been renamed to " + deprecatedKey);
+      console.error(`The transformer ${key} has been renamed to ${deprecatedKey}`);
       rawKeys.push(deprecatedKey);
     } else if (transform.transformers[key]) {
       // valid key
@@ -37,7 +40,7 @@ transform._ensureTransformerNames = function (type, rawKeys) {
       keys = keys.concat(transform.namespaces[key]);
     } else {
       // invalid key
-      throw new ReferenceError("Unknown transformer " + key + " specified in " + type);
+      throw new ReferenceError(`Unknown transformer ${key} specified in ${type}`);
     }
   }
 
@@ -49,6 +52,7 @@ transform.transformers          = object();
 transform.namespaces            = object();
 
 transform.deprecatedTransformerMap = require("./transformers/deprecated");
+transform.aliasTransformerMap = require("./transformers/aliases");
 transform.moduleFormatters = require("./modules");
 
 import rawTransformers from "./transformers";

src/babel/transformation/modules/_default.js

@@ -42,8 +42,8 @@ var remapVisitor = {
 };
 
 var importsVisitor = {
-  enter(node, parent, scope, formatter) {
-    if (t.isImportDeclaration(node)) {
+  ImportDeclaration: {
+    enter(node, parent, scope, formatter) {
       formatter.hasLocalImports = true;
       extend(formatter.localImports, t.getBindingIdentifiers(node));
       formatter.bumpImportOccurences(node);
@@ -52,9 +52,9 @@ var importsVisitor = {
 };
 
 var exportsVisitor = {
-  enter(node, parent, scope, formatter) {
-    var declar = node && node.declaration;
-    if (t.isExportDeclaration(node)) {
+  ExportDeclaration: {
+    enter(node, parent, scope, formatter) {
+      var declar = node.declaration;
       formatter.hasLocalImports = true;
 
       if (declar && t.isStatement(declar)) {

src/babel/transformation/modules/index.js

@@ -1,4 +1,4 @@
-module.exports = {
+export default {
   commonStrict: require("./common-strict"),
   amdStrict:    require("./amd-strict"),
   umdStrict:    require("./umd-strict"),

src/babel/transformation/modules/system.js

@@ -142,9 +142,9 @@ export default class SystemFormatter extends AMDFormatter {
 
     return t.arrayExpression(map(this.ids, function (uid, source) {
       var state = {
+        hoistDeclarators: hoistDeclarators,
         source:           source,
-        nodes:            [],
-        hoistDeclarators: hoistDeclarators
+        nodes:            []
       };
 
       scope.traverse(block, runnerSettersVisitor, state);
@@ -161,11 +161,11 @@ export default class SystemFormatter extends AMDFormatter {
     var block = t.blockStatement(program.body);
 
     var runner = util.template("system", {
-      MODULE_NAME: moduleNameLiteral,
       MODULE_DEPENDENCIES: t.arrayExpression(this.buildDependencyLiterals()),
-      EXPORT_IDENTIFIER: this.exportIdentifier,
-      SETTERS: this.buildRunnerSetters(block, hoistDeclarators),
-      EXECUTE: t.functionExpression(null, [], block)
+      EXPORT_IDENTIFIER:   this.exportIdentifier,
+      MODULE_NAME:         moduleNameLiteral,
+      SETTERS:             this.buildRunnerSetters(block, hoistDeclarators),
+      EXECUTE:             t.functionExpression(null, [], block)
     }, true);
 
     var handlerBody = runner.expression.arguments[2].body.body;

src/babel/transformation/templates/create-class.js

@@ -0,0 +1,16 @@
+(function() {
+  function defineProperties(target, props) {
+    for (var key in props) {
+      var prop = props[key];
+      prop.configurable = true;
+      if (prop.value) prop.writable = true;
+    }
+    Object.defineProperties(target, props);
+  }
+
+  return function (Constructor, protoProps, staticProps) {
+    if (protoProps) defineProperties(Constructor.prototype, protoProps);
+    if (staticProps) defineProperties(Constructor, staticProps);
+    return Constructor;
+  };
+})()

src/babel/transformation/templates/prototype-properties.js

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

src/babel/transformation/templates/umd-commonjs-strict.js

@@ -0,0 +1,11 @@
+(function (root, factory) {
+  if (typeof define === "function" && define.amd) {
+    define(AMD_ARGUMENTS, factory);
+  } else if (typeof exports === 'object') {
+    factory(COMMON_ARGUMENTS);
+  } else {
+    factory(BROWSER_ARGUMENTS);
+  }
+})(UMD_ROOT, function (FACTORY_PARAMETERS) {
+  FACTORY_BODY
+});

src/babel/transformation/transformer-pass.js

@@ -56,7 +56,7 @@ export default class TransformerPass {
 
     var file = this.file;
 
-    file.debug("Running transformer " + this.transformer.key);
+    file.debug(`Running transformer ${this.transformer.key}`);
 
     file.scope.traverse(file.ast, this.handlers, file);
   }

src/babel/transformation/transformers/aliases.json

@@ -0,0 +1,3 @@
+{
+  "useStrict": "strict"
+}

src/babel/transformation/transformers/es5/properties.mutators.js

@@ -23,6 +23,6 @@ export function ObjectExpression(node) {
 
   return t.callExpression(
     t.memberExpression(t.identifier("Object"), t.identifier("defineProperties")),
-    [node, defineMap.build(mutatorMap)]
+    [node, defineMap.toDefineObject(mutatorMap)]
   );
 }

src/babel/transformation/transformers/es6/block-scoping-tdz.js

@@ -2,7 +2,7 @@ import t from "../../../types";
 
 var visitor = {
   enter(node, parent, scope, state) {
-    if (!t.isReferencedIdentifier(node, parent)) return;
+    if (!this.isReferencedIdentifier()) return;
 
     var declared = state.letRefs[node.name];
     if (!declared) return;
@@ -32,12 +32,10 @@ export function BlockStatement(node, parent, scope, file) {
   var letRefs = node._letReferences;
   if (!letRefs) return;
 
-  var state = {
+  scope.traverse(node, visitor, {
     letRefs: letRefs,
     file:    file
-  };
-
-  scope.traverse(node, visitor, state);
+  });
 }
 
 export { BlockStatement as Program, BlockStatement as Loop };

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

@@ -109,7 +109,7 @@ function traverseReplace(node, parent, scope, remaps) {
 
 var letReferenceBlockVisitor = {
   enter(node, parent, scope, state) {
-    if (t.isFunction(node)) {
+    if (this.isFunction()) {
       scope.traverse(node, letReferenceFunctionVisitor, state);
       return this.skip();
     }
@@ -119,7 +119,7 @@ var letReferenceBlockVisitor = {
 var letReferenceFunctionVisitor = {
   enter(node, parent, scope, state) {
     // not a direct reference
-    if (!t.isReferencedIdentifier(node, parent)) return;
+    if (!this.isReferencedIdentifier()) return;
 
     // this scope has a variable with the same name so it couldn't belong
     // to our let scope
@@ -134,17 +134,17 @@ var letReferenceFunctionVisitor = {
 
 var hoistVarDeclarationsVisitor = {
   enter(node, parent, scope, self) {
-    if (t.isForStatement(node)) {
+    if (this.isForStatement()) {
       if (isVar(node.init, node)) {
         node.init = t.sequenceExpression(self.pushDeclar(node.init));
       }
-    } else if (t.isFor(node)) {
+    } else if (this.isFor()) {
       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)) {
+    } else if (this.isFunction()) {
       return this.skip();
     }
   }
@@ -152,7 +152,7 @@ var hoistVarDeclarationsVisitor = {
 
 var loopLabelVisitor = {
   enter(node, parent, scope, state) {
-    if (t.isLabeledStatement(node)) {
+    if (this.isLabeledStatement()) {
       state.innerLabels.push(node.label.name);
     }
   }
@@ -170,13 +170,13 @@ var loopVisitor = {
   enter(node, parent, scope, state) {
     var replace;
 
-    if (t.isLoop(node)) {
+    if (this.isLoop()) {
       state.ignoreLabeless = true;
       scope.traverse(node, loopVisitor, state);
       state.ignoreLabeless = false;
     }
 
-    if (t.isFunction(node) || t.isLoop(node)) {
+    if (this.isFunction() || this.isLoop()) {
       return this.skip();
     }
 
@@ -189,7 +189,7 @@ var loopVisitor = {
           return;
         }
 
-        loopText = loopText + "|" + node.label.name;
+        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
@@ -204,7 +204,7 @@ var loopVisitor = {
       replace = t.literal(loopText);
     }
 
-    if (t.isReturnStatement(node)) {
+    if (this.isReturnStatement()) {
       state.hasReturn = true;
       replace = t.objectExpression([
         t.property("init", t.identifier("v"), node.argument || t.identifier("undefined"))

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

@@ -3,29 +3,54 @@ import * as nameMethod from "../../helpers/name-method";
 import * as defineMap from "../../helpers/define-map";
 import * as messages from "../../../messages";
 import * as util from  "../../../util";
+import traverse from "../../../traversal";
 import t from "../../../types";
 
 export var check = t.isClass;
 
 export function ClassDeclaration(node, parent, scope, file) {
-  return new ClassTransformer(node, file, scope, true).run();
+  return t.variableDeclaration("let", [
+    t.variableDeclarator(node.id, t.toExpression(node))
+  ]);
 }
 
 export function ClassExpression(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;
-    }
+  return new ClassTransformer(node, parent, scope, file).run();
+}
 
-    if (t.isVariableDeclarator(parent) && t.isIdentifier(parent.id)) {
-      // var foo = class {};
-      node.id = parent.id;
+var verifyConstructorVisitor = traverse.explode({
+  MethodDefinition: {
+    enter() {
+      this.skip();
+    }
+  },
+
+  Property: {
+    enter(node) {
+      if (node.method) this.skip();
+    }
+  },
+
+  CallExpression: {
+    enter(node, parent, scope, state) {
+      if (t.isIdentifier(node.callee, { name: "super" })) {
+        state.hasBareSuper = true;
+
+        if (!state.hasSuper) {
+          throw state.file.errorWithNode(node, "super call is only allowed in derived constructor");
+        }
+      }
+    }
+  },
+
+  ThisExpression: {
+    enter(node, parent, scope, state) {
+      if (state.hasSuper && !state.hasBareSuper) {
+        throw state.file.errorWithNode(node, "'this' is not allowed before super()");
+      }
     }
   }
-
-  return new ClassTransformer(node, file, scope, false).run();
-}
+});
 
 class ClassTransformer {
 
@@ -33,27 +58,31 @@ class ClassTransformer {
    * Description
    *
    * @param {Node} node
-   * @param {File} file
+   * @param {Node} parent
    * @param {Scope} scope
-   * @param {Boolean} isStatement
+   * @param {File} file
    */
 
-  constructor(node, file, scope, isStatement) {
-    this.isStatement = isStatement;
-    this.scope       = scope;
-    this.node        = node;
-    this.file        = file;
+  constructor(node, parent, scope, file) {
+    this.parent = parent;
+    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");
+
+    this.hasConstructor = false;
+    this.className      = node.id;
+    this.classRef       = node.id || scope.generateUidIdentifier("class");
+
+    this.superName = node.superClass || t.identifier("Function");
+    this.hasSuper  = !!node.superClass;
+
+    this.isLoose = file.isLoose("es6.classes");
   }
 
   /**
@@ -66,39 +95,35 @@ class ClassTransformer {
     var superName = this.superName;
     var className = this.className;
     var classBody = this.node.body.body;
+    var classRef  = this.classRef;
     var file      = this.file;
 
     //
 
     var body = this.body = [];
 
+    //
+
     var constructorBody = t.blockStatement([
       t.expressionStatement(t.callExpression(file.addHelper("class-call-check"), [
         t.thisExpression(),
-        className
+        classRef
       ]))
     ]);
 
     var constructor;
-    if (this.node.id) {
-      constructor = t.functionDeclaration(className, [], constructorBody);
+
+    if (this.className) {
+      constructor = t.functionDeclaration(this.className, [], constructorBody);
       body.push(constructor);
     } else {
-      var constructorName = null;
-      // when a class has no parent and there is only a constructor or no body
-      // then the constructor is not wrapped in a closure and needs to be named
-      var containsOnlyConstructor = classBody.length === 1 && classBody[0].key.name === "constructor";
-      if (!this.hasSuper && (classBody.length === 0 || containsOnlyConstructor)) {
-        constructorName = className;
-      }
-
-      constructor = t.functionExpression(constructorName, [], constructorBody);
-      body.push(t.variableDeclaration("var", [
-        t.variableDeclarator(className, constructor)
-      ]));
+      constructor = t.functionExpression(null, [], constructorBody);
     }
+
     this.constructor = constructor;
 
+    //
+
     var closureParams = [];
     var closureArgs = [];
 
@@ -107,40 +132,40 @@ class ClassTransformer {
     if (this.hasSuper) {
       closureArgs.push(superName);
 
-      if (!t.isIdentifier(superName)) {
-        superName = this.scope.generateUidBasedOnNode(superName, this.file);
-      }
-
+      superName = this.scope.generateUidBasedOnNode(superName, this.file);
       closureParams.push(superName);
 
       this.superName = superName;
-      body.push(t.expressionStatement(t.callExpression(file.addHelper("inherits"), [className, superName])));
+      body.push(t.expressionStatement(t.callExpression(file.addHelper("inherits"), [classRef, 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);
+    if (this.className) {
+      // named class with only a constructor
+      if (body.length === 1) return t.toExpression(body[0]);
     } else {
-      body.push(t.returnStatement(className));
-      init = t.callExpression(
-        t.functionExpression(null, closureParams, t.blockStatement(body)),
-        closureArgs
-      );
+      // infer class name if this is a nameless class expression
+      constructor = nameMethod.bare(constructor, this.parent, this.scope);
+
+      body.unshift(t.variableDeclaration("var", [
+        t.variableDeclarator(classRef, constructor)
+      ]));
+
+      t.inheritsComments(body[0], this.node);
     }
 
-    if (this.isStatement) {
-      return t.variableDeclaration("let", [
-        t.variableDeclarator(className, init)
-      ]);
-    } else {
-      return init;
-    }
+    //
+
+    body.push(t.returnStatement(classRef));
+
+    return t.callExpression(
+      t.functionExpression(null, closureParams, t.blockStatement(body)),
+      closureArgs
+    );
   }
 
   /**
@@ -157,18 +182,22 @@ class ClassTransformer {
     for (var i = 0; i < classBody.length; i++) {
       var node = classBody[i];
       if (t.isMethodDefinition(node)) {
+        var isConstructor = (!node.computed && t.isIdentifier(node.key, { name: "constructor" })) || t.isLiteral(node.key, { value: "constructor" });
+        if (isConstructor) this.verifyConstructor(node);
+
         var replaceSupers = new ReplaceSupers({
           methodNode: node,
-          className:  this.className,
-          superName:  this.superName,
+          objectRef:  this.classRef,
+          superRef:   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" })) {
+        if (isConstructor) {
           this.pushConstructor(node);
         } else {
           this.pushMethod(node);
@@ -182,7 +211,7 @@ class ClassTransformer {
     }
 
     // we have no constructor, we have a super, and the super doesn't appear to be falsy
-    if (!this.hasConstructor && this.hasSuper && t.evaluateTruthy(superName) !== false) {
+    if (!this.hasConstructor && this.hasSuper && t.evaluateTruthy(superName, this.scope) !== false) {
       var helperName = "class-super-constructor-call";
       if (this.isLoose) helperName += "-loose";
       constructor.body.body.push(util.template(helperName, {
@@ -195,25 +224,47 @@ class ClassTransformer {
     var staticProps;
 
     if (this.hasInstanceMutators) {
-      instanceProps = defineMap.build(this.instanceMutatorMap);
+      instanceProps = defineMap.toClassObject(this.instanceMutatorMap);
     }
 
     if (this.hasStaticMutators) {
-      staticProps = defineMap.build(this.staticMutatorMap);
+      staticProps = defineMap.toClassObject(this.staticMutatorMap);
     }
 
     if (instanceProps || staticProps) {
-      staticProps ||= t.literal(null);
+      instanceProps ||= t.literal(null);
 
-      var args = [className, staticProps];
-      if (instanceProps) args.push(instanceProps);
+      var args = [this.classRef, instanceProps];
+      if (staticProps) args.push(staticProps);
 
       body.push(t.expressionStatement(
-        t.callExpression(this.file.addHelper("prototype-properties"), args)
+        t.callExpression(this.file.addHelper("create-class"), args)
       ));
     }
   }
 
+  /**
+   * Description
+   *
+   * @param {Node} node
+   */
+
+   verifyConstructor(node) {
+    return; // enable this for the next major
+
+    var state = {
+      hasBareSuper: false,
+      hasSuper:     this.hasSuper,
+      file:         this.file
+    };
+
+    traverse(node, verifyConstructorVisitor, this.scope, state);
+
+    if (!state.hasBareSuper && this.hasSuper) {
+      throw this.file.errorWithNode(node, "Derived constructor must call super()");
+    }
+   }
+
   /**
    * Push a method to its respective mutatorMap.
    *
@@ -231,9 +282,9 @@ class ClassTransformer {
       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 classRef = this.classRef;
+        if (!node.static) classRef = t.memberExpression(classRef, t.identifier("prototype"));
+        methodName = t.memberExpression(classRef, methodName, node.computed);
 
         var expr = t.expressionStatement(t.assignmentExpression("=", methodName, node.value));
         t.inheritsComments(expr, node);
@@ -253,7 +304,6 @@ class ClassTransformer {
     }
 
     defineMap.push(mutatorMap, methodName, kind, node.computed, node);
-    defineMap.push(mutatorMap, methodName, "enumerable", node.computed, false);
   }
 
   /**
@@ -268,7 +318,7 @@ class ClassTransformer {
     var key;
 
     if (node.static) {
-      key = t.memberExpression(this.className, node.key);
+      key = t.memberExpression(this.classRef, node.key);
       this.body.push(
         t.expressionStatement(t.assignmentExpression("=", key, node.value))
       );
@@ -301,6 +351,8 @@ class ClassTransformer {
 
     construct._ignoreUserWhitespace = true;
     construct.params                = fn.params;
-    construct.body.body             = construct.body.body.concat(fn.body.body);
+
+    t.inherits(construct.body, fn.body);
+    construct.body.body = construct.body.body.concat(fn.body.body);
   }
 }

src/babel/transformation/transformers/es6/constants.js

@@ -7,8 +7,8 @@ export function check(node) {
 
 var visitor = {
   enter(node, parent, scope, state) {
-    if (t.isAssignmentExpression(node) || t.isUpdateExpression(node)) {
-      var ids = t.getBindingIdentifiers(node);
+    if (this.isAssignmentExpression() || this.isUpdateExpression()) {
+      var ids = this.getBindingIdentifiers();
 
       for (var name in ids) {
         var id = ids[name];
@@ -30,7 +30,7 @@ var visitor = {
 
         throw state.file.errorWithNode(id, messages.get("readOnly", name));
       }
-    } else if (t.isScope(node, parent)) {
+    } else if (this.isScope()) {
       this.skip();
     }
   }

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

@@ -56,12 +56,12 @@ export { ForOfStatement as ForInStatement };
 exports.Function = function (node, parent, scope, file) {
   var nodes = [];
 
-  var hasDestructuringTransformer = false;
+  var hasDestructuring = false;
 
   node.params = node.params.map(function (pattern, i) {
     if (!t.isPattern(pattern)) return pattern;
 
-    hasDestructuringTransformer = true;
+    hasDestructuring = true;
     var ref = scope.generateUidIdentifier("ref");
 
     var destructuring = new DestructuringTransformer({
@@ -69,15 +69,16 @@ exports.Function = function (node, parent, scope, file) {
       nodes:      nodes,
       scope:      scope,
       file:       file,
-      kind:       "var",
+      kind:       "let"
     });
     destructuring.init(pattern, ref);
 
     return ref;
   });
 
-  if (!hasDestructuringTransformer) return;
+  if (!hasDestructuring) return;
 
+  file.checkNode(nodes);
   t.ensureBlock(node);
 
   var block = node.body;
@@ -218,7 +219,7 @@ export function VariableDeclaration(node, parent, scope, file) {
   }
 
   return nodes;
-};
+}
 
 var hasRest = function (pattern) {
   for (var i = 0; i < pattern.elements.length; i++) {

src/babel/transformation/transformers/es6/for-of.js

@@ -41,17 +41,20 @@ export function ForOfStatement(node, parent, scope, file) {
 
 var breakVisitor = {
   enter(node, parent, scope, state) {
-    if (t.isLoop(node)) {
+    if (this.isLoop()) {
       state.ignoreLabeless = true;
       scope.traverse(node, breakVisitor, state);
       state.ignoreLabeless = false;
       return this.skip();
     }
 
-    if (t.isBreakStatement(node)) {
+    if (this.isBreakStatement()) {
       if (!node.label && state.ignoreLabeless) return;
       if (node.label && node.label.name !== state.label) return;
 
+      // break statements mean something different in this context
+      if (t.isSwitchCase(parent)) return;
+
       var ret = t.expressionStatement(
         t.callExpression(t.memberExpression(state.iteratorKey, t.identifier("return")), [])
       );
@@ -103,7 +106,7 @@ var loose = function (node, parent, scope, file) {
     iteratorKey: iteratorKey,
     label:       t.isLabeledStatement(parent) && parent.label.name,
 
-    wrapReturn: function (node) {
+    wrapReturn(node) {
       return t.ifStatement(
         t.logicalExpression(
           "&&",
@@ -124,8 +127,6 @@ var loose = function (node, parent, scope, file) {
 };
 
 var spec = function (node, parent, scope, file) {
-
-
   var left = node.left;
   var declar;
 
@@ -173,7 +174,7 @@ var spec = function (node, parent, scope, file) {
     iteratorKey: iteratorKey,
     label:       isLabeledParent && parent.label.name,
 
-    wrapReturn: function (node) {
+    wrapReturn(node) {
       return t.ifStatement(t.memberExpression(iteratorKey, t.identifier("return")), node);
     }
   });

src/babel/transformation/transformers/es6/object-super.js

@@ -5,7 +5,7 @@ export function check(node) {
   return t.isIdentifier(node, { name: "super" });
 }
 
-export function Property(node, parent, scope, file) {
+function Property(node, scope, getObjectRef, file) {
   if (!node.method) return;
 
   var value = node.value;
@@ -13,8 +13,8 @@ export function Property(node, parent, scope, file) {
 
   var replaceSupers = new ReplaceSupers({
     topLevelThisReference: thisExpr,
+    getObjectRef:          getObjectRef,
     methodNode:            node,
-    className:             thisExpr,
     isStatic:              true,
     scope:                 scope,
     file:                  file
@@ -30,3 +30,20 @@ export function Property(node, parent, scope, file) {
     );
   }
 }
+
+export function ObjectExpression(node, parent, scope, file) {
+  var objectRef;
+  var getObjectRef = () => objectRef ||= scope.generateUidIdentifier("obj");
+
+  for (var i = 0; i < node.properties.length; i++) {
+    Property(node.properties[i], scope, getObjectRef, file);
+  }
+
+  if (objectRef) {
+    scope.push({
+      id: objectRef
+    });
+
+    return t.assignmentExpression("=", objectRef, node);
+  }
+}

src/babel/transformation/transformers/es6/parameters.default.js

@@ -14,7 +14,7 @@ var hasDefaults = function (node) {
 
 var iifeVisitor = {
   enter(node, parent, scope, state) {
-    if (!t.isReferencedIdentifier(node, parent)) return;
+    if (!this.isReferencedIdentifier()) return;
     if (!state.scope.hasOwnBinding(node.name)) return;
     if (state.scope.bindingIdentifierEquals(node.name, node)) return;
 
@@ -61,7 +61,7 @@ exports.Function = function (node, parent, scope, file) {
         scope.traverse(param, iifeVisitor, state);
       }
 
-      if (file.transformers["es6.blockScopingTDZ"].canRun()) {
+      if (file.transformers["es6.blockScopingTDZ"].canRun() && t.isIdentifier(param)) {
         pushDefNode(param, t.identifier("undefined"), i);
       }
 

src/babel/transformation/transformers/es6/parameters.rest.js

@@ -7,13 +7,13 @@ export var check = t.isRestElement;
 var memberExpressionOptimisationVisitor = {
   enter(node, parent, scope, state) {
     // check if this scope has a local binding that will shadow the rest parameter
-    if (t.isScope(node, parent) && !scope.bindingIdentifierEquals(state.name, state.outerBinding)) {
+    if (this.isScope() && !scope.bindingIdentifierEquals(state.name, state.outerBinding)) {
       return this.skip();
     }
 
     // skip over functions as whatever `arguments` we reference inside will refer
     // to the wrong function
-    if (t.isFunctionDeclaration(node) || t.isFunctionExpression(node)) {
+    if (this.isFunctionDeclaration() || this.isFunctionExpression()) {
       state.noOptimise = true;
       scope.traverse(node, memberExpressionOptimisationVisitor, state);
       state.noOptimise = false;
@@ -21,7 +21,7 @@ var memberExpressionOptimisationVisitor = {
     }
 
     // is this a referenced identifier and is it referencing the rest parameter?
-    if (!t.isReferencedIdentifier(node, parent, { name: state.name })) return;
+    if (!this.isReferencedIdentifier({ name: state.name })) return;
 
     if (!state.noOptimise && t.isMemberExpression(parent) && parent.computed) {
       // if we know that this member expression is referencing a number then we can safely
@@ -55,7 +55,7 @@ var hasRest = function (node) {
   return t.isRestElement(node.params[node.params.length - 1]);
 };
 
-exports.Function = function (node, parent, scope) {
+exports.Function = function (node, parent, scope, file) {
   if (!hasRest(node)) return;
 
   var rest = node.params.pop().argument;
@@ -69,10 +69,12 @@ exports.Function = function (node, parent, scope) {
   if (t.isPattern(rest)) {
     var pattern = rest;
     rest = scope.generateUidIdentifier("ref");
-    var declar = t.variableDeclaration("var", pattern.elements.map(function (elem, index) {
+
+    var declar = t.variableDeclaration("let", pattern.elements.map(function (elem, index) {
       var accessExpr = t.memberExpression(rest, t.literal(index), true);
       return t.variableDeclarator(elem, accessExpr);
     }));
+    file.checkNode(declar);
     node.body.body.unshift(declar);
   }
 

src/babel/transformation/transformers/es6/properties.shorthand.js

@@ -1,4 +1,3 @@
-import clone from "lodash/lang/clone";
 import t from "../../../types";
 
 export function check(node) {
@@ -12,6 +11,6 @@ export function Property(node) {
 
   if (node.shorthand) {
     node.shorthand = false;
-    node.key = t.removeComments(clone(node.key));
+    node.key = t.removeComments(t.clone(node.key));
   }
 }

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

@@ -17,7 +17,7 @@ function returnBlock(expr) {
 // looks for and replaces tail recursion calls
 var firstPass = {
   enter(node, parent, scope, state) {
-    if (t.isIfStatement(node)) {
+    if (this.isIfStatement()) {
       if (t.isReturnStatement(node.alternate)) {
         t.ensureBlock(node, "alternate");
       }
@@ -25,7 +25,7 @@ var firstPass = {
       if (t.isReturnStatement(node.consequent)) {
         t.ensureBlock(node, "consequent");
       }
-    } else if (t.isReturnStatement(node)) {
+    } else if (this.isReturnStatement()) {
       this.skip();
       return state.subTransform(node.argument);
     } else if (t.isTryStatement(parent)) {
@@ -34,9 +34,9 @@ var firstPass = {
       } else if (parent.finalizer && node !== parent.finalizer) {
         this.skip();
       }
-    } else if (t.isFunction(node)) {
+    } else if (this.isFunction()) {
       this.skip();
-    } else if (t.isVariableDeclaration(node)) {
+    } else if (this.isVariableDeclaration()) {
       this.skip();
       state.vars.push(node);
     }
@@ -47,15 +47,15 @@ var firstPass = {
 // them as needed
 var secondPass = {
   enter(node, parent, scope, state) {
-    if (t.isThisExpression(node)) {
+    if (this.isThisExpression()) {
       state.needsThis = true;
       return state.getThisId();
-    } else if (t.isReferencedIdentifier(node, parent, { name: "arguments" })) {
+    } else if (this.isReferencedIdentifier({ name: "arguments" })) {
       state.needsArguments = true;
       return state.getArgumentsId();
-    } else if (t.isFunction(node)) {
+    } else if (this.isFunction()) {
       this.skip();
-      if (t.isFunctionDeclaration(node)) {
+      if (this.isFunctionDeclaration()) {
         node = t.variableDeclaration("var", [
           t.variableDeclarator(node.id, t.toExpression(node))
         ]);
@@ -69,7 +69,7 @@ var secondPass = {
 // optimizes recursion by removing `this` and `arguments` if they aren't used
 var thirdPass = {
   enter(node, parent, scope, state) {
-    if (!t.isExpressionStatement(node)) return;
+    if (!this.isExpressionStatement()) return;
 
     var expr = node.expression;
     if (!t.isAssignmentExpression(expr)) return;
@@ -229,7 +229,7 @@ class TailCallTransformer {
   subTransform(node) {
     if (!node) return;
 
-    var handler = this["subTransform" + node.type];
+    var handler = this[`subTransform${node.type}`];
     if (handler) return handler.call(this, node);
   }
 

src/babel/transformation/transformers/index.js

@@ -1,9 +1,9 @@
 export default {
-  useStrict:                               require("./other/use-strict"),
+  strict:                                  require("./other/strict"),
+
+  _validation:                             require("./internal/validation"),
 
   "validation.undeclaredVariableCheck":    require("./validation/undeclared-variable-check"),
-  "validation.noForInOfAssignment":        require("./validation/no-for-in-of-assignment"),
-  "validation.setters":                    require("./validation/setters"),
   "validation.react":                      require("./validation/react"),
 
   // this goes at the start so we only transform the original user code
@@ -97,7 +97,7 @@ export default {
   "spec.typeofSymbol":                     require("./spec/typeof-symbol"),
   "spec.undefinedToVoid":                  require("./spec/undefined-to-void"),
 
-  _useStrict:                              require("./internal/use-strict"),
+  _strict:                                 require("./internal/strict"),
   _moduleFormatter:                        require("./internal/module-formatter"),
 
   "es3.propertyLiterals":                  require("./es3/property-literals"),

src/babel/transformation/transformers/internal/alias-functions.js

@@ -2,7 +2,7 @@ import t from "../../../types";
 
 var functionChildrenVisitor = {
   enter(node, parent, scope, state) {
-    if (t.isFunction(node) && !node._aliasFunction) {
+    if (this.isFunction() && !node._aliasFunction) {
       return this.skip();
     }
 
@@ -10,22 +10,22 @@ var functionChildrenVisitor = {
 
     var getId;
 
-    if (t.isIdentifier(node) && node.name === "arguments") {
+    if (this.isIdentifier() && node.name === "arguments") {
       getId = state.getArgumentsId;
-    } else if (t.isThisExpression(node)) {
+    } else if (this.isThisExpression()) {
       getId = state.getThisId;
     } else {
       return;
     }
 
-    if (t.isReferenced(node, parent)) return getId();
+    if (this.isReferenced()) return getId();
   }
 };
 
 var functionVisitor = {
   enter(node, parent, scope, state) {
     if (!node._aliasFunction) {
-      if (t.isFunction(node)) {
+      if (this.isFunction()) {
         // stop traversal of this node as it'll be hit again by this transformer
         return this.skip();
       } else {

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

@@ -1,4 +1,4 @@
-import * as useStrict from "../../helpers/use-strict";
+import * as strict from "../../helpers/strict";
 import t from "../../../types";
 
 export var secondPass = true;
@@ -6,7 +6,7 @@ export var secondPass = true;
 export function BlockStatement(node, parent, scope, file) {
   if (!node._declarations) return;
 
-  useStrict.wrap(node, function () {
+  strict.wrap(node, function () {
     var kinds = {};
     var kind;
 

src/babel/transformation/transformers/internal/module-formatter.js

@@ -1,12 +1,12 @@
-import * as useStrict from "../../helpers/use-strict";
+import * as strict from "../../helpers/strict";
 
 export function Program(program, parent, scope, file) {
-  if (!file.transformers["es6.modules"].canRun()) return;
-
-  useStrict.wrap(program, function () {
+  strict.wrap(program, function () {
     program.body = file.dynamicImports.concat(program.body);
   });
 
+  if (!file.transformers["es6.modules"].canRun()) return;
+
   if (file.moduleFormatter.transform) {
     file.moduleFormatter.transform(program);
   }

src/babel/transformation/transformers/internal/modules.js

@@ -13,7 +13,7 @@ export function check(node) {
 export function ImportDeclaration(node, parent, scope, file) {
   var resolveModuleSource = file.opts.resolveModuleSource;
   if (node.source && resolveModuleSource) {
-    node.source.value = resolveModuleSource(node.source.value);
+    node.source.value = resolveModuleSource(node.source.value, file.opts.filename);
   }
 }
 
@@ -52,6 +52,16 @@ export function ExportDeclaration(node, parent, scope) {
       node.declaration = null;
       node._blockHoist = 2;
       return [getDeclar(), node];
+    } else if (t.isVariableDeclaration(declar)) {
+      var specifiers = [];
+
+      var bindings = t.getBindingIdentifiers(declar);
+      for (var key in bindings) {
+        var id = bindings[key];
+        specifiers.push(t.exportSpecifier(id, id));
+      }
+
+      return [declar, t.exportDeclaration(null, specifiers)];
     }
   }
 }

src/babel/transformation/transformers/internal/strict.js

@@ -1,7 +1,7 @@
 import t from "../../../types";
 
 export function Program(program, parent, scope, file) {
-  if (file.transformers.useStrict.canRun()) {
+  if (file.transformers.strict.canRun()) {
     program.body.unshift(t.expressionStatement(t.literal("use strict")));
   }
 }

src/babel/transformation/transformers/internal/validation.js

@@ -0,0 +1,27 @@
+import * as messages from "../../../messages";
+import t from "../../../types";
+
+export function ForOfStatement(node, parent, scope, file) {
+  var left = node.left;
+  if (t.isVariableDeclaration(left)) {
+    var declar = left.declarations[0];
+    if (declar.init) throw file.errorWithNode(declar, messages.get("noAssignmentsInForHead"));
+  }
+}
+
+export { ForOfStatement as ForInStatement };
+
+export function Property(node, parent, scope, file) {
+  if (node.kind === "set") {
+    if (node.value.params.length !== 1) {
+      throw file.errorWithNode(node.value, messages.get("settersInvalidParamLength"));
+    }
+
+    var first = node.value.params[0];
+    if (t.isRestElement(first)) {
+      throw file.errorWithNode(first, messages.get("settersNoRest"));
+    }
+  }
+}
+
+export { Property as MethodDefinition };

src/babel/transformation/transformers/other/flow.js

@@ -13,12 +13,12 @@ export function Class(node) {
   node.implements = null;
 }
 
-export function Function(node) {
+exports.Function = function (node) {
   for (var i = 0; i < node.params.length; i++) {
     var param = node.params[i];
     param.optional = false;
   }
-}
+};
 
 export function TypeCastExpression(node) {
   return node.expression;

src/babel/transformation/transformers/other/runtime.js

@@ -16,14 +16,15 @@ var ALIASABLE_CONSTRUCTORS = [
   "Map",
   "WeakMap",
   "Set",
-  "WeakSet"
+  "WeakSet",
+  "Number"
 ];
 
 var astVisitor = {
   enter(node, parent, scope, file) {
     var prop;
 
-    if (t.isMemberExpression(node) && t.isReferenced(node, parent)) {
+    if (this.isMemberExpression() && this.isReferenced()) {
       // Array.from -> _core.Array.from
       var obj = node.object;
       prop = node.property;
@@ -34,10 +35,10 @@ var astVisitor = {
         this.skip();
         return t.prependToMemberExpression(node, file.get("coreIdentifier"));
       }
-    } else if (t.isReferencedIdentifier(node, parent) && !t.isMemberExpression(parent) && includes(ALIASABLE_CONSTRUCTORS, node.name) && !scope.getBindingIdentifier(node.name)) {
+    } else if (this.isReferencedIdentifier() && !t.isMemberExpression(parent) && includes(ALIASABLE_CONSTRUCTORS, node.name) && !scope.getBindingIdentifier(node.name)) {
       // Symbol() -> _core.Symbol(); new Promise -> new _core.Promise
       return t.memberExpression(file.get("coreIdentifier"), node);
-    } else if (t.isCallExpression(node)) {
+    } else if (this.isCallExpression()) {
       // arr[Symbol.iterator]() -> _core.$for.getIterator(arr)
 
       var callee = node.callee;
@@ -53,7 +54,7 @@ var astVisitor = {
         CORE_ID: file.get("coreIdentifier"),
         VALUE:   callee.object
       });
-    } else if (t.isBinaryExpression(node)) {
+    } else if (this.isBinaryExpression()) {
       // Symbol.iterator in arr -> core.$for.isIterable(arr)
 
       if (node.operator !== "in") return;
@@ -94,7 +95,7 @@ export function pre(file) {
 }
 
 export function Identifier(node, parent, scope, file) {
-  if (t.isReferencedIdentifier(node, parent, { name: "regeneratorRuntime" })) {
+  if (this.isReferencedIdentifier({ name: "regeneratorRuntime" })) {
     return file.get("regeneratorIdentifier");
   }
 }

src/babel/transformation/transformers/playground/mallet-operator.js

@@ -6,8 +6,7 @@ export var playground = true;
 
 build(exports, {
   is(node, file) {
-    var is = t.isAssignmentExpression(node) && node.operator === "||=";
-    if (is) {
+    if (t.isAssignmentExpression(node, { operator: "||=" })) {
       var left = node.left;
       if (!t.isMemberExpression(left) && !t.isIdentifier(left)) {
         throw file.errorWithNode(left, messages.get("expectedMemberExpressionOrIdentifier"));

src/babel/transformation/transformers/playground/memoization-operator.js

@@ -5,7 +5,7 @@ export var playground = true;
 
 build(exports, {
   is(node) {
-    var is = t.isAssignmentExpression(node) && node.operator === "?=";
+    var is = t.isAssignmentExpression(node, { operator: "?=" });
     if (is) t.assertMemberExpression(node.left);
     return is;
   },

src/babel/transformation/transformers/playground/object-getter-memoization.js

@@ -4,9 +4,9 @@ export var playground = true;
 
 var visitor = {
   enter(node, parent, scope, state) {
-    if (t.isFunction(node)) return this.skip();
+    if (this.isFunction()) return this.skip();
 
-    if (t.isReturnStatement(node) && node.argument) {
+    if (this.isReturnStatement() && node.argument) {
       node.argument = t.memberExpression(t.callExpression(state.file.addHelper("define-property"), [
         t.thisExpression(),
         state.key,

src/babel/transformation/transformers/spec/undefined-to-void.js

@@ -3,7 +3,7 @@ import t from "../../../types";
 export var optional = true;
 
 export function Identifier(node, parent) {
-  if (node.name === "undefined" && t.isReferenced(node, parent)) {
+  if (node.name === "undefined" && this.isReferenced()) {
     return t.unaryExpression("void", t.literal(0), true);
   }
 }

src/babel/transformation/transformers/utility/dead-code-elimination.js

@@ -19,8 +19,8 @@ function toStatements(node) {
 
 export var optional = true;
 
-export function ConditionalExpression(node) {
-  var evaluateTest = t.evaluateTruthy(node.test);
+export function ConditionalExpression(node, parent, scope) {
+  var evaluateTest = t.evaluateTruthy(node.test, scope);
   if (evaluateTest === true) {
     return node.consequent;
   } else if (evaluateTest === false) {
@@ -29,12 +29,12 @@ export function ConditionalExpression(node) {
 }
 
 export var IfStatement = {
-  exit(node) {
+  exit(node, parent, scope) {
     var consequent = node.consequent;
     var alternate  = node.alternate;
     var test       = node.test;
 
-    var evaluateTest = t.evaluateTruthy(test);
+    var evaluateTest = t.evaluateTruthy(test, scope);
 
     // we can check if a test will be truthy 100% and if so then we can inline
     // the consequent and completely ignore the alternate
@@ -77,7 +77,7 @@ export var IfStatement = {
     //   if (foo) {} else { bar; } -> if (!foo) { bar; }
     //
 
-    if (t.blockStatement(consequent) && !consequent.body.length && t.isBlockStatement(alternate) && alternate.body.length) {
+    if (t.isBlockStatement(consequent) && !consequent.body.length && t.isBlockStatement(alternate) && alternate.body.length) {
       node.consequent = node.alternate;
       node.alternate  = null;
       node.test       = t.unaryExpression("!", test, true);

src/babel/transformation/transformers/utility/inline-expressions.js

@@ -2,7 +2,11 @@ import t from "../../../types";
 
 export var optional = true;
 
-export function Expression(node) {
-  var res = t.evaluate(node);
+export function Expression(node, parent, scope) {
+  var res = t.evaluate(node, scope);
   if (res.confident) return t.valueToNode(res.value);
 }
+
+export function Identifier() {
+  // override Expression
+}

src/babel/transformation/transformers/utility/remove-debugger.js

@@ -3,7 +3,7 @@ import t from "../../../types";
 export var optional = true;
 
 export function ExpressionStatement(node) {
-  if (t.isIdentifier(node.expression, { name: "debugger" })) {
+  if (this.get("expression").isIdentifier({ name: "debugger" })) {
     this.remove();
   }
 }

src/babel/transformation/transformers/validation/no-for-in-of-assignment.js

@@ -1,14 +0,0 @@
-import * as messages from "../../../messages";
-import t from "../../../types";
-
-export { isFor as check } from "../../../types";
-
-export function ForOfStatement(node, parent, scope, file) {
-  var left = node.left;
-  if (t.isVariableDeclaration(left)) {
-    var declar = left.declarations[0];
-    if (declar.init) throw file.errorWithNode(declar, messages.get("noAssignmentsInForHead"));
-  }
-}
-
-export { ForOfStatement as ForInStatement };

src/babel/transformation/transformers/validation/react.js

@@ -2,7 +2,7 @@ import * as messages from "../../../messages";
 import t from "../../../types";
 
 // check if the input Literal `source` is an alternate casing of "react"
-var check = function (source, file) {
+function check(source, file) {
   if (t.isLiteral(source)) {
     var name  = source.value;
     var lower = name.toLowerCase();
@@ -11,7 +11,7 @@ var check = function (source, file) {
       throw file.errorWithNode(source, messages.get("didYouMean", "react"));
     }
   }
-};
+}
 
 export function CallExpression(node, parent, scope, file) {
   if (t.isIdentifier(node.callee, { name: "require" }) && node.arguments.length === 1) {

src/babel/transformation/transformers/validation/setters.js

@@ -1,13 +0,0 @@
-import * as messages from "../../../messages";
-
-export function check(node) {
-  return node.kind === "set";
-}
-
-export function Property(node, parent, scope, file) {
-  if (node.kind === "set" && node.value.params.length !== 1) {
-    throw file.errorWithNode(node.value, messages.get("settersInvalidParamLength"));
-  }
-}
-
-export { Property as MethodDefinition };

src/babel/transformation/transformers/validation/undeclared-variable-check.js

@@ -1,11 +1,10 @@
 import levenshtein from "leven";
 import * as messages from "../../../messages";
-import t from "../../../types";
 
 export var optional = true;
 
 export function Identifier(node, parent, scope, file) {
-  if (!t.isReferenced(node, parent)) return;
+  if (!this.isReferenced()) return;
   if (scope.hasBinding(node.name)) return;
 
   // get the closest declaration to offer as a suggestion

src/babel/traversal/context.js

@@ -2,14 +2,13 @@ import TraversalPath from "./path";
 import flatten from "lodash/array/flatten";
 import compact from "lodash/array/compact";
 
-export default class TraversalConext {
+export default class TraversalContext {
   constructor(scope, opts, state, parentPath) {
     this.shouldFlatten = false;
     this.parentPath    = parentPath;
-
-    this.scope = scope;
-    this.state = state;
-    this.opts  = opts;
+    this.scope         = scope;
+    this.state         = state;
+    this.opts          = opts;
   }
 
   flatten() {
@@ -17,7 +16,7 @@ export default class TraversalConext {
   }
 
   visitNode(node, obj, key) {
-    var iteration = new TraversalPath(this, node, obj, key);
+    var iteration = TraversalPath.get(this.parentPath, this, node, obj, key);
     return iteration.visit();
   }
 

src/babel/traversal/index.js

@@ -9,7 +9,7 @@ function traverse(parent, opts, scope, state) {
 
   if (!opts.noScope && !scope) {
     if (parent.type !== "Program" && parent.type !== "File") {
-      throw new Error("Must pass a scope unless traversing a Program/File got a " + parent.type + " node");
+      throw new Error(`Must pass a scope unless traversing a Program/File got a ${parent.type} node`);
     }
   }
 
@@ -42,13 +42,14 @@ traverse.node = function (node, opts, scope, state, parentPath) {
 function clearNode(node) {
   node._declarations = null;
   node.extendedRange = null;
-  node._scopeInfo = null;
-  node.tokens = null;
-  node.range = null;
-  node.start = null;
-  node.end = null;
-  node.loc = null;
-  node.raw = null;
+  node._scopeInfo    = null;
+  node._paths        = null;
+  node.tokens        = null;
+  node.range         = null;
+  node.start         = null;
+  node.end           = null;
+  node.loc           = null;
+  node.raw           = null;
 
   if (Array.isArray(node.trailingComments)) {
     clearComments(node.trailingComments);
@@ -57,11 +58,18 @@ function clearNode(node) {
   if (Array.isArray(node.leadingComments)) {
     clearComments(node.leadingComments);
   }
+
+  for (var key in node) {
+    var val = node[key];
+    if (Array.isArray(val)) {
+      delete val._paths;
+    }
+  }
 }
 
 var clearVisitor = {
   noScope: true,
-  enter: clearNode
+  exit: clearNode
 };
 
 function clearComments(comments) {
@@ -71,8 +79,8 @@ function clearComments(comments) {
 }
 
 traverse.removeProperties = function (tree) {
-  clearNode(tree);
   traverse(tree, clearVisitor);
+  clearNode(tree);
 
   return tree;
 };

src/babel/traversal/path.js

@@ -4,23 +4,33 @@ import Scope from "./scope";
 import t from "../types";
 
 export default class TraversalPath {
-  constructor(context, parent, container, key) {
-    this.shouldRemove = false;
-    this.shouldSkip   = false;
-    this.shouldStop   = false;
-
-    this.parentPath = context.parentPath;
-    this.context    = context;
-    this.state      = this.context.state;
-    this.opts       = this.context.opts;
-
+  constructor(parent, container) {
     this.container = container;
-    this.key       = key;
+    this.parent    = parent;
+    this.data      = {};
+  }
 
-    this.parent = parent;
-    this.state  = context.state;
+  static get(parentPath, context, parent, container, key) {
+    var targetNode = container[key];
+    var paths = container._paths ||= [];
+    var path;
 
-    this.setScope();
+    for (var i = 0; i < paths.length; i++) {
+      var pathCheck = paths[i];
+      if (pathCheck.node === targetNode) {
+        path = pathCheck;
+        break;
+      }
+    }
+
+    if (!path) {
+      path = new TraversalPath(parent, container);
+      paths.push(path);
+    }
+
+    path.setContext(parentPath, context, key);
+
+    return path;
   }
 
   static getScope(node, parent, scope) {
@@ -34,10 +44,32 @@ export default class TraversalPath {
     return ourScope;
   }
 
+  setData(key, val) {
+    return this.data[key] = val;
+  }
+
+  getData(key) {
+    return this.data[key];
+  }
+
   setScope() {
     this.scope = TraversalPath.getScope(this.node, this.parent, this.context.scope);
   }
 
+  setContext(parentPath, context, key) {
+    this.shouldRemove = false;
+    this.shouldSkip   = false;
+    this.shouldStop   = false;
+
+    this.parentPath = parentPath;
+    this.context    = context;
+    this.state      = context.state;
+    this.opts       = context.opts;
+    this.key        = key;
+
+    this.setScope();
+  }
+
   remove() {
     this.shouldRemove = true;
     this.shouldSkip   = true;
@@ -114,14 +146,13 @@ export default class TraversalPath {
     }
   }
 
-  visit() {
-    var opts = this.opts;
-    var node = this.node;
+  isBlacklisted() {
+    var blacklist = this.opts.blacklist;
+    return blacklist && blacklist.indexOf(this.node.type) > -1;
+  }
 
-    // type is blacklisted
-    if (opts.blacklist && opts.blacklist.indexOf(node.type) > -1) {
-      return false;
-    }
+  visit() {
+    if (this.isBlacklisted()) return false;
 
     this.call("enter");
 
@@ -129,7 +160,8 @@ export default class TraversalPath {
       return this.shouldStop;
     }
 
-    node = this.node;
+    var node = this.node;
+    var opts = this.opts;
 
     if (Array.isArray(node)) {
       // traverse over these replacement nodes we purposely don't call exitNode
@@ -139,13 +171,38 @@ export default class TraversalPath {
       }
     } else {
       traverse.node(node, opts, this.scope, this.state, this);
+
       this.call("exit");
     }
 
     return this.shouldStop;
   }
 
-  isReferencedIdentifier() {
-    return t.isReferencedIdentifier(this.node);
+  get(key) {
+    return TraversalPath.get(this, this.context, this.node, this.node, key);
+  }
+
+  isReferencedIdentifier(opts) {
+    return t.isReferencedIdentifier(this.node, this.parent, opts);
+  }
+
+  isReferenced() {
+    return t.isReferenced(this.node, this.parent);
+  }
+
+  isScope() {
+    return t.isScope(this.node, this.parent);
+  }
+
+  getBindingIdentifiers() {
+    return t.getBindingIdentifiers(this.node);
   }
 }
+
+for (var i = 0; i < t.TYPES.length; i++) {
+  let type = t.TYPES[i];
+  let typeKey = `is${type}`;
+  TraversalPath.prototype[typeKey] = function (opts) {
+    return t[typeKey](this.node, opts);
+  };
+}

src/babel/traversal/scope.js

@@ -82,6 +82,7 @@ export default class Scope {
   }
 
   static globals = flatten([globals.builtin, globals.browser, globals.node].map(Object.keys));
+  static contextVariables = ["this", "arguments"];
 
   /**
    * Description
@@ -143,7 +144,7 @@ export default class Scope {
   _generateUid(name, i) {
     var id = name;
     if (i > 1) id += i;
-    return "_" + id;
+    return `_${id}`;
   }
 
   /*
@@ -415,7 +416,7 @@ export default class Scope {
   registerVariableDeclaration(declar) {
     var declars = declar.declarations;
     for (var i = 0; i < declars.length; i++) {
-      this.registerBinding(declars[i], declar.kind);
+      this.registerBinding(declar.kind, declars[i]);
     }
   }
 
@@ -533,12 +534,12 @@ export default class Scope {
     if (t.isBlockStatement(block) || t.isProgram(block)) {
       block._declarations ||= {};
       block._declarations[opts.key] = {
-        kind: opts.kind,
+        kind: opts.kind || "var",
         id: opts.id,
         init: opts.init
       };
     } else {
-      throw new TypeError("cannot add a declaration here in node type " + block.type);
+      throw new TypeError(`cannot add a declaration here in node type ${block.type}`);
     }
   }
 
@@ -626,6 +627,37 @@ export default class Scope {
     return binding && binding.identifier;
   }
 
+
+  getOwnImmutableBindingValue(name) {
+    return this._immutableBindingInfoToValue(this.getOwnBindingInfo(name));
+  }
+
+  getImmutableBindingValue(name) {
+    return this._immutableBindingInfoToValue(this.getBindingInfo(name));
+  }
+
+  _immutableBindingInfoToValue(info) {
+    if (!info) return;
+
+    // can't guarantee this value is the same
+    if (info.reassigned) return;
+
+    var node = info.node;
+    if (t.isVariableDeclarator(node)) {
+      if (t.isIdentifier(node.id)) {
+        node = node.init;
+      } else {
+        // otherwise it's probably a destructuring like:
+        // var { foo } = "foo";
+        return;
+      }
+    }
+
+    if (t.isImmutable(node)) {
+      return node;
+    }
+  }
+
   // has
 
   hasOwnBinding(name) {
@@ -637,6 +669,7 @@ export default class Scope {
     if (this.hasOwnBinding(name)) return true;
     if (this.parentHasBinding(name)) return true;
     if (includes(Scope.globals, name)) return true;
+    if (includes(Scope.contextVariables, name)) return true;
     return false;
   }
 

src/babel/types/index.js

@@ -1,4 +1,4 @@
-import toFastProperties from "../helpers/to-fast-properties";
+import toFastProperties from "to-fast-properties";
 import isPlainObject from "lodash/lang/isPlainObject";
 import isNumber from "lodash/lang/isNumber";
 import isRegExp from "lodash/lang/isRegExp";
@@ -6,6 +6,7 @@ import isString from "lodash/lang/isString";
 import compact from "lodash/array/compact";
 import esutils from "esutils";
 import object from "../helpers/object";
+import clone from "lodash/lang/clone";
 import each from "lodash/collection/each";
 import uniq from "lodash/array/uniq";
 
@@ -21,19 +22,19 @@ export default t;
  */
 
 function registerType(type, skipAliasCheck) {
-  var is = t["is" + type] = function (node, opts) {
+  var is = t[`is${type}`] = function (node, opts) {
     return t.is(type, node, opts, skipAliasCheck);
   };
 
-  t["assert" + type] = function (node, opts) {
+  t[`assert${type}`] = function (node, opts) {
     opts ||= {};
     if (!is(node, opts)) {
-      throw new Error("Expected type " + JSON.stringify(type) + " with option " + JSON.stringify(opts));
+      throw new Error(`Expected type ${JSON.stringify(type)} with option ${JSON.stringify(opts)}`);
     }
   };
 }
 
-t.STATEMENT_OR_BLOCK_KEYS = ["consequent", "body"];
+t.STATEMENT_OR_BLOCK_KEYS = ["consequent", "body", "alternate"];
 t.NATIVE_TYPE_NAMES       = ["Array", "Object", "Number", "Boolean", "Date", "Array", "String"];
 t.FOR_INIT_KEYS           = ["left", "init"];
 
@@ -48,7 +49,7 @@ each(t.VISITOR_KEYS, function (keys, type) {
 
 each(t.ALIAS_KEYS, function (aliases, type) {
   each(aliases, function (alias) {
-    var types = t.FLIPPED_ALIAS_KEYS[alias] = t.FLIPPED_ALIAS_KEYS[alias] || [];
+    var types = t.FLIPPED_ALIAS_KEYS[alias] ||= [];
     types.push(type);
   });
 });
@@ -58,6 +59,8 @@ each(t.FLIPPED_ALIAS_KEYS, function (types, type) {
   registerType(type, false);
 });
 
+t.TYPES = Object.keys(t.VISITOR_KEYS).concat(Object.keys(t.FLIPPED_ALIAS_KEYS));
+
 /**
  * Returns whether `node` is of given `type`.
  *
@@ -141,22 +144,6 @@ t.toComputedKey = function (node, key) {
   return key;
 };
 
-/*
- * Shallowly checks to see if the passed `node` is falsy.
- *
- * @param {Object} node
- * @returns {Boolean}
- */
-
-t.isFalsyExpression = function (node) {
-  if (t.isLiteral(node)) {
-    return !node.value;
-  } else if (t.isIdentifier(node)) {
-    return node.name === "undefined";
-  }
-  return false;
-};
-
 /**
  * Turn an array of statement `nodes` into a `SequenceExpression`.
  *
@@ -292,6 +279,16 @@ t.isReferenced = function (node, parent) {
     return parent.id !== node;
   }
 
+  // no: export { foo as NODE };
+  if (t.isExportSpecifier(parent, { name: node })) {
+    return false;
+  }
+
+  // no: import { NODE as foo } from "foo";
+  if (t.isImportSpecifier(parent, { id: node })) {
+    return false;
+  }
+
   // no: class NODE {}
   if (t.isClass(parent)) {
     return parent.id !== node;
@@ -395,7 +392,7 @@ t.toIdentifier = function (name) {
   });
 
   if (!t.isValidIdentifier(name)) {
-    name = "_" + name;
+    name = `_${name}`;
   }
 
   return name || "_";
@@ -413,6 +410,51 @@ t.ensureBlock = function (node, key) {
   return node[key] = t.toBlock(node[key], node);
 };
 
+/**
+ * Description
+ *
+ * @param {Object} node
+ * @returns {Object}
+ */
+
+t.clone = function (node) {
+  var newNode = {};
+  for (var key in node) {
+    if (key[0] === "_") continue;
+    newNode[key] = node[key];
+  }
+  return newNode;
+};
+
+/**
+ * Description
+ *
+ * @param {Object} node
+ * @returns {Object}
+ */
+
+t.cloneDeep = function (node) {
+  var newNode = {};
+
+  for (var key in node) {
+    if (key[0] === "_") continue;
+
+    var val = node[key];
+
+    if (val) {
+      if (val.type) {
+        val = t.cloneDeep(val);
+      } else if (Array.isArray(val)) {
+        val = val.map(t.cloneDeep);
+      }
+    }
+
+    newNode[key] = val;
+  }
+
+  return newNode;
+};
+
 /**
  * Build a function that when called will return whether or not the
  * input `node` `MemberExpression` matches the input `match`.
@@ -506,7 +548,7 @@ t.toStatement = function (node, ignore) {
     if (ignore) {
       return false;
     } else {
-      throw new Error("cannot turn " + node.type + " to a statement");
+      throw new Error(`cannot turn ${node.type} to a statement`);
     }
   }
 
@@ -536,7 +578,7 @@ t.toExpression = function (node) {
   if (t.isExpression(node)) {
     return node;
   } else {
-    throw new Error("cannot turn " + node.type + " to an expression");
+    throw new Error(`cannot turn ${node.type} to an expression`);
   }
 };
 
@@ -807,6 +849,35 @@ t.isScope = function (node, parent) {
   return t.isScopable(node);
 };
 
+/**
+ * Description
+ *
+ * @param {Node} node
+ * @returns {Boolean}
+ */
+
+t.isImmutable = function (node) {
+  if (t.isLiteral(node)) {
+    if (node.regex) {
+      // regexes are mutable
+      return false;
+    } else {
+      // immutable!
+      return true;
+    }
+  } else if (t.isIdentifier(node)) {
+    if (node.name === "undefined") {
+      // immutable!
+      return true;
+    } else {
+      // no idea...
+      return false;
+    }
+  }
+
+  return false;
+};
+
 /**
  * Walk the input `node` and statically evaluate if it's truthy.
  *
@@ -824,11 +895,12 @@ t.isScope = function (node, parent) {
  *   if (!t.evaluateTruthy(node)) falsyLogic();
  *
  * @param {Node} node
+ * @param {Scope} scope
  * @returns {Boolean}
  */
 
-t.evaluateTruthy = function (node) {
-  var res = t.evaluate(node);
+t.evaluateTruthy = function (node, scope) {
+  var res = t.evaluate(node, scope);
   if (res.confident) return !!res.value;
 };
 
@@ -846,10 +918,11 @@ t.evaluateTruthy = function (node) {
  *   t.evaluate(parse("foo + foo")) // { confident: false, value: undefined }
  *
  * @param {Node} node
+ * @param {Scope} scope
  * @returns {Object}
  */
 
-t.evaluate = function (node) {
+t.evaluate = function (node, scope) {
   var confident = true;
 
   var value = evaluate(node);
@@ -882,30 +955,26 @@ t.evaluate = function (node) {
       }
     }
 
-    if (t.isIdentifier(node, { name: "undefined" })) {
-      return undefined;
+    if (t.isIdentifier(node)) {
+      if (node.name === "undefined") {
+        return undefined;
+      } else {
+        return evaluate(scope.getImmutableBindingValue(node.name));
+      }
     }
 
     if (t.isUnaryExpression(node, { prefix: true })) {
+      var arg = evaluate(node.argument);
       switch (node.operator) {
         case "void": return undefined;
-        case "!": return !evaluate(node.argument);
-        case "+": return +evaluate(node.argument);
-        case "-": return -evaluate(node.argument);
+        case "!": return !arg;
+        case "+": return +arg;
+        case "-": return -arg;
       }
     }
 
-    if (t.isArrayExpression(node)) {
-      // possible perf issues - could deopt on X elements
-      var values = [];
-      for (var i = 0; i < node.elements.length; i++) {
-        values.push(evaluate(node.elements[i]));
-      }
-      return values;
-    }
-
-    if (t.isObjectExpression(node)) {
-      // todo: deopt on mutable computed property keys etc
+    if (t.isArrayExpression(node) || t.isObjectExpression(node)) {
+      // we could evaluate these but it's probably impractical and not very useful
     }
 
     if (t.isLogicalExpression(node)) {

src/babel/util.js

@@ -3,6 +3,7 @@ import "./patch";
 import buildDebug from "debug/node";
 import cloneDeep from "lodash/lang/cloneDeep";
 import isBoolean from "lodash/lang/isBoolean";
+import * as messages from "./messages";
 import contains from "lodash/collection/contains";
 import traverse from "./traversal";
 import isString from "lodash/lang/isString";
@@ -20,7 +21,7 @@ export { inherits, inspect } from "util";
 export var debug = buildDebug("babel");
 
 export function canCompile(filename, altExts) {
-  var exts = altExts || exports.canCompile.EXTENSIONS;
+  var exts = altExts || canCompile.EXTENSIONS;
   var ext = path.extname(filename);
   return contains(exts, ext);
 }
@@ -50,7 +51,7 @@ export function regexify(val) {
 export function arrayify(val) {
   if (!val) return [];
   if (isBoolean(val)) return [val];
-  if (isString(val)) return exports.list(val);
+  if (isString(val)) return list(val);
   if (Array.isArray(val)) return val;
   throw new TypeError("illegal type for arrayify");
 }
@@ -71,11 +72,13 @@ var templateVisitor = {
       return nodes[node.name];
     }
   }
-};
+}
+
+//
 
 export function template(name, nodes, keepExpression) {
   var ast = exports.templates[name];
-  if (!ast) throw new ReferenceError("unknown template " + name);
+  if (!ast) throw new ReferenceError(`unknown template ${name}`);
 
   if (nodes === true) {
     keepExpression = true;
@@ -101,7 +104,8 @@ export function template(name, nodes, keepExpression) {
 
 export function parseTemplate(loc, code) {
   var ast = parse({ filename: loc }, code).program;
-  return traverse.removeProperties(ast);
+  ast = traverse.removeProperties(ast);
+  return ast;
 }
 
 function loadTemplates() {
@@ -109,9 +113,7 @@ function loadTemplates() {
 
   var templatesLoc = path.join(__dirname, "transformation/templates");
   if (!fs.existsSync(templatesLoc)) {
-    throw new Error("no templates directory - this is most likely the " +
-                    "result of a broken `npm publish`. Please report to " +
-                    "https://github.com/babel/babel/issues");
+    throw new ReferenceError(messages.get("missingTemplatesDirectory"));
   }
 
   each(fs.readdirSync(templatesLoc), function (name) {
@@ -131,6 +133,5 @@ try {
   exports.templates = require("../../templates.json");
 } catch (err) {
   if (err.code !== "MODULE_NOT_FOUND") throw err;
-
   exports.templates = loadTemplates();
 }

test/_transformation-helper.js

@@ -1,17 +1,20 @@
-var genHelpers = require("./_generator-helpers");
-var transform  = require("../lib/babel/transformation");
-var sourceMap  = require("source-map");
-var codeFrame  = require("../lib/babel/helpers/code-frame");
-var Module     = require("module");
-var helper     = require("./_helper");
-var assert     = require("assert");
-var chai       = require("chai");
-var path       = require("path");
-var util       = require("../lib/babel/util");
-var _          = require("lodash");
+var genHelpers          = require("./_generator-helpers");
+var transform           = require("../lib/babel/transformation");
+var buildExernalHelpers = require("../lib/babel/build-external-helpers");
+var sourceMap           = require("source-map");
+var codeFrame           = require("../lib/babel/helpers/code-frame");
+var Module              = require("module");
+var helper              = require("./_helper");
+var assert              = require("assert");
+var chai                = require("chai");
+var path                = require("path");
+var util                = require("../lib/babel/util");
+var _                   = require("lodash");
 
 require("../lib/babel/polyfill");
 
+eval(buildExernalHelpers());
+
 global.assertNoOwnProperties = function (obj) {
   assert.equal(Object.getOwnPropertyNames(obj).length, 0);
 };
@@ -83,8 +86,8 @@ var run = function (task, done) {
         }
       };
 
-      var fn = new Function("require", "done", execCode);
-      fn.call(global, fakeRequire, chai.assert, done);
+      var fn = new Function("require", "done", "exports", execCode);
+      fn.call(global, fakeRequire, chai.assert, {}, done);
     } catch (err) {
       err.message = exec.loc + ": " + err.message;
       err.message += codeFrame(execCode);

test/fixtures/transformation/async-to-generator/async/expected.js

@@ -1,25 +1,16 @@
 "use strict";
 
-var _asyncToGenerator = function (fn) { return function () { var gen = fn.apply(this, arguments); return new Promise(function (resolve, reject) { var callNext = step.bind(null, "next"); var callThrow = step.bind(null, "throw"); function step(key, arg) { try { var info = gen[key](arg); var value = info.value; } catch (error) { reject(error); return; } if (info.done) { resolve(value); } else { Promise.resolve(value).then(callNext, callThrow); } } callNext(); }); }; };
-
-var _prototypeProperties = function (child, staticProps, instanceProps) { if (staticProps) Object.defineProperties(child, staticProps); if (instanceProps) Object.defineProperties(child.prototype, instanceProps); };
-
-var _classCallCheck = function (instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } };
-
 var Foo = (function () {
   function Foo() {
-    _classCallCheck(this, Foo);
+    babelHelpers.classCallCheck(this, Foo);
   }
 
-  _prototypeProperties(Foo, null, {
+  babelHelpers.createClass(Foo, {
     foo: {
-      value: _asyncToGenerator(function* () {
+      value: babelHelpers.asyncToGenerator(function* () {
         var wat = yield bar();
-      }),
-      writable: true,
-      configurable: true
+      })
     }
   });
-
   return Foo;
 })();

test/fixtures/transformation/async-to-generator/expression/expected.js

@@ -1,7 +1,5 @@
 "use strict";
 
-var _asyncToGenerator = function (fn) { return function () { var gen = fn.apply(this, arguments); return new Promise(function (resolve, reject) { var callNext = step.bind(null, "next"); var callThrow = step.bind(null, "throw"); function step(key, arg) { try { var info = gen[key](arg); var value = info.value; } catch (error) { reject(error); return; } if (info.done) { resolve(value); } else { Promise.resolve(value).then(callNext, callThrow); } } callNext(); }); }; };
-
-var foo = _asyncToGenerator(function* () {
+var foo = babelHelpers.asyncToGenerator(function* () {
   var wat = yield bar();
-});
+});

test/fixtures/transformation/async-to-generator/options.json

@@ -1,4 +1,5 @@
 {
+  "externalHelpers": true,
   "noCheckAst": true,
   "optional": ["asyncToGenerator"]
 }

test/fixtures/transformation/async-to-generator/statement/expected.js

@@ -1,7 +1,5 @@
 "use strict";
 
-var _asyncToGenerator = function (fn) { return function () { var gen = fn.apply(this, arguments); return new Promise(function (resolve, reject) { var callNext = step.bind(null, "next"); var callThrow = step.bind(null, "throw"); function step(key, arg) { try { var info = gen[key](arg); var value = info.value; } catch (error) { reject(error); return; } if (info.done) { resolve(value); } else { Promise.resolve(value).then(callNext, callThrow); } } callNext(); }); }; };
-
-var foo = _asyncToGenerator(function* () {
+var foo = babelHelpers.asyncToGenerator(function* () {
   var wat = yield bar();
-});
+});

test/fixtures/transformation/bluebird-coroutines/class/expected.js

@@ -2,7 +2,7 @@
 
 var _bluebird = require("bluebird");
 
-var _prototypeProperties = function (child, staticProps, instanceProps) { if (staticProps) Object.defineProperties(child, staticProps); if (instanceProps) Object.defineProperties(child.prototype, instanceProps); };
+var _createClass = (function () { function defineProperties(target, props) { for (var key in props) { var prop = props[key]; prop.configurable = true; if (prop.value) prop.writable = true; } Object.defineProperties(target, props); } return function (Constructor, protoProps, staticProps) { if (protoProps) defineProperties(Constructor.prototype, protoProps); if (staticProps) defineProperties(Constructor, staticProps); return Constructor; }; })();
 
 var _classCallCheck = function (instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } };
 
@@ -11,13 +11,11 @@ var Foo = (function () {
     _classCallCheck(this, Foo);
   }
 
-  _prototypeProperties(Foo, null, {
+  _createClass(Foo, {
     foo: {
       value: _bluebird.coroutine(function* () {
         var wat = yield bar();
-      }),
-      writable: true,
-      configurable: true
+      })
     }
   });
 

test/fixtures/transformation/bluebird-coroutines/expression/expected.js

@@ -4,4 +4,4 @@ var _bluebird = require("bluebird");
 
 var foo = _bluebird.coroutine(function* () {
   var wat = yield bar();
-});
+});

test/fixtures/transformation/bluebird-coroutines/statement/expected.js

@@ -4,4 +4,4 @@ var _bluebird = require("bluebird");
 
 var foo = _bluebird.coroutine(function* () {
   var wat = yield bar();
-});
+});

test/fixtures/transformation/es5-property.mutators/getter-and-setter/expected.js

@@ -8,7 +8,7 @@ var obj = Object.defineProperties({}, {
     set: function (value) {
       this._foo = value;
     },
-    enumerable: true,
-    configurable: true
+    configurable: true,
+    enumerable: true
   }
-});
+});

test/fixtures/transformation/es5-property.mutators/getter/expected.js

@@ -5,7 +5,7 @@ var obj = Object.defineProperties({}, {
     get: function () {
       return 5 + 5;
     },
-    enumerable: true,
-    configurable: true
+    configurable: true,
+    enumerable: true
   }
-});
+});

test/fixtures/transformation/es5-property.mutators/setter/expected.js

@@ -5,7 +5,7 @@ var obj = Object.defineProperties({}, {
     set: function (value) {
       this._foo = value;
     },
-    enumerable: true,
-    configurable: true
+    configurable: true,
+    enumerable: true
   }
-});
+});

test/fixtures/transformation/es6-block-scoping-tdz-fail/destructuring.js

@@ -0,0 +1,9 @@
+function foo(
+   { x: { y: { z: a = b } = {}, w: b = 20 }, a: c = 30 }
+) {
+  assert.equal(a, 10);
+  assert.equal(b, 20);
+  assert.equal(c, 30);
+}
+
+foo({ x: {} });

test/fixtures/transformation/es6-block-scoping-tdz-fail/export.js

@@ -0,0 +1,2 @@
+a;
+export const a = 1;

test/fixtures/transformation/es6-block-scoping-tdz-pass/destructuring.js

@@ -0,0 +1,9 @@
+function foo(
+   { x: { y: { z: a = 10 } = {}, w: b = 20 }, a: c = 30 }
+) {
+  assert.equal(a, 10);
+  assert.equal(b, 20);
+  assert.equal(c, 30);
+}
+
+foo({ x: {} });