v5.5.8

Really fix "--help"

.eslintrc

@@ -3,18 +3,21 @@
   "rules": {
     "strict": 0,
     "no-underscore-dangle": 0,
-    "no-unused-vars": 0,
     "curly": 0,
     "no-multi-spaces": 0,
     "key-spacing": 0,
     "no-return-assign": 0,
     "consistent-return": 0,
     "no-shadow": 0,
-    "no-comma-dangle": 0,
+    "comma-dangle": 0,
     "no-use-before-define": 0,
     "no-empty": 0,
     "new-parens": 0,
-    "no-cond-assign": 0
+    "no-cond-assign": 0,
+    "no-fallthrough": 0,
+    "new-cap": 0,
+    "no-loop-func": 0,
+    "no-unreachable": 0
   },
   "env": {
     "node": true

.gitignore

@@ -8,10 +8,10 @@ test/core/tmp
 /browser.js
 /browser-polyfill.js
 /runtime.js
-coverage
-dist
-.package.json
-packages/babel-runtime/core-js
-packages/babel-runtime/helpers/*.js
-packages/babel-runtime/regenerator/*.js
-lib
+/coverage
+/dist
+/.package.json
+/packages/babel-runtime/core-js
+/packages/babel-runtime/helpers/*.js
+/packages/babel-runtime/regenerator/*.js
+/lib

.travis.yml

@@ -11,9 +11,4 @@ before_script: "npm install -g codeclimate-test-reporter"
 script: "make test-travis"
 
 notifications:
-  webhooks:
-    urls:
-      - https://webhooks.gitter.im/e/acf1870e9d223c65e8d5
-    on_success: always
-    on_failure: always
-    on_start: false
+  slack: babeljs:5Wy4QX13KVkGy9CnU0rmvgeK

CHANGELOG.md

@@ -13,6 +13,65 @@ _Note: Gaps between patch versions are faulty/broken releases._
 
 See [CHANGELOG - 6to5](CHANGELOG-6to5.md) for the pre-4.0.0 version changelog.
 
+## 5.5.6
+
+ * **Bug Fix**
+  * Fix `let` binding collision in loop head not properly replacing `AssignmentExpression`s.
+
+## 5.5.5
+
+ * **Bug Fix**
+  * Fix `file.opts` not being set before `file.log.deprecate` was called causing a `ReferenceError` as it was checking for a property on it.
+
+## 5.5.4
+
+ * **Bug Fix**
+  * Add back missing `shouldIgnore` check.
+  * Log message on deprecated options rather than throw an error.
+  * Fix name of `auxiliaryComment` option when attempting Istanbul interop in `babel/register`.
+
+## 5.5.3
+
+ * **Bug Fix**
+  * Fix weird state bug when traversing overa  `node` `ClassProperty` instead of `path` in the `es6.classes` transformer.
+
+## 5.5.2
+
+ * **Bug Fix**
+  * Fix `NodePath#isPure` on `Property` nodes.
+  * Use cwd instead of entry file directory when working out relative directory for `babel/register`.
+ * **Internal**
+  * Add scary warning for those few who choose to use the WIP experimental transformers.
+
+## 5.5.1
+
+ * **Bug Fix**
+  * Remove `ClassProperty` nodes always in the `Flow` transformer. This is fine now since class properties aren't supported in any engine that supports classes but the `es7.classProperties` transformer will need to be updated in the future to desugar to ES6 classes instead of relying on the `es6.classes` transformer from being ran.
+
+## 5.5.0
+
+ * **Bug Fix**
+  * Allow pushing declarations to `SwitchStatement`s.
+  * Fix `minification.removeDebugger` to remove `DebuggerStatement`s rather than `ExpressionStatement`s with an identifier of `debugger`.
+  * Check LHS in `ForInStatement` and `ForOfStatement` for constant violations.
+  * Register function `id` as a reference when naming methods to avoid collisions.
+  * Support key literals when checking for the existence of `displayName` property when attempting to add it for `React.createClass`.
+  * Remove `ExportDefaultSpecifier` check from `t.isDefaultSpecifier`.
+  * Don't consider `JSXIdentifier` HTML tag identifiers to be references.
+ * **Polish**
+  * Update `minification.deadCodeElimination` transformer to remove all statements after completion statements.
+  * Update `minification.deadCodeElimination` transformer to not inline single used bindings that exist in different scopes.
+  * When performing Istanbul interop in `babel/register`, add the auxiliary comment `"istanbul ignore text"` to get more accurate coverage.
+  * Add `--nolazy` argument to `babel-node`.
+  * Add support for `cluster` forking.
+  * Perform scope tracking in a single pass instead of multiple.
+  * Smarten up type inferrence and resolution to support the whole array of language constructs.
+  * Optimise module metadata retrieval into a single pass.
+  * Ignore trailing commas when inferring newlines.
+  * Rename `minification.inlineExpressions` transformer to `minification.constantFolding`.
+  * Check path relative to entry file when checking to see if we're inside `node_modules` when using `babel/register`.
+  * Upgrade `regenerator`.
+
 ## 5.4.7
 
  * **Bug Fix**

CONTRIBUTING.md

@@ -1,3 +1,7 @@
+# NOTE: BEFORE OPENING AN ISSUE PLEASE SEE THE [README](https://github.com/babel/babel#readme).
+
+----
+
 <p align="center">
    <strong><a href="#setup">Setup</a></strong>
    |
@@ -8,6 +12,8 @@
    <strong><a href="#dependencies">Dependencies</a></strong>
    |
    <strong><a href="#code-standards">Code Standards</a></strong>
+   |
+   <strong><a href="#internals">Internals</a></strong>
 </p>
 
 ----
@@ -21,6 +27,9 @@ contributing, please read the
 
 ## Developing
 
+>Note: Babel moves fast. Only the latest release is guaranteed to build correctly.
+>Older releases are not officially supported. If you attempt to build them, do that at your own risk.
+
 #### Setup
 
 ```sh
@@ -79,7 +88,6 @@ your [`$PATH`](http://unix.stackexchange.com/questions/26047/how-to-correctly-ad
 * Ensure the test are passing (`make test`)
 * Create new pull request explaining your proposed change or reference an issue in your commit message
 
-
 #### Dependencies
 
 + [ast-types](http://ghub.io/ast-types) This is required to monkeypatch regenerators AST definitions. Could be improved in the future.
@@ -167,3 +175,6 @@ your [`$PATH`](http://unix.stackexchange.com/questions/26047/how-to-correctly-ad
  * **Declaration**
    * No unused variables
    * No pollution of global variables and prototypes
+
+#### Internals
+Please see [`/doc`](/doc) for internals documentation relevant to developing babel.

Makefile

@@ -5,6 +5,7 @@ UGLIFY_CMD = node_modules/uglify-js/bin/uglifyjs
 #UGLIFY_CMD = node_modules/uglify-js/bin/uglifyjs --mangle sort
 MOCHA_CMD = node_modules/mocha/bin/_mocha
 BABEL_CMD = node_modules/babel/bin/babel
+BROWSERIFY_IGNORE = -i esprima-fb
 
 export NODE_ENV = test
 
@@ -22,6 +23,9 @@ watch-core: clean-core
 clean-core:
 	rm -rf lib
 
+lint:
+	eslint src/babel
+
 build:
 	mkdir -p dist
 	make build-core
@@ -31,8 +35,10 @@ build:
 	node $(BROWSERIFY_CMD) -e lib/babel/polyfill.js >dist/polyfill.js
 	node $(UGLIFY_CMD) dist/polyfill.js >dist/polyfill.min.js
 
-	node $(BROWSERIFY_CMD) lib/babel/api/browser.js -s babel >dist/babel.js
-	node $(UGLIFY_CMD) dist/babel.js >dist/babel.min.js
+	node $(BROWSERIFY_CMD) lib/babel/api/browser.js -s babel $(BROWSERIFY_IGNORE) >dist/browser.js
+	node $(UGLIFY_CMD) dist/browser.js >dist/browser.min.js
+
+	node $(BROWSERIFY_CMD) lib/babel/api/node.js --node $(BROWSERIFY_IGNORE) >dist/node.js
 
 	node packages/babel-cli/bin/babel-external-helpers >dist/external-helpers.js
 	node $(UGLIFY_CMD) dist/external-helpers.js >dist/external-helpers.min.js
@@ -61,7 +67,7 @@ test-cov:
 test-parser:
 	node test/acorn/run.js
 
-test-travis: bootstrap build test
+test-travis: bootstrap lint build test
 
 test-browser:
 	mkdir -p dist
@@ -73,7 +79,7 @@ test-browser:
 
 	test -n "`which open`" && open test/browser.html
 
-publish:
+publish: lint
 	git pull --rebase
 
 	make test
@@ -83,8 +89,8 @@ publish:
 
 	make build
 
-	cp dist/babel.js browser.js
-	cp dist/babel.min.js browser.min.js
+	cp dist/browser.js browser.js
+	cp dist/browser.min.js browser.min.js
 
 	cp dist/polyfill.js browser-polyfill.js
 	cp dist/polyfill.min.js browser-polyfill.min.js

README.md

@@ -9,7 +9,11 @@
 </p>
 
 <p align="center">
-  For questions and support please visit the <a href="https://gitter.im/babel/babel">gitter room</a> or <a href="http://stackoverflow.com/questions/tagged/babeljs">StackOverflow</a>. The Babel issue tracker is <strong>exclusively</strong> for bug reports and feature requests.
+  For questions and support please visit the <a href="https://babel-slack.herokuapp.com">slack channel</a> or <a href="http://stackoverflow.com/questions/tagged/babeljs">StackOverflow</a>. The Babel issue tracker is <strong>exclusively</strong> for bug reports and feature requests.
+</p>
+
+<p align="center">
+  Issues without instructions to reproduce <strong>will be immediately closed<strong>.
 </p>
 
 <p align="center">

doc/index.md

@@ -0,0 +1,4 @@
+This is a collection of documentation about babel internals, for use in development of babel.
+
+# [Properties of nodes](/doc/node-props.md)
+These are properties babel stores in AST node objects for internal use, as opposed to properties that are part of the AST spec (ESTree at the time of this writing).

doc/node-props.md

@@ -0,0 +1,11 @@
+# Properties of nodes
+These are properties babel stores in AST node objects for internal use, as opposed to properties that are part of the AST spec (ESTree at the time of this writing).
+
+## `_blockHoist`
+`node._blockHoist != null` triggers the [block-hoist transformer](/src/babel/transformation/transformers/internal/block-hoist.js). Value should be `true` or an integer in the range `0..3`. `true` is equivalent to `2`. The value indicates whether the node should be hoisted and to what degree. See the source code for more detailed information.
+
+## `_paths`
+Stores a representation of a node's position in the tree and relationship to other nodes.
+
+## `shadow`
+A truthy value on a function node triggers the [shadow-functions transformer](/src/babel/transformation/transformers/internal/shadow-functions.js), which transforms the node so that it references (or inherits) `arguments` and `this` from the parent scope. It is invoked for arrow functions, for example.

package.json

@@ -1,7 +1,7 @@
 {
   "name": "babel-core",
   "description": "A compiler for writing next generation JavaScript",
-  "version": "5.4.7",
+  "version": "5.5.8",
   "author": "Sebastian McKenzie <sebmck@gmail.com>",
   "homepage": "https://babeljs.io/",
   "license": "MIT",
@@ -51,7 +51,7 @@
     "output-file-sync": "^1.1.0",
     "path-is-absolute": "^1.0.0",
     "private": "^0.1.6",
-    "regenerator": "^0.8.20",
+    "regenerator": "0.8.28",
     "regexpu": "^1.1.2",
     "repeating": "^1.1.2",
     "resolve": "^1.1.6",
@@ -67,8 +67,8 @@
     "babel": "5.3.1",
     "browserify": "^9.0.8",
     "chai": "^2.2.0",
-    "eslint": "^0.18.0",
-    "babel-eslint": "^2.0.0",
+    "eslint": "^0.21.2",
+    "babel-eslint": "^3.1.9",
     "esvalid": "^1.1.0",
     "istanbul": "^0.3.5",
     "matcha": "^0.6.0",

packages/babel-cli/bin/_babel-node

@@ -107,6 +107,7 @@ if (program.eval || program.print) {
 
     // add back on node and concat the sliced args
     process.argv = ["node"].concat(args);
+    process.execArgv.unshift(__filename);
 
     Module.runMain();
   } else {

packages/babel-cli/bin/babel-node

@@ -412,6 +412,7 @@ babelArgs.forEach(function(arg){
     case "--prof_auto":
     case "--prof_lazy":
     case "--sliding_state_window":
+    case "--nolazy":
       args.unshift(arg);
       break;
 

packages/babel-cli/bin/babel/index.js

@@ -35,7 +35,7 @@ each(options, function (option, key) {
   if (option.description) desc.push(option.description);
 
   commander.option(arg, desc.join(" "));
-})
+});
 
 commander.option("-x, --extensions [extensions]", "List of extensions to compile when a directory has been input [.es6,.js,.es,.jsx]");
 commander.option("-w, --watch", "Recompile files on changes");
@@ -51,7 +51,7 @@ commander.on("--help", function () {
     each(keys(obj).sort(), function (key) {
       if (key[0] === "_") return;
 
-      if (obj[key].optional) key = "[" + key + "]";
+      if (obj[key].metadata && obj[key].metadata.optional) key = "[" + key + "]";
 
       console.log("    - " + key);
     });
@@ -118,11 +118,16 @@ if (errors.length) {
 var opts = exports.opts = {};
 
 each(options, function (opt, key) {
-  opts[key] = commander[key];
+  if (commander[key] !== undefined) {
+    opts[key] = commander[key];
+  }
 });
 
 opts.ignore = util.arrayify(opts.ignore, util.regexify);
-opts.only   = util.arrayify(opts.only, util.regexify);
+
+if (opts.only) {
+  opts.only = util.arrayify(opts.only, util.regexify);
+}
 
 var fn;
 

packages/babel-cli/package.json

@@ -1,14 +1,14 @@
 {
   "name": "babel",
   "description": "Turn ES6 code into readable vanilla ES5 with source maps",
-  "version": "5.4.6",
+  "version": "5.5.7",
   "author": "Sebastian McKenzie <sebmck@gmail.com>",
   "homepage": "https://babeljs.io/",
   "license": "MIT",
   "repository": "babel/babel",
   "preferGlobal": true,
   "dependencies": {
-    "babel-core": "^5.4.6",
+    "babel-core": "^5.5.7",
     "chokidar": "^1.0.0",
     "commander": "^2.6.0",
     "convert-source-map": "^1.1.0",

packages/babel-runtime/package.json

@@ -1,7 +1,7 @@
 {
   "name": "babel-runtime",
   "description": "babel selfContained runtime",
-  "version": "5.4.6",
+  "version": "5.5.7",
   "license": "MIT",
   "repository": "babel/babel",
   "author": "Sebastian McKenzie <sebmck@gmail.com>",

src/acorn/plugins/flow.js

@@ -415,6 +415,9 @@ pp.flow_identToTypeAnnotation = function (start, node, id) {
     case "boolean":
       return this.finishNode(node, "BooleanTypeAnnotation")
 
+    case "mixed":
+      return this.finishNode(node, "MixedTypeAnnotation")
+
     case "number":
       return this.finishNode(node, "NumberTypeAnnotation")
 

src/acorn/src/expression.js

@@ -274,7 +274,13 @@ pp.parseExprAtom = function(refShorthandDefaultPos) {
     if (this.options.features["es7.doExpressions"]) {
       let node = this.startNode()
       this.next()
+      var oldInFunction = this.inFunction
+      var oldLabels = this.labels
+      this.labels = []
+      this.inFunction = false
       node.body = this.parseBlock()
+      this.inFunction = oldInFunction
+      this.labels = oldLabels
       return this.finishNode(node, "DoExpression")
     }
 
@@ -286,7 +292,7 @@ pp.parseExprAtom = function(refShorthandDefaultPos) {
     //
     if (this.options.features["es7.asyncFunctions"]) {
       // async functions!
-      if (id.name === "async") {
+      if (id.name === "async" && !this.canInsertSemicolon()) {
         // arrow functions
         if (this.type === tt.parenL) {
           let expr = this.parseParenAndDistinguishExpression(start, true, true)
@@ -507,7 +513,7 @@ pp.parseNew = function() {
 pp.parseTemplateElement = function() {
   let elem = this.startNode()
   elem.value = {
-    raw: this.input.slice(this.start, this.end),
+    raw: this.input.slice(this.start, this.end).replace(/\r\n?/g, '\n'),
     cooked: this.value
   }
   this.next()

src/acorn/src/lookahead.js

@@ -9,6 +9,7 @@ var STATE_KEYS = [
   "lastTokEnd",
   "lineStart",
   "startLoc",
+  "curLine",
   "endLoc",
   "start",
   "pos",

src/acorn/src/statement.js

@@ -83,10 +83,13 @@ pp.parseStatement = function(declaration, topLevel) {
     return starttype === tt._import ? this.parseImport(node) : this.parseExport(node)
 
   case tt.name:
-    if (this.options.features["es7.asyncFunctions"] && this.value === "async" && this.lookahead().type === tt._function) {
-      this.next();
-      this.expect(tt._function);
-      return this.parseFunction(node, true, false, true);
+    if (this.options.features["es7.asyncFunctions"] && this.value === "async") {
+      var lookahead = this.lookahead();
+      if (lookahead.type === tt._function && !this.canInsertSemicolon.call(lookahead)) {
+        this.next();
+        this.expect(tt._function);
+        return this.parseFunction(node, true, false, true);
+      }
     }
 
     // If the statement does not start with a statement keyword or a
@@ -168,12 +171,6 @@ pp.parseDoStatement = function(node) {
   this.labels.push(loopLabel)
   node.body = this.parseStatement(false)
   this.labels.pop()
-  if (this.options.features["es7.doExpressions"] && this.type !== tt._while) {
-    let container = this.startNodeAt(start)
-    container.expression = this.finishNode(node, "DoExpression")
-    this.semicolon()
-    return this.finishNode(container, "ExpressionStatement")
-  }
   this.expect(tt._while)
   node.test = this.parseParenExpression()
   if (this.options.ecmaVersion >= 6)
@@ -574,7 +571,7 @@ pp.parseExport = function(node) {
       this.parseExportFrom(node)
       return this.finishNode(node, "ExportAllDeclaration")
     }
-  } else if (this.isExportDefaultSpecifier()) {
+  } else if (this.options.features["es7.exportExtensions"] && this.isExportDefaultSpecifier()) {
     let specifier = this.startNode()
     specifier.exported = this.parseIdent(true)
     node.specifiers = [this.finishNode(specifier, "ExportDefaultSpecifier")]

src/acorn/src/tokenize.js

@@ -577,11 +577,15 @@ pp.readTmplToken = function() {
     } else if (isNewLine(ch)) {
       out += this.input.slice(chunkStart, this.pos)
       ++this.pos
-      if (ch === 13 && this.input.charCodeAt(this.pos) === 10) {
-        ++this.pos
-        out += "\n"
-      } else {
-        out += String.fromCharCode(ch)
+      switch (ch) {
+        case 13:
+          if (this.input.charCodeAt(this.pos) === 10) ++this.pos;
+        case 10:
+          out += "\n";
+          break;
+        default:
+          out += String.fromCharCode(ch);
+          break;
       }
       if (this.options.locations) {
         ++this.curLine

src/babel/api/browser.js

@@ -1,3 +1,5 @@
+/* eslint no-new-func: 0 */
+
 require("./node");
 var transform = module.exports = require("../transformation");
 

src/babel/api/node.js

@@ -8,7 +8,7 @@ export { util, acorn, transform };
 export { pipeline } from "../transformation";
 export { canCompile } from "../util";
 
-export { default as options } from "../transformation/file/options";
+export { default as options } from "../transformation/file/options/config";
 export { default as Transformer } from "../transformation/transformer";
 export { default as TransformerPipeline } from "../transformation/transformer-pipeline";
 export { default as traverse } from "../traversal";

src/babel/api/register/browser.js

@@ -1,5 +1,5 @@
 // required to safely use babel/register within a browserify codebase
 
-export default function () {};
+export default function () {}
 
 import "../../polyfill";

src/babel/api/register/cache.js

@@ -1,5 +1,4 @@
 import path from "path";
-import os from "os";
 import fs from "fs";
 import homeOrTmp from "home-or-tmp";
 

src/babel/api/register/node.js

@@ -1,12 +1,12 @@
 import sourceMapSupport from "source-map-support";
 import * as registerCache from "./cache";
-import resolveRc from "../../tools/resolve-rc";
+import resolveRc from "../../transformation/file/options/resolve-rc";
 import extend from "lodash/object/extend";
 import * as babel from "../node";
 import each from "lodash/collection/each";
 import * as util from  "../../util";
 import fs from "fs";
-import slash from "slash";
+import path from "path";
 
 sourceMapSupport.install({
   handleUncaughtExceptions: false,
@@ -38,14 +38,20 @@ var only;
 var oldHandlers   = {};
 var maps          = {};
 
+var cwd = process.cwd();
+
+var getRelativePath = function (filename){
+  return path.relative(cwd, filename);
+};
+
 var mtime = function (filename) {
   return +fs.statSync(filename).mtime;
 };
 
-var compile = function (filename) {
+var compile = function (filename, opts = {}) {
   var result;
 
-  var opts = extend({}, transformOpts);
+  opts = extend(opts, transformOpts);
 
   // this will be done when the file is transformed anyway but we need all
   // the options so we can generate the cache key
@@ -82,9 +88,9 @@ var compile = function (filename) {
 
 var shouldIgnore = function (filename) {
   if (!ignore && !only) {
-    return /node_modules/.test(filename);
+    return getRelativePath(filename).split(path.sep).indexOf("node_modules") >= 0;
   } else {
-    return util.shouldIgnore(filename, ignore || [], only || []);
+    return util.shouldIgnore(filename, ignore || [], only);
   }
 };
 
@@ -98,7 +104,9 @@ if (process.env.running_under_istanbul) {
   fs.readFileSync = function (filename) {
     if (istanbulMonkey[filename]) {
       delete istanbulMonkey[filename];
-      var code = compile(filename);
+      var code = compile(filename, {
+        auxiliaryComment: "istanbul ignore next"
+      });
       istanbulMonkey[filename] = true;
       return code;
     } else {
@@ -164,4 +172,4 @@ export default function (opts = {}) {
   delete opts.only;
 
   extend(transformOpts, opts);
-};
+}

src/babel/generation/generators/base.js

@@ -1,5 +1,5 @@
 export function File(node, print) {
-  print(node.program);
+  print.plain(node.program);
 }
 
 export function Program(node, print) {
@@ -17,3 +17,7 @@ export function BlockStatement(node, print) {
     this.rightBrace();
   }
 }
+
+export function Noop() {
+
+}

src/babel/generation/generators/classes.js

@@ -4,15 +4,15 @@ export function ClassDeclaration(node, print) {
 
   if (node.id) {
     this.push(" ");
-    print(node.id);
+    print.plain(node.id);
   }
 
-  print(node.typeParameters);
+  print.plain(node.typeParameters);
 
   if (node.superClass) {
     this.push(" extends ");
-    print(node.superClass);
-    print(node.superTypeParameters);
+    print.plain(node.superClass);
+    print.plain(node.superTypeParameters);
   }
 
   if (node.implements) {
@@ -21,7 +21,7 @@ export function ClassDeclaration(node, print) {
   }
 
   this.space();
-  print(node.body);
+  print.plain(node.body);
 }
 
 export { ClassDeclaration as ClassExpression };
@@ -46,13 +46,13 @@ export function ClassProperty(node, print) {
   print.list(node.decorators);
 
   if (node.static) this.push("static ");
-  print(node.key);
-  print(node.typeAnnotation);
+  print.plain(node.key);
+  print.plain(node.typeAnnotation);
   if (node.value) {
     this.space();
     this.push("=");
     this.space();
-    print(node.value);
+    print.plain(node.value);
   }
   this.semicolon();
 }

src/babel/generation/generators/comprehensions.js

@@ -1,9 +1,9 @@
 export function ComprehensionBlock(node, print) {
   this.keyword("for");
   this.push("(");
-  print(node.left);
+  print.plain(node.left);
   this.push(" of ");
-  print(node.right);
+  print.plain(node.right);
   this.push(")");
 }
 
@@ -16,12 +16,12 @@ export function ComprehensionExpression(node, print) {
   if (node.filter) {
     this.keyword("if");
     this.push("(");
-    print(node.filter);
+    print.plain(node.filter);
     this.push(")");
     this.space();
   }
 
-  print(node.body);
+  print.plain(node.body);
 
   this.push(node.generator ? ")" : "]");
 }

src/babel/generation/generators/expressions.js

@@ -16,40 +16,40 @@ export function UnaryExpression(node, print) {
 
   this.push(node.operator);
   if (hasSpace) this.push(" ");
-  print(node.argument);
+  print.plain(node.argument);
 }
 
 export function DoExpression(node, print) {
   this.push("do");
   this.space();
-  print(node.body);
+  print.plain(node.body);
 }
 
 export function UpdateExpression(node, print) {
   if (node.prefix) {
     this.push(node.operator);
-    print(node.argument);
+    print.plain(node.argument);
   } else {
-    print(node.argument);
+    print.plain(node.argument);
     this.push(node.operator);
   }
 }
 
 export function ConditionalExpression(node, print) {
-  print(node.test);
+  print.plain(node.test);
   this.space();
   this.push("?");
   this.space();
-  print(node.consequent);
+  print.plain(node.consequent);
   this.space();
   this.push(":");
   this.space();
-  print(node.alternate);
+  print.plain(node.alternate);
 }
 
 export function NewExpression(node, print) {
   this.push("new ");
-  print(node.callee);
+  print.plain(node.callee);
   this.push("(");
   print.list(node.arguments);
   this.push(")");
@@ -69,11 +69,12 @@ export function Super() {
 
 export function Decorator(node, print) {
   this.push("@");
-  print(node.expression);
+  print.plain(node.expression);
+  this.newline();
 }
 
 export function CallExpression(node, print) {
-  print(node.callee);
+  print.plain(node.callee);
 
   this.push("(");
 
@@ -109,7 +110,7 @@ var buildYieldAwait = function (keyword) {
 
     if (node.argument) {
       this.push(" ");
-      print(node.argument);
+      print.plain(node.argument);
     }
   };
 };
@@ -122,23 +123,23 @@ export function EmptyStatement() {
 }
 
 export function ExpressionStatement(node, print) {
-  print(node.expression);
+  print.plain(node.expression);
   this.semicolon();
 }
 
 export function AssignmentExpression(node, print) {
   // todo: add cases where the spaces can be dropped when in compact mode
-  print(node.left);
+  print.plain(node.left);
   this.push(" ");
   this.push(node.operator);
   this.push(" ");
-  print(node.right);
+  print.plain(node.right);
 }
 
 export function BindExpression(node, print) {
-  print(node.object);
+  print.plain(node.object);
   this.push("::");
-  print(node.callee);
+  print.plain(node.callee);
 }
 
 export {
@@ -151,7 +152,7 @@ var SCIENTIFIC_NOTATION = /e/i;
 
 export function MemberExpression(node, print) {
   var obj = node.object;
-  print(obj);
+  print.plain(obj);
 
   if (!node.computed && t.isMemberExpression(node.property)) {
     throw new TypeError("Got a MemberExpression for MemberExpression property");
@@ -164,7 +165,7 @@ export function MemberExpression(node, print) {
 
   if (computed) {
     this.push("[");
-    print(node.property);
+    print.plain(node.property);
     this.push("]");
   } else {
     // 5..toFixed(2);
@@ -173,12 +174,12 @@ export function MemberExpression(node, print) {
     }
 
     this.push(".");
-    print(node.property);
+    print.plain(node.property);
   }
 }
 
 export function MetaProperty(node, print) {
-  print(node.meta);
+  print.plain(node.meta);
   this.push(".");
-  print(node.property);
+  print.plain(node.property);
 }

src/babel/generation/generators/flow.js

@@ -5,7 +5,7 @@ export function AnyTypeAnnotation() {
 }
 
 export function ArrayTypeAnnotation(node, print) {
-  print(node.elementType);
+  print.plain(node.elementType);
   this.push("[");
   this.push("]");
 }
@@ -21,27 +21,27 @@ export function DeclareClass(node, print) {
 
 export function DeclareFunction(node, print) {
   this.push("declare function ");
-  print(node.id);
-  print(node.id.typeAnnotation.typeAnnotation);
+  print.plain(node.id);
+  print.plain(node.id.typeAnnotation.typeAnnotation);
   this.semicolon();
 }
 
 export function DeclareModule(node, print) {
   this.push("declare module ");
-  print(node.id);
+  print.plain(node.id);
   this.space();
-  print(node.body);
+  print.plain(node.body);
 }
 
 export function DeclareVariable(node, print) {
   this.push("declare var ");
-  print(node.id);
-  print(node.id.typeAnnotation);
+  print.plain(node.id);
+  print.plain(node.id.typeAnnotation);
   this.semicolon();
 }
 
 export function FunctionTypeAnnotation(node, print, parent) {
-  print(node.typeParameters);
+  print.plain(node.typeParameters);
   this.push("(");
   print.list(node.params);
 
@@ -51,7 +51,7 @@ export function FunctionTypeAnnotation(node, print, parent) {
       this.space();
     }
     this.push("...");
-    print(node.rest);
+    print.plain(node.rest);
   }
 
   this.push(")");
@@ -65,33 +65,33 @@ export function FunctionTypeAnnotation(node, print, parent) {
   }
 
   this.space();
-  print(node.returnType);
+  print.plain(node.returnType);
 }
 
 export function FunctionTypeParam(node, print) {
-  print(node.name);
+  print.plain(node.name);
   if (node.optional) this.push("?");
   this.push(":");
   this.space();
-  print(node.typeAnnotation);
+  print.plain(node.typeAnnotation);
 }
 
 export function InterfaceExtends(node, print) {
-  print(node.id);
-  print(node.typeParameters);
+  print.plain(node.id);
+  print.plain(node.typeParameters);
 }
 
 export { InterfaceExtends as ClassImplements, InterfaceExtends as GenericTypeAnnotation };
 
 export function _interfaceish(node, print) {
-  print(node.id);
-  print(node.typeParameters);
+  print.plain(node.id);
+  print.plain(node.typeParameters);
   if (node.extends.length) {
     this.push(" extends ");
     print.join(node.extends, { separator: ", " });
   }
   this.space();
-  print(node.body);
+  print.plain(node.body);
 }
 
 export function InterfaceDeclaration(node, print) {
@@ -103,9 +103,13 @@ export function IntersectionTypeAnnotation(node, print) {
   print.join(node.types, { separator: " & " });
 }
 
+export function MixedTypeAnnotation() {
+  this.push("mixed");
+}
+
 export function NullableTypeAnnotation(node, print) {
   this.push("?");
-  print(node.typeAnnotation);
+  print.plain(node.typeAnnotation);
 }
 
 export function NumberTypeAnnotation() {
@@ -128,17 +132,17 @@ export function TupleTypeAnnotation(node, print) {
 
 export function TypeofTypeAnnotation(node, print) {
   this.push("typeof ");
-  print(node.argument);
+  print.plain(node.argument);
 }
 
 export function TypeAlias(node, print) {
   this.push("type ");
-  print(node.id);
-  print(node.typeParameters);
+  print.plain(node.id);
+  print.plain(node.typeParameters);
   this.space();
   this.push("=");
   this.space();
-  print(node.right);
+  print.plain(node.right);
   this.semicolon();
 }
 
@@ -146,7 +150,7 @@ export function TypeAnnotation(node, print) {
   this.push(":");
   this.space();
   if (node.optional) this.push("?");
-  print(node.typeAnnotation);
+  print.plain(node.typeAnnotation);
 }
 
 export function TypeParameterInstantiation(node, print) {
@@ -183,37 +187,37 @@ export function ObjectTypeAnnotation(node, print) {
 
 export function ObjectTypeCallProperty(node, print) {
   if (node.static) this.push("static ");
-  print(node.value);
+  print.plain(node.value);
 }
 
 export function ObjectTypeIndexer(node, print) {
   if (node.static) this.push("static ");
   this.push("[");
-  print(node.id);
+  print.plain(node.id);
   this.push(":");
   this.space();
-  print(node.key);
+  print.plain(node.key);
   this.push("]");
   this.push(":");
   this.space();
-  print(node.value);
+  print.plain(node.value);
 }
 
 export function ObjectTypeProperty(node, print) {
   if (node.static) this.push("static ");
-  print(node.key);
+  print.plain(node.key);
   if (node.optional) this.push("?");
   if (!t.isFunctionTypeAnnotation(node.value)) {
     this.push(":");
     this.space();
   }
-  print(node.value);
+  print.plain(node.value);
 }
 
 export function QualifiedTypeIdentifier(node, print) {
-  print(node.qualification);
+  print.plain(node.qualification);
   this.push(".");
-  print(node.id);
+  print.plain(node.id);
 }
 
 export function UnionTypeAnnotation(node, print) {
@@ -222,8 +226,8 @@ export function UnionTypeAnnotation(node, print) {
 
 export function TypeCastExpression(node, print) {
   this.push("(");
-  print(node.expression);
-  print(node.typeAnnotation);
+  print.plain(node.expression);
+  print.plain(node.typeAnnotation);
   this.push(")");
 }
 

src/babel/generation/generators/jsx.js

@@ -1,11 +1,10 @@
-import each from "lodash/collection/each";
 import * as t from "../../types";
 
 export function JSXAttribute(node, print) {
-  print(node.name);
+  print.plain(node.name);
   if (node.value) {
     this.push("=");
-    print(node.value);
+    print.plain(node.value);
   }
 }
 
@@ -14,32 +13,32 @@ export function JSXIdentifier(node) {
 }
 
 export function JSXNamespacedName(node, print) {
-  print(node.namespace);
+  print.plain(node.namespace);
   this.push(":");
-  print(node.name);
+  print.plain(node.name);
 }
 
 export function JSXMemberExpression(node, print) {
-  print(node.object);
+  print.plain(node.object);
   this.push(".");
-  print(node.property);
+  print.plain(node.property);
 }
 
 export function JSXSpreadAttribute(node, print) {
   this.push("{...");
-  print(node.argument);
+  print.plain(node.argument);
   this.push("}");
 }
 
 export function JSXExpressionContainer(node, print) {
   this.push("{");
-  print(node.expression);
+  print.plain(node.expression);
   this.push("}");
 }
 
 export function JSXElement(node, print) {
   var open = node.openingElement;
-  print(open);
+  print.plain(open);
   if (open.selfClosing) return;
 
   this.indent();
@@ -47,17 +46,17 @@ export function JSXElement(node, print) {
     if (t.isLiteral(child)) {
       this.push(child.value, true);
     } else {
-      print(child);
+      print.plain(child);
     }
   }
   this.dedent();
 
-  print(node.closingElement);
+  print.plain(node.closingElement);
 }
 
 export function JSXOpeningElement(node, print) {
   this.push("<");
-  print(node.name);
+  print.plain(node.name);
   if (node.attributes.length > 0) {
     this.push(" ");
     print.join(node.attributes, { separator: " " });
@@ -67,7 +66,7 @@ export function JSXOpeningElement(node, print) {
 
 export function JSXClosingElement(node, print) {
   this.push("</");
-  print(node.name);
+  print.plain(node.name);
   this.push(">");
 }
 

src/babel/generation/generators/methods.js

@@ -1,18 +1,18 @@
 import * as t from "../../types";
 
 export function _params(node, print) {
-  print(node.typeParameters);
+  print.plain(node.typeParameters);
   this.push("(");
   print.list(node.params, {
     iterator: (node) =>{
       if (node.optional) this.push("?");
-      print(node.typeAnnotation);
+      print.plain(node.typeAnnotation);
     }
   });
   this.push(")");
 
   if (node.returnType) {
-    print(node.returnType);
+    print.plain(node.returnType);
   }
 }
 
@@ -35,15 +35,15 @@ export function _method(node, print) {
 
   if (node.computed) {
     this.push("[");
-    print(key);
+    print.plain(key);
     this.push("]");
   } else {
-    print(key);
+    print.plain(key);
   }
 
   this._params(value, print);
   this.push(" ");
-  print(value.body);
+  print.plain(value.body);
 }
 
 export function FunctionExpression(node, print) {
@@ -53,14 +53,14 @@ export function FunctionExpression(node, print) {
 
   if (node.id) {
     this.push(" ");
-    print(node.id);
+    print.plain(node.id);
   } else {
     this.space();
   }
 
   this._params(node, print);
   this.space();
-  print(node.body);
+  print.plain(node.body);
 }
 
 export { FunctionExpression as FunctionDeclaration };
@@ -69,7 +69,7 @@ export function ArrowFunctionExpression(node, print) {
   if (node.async) this.push("async ");
 
   if (node.params.length === 1 && t.isIdentifier(node.params[0])) {
-    print(node.params[0]);
+    print.plain(node.params[0]);
   } else {
     this._params(node, print);
   }
@@ -82,7 +82,7 @@ export function ArrowFunctionExpression(node, print) {
     this.push("(");
   }
 
-  print(node.body);
+  print.plain(node.body);
 
   if (bodyNeedsParens) {
     this.push(")");

src/babel/generation/generators/modules.js

@@ -1,43 +1,42 @@
-import each from "lodash/collection/each";
 import * as t from "../../types";
 
 export function ImportSpecifier(node, print) {
-  print(node.imported);
+  print.plain(node.imported);
   if (node.local && node.local.name !== node.imported.name) {
     this.push(" as ");
-    print(node.local);
+    print.plain(node.local);
   }
 }
 
 export function ImportDefaultSpecifier(node, print) {
-  print(node.local);
+  print.plain(node.local);
 }
 
 export function ExportDefaultSpecifier(node, print) {
-  print(node.exported);
+  print.plain(node.exported);
 }
 
 export function ExportSpecifier(node, print) {
-  print(node.local);
+  print.plain(node.local);
   if (node.exported && node.local.name !== node.exported.name) {
     this.push(" as ");
-    print(node.exported);
+    print.plain(node.exported);
   }
 }
 
 export function ExportNamespaceSpecifier(node, print) {
   this.push("* as ");
-  print(node.exported);
+  print.plain(node.exported);
 }
 
 export function ExportAllDeclaration(node, print) {
   this.push("export *");
   if (node.exported) {
     this.push(" as ");
-    print(node.exported);
+    print.plain(node.exported);
   }
   this.push(" from ");
-  print(node.source);
+  print.plain(node.source);
   this.semicolon();
 }
 
@@ -56,14 +55,14 @@ function ExportDeclaration(node, print) {
 
   if (node.declaration) {
     var declar = node.declaration;
-    print(declar);
+    print.plain(declar);
     if (t.isStatement(declar) || t.isFunction(declar) || t.isClass(declar)) return;
   } else {
     var first = specifiers[0];
     var hasSpecial = false;
     if (t.isExportDefaultSpecifier(first) || t.isExportNamespaceSpecifier(first)) {
       hasSpecial = true;
-      print(specifiers.shift());
+      print.plain(specifiers.shift());
       if (specifiers.length) {
         this.push(", ");
       }
@@ -81,7 +80,7 @@ function ExportDeclaration(node, print) {
 
     if (node.source) {
       this.push(" from ");
-      print(node.source);
+      print.plain(node.source);
     }
   }
 
@@ -99,7 +98,7 @@ export function ImportDeclaration(node, print) {
   if (specfiers && specfiers.length) {
     var first = node.specifiers[0];
     if (t.isImportDefaultSpecifier(first) || t.isImportNamespaceSpecifier(first)) {
-      print(node.specifiers.shift());
+      print.plain(node.specifiers.shift());
       if (node.specifiers.length) {
         this.push(", ");
       }
@@ -107,20 +106,20 @@ export function ImportDeclaration(node, print) {
 
     if (node.specifiers.length) {
       this.push("{");
-      this.space()
+      this.space();
       print.join(node.specifiers, { separator: ", " });
-      this.space()
+      this.space();
       this.push("}");
     }
 
     this.push(" from ");
   }
 
-  print(node.source);
+  print.plain(node.source);
   this.semicolon();
 }
 
 export function ImportNamespaceSpecifier(node, print) {
   this.push("* as ");
-  print(node.local);
+  print.plain(node.local);
 }

src/babel/generation/generators/statements.js

@@ -4,7 +4,7 @@ import * as t from "../../types";
 export function WithStatement(node, print) {
   this.keyword("with");
   this.push("(");
-  print(node.object);
+  print.plain(node.object);
   this.push(")");
   print.block(node.body);
 }
@@ -12,7 +12,7 @@ export function WithStatement(node, print) {
 export function IfStatement(node, print) {
   this.keyword("if");
   this.push("(");
-  print(node.test);
+  print.plain(node.test);
   this.push(")");
   this.space();
 
@@ -29,18 +29,18 @@ export function ForStatement(node, print) {
   this.keyword("for");
   this.push("(");
 
-  print(node.init);
+  print.plain(node.init);
   this.push(";");
 
   if (node.test) {
     this.push(" ");
-    print(node.test);
+    print.plain(node.test);
   }
   this.push(";");
 
   if (node.update) {
     this.push(" ");
-    print(node.update);
+    print.plain(node.update);
   }
 
   this.push(")");
@@ -50,7 +50,7 @@ export function ForStatement(node, print) {
 export function WhileStatement(node, print) {
   this.keyword("while");
   this.push("(");
-  print(node.test);
+  print.plain(node.test);
   this.push(")");
   print.block(node.body);
 }
@@ -59,9 +59,9 @@ var buildForXStatement = function (op) {
   return function (node, print) {
     this.keyword("for");
     this.push("(");
-    print(node.left);
+    print.plain(node.left);
     this.push(` ${op} `);
-    print(node.right);
+    print.plain(node.right);
     this.push(")");
     print.block(node.body);
   };
@@ -72,11 +72,11 @@ export var ForOfStatement = buildForXStatement("of");
 
 export function DoWhileStatement(node, print) {
   this.push("do ");
-  print(node.body);
+  print.plain(node.body);
   this.space();
   this.keyword("while");
   this.push("(");
-  print(node.test);
+  print.plain(node.test);
   this.push(");");
 }
 
@@ -87,7 +87,7 @@ var buildLabelStatement = function (prefix, key) {
     var label = node[key || "label"];
     if (label) {
       this.push(" ");
-      print(label);
+      print.plain(label);
     }
 
     this.semicolon();
@@ -99,50 +99,50 @@ export var ReturnStatement   = buildLabelStatement("return", "argument");
 export var BreakStatement    = buildLabelStatement("break");
 
 export function LabeledStatement(node, print) {
-  print(node.label);
+  print.plain(node.label);
   this.push(": ");
-  print(node.body);
+  print.plain(node.body);
 }
 
 export function TryStatement(node, print) {
   this.keyword("try");
-  print(node.block);
+  print.plain(node.block);
   this.space();
 
   // Esprima bug puts the catch clause in a `handlers` array.
   // see https://code.google.com/p/esprima/issues/detail?id=433
   // We run into this from regenerator generated ast.
   if (node.handlers) {
-    print(node.handlers[0]);
+    print.plain(node.handlers[0]);
   } else {
-    print(node.handler);
+    print.plain(node.handler);
   }
 
   if (node.finalizer) {
     this.space();
     this.push("finally ");
-    print(node.finalizer);
+    print.plain(node.finalizer);
   }
 }
 
 export function CatchClause(node, print) {
   this.keyword("catch");
   this.push("(");
-  print(node.param);
+  print.plain(node.param);
   this.push(") ");
-  print(node.body);
+  print.plain(node.body);
 }
 
 export function ThrowStatement(node, print) {
   this.push("throw ");
-  print(node.argument);
+  print.plain(node.argument);
   this.semicolon();
 }
 
 export function SwitchStatement(node, print) {
   this.keyword("switch");
   this.push("(");
-  print(node.discriminant);
+  print.plain(node.discriminant);
   this.push(")");
   this.space();
   this.push("{");
@@ -160,7 +160,7 @@ export function SwitchStatement(node, print) {
 export function SwitchCase(node, print) {
   if (node.test) {
     this.push("case ");
-    print(node.test);
+    print.plain(node.test);
     this.push(":");
   } else {
     this.push("default:");
@@ -207,12 +207,12 @@ export function VariableDeclaration(node, print, parent) {
 }
 
 export function VariableDeclarator(node, print) {
-  print(node.id);
-  print(node.id.typeAnnotation);
+  print.plain(node.id);
+  print.plain(node.id.typeAnnotation);
   if (node.init) {
     this.space();
     this.push("=");
     this.space();
-    print(node.init);
+    print.plain(node.init);
   }
 }

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

@@ -1,8 +1,6 @@
-import each from "lodash/collection/each";
-
 export function TaggedTemplateExpression(node, print) {
-  print(node.tag);
-  print(node.quasi);
+  print.plain(node.tag);
+  print.plain(node.quasi);
 }
 
 export function TemplateElement(node) {
@@ -16,11 +14,11 @@ export function TemplateLiteral(node, print) {
   var len    = quasis.length;
 
   for (var i = 0; i < len; i++) {
-    print(quasis[i]);
+    print.plain(quasis[i]);
 
     if (i + 1 < len) {
       this.push("${ ");
-      print(node.expressions[i]);
+      print.plain(node.expressions[i]);
       this.push(" }");
     }
   }

src/babel/generation/generators/types.js

@@ -1,4 +1,5 @@
-import each from "lodash/collection/each";
+/* eslint quotes: 0 */
+
 import * as t from "../../types";
 
 export function Identifier(node) {
@@ -7,7 +8,7 @@ export function Identifier(node) {
 
 export function RestElement(node, print) {
   this.push("...");
-  print(node.argument);
+  print.plain(node.argument);
 }
 
 export { RestElement as SpreadElement, RestElement as SpreadProperty };
@@ -36,16 +37,16 @@ export function Property(node, print) {
   } else {
     if (node.computed) {
       this.push("[");
-      print(node.key);
+      print.plain(node.key);
       this.push("]");
     } else {
       // print `({ foo: foo = 5 } = {})` as `({ foo = 5 } = {});`
       if (t.isAssignmentPattern(node.value) && t.isIdentifier(node.key) && node.key.name === node.value.left.name) {
-        print(node.value);
+        print.plain(node.value);
         return;
       }
 
-      print(node.key);
+      print.plain(node.key);
 
       // shorthand!
       if (node.shorthand &&
@@ -58,7 +59,7 @@ export function Property(node, print) {
 
     this.push(":");
     this.space();
-    print(node.value);
+    print.plain(node.value);
   }
 }
 
@@ -79,7 +80,7 @@ export function ArrayExpression(node, print) {
       this.push(",");
     } else {
       if (i > 0) this.push(" ");
-      print(elem);
+      print.plain(elem);
       if (i < len - 1) this.push(",");
     }
   }

src/babel/generation/index.js

@@ -1,5 +1,6 @@
 import detectIndent from "detect-indent";
 import Whitespace from "./whitespace";
+import NodePrinter from "./node/printer";
 import repeating from "repeating";
 import SourceMap from "./source-map";
 import Position from "./position";
@@ -20,7 +21,7 @@ class CodeGenerator {
     this.opts     = opts;
     this.ast      = ast;
 
-    this.whitespace = new Whitespace(this.tokens, this.comments, this.format);
+    this.whitespace = new Whitespace(this.tokens);
     this.position   = new Position;
     this.map        = new SourceMap(this.position, opts, code);
     this.buffer     = new Buffer(this.position, this.format);
@@ -67,7 +68,6 @@ class CodeGenerator {
     for (var i = 0; i < tokens.length; i++) {
       var token = tokens[i];
       if (token.type.label !== "string") continue;
-      if (checked >= 3) continue;
 
       var raw = code.slice(token.start, token.end);
       if (raw[0] === "'") {
@@ -77,6 +77,7 @@ class CodeGenerator {
       }
 
       checked++;
+      if (checked >= 3) break;
     }
 
     if (occurences.single > occurences.double) {
@@ -120,33 +121,7 @@ class CodeGenerator {
   }
 
   buildPrint(parent) {
-    var print = (node, opts) => {
-      return this.print(node, parent, opts);
-    };
-
-    print.sequence = (nodes, opts = {}) => {
-      opts.statement = true;
-      return this.printJoin(print, nodes, opts);
-    };
-
-    print.join = (nodes, opts) => {
-      return this.printJoin(print, nodes, opts);
-    };
-
-    print.list = function (items, opts = {}) {
-      if (opts.separator == null) opts.separator = ", ";
-      print.join(items, opts);
-    };
-
-    print.block = (node) => {
-      return this.printBlock(print, node);
-    };
-
-    print.indentOnComments = (node) => {
-      return this.printAndIndentOnComments(print, node);
-    };
-
-    return print;
+    return new NodePrinter(this, parent);
   }
 
   catchUp(node, parent, leftParenPrinted) {
@@ -166,6 +141,36 @@ class CodeGenerator {
     return false;
   }
 
+  _printNewline(leading, node, parent, opts) {
+    if (!opts.statement && !n.isUserWhitespacable(node, parent)) {
+      return;
+    }
+
+    var lines = 0;
+
+    if (node.start != null && !node._ignoreUserWhitespace) {
+      // user node
+      if (leading) {
+        lines = this.whitespace.getNewlinesBefore(node);
+      } else {
+        lines = this.whitespace.getNewlinesAfter(node);
+      }
+    } else {
+      // generated node
+      if (!leading) lines++; // always include at least a single line after
+      if (opts.addNewlines) lines += opts.addNewlines(leading, node) || 0;
+
+      var needs = n.needsWhitespaceAfter;
+      if (leading) needs = n.needsWhitespaceBefore;
+      if (needs(node, parent)) lines++;
+
+      // generated nodes can't add starting file whitespace
+      if (!this.buffer.buf) lines = 0;
+    }
+
+    this.newline(lines);
+  }
+
   print(node, parent, opts = {}) {
     if (!node) return;
 
@@ -178,36 +183,6 @@ class CodeGenerator {
       this.format.concise = true;
     }
 
-    var newline = (leading) => {
-      if (!opts.statement && !n.isUserWhitespacable(node, parent)) {
-        return;
-      }
-
-      var lines = 0;
-
-      if (node.start != null && !node._ignoreUserWhitespace) {
-        // user node
-        if (leading) {
-          lines = this.whitespace.getNewlinesBefore(node);
-        } else {
-          lines = this.whitespace.getNewlinesAfter(node);
-        }
-      } else {
-        // generated node
-        if (!leading) lines++; // always include at least a single line after
-        if (opts.addNewlines) lines += opts.addNewlines(leading, node) || 0;
-
-        var needs = n.needsWhitespaceAfter;
-        if (leading) needs = n.needsWhitespaceBefore;
-        if (needs(node, parent)) lines++;
-
-        // generated nodes can't add starting file whitespace
-        if (!this.buffer.buf) lines = 0;
-      }
-
-      this.newline(lines);
-    };
-
     if (this[node.type]) {
       var needsNoLineTermParens = n.needsParensNoLineTerminator(node, parent);
       var needsParens           = needsNoLineTermParens || n.needsParens(node, parent);
@@ -219,7 +194,7 @@ class CodeGenerator {
 
       var needsParensFromCatchup = this.catchUp(node, parent, needsParens);
 
-      newline(true);
+      this._printNewline(true, node, parent, opts);
 
       if (opts.before) opts.before();
       this.map.mark(node, "start");
@@ -237,7 +212,7 @@ class CodeGenerator {
 
       this.format.concise = oldConcise;
 
-      newline(false);
+      this._printNewline(false, node, parent, opts);
 
       this.printTrailingComments(node, parent);
     } else {
@@ -252,21 +227,23 @@ class CodeGenerator {
 
     if (opts.indent) this.indent();
 
+    var printOpts = {
+      statement: opts.statement,
+      addNewlines: opts.addNewlines,
+      after: () => {
+        if (opts.iterator) {
+          opts.iterator(node, i);
+        }
+
+        if (opts.separator && i < len - 1) {
+          this.push(opts.separator);
+        }
+      }
+    };
+
     for (var i = 0; i < nodes.length; i++) {
       var node = nodes[i];
-      print(node, {
-        statement: opts.statement,
-        addNewlines: opts.addNewlines,
-        after: () => {
-          if (opts.iterator) {
-            opts.iterator(node, i);
-          }
-
-          if (opts.separator && i < len - 1) {
-            this.push(opts.separator);
-          }
-        }
-      });
+      print.plain(node, printOpts);
     }
 
     if (opts.indent) this.dedent();
@@ -275,7 +252,7 @@ class CodeGenerator {
   printAndIndentOnComments(print, node) {
     var indent = !!node.leadingComments;
     if (indent) this.indent();
-    print(node);
+    print.plain(node);
     if (indent) this.dedent();
   }
 
@@ -284,13 +261,13 @@ class CodeGenerator {
       this.semicolon();
     } else {
       this.push(" ");
-      print(node);
+      print.plain(node);
     }
   }
 
   generateComment(comment) {
     var val = comment.value;
-    if (comment.type === "Line") {
+    if (comment.type === "CommentLine") {
       val = `//${val}`;
     } else {
       val = `/*${val}*/`;
@@ -318,7 +295,7 @@ class CodeGenerator {
       nodes.push(node.argument);
     }
 
-    for (var node of (nodes: Array)) {
+    for (let node of (nodes: Array)) {
       comments = comments.concat(this._getComments(key, node));
     }
 
@@ -366,8 +343,8 @@ class CodeGenerator {
       }
 
       //
-      if (comment.type === "Block" && this.format.indent.adjustMultilineComment) {
-        var offset = comment.loc.start.column;
+      if (comment.type === "CommentBlock" && this.format.indent.adjustMultilineComment) {
+        var offset = comment.loc && comment.loc.start.column;
         if (offset) {
           var newlineRegex = new RegExp("\\n\\s{1," + offset + "}", "g");
           val = val.replace(newlineRegex, "\n");
@@ -383,7 +360,7 @@ class CodeGenerator {
 
       // force a newline for line comments when retainLines is set in case the next printed node
       // doesn't catch up
-      if (this.format.retainLines && comment.type === "Line") {
+      if (this.format.retainLines && comment.type === "CommentLine") {
         val += "\n";
       }
 

src/babel/generation/node/printer.js

@@ -0,0 +1,32 @@
+export default class NodePrinter {
+  constructor(generator, parent) {
+    this.generator = generator;
+    this.parent = parent;
+  }
+
+  plain(node, opts) {
+    return this.generator.print(node, this.parent, opts);
+  }
+
+  sequence(nodes, opts = {}) {
+    opts.statement = true;
+    return this.generator.printJoin(this, nodes, opts);
+  }
+
+  join(nodes, opts) {
+    return this.generator.printJoin(this, nodes, opts);
+  }
+
+  list(items, opts = {}) {
+    if (opts.separator == null) opts.separator = ", ";
+    return this.join(items, opts);
+  }
+
+  block(node) {
+    return this.generator.printBlock(this, node);
+  }
+
+  indentOnComments(node) {
+    return this.generator.printAndIndentOnComments(this, node);
+  }
+}

src/babel/generation/whitespace.js

@@ -1,5 +1,3 @@
-import sortBy from "lodash/collection/sortBy";
-
 /**
  * Returns `i`th number from `base`, continuing from 0 when `max` is reached.
  * Useful for shifting `for` loop by a fixed number but going over all items.
@@ -21,8 +19,8 @@ function getLookupIndex(i, base, max) {
 }
 
 export default class Whitespace {
-  constructor(tokens, comments) {
-    this.tokens = sortBy(tokens.concat(comments), "start");
+  constructor(tokens) {
+    this.tokens = tokens;
     this.used   = {};
 
     // Profiling this code shows that while generator passes over it, indexes
@@ -40,12 +38,11 @@ export default class Whitespace {
     var startToken;
     var endToken;
     var tokens = this.tokens;
-    var token;
 
     for (var j = 0; j < tokens.length; j++) {
       // optimize for forward traversal by shifting for loop index
       var i = getLookupIndex(j, this._lastFoundIndex, this.tokens.length);
-      token = tokens[i];
+      var token = tokens[i];
 
       // this is the token this node starts with
       if (node.start === token.start) {
@@ -64,17 +61,17 @@ export default class Whitespace {
     var startToken;
     var endToken;
     var tokens = this.tokens;
-    var token;
 
     for (var j = 0; j < tokens.length; j++) {
       // optimize for forward traversal by shifting for loop index
       var i = getLookupIndex(j, this._lastFoundIndex, this.tokens.length);
-      token = tokens[i];
+      var token = tokens[i];
 
       // this is the token this node ends with
       if (node.end === token.end) {
         startToken = token;
         endToken = tokens[i + 1];
+        if (endToken.type.label === ",") endToken = tokens[i + 2];
 
         this._lastFoundIndex = i;
         break;
@@ -85,7 +82,7 @@ export default class Whitespace {
       return 1;
     } else {
       var lines = this.getNewlinesBetween(startToken, endToken);
-      if (node.type === "Line" && !lines) {
+      if (node.type === "CommentLine" && !lines) {
         // line comment
         return 1;
       } else {

src/babel/helpers/code-frame.js

@@ -85,4 +85,4 @@ export default function (lines: number, lineNumber: number, colNumber: number, o
       params.before = params.before.replace(/^./, ">");
     }
   }).join("\n");
-};
+}

src/babel/helpers/normalize-ast.js

@@ -6,4 +6,4 @@ export default function (ast, comments, tokens) {
   } else {
     throw new Error("Not a valid ast?");
   }
-};
+}

src/babel/helpers/object.js

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

src/babel/helpers/parse.js

@@ -3,8 +3,9 @@ import estraverse from "estraverse";
 import * as acorn from "../../acorn";
 
 export default function (code, opts = {}) {
-  var comments = [];
-  var tokens   = [];
+  var commentsAndTokens = [];
+  var comments          = [];
+  var tokens            = [];
 
   var parseOpts = {
     allowImportExportEverywhere: opts.looseModules,
@@ -14,13 +15,31 @@ export default function (code, opts = {}) {
     strictMode:                  opts.strictMode,
     sourceType:                  opts.sourceType,
     locations:                   true,
-    onComment:                   comments,
     features:                    opts.features || {},
     plugins:                     opts.plugins || {},
     onToken:                     tokens,
     ranges:                      true
   };
 
+  parseOpts.onToken = function (token) {
+    tokens.push(token);
+    commentsAndTokens.push(token);
+  };
+
+  parseOpts.onComment = function (block, text, start, end, startLoc, endLoc) {
+    var comment = {
+      type: block ? "CommentBlock" : "CommentLine",
+      value: text,
+      start: start,
+      end: end,
+      loc: new acorn.SourceLocation(this, startLoc, endLoc),
+      range: [start, end]
+    };
+
+    commentsAndTokens.push(comment);
+    comments.push(comment);
+  };
+
   if (opts.nonStandard) {
     parseOpts.plugins.jsx = true;
     parseOpts.plugins.flow = true;
@@ -28,6 +47,6 @@ export default function (code, opts = {}) {
 
   var ast = acorn.parse(code, parseOpts);
   estraverse.attachComments(ast, comments, tokens);
-  ast = normalizeAst(ast, comments, tokens);
+  ast = normalizeAst(ast, comments, commentsAndTokens);
   return ast;
 }

src/babel/messages.js

@@ -7,8 +7,6 @@ export const MESSAGES = {
   classesIllegalSuperCall: "Direct super call is illegal in non-constructor, use super.$1() instead",
   classesIllegalConstructorKind: "Illegal kind for constructor method",
   scopeDuplicateDeclaration: "Duplicate declaration $1",
-  undeclaredVariable: "Reference to undeclared variable $1",
-  undeclaredVariableSuggestion: "Reference to undeclared variable $1 - did you mean $2?",
   settersInvalidParamLength: "Setters must have exactly one parameter",
   settersNoRest: "Setters aren't allowed to have a rest",
   noAssignmentsInForHead: "No assignments allowed in for-in/of head",
@@ -24,6 +22,10 @@ export const MESSAGES = {
   illegalMethodName: "Illegal method name $1",
   lostTrackNodePath: "We lost track of this nodes position, likely because the AST was directly manipulated",
 
+  undeclaredVariable: "Reference to undeclared variable $1",
+  undeclaredVariableType: "Referencing a type alias outside of a type annotation",
+  undeclaredVariableSuggestion: "Reference to undeclared variable $1 - did you mean $2?",
+
   traverseNeedsParent: "Must pass a scope and parentPath unless traversing a Program/File got a $1 node",
   traverseVerifyRootFunction: "You passed `traverse()` a function when it expected a visitor object, are you sure you didn't mean `{ enter: Function }`?",
   traverseVerifyVisitorProperty: "You passed `traverse()` a visitor object with the property $1 that has the invalid property $2",

src/babel/patch.js

@@ -17,6 +17,8 @@ var or  = types.Type.or;
 //  .build("program")
 //  .field("program", def("Program"));
 
+def("Noop");
+
 def("AssignmentPattern")
   .bases("Pattern")
   .build("left", "right")

src/babel/tools/build-external-helpers.js

@@ -83,4 +83,4 @@ export default function (whitelist, outputType = "global") {
   }
 
   return generator(tree).code;
-};
+}

src/babel/transformation/file/index.js

@@ -1,29 +1,27 @@
+import { validateOption, normaliseOptions, config as optionsConfig } from "./options";
 import convertSourceMap from "convert-source-map";
-import * as optionParsers from "./option-parsers";
 import moduleFormatters from "../modules";
 import PluginManager from "./plugin-manager";
 import shebangRegex from "shebang-regex";
-import TraversalPath from "../../traversal/path";
+import NodePath from "../../traversal/path";
 import Transformer from "../transformer";
 import isFunction from "lodash/lang/isFunction";
 import isAbsolute from "path-is-absolute";
-import resolveRc from "../../tools/resolve-rc";
+import resolveRc from "./options/resolve-rc";
 import sourceMap from "source-map";
-import transform from "./../index";
 import generate from "../../generation";
 import codeFrame from "../../helpers/code-frame";
 import defaults from "lodash/object/defaults";
 import includes from "lodash/collection/includes";
 import traverse from "../../traversal";
+import Hub from "../../traversal/hub";
 import assign from "lodash/object/assign";
 import Logger from "./logger";
 import parse from "../../helpers/parse";
-import Scope from "../../traversal/scope";
 import merge from "../../helpers/merge";
 import slash from "slash";
 import clone from "lodash/lang/clone";
 import * as util from  "../../util";
-import * as api from  "../../api/node";
 import path from "path";
 import * as t from "../../types";
 
@@ -38,15 +36,27 @@ export default class File {
     this.declarations = {};
     this.usedHelpers  = {};
     this.dynamicData  = {};
-    this.metadata     = {};
     this.data         = {};
 
+    this.metadata = {
+      modules: {
+        imports: [],
+        exports: {
+          exported: [],
+          specifiers: []
+        }
+      }
+    };
+
     this.pipeline = pipeline;
     this.log      = new Logger(this, opts.filename || "unknown");
-    this.opts     = this.normalizeOptions(opts);
     this.ast      = {};
 
+    this.normaliseOptions(opts);
+
     this.buildTransformers();
+
+    this.hub = new Hub(this);
   }
 
   static helpers = [
@@ -88,19 +98,19 @@ export default class File {
 
   static soloHelpers = [];
 
-  static options = require("./options");
+  static options = optionsConfig;
 
-  normalizeOptions(opts: Object) {
-    opts = assign({}, opts);
+  normaliseOptions(opts: Object) {
+    opts = this.opts = normaliseOptions(assign({}, opts));
 
+    // resolve babelrc
     if (opts.filename) {
       var rcFilename = opts.filename;
       if (!isAbsolute(rcFilename)) rcFilename = path.join(process.cwd(), rcFilename);
       opts = resolveRc(rcFilename, opts);
     }
 
-    //
-
+    // check for unknown options
     for (let key in opts) {
       if (key[0] === "_") continue;
 
@@ -108,26 +118,30 @@ export default class File {
       if (!option) this.log.error(`Unknown option: ${key}`, ReferenceError);
     }
 
+    // merge in environment options
     var envKey = process.env.BABEL_ENV || process.env.NODE_ENV || "development";
-    if (opts.env) merge(opts, opts.env[envKey]);
+    if (opts.env) merge(opts, normaliseOptions(opts.env[envKey]));
 
+    // normalise options
     for (let key in File.options) {
       let option = File.options[key];
+      var val    = opts[key];
 
-      var val = opts[key];
+      // optional
       if (!val && option.optional) continue;
 
+      // deprecated
       if (val && option.deprecated) {
-        throw new Error("Deprecated option " + key + ": " + option.deprecated);
+        this.log.deprecate("Deprecated option " + key + ": " + option.deprecated);
       }
 
-      if (val == null) {
-        val = clone(option.default);
-      }
+      // default
+      if (val == null) val = clone(option.default);
 
-      var optionParser = optionParsers[option.type];
-      if (optionParser) val = optionParser(key, val, this.pipeline);
+      // validate
+      if (val) val = validateOption(key, val, this.pipeline);
 
+      // aaliases
       if (option.alias) {
         opts[option.alias] = opts[option.alias] || val;
       } else {
@@ -152,7 +166,10 @@ export default class File {
     opts.basename = path.basename(opts.filename, path.extname(opts.filename));
 
     opts.ignore = util.arrayify(opts.ignore, util.regexify);
-    opts.only   = util.arrayify(opts.only, util.regexify);
+
+    if (opts.only) {
+      opts.only = util.arrayify(opts.only, util.regexify);
+    }
 
     defaults(opts, {
       moduleRoot: opts.sourceRoot
@@ -195,7 +212,7 @@ export default class File {
     // build internal transformers
     for (var key in this.pipeline.transformers) {
       var transformer = this.pipeline.transformers[key];
-      var pass = transformers[key] = transformer.buildPass(file);
+      let pass = transformers[key] = transformer.buildPass(file);
 
       if (pass.canTransform()) {
         stack.push(pass);
@@ -228,7 +245,7 @@ export default class File {
     this.uncollapsedTransformerStack = stack = stack.concat(secondaryStack);
 
     // build dependency graph
-    for (var pass of (stack: Array)) {
+    for (let pass of (stack: Array)) {
       for (var dep of (pass.transformer.dependencies: Array)) {
         this.transformerDependencies[dep] = pass.key;
       }
@@ -268,7 +285,6 @@ export default class File {
       }
       var visitor = traverse.visitors.merge(visitors);
       var mergeTransformer = new Transformer(group, visitor);
-      //console.log(mergeTransformer);
       stack.push(mergeTransformer.buildPass(this));
     }
 
@@ -330,14 +346,24 @@ export default class File {
   }
 
   attachAuxiliaryComment(node: Object): Object {
-    var comment = this.opts.auxiliaryComment;
-    if (comment) {
+    var beforeComment = this.opts.auxiliaryCommentBefore;
+    if (beforeComment) {
       node.leadingComments = node.leadingComments || [];
       node.leadingComments.push({
-        type: "Line",
-        value: " " + comment
+        type: "CommentLine",
+        value: " " + beforeComment
       });
     }
+
+    var afterComment = this.opts.auxiliaryCommentAfter;
+    if (afterComment) {
+      node.trailingComments = node.trailingComments || [];
+      node.trailingComments.push({
+        type: "CommentLine",
+        value: " " + afterComment
+      });
+    }
+
     return node;
   }
 
@@ -348,8 +374,6 @@ export default class File {
       throw new ReferenceError(`Unknown helper ${name}`);
     }
 
-    var program = this.ast.program;
-
     var declar = this.declarations[name];
     if (declar) return declar;
 
@@ -390,9 +414,15 @@ export default class File {
   }
 
   errorWithNode(node, msg, Error = SyntaxError) {
-    var loc = node.loc.start;
-    var err = new Error(`Line ${loc.line}: ${msg}`);
-    err.loc = loc;
+    var err;
+    if (node && node.loc) {
+      var loc = node.loc.start;
+      err = new Error(`Line ${loc.line}: ${msg}`);
+      err.loc = loc;
+    } else {
+      // todo: find errors with nodes inside to at least point to something
+      err = new Error("There's been an error on a dynamic node. This is almost certainly an internal error. Please report it.");
+    }
     return err;
   }
 
@@ -410,7 +440,7 @@ export default class File {
       outputMapGenerator.applySourceMap(inputMapConsumer);
 
       var mergedMap = outputMapGenerator.toJSON();
-      mergedMap.sources = inputMap.sources
+      mergedMap.sources = inputMap.sources;
       mergedMap.file    = inputMap.file;
       return mergedMap;
     }
@@ -467,7 +497,13 @@ export default class File {
   }
 
   _addAst(ast) {
-    this.path  = TraversalPath.get(null, ast, ast, "program", this).setContext(null, this);
+    this.path = NodePath.get({
+      hub: this.hub,
+      parentPath: null,
+      parent: ast,
+      container: ast,
+      key: "program"
+    }).setContext();
     this.scope = this.path.scope;
     this.ast   = ast;
   }
@@ -483,12 +519,16 @@ export default class File {
       modFormatter.init();
     }
     this.log.debug("End module formatter init");
+  }
 
+  transform() {
     this.call("pre");
     for (var pass of (this.transformerStack: Array)) {
       pass.transform();
     }
     this.call("post");
+
+    return this.generate();
   }
 
   wrap(code, callback) {
@@ -496,18 +536,10 @@ export default class File {
 
     try {
       if (this.shouldIgnore()) {
-        return {
-          metadata: this.metadata,
-          ignored:  true,
-          code:     code,
-          map:      null,
-          ast:      null
-        };
+        return this.makeResult({ code, ignored: true });
+      } else {
+        return callback();
       }
-
-      callback();
-
-      return this.generate();
     } catch (err) {
       if (err._babel) {
         throw err;
@@ -536,15 +568,15 @@ export default class File {
     }
   }
 
-  addCode(code: string, parseCode?) {
+  addCode(code: string) {
     code = (code || "") + "";
     code = this.parseInputSourceMap(code);
     this.code = code;
+  }
 
-    if (parseCode) {
-      this.parseShebang();
-      this.addAst(this.parse(this.code));
-    }
+  parseCode() {
+    this.parseShebang();
+    this.addAst(this.parse(this.code));
   }
 
   shouldIgnore() {
@@ -581,28 +613,37 @@ export default class File {
     }
   }
 
-  generate(): {
-    usedHelpers?: Array<string>;
-    code: string;
-    map?: Object;
-    ast?: Object;
-  } {
-    var opts = this.opts;
-    var ast  = this.ast;
-
+  makeResult({ code, map = null, ast, ignored }) {
     var result = {
-      metadata: this.metadata,
-      code:     "",
-      map:      null,
-      ast:      null
+      metadata: null,
+      ignored:  !!ignored,
+      code:     null,
+      ast:      null,
+      map:      map
     };
 
-    if (this.opts.metadataUsedHelpers) {
+    if (this.opts.code) {
+      result.code = code;
+    }
+
+    if (this.opts.ast) {
+      result.ast = ast;
+    }
+
+    if (this.opts.metadata) {
+      result.metadata = this.metadata;
       result.metadata.usedHelpers = Object.keys(this.usedHelpers);
     }
 
-    if (opts.ast) result.ast = ast;
-    if (!opts.code) return result;
+    return result;
+  }
+
+  generate() {
+    var opts = this.opts;
+    var ast  = this.ast;
+
+    var result = { ast };
+    if (!opts.code) return this.makeResult(result);
 
     this.log.debug("Generation start");
 
@@ -629,6 +670,6 @@ export default class File {
       result.map = null;
     }
 
-    return result;
+    return this.makeResult(result);
   }
 }

src/babel/transformation/file/logger.js

@@ -1,3 +1,4 @@
+import type File from "./index";
 import buildDebug from "debug/node";
 
 var verboseDebug = buildDebug("babel:verbose");
@@ -15,6 +16,10 @@ export default class Logger {
     return parts;
   }
 
+  warn(msg) {
+    console.warn(this._buildMessage(msg));
+  }
+
   error(msg: string, Constructor = Error) {
     throw new Constructor(this._buildMessage(msg));
   }

src/babel/transformation/file/option-parsers.js

@@ -1,27 +0,0 @@
-import * as util from  "../../util";
-
-export function transformerList(key, val, pipeline) {
-  val = util.arrayify(val);
-
-  if (val.indexOf("all") >= 0 || val.indexOf(true) >= 0) {
-    val = Object.keys(pipeline.transformers);
-  }
-
-  return pipeline._ensureTransformerNames(key, val);
-}
-
-export function number(key, val) {
-  return +val;
-}
-
-export function boolean(key, val) {
-  return !!val;
-}
-
-export function booleanString(key, val) {
-  return util.booleanify(val);
-}
-
-export function list(key, val) {
-  return util.list(val);
-}

src/babel/transformation/file/options/config.json

@@ -47,7 +47,9 @@
   },
 
   "experimental": {
-    "deprecated": "use `--stage 0`/`{ stage: 0 }` instead"
+    "type": "boolean",
+    "description": "allow use of experimental transformers",
+    "default": false
   },
 
   "highlightCode": {
@@ -76,7 +78,8 @@
   "blacklist": {
     "type": "transformerList",
     "description": "blacklist of transformers to NOT use",
-    "shorthand": "b"
+    "shorthand": "b",
+    "default": []
   },
 
   "whitelist": {
@@ -88,7 +91,8 @@
 
   "optional": {
     "type": "transformerList",
-    "description": "list of optional transformers to enable"
+    "description": "list of optional transformers to enable",
+    "default": []
   },
 
   "modules": {
@@ -120,12 +124,14 @@
 
   "plugins": {
     "type": "list",
-    "description": ""
+    "description": "",
+    "default": []
   },
 
   "ignore": {
     "type": "list",
-    "description": "list of glob paths to **not** compile"
+    "description": "list of glob paths to **not** compile",
+    "default": []
   },
 
   "only": {
@@ -139,6 +145,12 @@
     "type": "boolean"
   },
 
+  "metadata": {
+    "hidden": true,
+    "default": true,
+    "type": "boolean"
+  },
+
   "ast": {
     "hidden": true,
     "default": true,
@@ -165,12 +177,23 @@
   },
 
   "auxiliaryComment": {
+    "deprecated": "renamed to auxiliaryCommentBefore",
+    "shorthand": "a",
+    "alias": "auxiliaryCommentBefore"
+  },
+
+  "auxiliaryCommentBefore": {
     "type": "string",
     "default": "",
-    "shorthand": "a",
     "description": "attach a comment before all helper declarations and auxiliary code"
   },
 
+  "auxiliaryCommentAfter": {
+    "type": "string",
+    "default": "",
+    "description": "attach a comment after all helper declarations and auxiliary code"
+  },
+
   "externalHelpers": {
     "type": "boolean",
     "default": false,
@@ -179,6 +202,7 @@
   },
 
   "metadataUsedHelpers": {
+    "deprecated": "Not required anymore as this is enabled by default",
     "type": "boolean",
     "default": false,
     "hidden": true

src/babel/transformation/file/options/index.js

@@ -0,0 +1,31 @@
+import * as parsers from "./parsers";
+import config from "./config";
+
+export { config };
+
+export function validateOption(key, val, pipeline) {
+  var opt = config[key];
+  var parser = opt && parsers[opt.type];
+  if (parser && parser.validate) {
+    return parser.validate(key, val, pipeline);
+  } else {
+    return val;
+  }
+}
+
+export function normaliseOptions(options = {}) {
+  for (var key in options) {
+    var val = options[key];
+    if (val == null) continue;
+
+    var opt = config[key];
+    if (!opt) continue;
+
+    var parser = parsers[opt.type];
+    if (parser) val = parser(val);
+
+    options[key] = val;
+  }
+
+  return options;
+}

src/babel/transformation/file/options/parsers.js

@@ -0,0 +1,29 @@
+import * as util from "../../../util";
+
+export function transformerList(val) {
+  return util.arrayify(val);
+}
+
+transformerList.validate = function (key, val, pipeline) {
+  if (val.indexOf("all") >= 0 || val.indexOf(true) >= 0) {
+    val = Object.keys(pipeline.transformers);
+  }
+
+  return pipeline._ensureTransformerNames(key, val);
+};
+
+export function number(val) {
+  return +val;
+}
+
+export function boolean(val) {
+  return !!val;
+}
+
+export function booleanString(val) {
+  return util.booleanify(val);
+}
+
+export function list(val) {
+  return util.list(val);
+}

src/babel/transformation/file/options/resolve-rc.js

@@ -1,5 +1,6 @@
 import stripJsonComments from "strip-json-comments";
-import merge from "../helpers/merge";
+import { normaliseOptions } from "./index";
+import merge from "../../../helpers/merge";
 import path from "path";
 import fs from "fs";
 
@@ -34,6 +35,7 @@ export default function (loc, opts = {}) {
 
       try {
         json = jsons[content] = jsons[content] || JSON.parse(stripJsonComments(content));
+        normaliseOptions(json);
       } catch (err) {
         err.message = `${file}: ${err.message}`;
         throw err;
@@ -42,6 +44,7 @@ export default function (loc, opts = {}) {
       opts.babelrc.push(file);
 
       if (json.breakConfig) return;
+
       merge(opts, json);
     }
 
@@ -56,4 +59,4 @@ export default function (loc, opts = {}) {
   }
 
   return opts;
-};
+}

src/babel/transformation/file/plugin-manager.js

@@ -37,9 +37,10 @@ export default class PluginManager {
 
     var loc = util.resolveRelative(`babel-plugin-${name}`) || util.resolveRelative(name);
     if (loc) {
+      var plugin = require(loc);
       return {
         position: position,
-        plugin:   require(loc)
+        plugin:   plugin.default || plugin
       };
     } else {
       throw new ReferenceError(messages.get("pluginUnknown", name));

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

@@ -44,4 +44,4 @@ export default function (opts) {
   };
 
   return exports;
-};
+}

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

@@ -42,4 +42,4 @@ export default function (exports, opts) {
 
     return nodes;
   };
-};
+}

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

@@ -10,7 +10,7 @@ import * as react from "./react";
 import * as t from "../../types";
 
 export default function (exports, opts) {
-  exports.JSXIdentifier = function (node, parent) {
+  exports.JSXIdentifier = function (node) {
     if (node.name === "this" && this.isReferenced()) {
       return t.thisExpression();
     } else if (esutils.keyword.isIdentifierNameES6(node.name)) {
@@ -20,7 +20,7 @@ export default function (exports, opts) {
     }
   };
 
-  exports.JSXNamespacedName = function (node, parent, scope, file) {
+  exports.JSXNamespacedName = function () {
     throw this.errorWithNode(messages.get("JSXNamespacedTags"));
   };
 
@@ -161,7 +161,8 @@ export default function (exports, opts) {
 
     for (var i = 0; i < props.length; i++) {
       var prop = props[i];
-      if (t.isIdentifier(prop.key, { name: "displayName" })) {
+      var key = t.toComputedKey(prop);
+      if (t.isLiteral(key, { value: "displayName" })) {
         safe = false;
         break;
       }
@@ -202,4 +203,4 @@ export default function (exports, opts) {
       addDisplayName(left.name, right);
     }
   };
-};
+}

src/babel/transformation/helpers/call-delegate.js

@@ -1,4 +1,3 @@
-import traverse from "../../traversal";
 import * as t from "../../types";
 
 var visitor = {
@@ -7,10 +6,10 @@ var visitor = {
       state.found = true;
       this.stop();
     }
+  },
 
-    if (this.isFunction()) {
-      this.skip();
-    }
+  Function() {
+    this.skip();
   }
 };
 

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

@@ -1,5 +1,3 @@
-import cloneDeep from "lodash/lang/cloneDeep";
-import traverse from "../../traversal";
 import each from "lodash/collection/each";
 import has from "lodash/object/has";
 import * as t from "../../types";

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

@@ -68,4 +68,4 @@ export default function (node, nodes, file, scope, allowedSingleIdent) {
     uid: uid,
     ref: ref
   };
-};
+}

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

@@ -3,7 +3,10 @@ import * as t from "../../types";
 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;
+    var param = node.params[i];
+    if (!t.isAssignmentPattern(param) && !t.isRestElement(param)) {
+      lastNonDefault = i + 1;
+    }
   }
   return lastNonDefault;
-};
+}

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

@@ -2,19 +2,29 @@ import getFunctionArity from "./get-function-arity";
 import * as util from  "../../util";
 import * as t from "../../types";
 
+function visitIdentifier(context, node, scope, state) {
+  // check if this node matches our function id
+  if (node.name !== state.name) return;
+
+  // check that we don't have a local variable declared as that removes the need
+  // for the wrapper
+  var localDeclar = scope.getBindingIdentifier(state.name);
+  if (localDeclar !== state.outerDeclar) return;
+
+  state.selfReference = true;
+  context.stop();
+}
+
 var visitor = {
-  enter(node, parent, scope, state) {
-    // check if this node is a referenced identifier that matches the same as our
-    // function id
-    if (!this.isReferencedIdentifier({ name: state.name })) return;
+  ReferencedIdentifier(node, parent, scope, state) {
+    visitIdentifier(this, node, scope, state);
+  },
 
-    // check that we don't have a local variable declared as that removes the need
-    // for the wrapper
-    var localDeclar = scope.getBindingIdentifier(state.name);
-    if (localDeclar !== state.outerDeclar) return;
-
-    state.selfReference = true;
-    this.stop();
+  AssignmentExpression(node, parent, scope, state) {
+    var ids = this.getBindingIdentifiers();
+    for (var name in ids) {
+      visitIdentifier(this, ids[name], scope, state);
+    }
   }
 };
 
@@ -46,6 +56,7 @@ var wrap = function (state, method, id, scope) {
   }
 
   method.id = id;
+  scope.getProgramParent().references[id.name] = true;
 };
 
 var visit = function (node, name, scope) {
@@ -60,7 +71,7 @@ var visit = function (node, name, scope) {
   // check to see if we have a local binding of the id we're setting inside of
   // the function, this is important as there are caveats associated
 
-  var bindingInfo = scope.getOwnBindingInfo(name);
+  var bindingInfo = scope.getOwnBinding(name);
 
   if (bindingInfo) {
     if (bindingInfo.kind === "param") {

src/babel/transformation/helpers/react.js

@@ -1,4 +1,3 @@
-import isString from "lodash/lang/isString";
 import * as t from "../../types";
 
 var isCreateClassCallExpression = t.buildMatchMemberExpression("React.createClass");
@@ -26,10 +25,6 @@ export function isCompatTag(tagName) {
   return tagName && /^[a-z]|\-/.test(tagName);
 }
 
-function isStringLiteral(node) {
-  return t.isLiteral(node) && isString(node.value);
-}
-
 function cleanJSXElementLiteralChild(child, args) {
   var lines = child.value.split(/\r\n|\n|\r/);
 

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

@@ -1,35 +1,37 @@
 import * as t from "../../types";
 
 var awaitVisitor = {
-  enter(node, parent, scope, state) {
-    if (t.isFunction(node)) this.skip();
+  Function() {
+    this.skip();
+  },
 
-    if (t.isAwaitExpression(node)) {
-      node.type = "YieldExpression";
+  AwaitExpression(node) {
+    node.type = "YieldExpression";
 
-      if (node.all) {
-        // await* foo; -> yield Promise.all(foo);
-        node.all = false;
-        node.argument = t.callExpression(t.memberExpression(t.identifier("Promise"), t.identifier("all")), [node.argument]);
-      }
+    if (node.all) {
+      // await* foo; -> yield Promise.all(foo);
+      node.all = false;
+      node.argument = t.callExpression(t.memberExpression(t.identifier("Promise"), t.identifier("all")), [node.argument]);
     }
   }
 };
 
 var referenceVisitor = {
-  enter(node, parent, scope, state) {
+  ReferencedIdentifier(node, parent, scope, state) {
     var name = state.id.name;
-    if (this.isReferencedIdentifier({ name: name }) && scope.bindingIdentifierEquals(name, state.id)) {
+    if (node.name === name && scope.bindingIdentifierEquals(name, state.id)) {
       return state.ref = state.ref || scope.generateUidIdentifier(name);
     }
   }
 };
 
-export default function (node, callId, scope) {
+export default function (path, callId) {
+  var node = path.node;
+
   node.async = false;
   node.generator = true;
 
-  scope.traverse(node, awaitVisitor, state);
+  path.traverse(awaitVisitor, state);
 
   var call = t.callExpression(callId, [node]);
 
@@ -44,15 +46,15 @@ export default function (node, callId, scope) {
     return declar;
   } else {
     if (id) {
-      var state = { id: id };
-      scope.traverse(node, referenceVisitor, state);
+      var state = { id };
+      path.traverse(referenceVisitor, state);
 
       if (state.ref) {
-        scope.parent.push({ id: state.ref });
+        path.scope.parent.push({ id: state.ref });
         return t.assignmentExpression("=", state.ref, call);
       }
     }
 
     return call;
   }
-};
+}

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

@@ -1,3 +1,4 @@
+import type NodePath from "../../traversal/path";
 import * as messages from "../../messages";
 import * as t from "../../types";
 
@@ -130,7 +131,7 @@ export default class ReplaceSupers {
    * Description
    */
 
-  traverseLevel(path: TraversalPath, topLevel: boolean) {
+  traverseLevel(path: NodePath, topLevel: boolean) {
     var state = { self: this, topLevel: topLevel };
     path.traverse(visitor, state);
   }
@@ -192,7 +193,7 @@ export default class ReplaceSupers {
    * Description
    */
 
-  looseHandle(path: TraversalPath, getThisReference: Function) {
+  looseHandle(path: NodePath, getThisReference: Function) {
     var node = path.node;
     if (path.isSuper()) {
       return this.getLooseSuperProperty(node, path.parent);
@@ -234,7 +235,7 @@ export default class ReplaceSupers {
    * Description
    */
 
-  specHandle(path: TraversalPath, getThisReference: Function) {
+  specHandle(path: NodePath, getThisReference: Function) {
     var methodNode = this.methodNode;
     var property;
     var computed;
@@ -274,7 +275,7 @@ export default class ReplaceSupers {
       property = node.property;
       computed = node.computed;
     } else if (t.isUpdateExpression(node) && isMemberExpressionSuper(node.argument)) {
-      var binary = t.binaryExpression(node.operator[0], node.argument, t.literal(1))
+      var binary = t.binaryExpression(node.operator[0], node.argument, t.literal(1));
       if (node.prefix) {
         // ++super.foo; -> super.foo += 1;
         return this.specHandleAssignmentExpression(null, path, binary, getThisReference);

src/babel/transformation/helpers/strict.js

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

src/babel/transformation/modules/_default.js

@@ -1,12 +1,11 @@
 import * as messages from "../../messages";
-import traverse from "../../traversal";
 import extend from "lodash/object/extend";
 import object from "../../helpers/object";
 import * as util from  "../../util";
 import * as t from "../../types";
 
 var remapVisitor = {
-  enter(node, parent, scope, formatter) {
+  enter(node) {
     if (node._skipModulesRemap) {
       return this.skip();
     }
@@ -69,46 +68,158 @@ var remapVisitor = {
   }
 };
 
-var importsVisitor = {
+var metadataVisitor = {
+  ModuleDeclaration: {
+    enter(node, parent, scope, formatter) {
+      if (node.source) {
+        node.source.value = formatter.file.resolveModuleSource(node.source.value);
+      }
+    }
+  },
+
   ImportDeclaration: {
-    enter(node, parent, scope, formatter) {
+    exit(node, parent, scope, formatter) {
       formatter.hasLocalImports = true;
-      extend(formatter.localImports, this.getBindingIdentifiers());
-    }
-  }
-};
 
-var exportsVisitor = {
-  ExportDeclaration: {
-    enter(node, parent, scope, formatter) {
-      formatter.hasLocalExports = true;
+      var specifiers = [];
+      var imported = [];
+      formatter.metadata.imports.push({
+        source: node.source.value,
+        imported,
+        specifiers
+      });
 
-      var declar = this.get("declaration");
-      if (declar.isStatement()) {
-        var bindings = declar.getBindingIdentifiers()
-        for (var name in bindings) {
-          var binding = bindings[name];
-          formatter._addExport(name, binding);
+      for (var specifier of (this.get("specifiers"): Array)) {
+        var ids = specifier.getBindingIdentifiers();
+        extend(formatter.localImports, ids);
+
+        var local = specifier.node.local.name;
+
+        if (specifier.isImportDefaultSpecifier()) {
+          imported.push("default");
+          specifiers.push({
+            kind: "named",
+            imported: "default",
+            local
+          });
         }
-      }
 
-      if (this.isExportNamedDeclaration() && node.specifiers) {
-        for (var i = 0; i < node.specifiers.length; i++) {
-          var specifier = node.specifiers[i];
-          var local = specifier.local;
-          if (!local) continue;
-
-          formatter._addExport(local.name, specifier.exported);
+        if (specifier.isImportSpecifier()) {
+          var importedName = specifier.node.imported.name;
+          imported.push(importedName);
+          specifiers.push({
+            kind: "named",
+            imported: importedName,
+            local
+          });
         }
-      }
 
-      if (!t.isExportDefaultDeclaration(node)) {
-        var onlyDefault = node.specifiers && node.specifiers.length === 1 && t.isSpecifierDefault(node.specifiers[0]);
-        if (!onlyDefault) {
-          formatter.hasNonDefaultExports = true;
+        if (specifier.isImportNamespaceSpecifier()) {
+          imported.push("*");
+          specifiers.push({
+            kind: "namespace",
+            local
+          });
         }
       }
     }
+  },
+
+  ExportDeclaration(node, parent, scope, formatter) {
+    formatter.hasLocalExports = true;
+
+    var source = node.source ? node.source.value : null;
+    var exports = formatter.metadata.exports;
+
+    // export function foo() {}
+    // export var foo = "bar";
+    var declar = this.get("declaration");
+    if (declar.isStatement()) {
+      var bindings = declar.getBindingIdentifiers();
+
+      for (var name in bindings) {
+        var binding = bindings[name];
+        formatter._addExport(name, binding);
+
+        exports.exported.push(name);
+        exports.specifiers.push({
+          kind: "local",
+          local: name,
+          exported: this.isExportDefaultDeclaration() ? "default" : name
+        });
+      }
+    }
+
+    if (this.isExportNamedDeclaration() && node.specifiers) {
+      for (var specifier of (node.specifiers: Array)) {
+        var exported = specifier.exported.name;
+        exports.exported.push(exported);
+
+        // export foo from "bar";
+        if (t.isExportDefaultSpecifier(specifier)) {
+          exports.specifiers.push({
+            kind: "external",
+            local: exported,
+            exported,
+            source
+          });
+        }
+
+        // export * as foo from "bar";
+        if (t.isExportNamespaceSpecifier(specifier)) {
+          exports.specifiers.push({
+            kind: "external-namespace",
+            exported,
+            source
+          });
+        }
+
+        var local = specifier.local;
+        if (!local) continue;
+
+        formatter._addExport(local.name, specifier.exported);
+
+        // export { foo } from "bar";
+        // export { foo as bar } from "bar";
+        if (source) {
+          exports.specifiers.push({
+            kind: "external",
+            local: local.name,
+            exported,
+            source
+          });
+        }
+
+        // export { foo };
+        // export { foo as bar };
+        if (!source) {
+          exports.specifiers.push({
+            kind: "local",
+            local: local.name,
+            exported
+          });
+        }
+      }
+    }
+
+    // export * from "bar";
+    if (this.isExportAllDeclaration()) {
+      exports.specifiers.push({
+        kind: "external-all",
+        source
+      });
+    }
+
+    if (!t.isExportDefaultDeclaration(node) && !declar.isTypeAlias()) {
+      var onlyDefault = node.specifiers && node.specifiers.length === 1 && t.isSpecifierDefault(node.specifiers[0]);
+      if (!onlyDefault) {
+        formatter.hasNonDefaultExports = true;
+      }
+    }
+  },
+
+  Scope() {
+    this.skip();
   }
 };
 
@@ -128,8 +239,8 @@ export default class DefaultFormatter {
     this.localExports = object();
     this.localImports = object();
 
-    this.getLocalExports();
-    this.getLocalImports();
+    this.metadata = file.metadata.modules;
+    this.getMetadata();
   }
 
   isModuleType(node, type) {
@@ -145,12 +256,15 @@ export default class DefaultFormatter {
     return (t.isExportDefaultDeclaration(node) || t.isSpecifierDefault(node)) && !this.noInteropRequireExport && !this.hasNonDefaultExports;
   }
 
-  getLocalExports() {
-    this.file.path.traverse(exportsVisitor, this);
-  }
-
-  getLocalImports() {
-    this.file.path.traverse(importsVisitor, this);
+  getMetadata() {
+    var has = false;
+    for (var node of (this.file.ast.program.body: Array)) {
+      if (t.isModuleDeclaration(node)) {
+        has = true;
+        break;
+      }
+    }
+    if (has) this.file.path.traverse(metadataVisitor, this);
   }
 
   remapAssignments() {

src/babel/transformation/modules/_strict.js

@@ -10,4 +10,4 @@ export default function (Parent) {
   util.inherits(Constructor, Parent);
 
   return Constructor;
-};
+}

src/babel/transformation/modules/common.js

@@ -1,5 +1,4 @@
 import DefaultFormatter from "./_default";
-import includes from "lodash/collection/includes";
 import * as util from  "../../util";
 import * as t from "../../types";
 
@@ -84,7 +83,7 @@ export default class CommonJSFormatter extends DefaultFormatter {
     }, true));
   }
 
-  exportSpecifier(specifier, node, nodes) {
+  exportSpecifier(specifier) {
     if (this.doDefaultExportInterop(specifier)) {
       this.hasDefaultOnlyExport = true;
     }
@@ -92,7 +91,7 @@ export default class CommonJSFormatter extends DefaultFormatter {
     DefaultFormatter.prototype.exportSpecifier.apply(this, arguments);
   }
 
-  exportDeclaration(node, nodes) {
+  exportDeclaration(node) {
     if (this.doDefaultExportInterop(node)) {
       this.hasDefaultOnlyExport = true;
     }
@@ -101,8 +100,6 @@ export default class CommonJSFormatter extends DefaultFormatter {
   }
 
   _getExternalReference(node, nodes) {
-    var source = node.source.value;
-
     var call = t.callExpression(t.identifier("require"), [node.source]);
     var uid;
 

src/babel/transformation/modules/system.js

@@ -3,7 +3,6 @@ import AMDFormatter from "./amd";
 import object from  "../../helpers/object";
 import * as util from  "../../util";
 import last from "lodash/array/last";
-import each from "lodash/collection/each";
 import map from "lodash/collection/map";
 import * as t from "../../types";
 
@@ -45,12 +44,14 @@ var hoistVariablesVisitor = {
 };
 
 var hoistFunctionsVisitor = {
-  enter(node, parent, scope, state) {
-    if (t.isFunction(node)) this.skip();
+  Function() {
+    this.skip();
+  },
 
+  enter(node, parent, scope, state) {
     if (t.isFunctionDeclaration(node) || state.formatter._canHoist(node)) {
       state.handlerBody.push(node);
-      this.remove();
+      this.dangerouslyRemove();
     }
   }
 };
@@ -69,7 +70,7 @@ var runnerSettersVisitor = {
         state.nodes.push(node);
       }
 
-      this.remove();
+      this.dangerouslyRemove();
     }
   }
 };

src/babel/transformation/templates/default-parameter-assign.js

@@ -0,0 +1 @@
+if (VARIABLE_NAME === undefined) VARIABLE_NAME = DEFAULT_VALUE;

src/babel/transformation/transformer-pass.js

@@ -1,5 +1,6 @@
-import includes from "lodash/collection/includes";
+import type Transformer from "./transformer";
 import traverse from "../traversal";
+import type File from "./file";
 
 /**
  * This class is responsible for traversing over the provided `File`s
@@ -11,8 +12,13 @@ export default class TransformerPass {
     this.transformer = transformer;
     this.handlers    = transformer.handlers;
     this.file        = file;
-    this.ran         = false;
     this.key         = transformer.key;
+
+    if (this.canTransform() && transformer.metadata.experimental && !file.opts.experimental) {
+      file.log.warn(`THE TRANSFORMER ${this.key} HAS BEEN MARKED AS EXPERIMENTAL AND IS WIP. USE AT YOUR OWN RISK. ` +
+                    "THIS WILL HIGHLY LIKELY BREAK YOUR CODE SO USE WITH **EXTREME** CAUTION. ENABLE THE " +
+                    "`experimental` OPTION TO IGNORE THIS WARNING.");
+    }
   }
 
   canTransform(): boolean {
@@ -22,13 +28,8 @@ export default class TransformerPass {
 
   transform() {
     var file = this.file;
-
     file.log.debug(`Start transformer ${this.key}`);
-
     traverse(file.ast, this.handlers, file.scope, file);
-
     file.log.debug(`Finish transformer ${this.key}`);
-
-    this.ran = true;
   }
 }

src/babel/transformation/transformer-pipeline.js

@@ -57,10 +57,21 @@ export default class TransformerPipeline {
     return true;
   }
 
+  pretransform(code: string, opts?: Object) {
+    var file = new File(opts, this);
+    return file.wrap(code, function () {
+      file.addCode(code);
+      file.parseCode(code);
+      return file;
+    });
+  }
+
   transform(code: string, opts?: Object) {
     var file = new File(opts, this);
     return file.wrap(code, function () {
-      file.addCode(code, true);
+      file.addCode(code);
+      file.parseCode(code);
+      return file.transform();
     });
   }
 
@@ -71,6 +82,7 @@ export default class TransformerPipeline {
     return file.wrap(code, function () {
       file.addCode(code);
       file.addAst(ast);
+      return file.transform();
     });
   }
 

src/babel/transformation/transformer.js

@@ -4,7 +4,6 @@ import isFunction from "lodash/lang/isFunction";
 import traverse from "../traversal";
 import isObject from "lodash/lang/isObject";
 import assign from "lodash/object/assign";
-import * as acorn from "../../acorn";
 import File from "./file";
 import each from "lodash/collection/each";
 

src/babel/transformation/transformers/aliases.json

@@ -1,5 +1,6 @@
 {
   "useStrict": "strict",
   "es5.runtime": "runtime",
-  "es6.runtime": "runtime"
+  "es6.runtime": "runtime",
+  "minification.inlineExpressions": "minification.constantFolding"
 }

src/babel/transformation/transformers/deprecated.json

@@ -5,7 +5,7 @@
   "es6.symbols": "es6.spec.symbols",
   "es6.blockScopingTDZ": "es6.spec.blockScoping",
 
-  "utility.inlineExpressions": "minification.inlineExpressions",
+  "utility.inlineExpressions": "minification.constantFolding",
   "utility.deadCodeElimination": "minification.deadCodeElimination",
   "utility.removeConsoleCalls": "minification.removeConsole",
   "utility.removeDebugger": "minification.removeDebugger"

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

@@ -2,12 +2,19 @@ import * as defineMap from "../../helpers/define-map";
 import * as t from "../../../types";
 
 export function ObjectExpression(node, parent, scope, file) {
-  var mutatorMap = {};
   var hasAny = false;
+  for (var prop of (node.properties: Array)) {
+    if (prop.kind === "get" || prop.kind === "set") {
+      hasAny = true;
+      break;
+    }
+  }
+  if (!hasAny) return;
+
+  var mutatorMap = {};
 
   node.properties = node.properties.filter(function (prop) {
     if (prop.kind === "get" || prop.kind === "set") {
-      hasAny = true;
       defineMap.push(mutatorMap, prop, prop.kind, file);
       return false;
     } else {
@@ -15,8 +22,6 @@ export function ObjectExpression(node, parent, scope, file) {
     }
   });
 
-  if (!hasAny) return;
-
   return t.callExpression(
     t.memberExpression(t.identifier("Object"), t.identifier("defineProperties")),
     [node, defineMap.toDefineObject(mutatorMap)]

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

@@ -1,3 +1,6 @@
+import type NodePath from "../../../traversal/path";
+import type Scope from "../../../traversal/scope";
+import type File from "../../file";
 import traverse from "../../../traversal";
 import object from "../../../helpers/object";
 import * as util from  "../../../util";
@@ -113,6 +116,13 @@ function traverseReplace(node, parent, scope, remaps) {
     replace(node, parent, scope, remaps);
   }
 
+  if (t.isAssignmentExpression(node)) {
+    var ids = t.getBindingIdentifiers(node);
+    for (var name in ids) {
+      replace(ids[name], parent, scope, remaps);
+    }
+  }
+
   scope.traverse(node, replaceVisitor, remaps);
 }
 
@@ -258,7 +268,7 @@ class BlockScoping {
    * Description
    */
 
-  constructor(loopPath?: TraversalPath, blockPath: TraversalPath, parent: Object, scope: Scope, file: File) {
+  constructor(loopPath?: NodePath, blockPath: NodePath, parent: Object, scope: Scope, file: File) {
     this.parent = parent;
     this.scope  = scope;
     this.file   = file;
@@ -327,6 +337,7 @@ class BlockScoping {
       // this is the defining identifier of a declaration
       var ref = letRefs[key];
 
+      // todo: could skip this if the colliding binding is in another function
       if (scope.parentHasBinding(key) || scope.hasGlobal(key)) {
         var uid = scope.generateUidIdentifier(ref.name).name;
         ref.name = uid;
@@ -597,7 +608,6 @@ class BlockScoping {
       t.variableDeclarator(ret, call)
     ]));
 
-    var loop = this.loop;
     var retCheck;
     var has = this.has;
     var cases = [];

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

@@ -1,12 +1,11 @@
+import type NodePath from "../../../traversal/path";
+import type File from "../../file";
 import memoiseDecorators from "../../helpers/memoise-decorators";
 import ReplaceSupers from "../../helpers/replace-supers";
 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 each from "lodash/collection/each";
-import has from "lodash/object/has";
 import * as t from "../../../types";
 
 const PROPERTY_COLLISION_METHOD_NAME = "__initializeProperties";
@@ -35,22 +34,6 @@ var collectPropertyReferencesVisitor = {
   }
 };
 
-var constructorVisitor = {
-  ThisExpression: {
-    enter(node, parent, scope, ref) {
-      return ref;
-    }
-  },
-
-  Function: {
-    enter(node) {
-      if (!node.shadow) {
-        this.skip();
-      }
-    }
-  }
-};
-
 var verifyConstructorVisitor = {
   MethodDefinition: {
     enter() {
@@ -104,7 +87,7 @@ class ClassTransformer {
    * Description
    */
 
-  constructor(path: TraversalPath, file: File) {
+  constructor(path: NodePath, file: File) {
     this.parent = path.parent;
     this.scope  = path.scope;
     this.node   = path.node;
@@ -141,8 +124,6 @@ class ClassTransformer {
 
   run() {
     var superName = this.superName;
-    var className = this.className;
-    var classBody = this.node.body.body;
     var classRef  = this.classRef;
     var file      = this.file;
 
@@ -219,6 +200,8 @@ class ClassTransformer {
       }
     }
 
+    body = body.concat(this.staticPropBody);
+
     if (this.className) {
       // named class with only a constructor
       if (body.length === 1) return t.toExpression(body[0]);
@@ -233,8 +216,6 @@ class ClassTransformer {
       t.inheritsComments(body[0], this.node);
     }
 
-    body = body.concat(this.staticPropBody);
-
     //
 
     body.push(t.returnStatement(classRef));
@@ -262,7 +243,7 @@ class ClassTransformer {
     var map = defineMap.push(mutatorMap, node, kind, this.file);
 
     if (enumerable) {
-      map.enumerable = t.literal(true)
+      map.enumerable = t.literal(true);
     }
 
     if (map.decorators) {
@@ -276,9 +257,6 @@ class ClassTransformer {
 
   buildBody() {
     var constructorBody = this.constructorBody;
-    var constructor     = this.constructor;
-    var className       = this.className;
-    var superName       = this.superName;
     var classBody       = this.node.body.body;
     var body            = this.body;
 
@@ -315,7 +293,7 @@ class ClassTransformer {
           this.pushMethod(node, path);
         }
       } else if (t.isClassProperty(node)) {
-        this.pushProperty(node);
+        this.pushProperty(node, path);
       }
     }
 
@@ -375,7 +353,7 @@ class ClassTransformer {
       }
 
       var lastNonNullIndex = 0;
-      for (var i = 0; i < args.length; i++) {
+      for (let i = 0; i < args.length; i++) {
         if (args[i] !== nullNode) lastNonNullIndex = i;
       }
       args = args.slice(0, lastNonNullIndex + 1);
@@ -450,7 +428,7 @@ class ClassTransformer {
    * Description
    */
 
-   verifyConstructor(path: TraversalPath) {
+   verifyConstructor(path: NodePath) {
     var state = {
       hasBareSuper: false,
       bareSuper:    null,
@@ -471,7 +449,7 @@ class ClassTransformer {
    * Push a method to its respective mutatorMap.
    */
 
-  pushMethod(node: { type: "MethodDefinition" }, path?: TraversalPath, allowedIllegal?) {
+  pushMethod(node: { type: "MethodDefinition" }, path?: NodePath, allowedIllegal?) {
     if (!allowedIllegal && t.isLiteral(t.toComputedKey(node), { value: PROPERTY_COLLISION_METHOD_NAME })) {
       throw this.file.errorWithNode(node, messages.get("illegalMethodName", PROPERTY_COLLISION_METHOD_NAME));
     }
@@ -500,10 +478,8 @@ class ClassTransformer {
    * Description
    */
 
-  pushProperty(node: { type: "ClassProperty" }) {
-    var key;
-
-    this.scope.traverse(node, collectPropertyReferencesVisitor, {
+  pushProperty(node: { type: "ClassProperty" }, path: NodePath) {
+    path.traverse(collectPropertyReferencesVisitor, {
       references: this.instancePropRefs,
       scope:      this.scope
     });
@@ -519,7 +495,6 @@ class ClassTransformer {
       this.pushToMap(node, true, "initializer");
 
       var initializers;
-      var body;
       var target;
       if (node.static) {
         initializers = this.staticInitializersId = this.staticInitializersId || this.scope.generateUidIdentifier("staticInitializers");
@@ -558,7 +533,7 @@ class ClassTransformer {
    * Replace the constructor body of our class.
    */
 
-  pushConstructor(method: { type: "MethodDefinition" }, path: TraversalPath) {
+  pushConstructor(method: { type: "MethodDefinition" }, path: NodePath) {
     // https://github.com/babel/babel/issues/1077
     var fnPath = path.get("value");
     if (fnPath.scope.hasOwnBinding(this.classRef.name)) {

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

@@ -1,31 +1,18 @@
 import * as messages from "../../../messages";
-import * as t from "../../../types";
 
-export function AssignmentExpression(node, parent, scope, file) {
-  var ids = this.getBindingIdentifiers();
-
-  for (var name in ids) {
-    var id = ids[name];
-
-    var binding = scope.getBinding(name);
-
-    // no binding exists
-    if (!binding) continue;
+export function Scope(node, parent, scope) {
+  for (var name in scope.bindings) {
+    var binding = scope.bindings[name];
 
     // not a constant
     if (binding.kind !== "const" && binding.kind !== "module") continue;
 
-    // check if the assignment id matches the constant declaration id
-    // if it does then it was the id used to initially declare the
-    // constant so we can just ignore it
-    if (binding.identifier === id) continue;
-
-    throw file.errorWithNode(id, messages.get("readOnly", name));
+    for (var violation of (binding.constantViolations: Array)) {
+      throw violation.errorWithNode(messages.get("readOnly", name));
+    }
   }
 }
 
-export { AssignmentExpression as UpdateExpression };
-
 export function VariableDeclaration(node) {
   if (node.kind === "const") node.kind = "let";
 }

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

@@ -56,15 +56,22 @@ export function ForOfStatement(node, parent, scope, file) {
 export { ForOfStatement as ForInStatement };
 
 export function Func/*tion*/(node, parent, scope, file) {
+  var hasDestructuring = false;
+  for (let pattern of (node.params: Array)) {
+    if (t.isPattern(pattern)) {
+      hasDestructuring = true;
+      break;
+    }
+  }
+  if (!hasDestructuring) return;
+
   var nodes = [];
 
-  var hasDestructuring = false;
+  for (var i = 0; i < node.params.length; i++) {
+    let pattern = node.params[i];
+    if (!t.isPattern(pattern)) continue;
 
-  node.params = node.params.map(function (pattern, i) {
-    if (!t.isPattern(pattern)) return pattern;
-
-    hasDestructuring = true;
-    var ref = scope.generateUidIdentifier("ref");
+    var ref = node.params[i] = scope.generateUidIdentifier("ref");
     t.inherits(ref, pattern);
 
     var destructuring = new DestructuringTransformer({
@@ -74,12 +81,9 @@ export function Func/*tion*/(node, parent, scope, file) {
       file:       file,
       kind:       "let"
     });
+
     destructuring.init(pattern, ref);
-
-    return ref;
-  });
-
-  if (!hasDestructuring) return;
+  }
 
   t.ensureBlock(node);
 
@@ -107,30 +111,10 @@ export function CatchClause(node, parent, scope, file) {
   node.body.body = nodes.concat(node.body.body);
 }
 
-export function ExpressionStatement(node, parent, scope, file) {
-  var expr = node.expression;
-  if (expr.type !== "AssignmentExpression") return;
-  if (!t.isPattern(expr.left)) return;
-  if (this.isCompletionRecord()) return;
-
-  var destructuring = new DestructuringTransformer({
-    operator: expr.operator,
-    scope:    scope,
-    file:     file,
-  });
-
-  return destructuring.init(expr.left, expr.right);
-}
-
 export function AssignmentExpression(node, parent, scope, file) {
   if (!t.isPattern(node.left)) return;
 
-  var ref = scope.generateUidIdentifier("temp");
-
   var nodes = [];
-  nodes.push(t.variableDeclaration("var", [
-    t.variableDeclarator(ref, node.right)
-  ]));
 
   var destructuring = new DestructuringTransformer({
     operator: node.operator,
@@ -139,13 +123,24 @@ export function AssignmentExpression(node, parent, scope, file) {
     nodes: nodes
   });
 
-  if (t.isArrayExpression(node.right)) {
-    destructuring.arrays[ref.name] = true;
+  var ref;
+  if (this.isCompletionRecord() || !this.parentPath.isExpressionStatement()) {
+    ref = scope.generateUidIdentifierBasedOnNode(node.right, "ref");
+
+    nodes.push(t.variableDeclaration("var", [
+      t.variableDeclarator(ref, node.right)
+    ]));
+
+    if (t.isArrayExpression(node.right)) {
+      destructuring.arrays[ref.name] = true;
+    }
   }
 
-  destructuring.init(node.left, ref);
+  destructuring.init(node.left, ref || node.right);
 
-  nodes.push(t.expressionStatement(ref));
+  if (ref) {
+    nodes.push(t.expressionStatement(ref));
+  }
 
   return nodes;
 }
@@ -160,7 +155,7 @@ function variableDeclarationHasPattern(node) {
 }
 
 export function VariableDeclaration(node, parent, scope, file) {
-  if (t.isForInStatement(parent) || t.isForOfStatement(parent)) return;
+  if (t.isForXStatement(parent)) return;
   if (!variableDeclarationHasPattern(node)) return;
 
   var nodes = [];
@@ -225,8 +220,8 @@ function hasRest(pattern) {
 }
 
 var arrayUnpackVisitor = {
-  enter(node, parent, scope, state) {
-    if (this.isReferencedIdentifier() && state.bindings[node.name]) {
+  ReferencedIdentifier(node, parent, scope, state) {
+    if (state.bindings[node.name]) {
       state.deopt = true;
       this.stop();
     }
@@ -498,7 +493,6 @@ class DestructuringTransformer {
     // trying to destructure a value that we can't evaluate more than once so we
     // need to save it to a variable
 
-    var shouldMemoise = true;
     if (!t.isArrayExpression(ref) && !t.isMemberExpression(ref)) {
       var memo = this.scope.maybeGenerateMemoised(ref, true);
       if (memo) {

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

@@ -31,7 +31,7 @@ export function ForOfStatement(node, parent, scope, file) {
 
   if (build.replaceParent) {
     this.parentPath.replaceWithMultiple(build.node);
-    this.remove();
+    this.dangerouslyRemove();
   } else {
     return build.node;
   }
@@ -70,6 +70,10 @@ export function _ForOfStatementArray(node, scope, file) {
     loop.body.body.unshift(t.expressionStatement(t.assignmentExpression("=", left, iterationValue)));
   }
 
+  if (this.parentPath.isLabeledStatement()) {
+    loop = t.labeledStatement(this.parentPath.node.label, loop);
+  }
+
   nodes.push(loop);
 
   return nodes;

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

@@ -19,8 +19,8 @@ export function ImportDeclaration(node, parent, scope, file) {
   var nodes = [];
 
   if (node.specifiers.length) {
-    for (var i = 0; i < node.specifiers.length; i++) {
-      file.moduleFormatter.importSpecifier(node.specifiers[i], node, nodes, parent);
+    for (var specifier of (node.specifiers: Array)) {
+      file.moduleFormatter.importSpecifier(specifier, node, nodes, parent);
     }
   } else {
     file.moduleFormatter.importDeclaration(node, nodes, parent);

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

@@ -1,6 +1,6 @@
 import callDelegate from "../../helpers/call-delegate";
+import getFunctionArity from "../../helpers/get-function-arity";
 import * as util from  "../../../util";
-import traverse from  "../../../traversal";
 import * as t from "../../../types";
 
 var hasDefaults = function (node) {
@@ -25,37 +25,54 @@ var iifeVisitor = {
 export function Func/*tion*/(node, parent, scope, file) {
   if (!hasDefaults(node)) return;
 
+  // ensure it's a block, useful for arrow functions
   t.ensureBlock(node);
 
+  var state = {
+    iife: false,
+    scope: scope
+  };
+
   var body = [];
 
+  //
   var argsIdentifier = t.identifier("arguments");
   argsIdentifier._shadowedFunctionLiteral = true;
 
-  var lastNonDefaultParam = 0;
-
-  var state = { iife: false, scope: scope };
-
-  var pushDefNode = function (left, right, i) {
-    var defNode = util.template("default-parameter", {
-      VARIABLE_NAME: left,
-      DEFAULT_VALUE: right,
-      ARGUMENT_KEY:  t.literal(i),
-      ARGUMENTS:     argsIdentifier
-    }, true);
+  // push a default parameter definition
+  function pushDefNode(left, right, i) {
+    var defNode;
+    if (exceedsLastNonDefault(i) || t.isPattern(left) || file.transformers["es6.spec.blockScoping"].canTransform()) {
+      defNode = util.template("default-parameter", {
+        VARIABLE_NAME: left,
+        DEFAULT_VALUE: right,
+        ARGUMENT_KEY:  t.literal(i),
+        ARGUMENTS:     argsIdentifier
+      }, true);
+    } else {
+      defNode = util.template("default-parameter-assign", {
+        VARIABLE_NAME: left,
+        DEFAULT_VALUE: right
+      }, true);
+    }
     defNode._blockHoist = node.params.length - i;
     body.push(defNode);
-  };
+  }
 
+  // check if an index exceeds the functions arity
+  function exceedsLastNonDefault(i) {
+    return i + 1 > lastNonDefaultParam;
+  }
+
+  //
+  var lastNonDefaultParam = getFunctionArity(node);
+
+  //
   var params = this.get("params");
   for (var i = 0; i < params.length; i++) {
     var param = params[i];
 
     if (!param.isAssignmentPattern()) {
-      if (!param.isRestElement()) {
-        lastNonDefaultParam = i + 1;
-      }
-
       if (!param.isIdentifier()) {
         param.traverse(iifeVisitor, state);
       }
@@ -70,9 +87,13 @@ export function Func/*tion*/(node, parent, scope, file) {
     var left  = param.get("left");
     var right = param.get("right");
 
-    var placeholder = scope.generateUidIdentifier("x");
-    placeholder._isDefaultPlaceholder = true;
-    node.params[i] = placeholder;
+    if (exceedsLastNonDefault(i) || left.isPattern()) {
+      var placeholder = scope.generateUidIdentifier("x");
+      placeholder._isDefaultPlaceholder = true;
+      node.params[i] = placeholder;
+    } else {
+      node.params[i] = left.node;
+    }
 
     if (!state.iife) {
       if (right.isIdentifier() && scope.hasOwnBinding(right.node.name)) {

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

@@ -1,13 +1,21 @@
-import isNumber from "lodash/lang/isNumber";
 import * as util from  "../../../util";
 import * as t from "../../../types";
 
 var memberExpressionOptimisationVisitor = {
-  enter(node, parent, scope, state) {
+  Scope(node, parent, scope, state) {
     // check if this scope has a local binding that will shadow the rest parameter
-    if (this.isScope() && !scope.bindingIdentifierEquals(state.name, state.outerBinding)) {
-      return this.skip();
+    if (!scope.bindingIdentifierEquals(state.name, state.outerBinding)) {
+      this.skip();
     }
+  },
+
+  enter(node, parent, scope, state) {
+    var stop = () => {
+      state.canOptimise = false;
+      this.stop();
+    };
+
+    if (this.isArrowFunctionExpression()) return stop();
 
     // skip over functions as whatever `arguments` we reference inside will refer
     // to the wrong function
@@ -24,19 +32,20 @@ var memberExpressionOptimisationVisitor = {
     if (!state.noOptimise && t.isMemberExpression(parent) && parent.computed) {
       // if we know that this member expression is referencing a number then we can safely
       // optimise it
-      var prop = parent.property;
-      if (isNumber(prop.value) || t.isUnaryExpression(prop) || t.isBinaryExpression(prop)) {
+      var prop = this.parentPath.get("property");
+      if (prop.isBaseType("number")) {
         state.candidates.push(this);
         return;
       }
     }
 
-    state.canOptimise = false;
-    this.stop();
+    stop();
   }
 };
 
 function optimizeMemberExpression(parent, offset) {
+  if (offset === 0) return;
+
   var newExpr;
   var prop = parent.property;
 
@@ -90,8 +99,7 @@ export function Func/*tion*/(node, parent, scope, file) {
 
   // we only have shorthands and there's no other references
   if (state.canOptimise && state.candidates.length) {
-    for (var i = 0; i < state.candidates.length; i++) {
-      var candidate = state.candidates[i];
+    for (var candidate of (state.candidates: Array)) {
       candidate.replaceWith(argsId);
       optimizeMemberExpression(candidate.parent, node.params.length);
     }

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

@@ -1,29 +1,59 @@
-import traverse from "../../../traversal";
 import * as t from "../../../types";
 
+function buildAssert(node, file) {
+  return t.callExpression(
+    file.addHelper("temporal-assert-defined"),
+    [node, t.literal(node.name), file.addHelper("temporal-undefined")]
+  );
+}
+
+function references(node, scope, state) {
+  var declared = state.letRefs[node.name];
+  if (!declared) return false;
+
+  // declared node is different in this scope
+  return scope.getBindingIdentifier(node.name) === declared;
+}
+
 var visitor = {
   ReferencedIdentifier(node, parent, scope, state) {
     if (t.isFor(parent) && parent.left === node) return;
 
-    var declared = state.letRefs[node.name];
-    if (!declared) return;
+    if (!references(node, scope, state)) return;
 
-    // declared node is different in this scope
-    if (scope.getBindingIdentifier(node.name) !== declared) return;
-
-    var assert = t.callExpression(
-      state.file.addHelper("temporal-assert-defined"),
-      [node, t.literal(node.name), state.file.addHelper("temporal-undefined")]
-    );
+    var assert = buildAssert(node, state.file);
 
     this.skip();
 
-    if (t.isAssignmentExpression(parent) || t.isUpdateExpression(parent)) {
+    if (t.isUpdateExpression(parent)) {
       if (parent._ignoreBlockScopingTDZ) return;
       this.parentPath.replaceWith(t.sequenceExpression([assert, parent]));
     } else {
       return t.logicalExpression("&&", assert, node);
     }
+  },
+
+  AssignmentExpression: {
+    exit(node, parent, scope, state) {
+      if (node._ignoreBlockScopingTDZ) return;
+
+      var nodes = [];
+      var ids = this.getBindingIdentifiers();
+
+      for (var name in ids) {
+        var id = ids[name];
+
+        if (references(id, scope, state)) {
+          nodes.push(buildAssert(id, state.file));
+        }
+      }
+
+      if (nodes.length) {
+        node._ignoreBlockScopingTDZ = true;
+        nodes.push(node);
+        return nodes.map(t.expressionStatement);
+      }
+    }
   }
 };
 

src/babel/transformation/transformers/es6/spec.template-literals.js

@@ -1,7 +1,8 @@
 import * as t from "../../../types";
 
 export var metadata = {
-  optional: true
+  optional: true,
+  group: "builtin-pre"
 };
 
 export function TemplateLiteral(node, parent, scope, file) {

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

@@ -1,8 +1,7 @@
-import includes from "lodash/collection/includes";
 import * as t from "../../../types";
 
 function getSpreadLiteral(spread, scope) {
-  if (scope.file.isLoose("es6.spread")) {
+  if (scope.hub.file.isLoose("es6.spread")) {
     return spread.argument;
   } else {
     return scope.toArray(spread.argument, true);

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

@@ -1,7 +1,6 @@
 import reduceRight from "lodash/collection/reduceRight";
 import * as messages from "../../../messages";
 import flatten from "lodash/array/flatten";
-import traverse from "../../../traversal";
 import * as util from  "../../../util";
 import map from "lodash/collection/map";
 import * as t from "../../../types";
@@ -21,7 +20,7 @@ function returnBlock(expr) {
 }
 
 var visitor = {
-  enter(node, parent, scope, state) {
+  enter(node, parent) {
     if (t.isTryStatement(parent)) {
       if (node === parent.block) {
         this.skip();
@@ -35,7 +34,7 @@ var visitor = {
     return state.subTransform(node.argument);
   },
 
-  Function(node, parent, scope, state) {
+  Function() {
     this.skip();
   },
 
@@ -128,7 +127,6 @@ class TailCallTransformer {
   }
 
   run() {
-    var scope = this.scope;
     var node  = this.node;
 
     // only tail recursion can be optimized as for now, so we can skip anonymous
@@ -204,7 +202,7 @@ class TailCallTransformer {
     }
 
     if (this.needsArguments || this.setsArguments) {
-      for (var path of (this.argumentsPaths: Array)) {
+      for (let path of (this.argumentsPaths: Array)) {
         path.replaceWith(this.argumentsId);
       }
 
@@ -356,14 +354,14 @@ class TailCallTransformer {
       var elems = args.elements;
       for (let i = 0; i < elems.length && i < params.length; i++) {
         let param = params[i];
-        var elem = elems[i] || (elems[i] = t.identifier("undefined"));
+        let elem = elems[i] || (elems[i] = t.identifier("undefined"));
         if (!param._isDefaultPlaceholder) {
           elems[i] = t.assignmentExpression("=", param, elem);
         }
       }
 
       if (!this.needsArguments) {
-        for (var elem of (elems: Array)) {
+        for (let elem of (elems: Array)) {
           body.push(t.expressionStatement(elem));
         }
       }

src/babel/transformation/transformers/es6/template-literals.js

@@ -1,9 +1,26 @@
+/* eslint no-unused-vars: 0 */
+
 import * as t from "../../../types";
 
-var buildBinaryExpression = function (left, right) {
-  return t.binaryExpression("+", left, right);
+export var metadata = {
+  group: "builtin-pre"
 };
 
+function buildBinaryExpression(left, right) {
+  var node = t.binaryExpression("+", left, right);
+  node._templateLiteralProduced = true;
+  return node;
+}
+
+function crawl(path) {
+  if (path.is("_templateLiteralProduced")) {
+    crawl(path.get("left"));
+    crawl(path.get("right"));
+  } else if (!path.isBaseType("string") && !path.isBaseType("number")) {
+    path.replaceWith(t.callExpression(t.identifier("String"), [path.node]));
+  }
+}
+
 export function TaggedTemplateExpression(node, parent, scope, file) {
   var quasi = node.quasi;
   var args  = [];
@@ -11,8 +28,7 @@ export function TaggedTemplateExpression(node, parent, scope, file) {
   var strings = [];
   var raw     = [];
 
-  for (var i = 0; i < quasi.quasis.length; i++) {
-    var elem = quasi.quasis[i];
+  for (var elem of (quasi.quasis: Array)) {
     strings.push(t.literal(elem.value.cooked));
     raw.push(t.literal(elem.value.raw));
   }
@@ -31,11 +47,8 @@ export function TaggedTemplateExpression(node, parent, scope, file) {
 
 export function TemplateLiteral(node, parent, scope, file) {
   var nodes = [];
-  var i;
-
-  for (i = 0; i < node.quasis.length; i++) {
-    var elem = node.quasis[i];
 
+  for (let elem of (node.quasis: Array)) {
     nodes.push(t.literal(elem.value.cooked));
 
     var expr = node.expressions.shift();
@@ -49,11 +62,12 @@ export function TemplateLiteral(node, parent, scope, file) {
 
     var root = buildBinaryExpression(nodes.shift(), nodes.shift());
 
-    for (i = 0; i < nodes.length; i++) {
-      root = buildBinaryExpression(root, nodes[i]);
+    for (let node of (nodes: Array)) {
+      root = buildBinaryExpression(root, node);
     }
 
-    return root;
+    this.replaceWith(root);
+    //crawl(this);
   } else {
     return nodes[0];
   }

src/babel/transformation/transformers/es7/comprehensions.js

@@ -10,7 +10,7 @@ export var metadata = {
 export function ComprehensionExpression(node, parent, scope, file) {
   var callback = array;
   if (node.generator) callback = generator;
-  return callback(node, parent, scope, file);
+  return callback(node, parent, scope);
 }
 
 function generator(node) {
@@ -25,7 +25,7 @@ function generator(node) {
   return t.callExpression(container, []);
 }
 
-function array(node, parent, scope, file) {
+function array(node, parent, scope) {
   var uid = scope.generateUidIdentifierBasedOnNode(parent);
 
   var container = util.template("array-comprehension-container", {

src/babel/transformation/transformers/es7/decorators.js

@@ -10,8 +10,8 @@ export var metadata = {
 
 export function ObjectExpression(node, parent, scope, file) {
   var hasDecorators = false;
-  for (var i = 0; i < node.properties.length; i++) {
-    var prop = node.properties[i];
+  for (let i = 0; i < node.properties.length; i++) {
+    let prop = node.properties[i];
     if (prop.decorators) {
       hasDecorators = true;
       break;
@@ -21,12 +21,12 @@ export function ObjectExpression(node, parent, scope, file) {
 
   var mutatorMap = {};
 
-  for (var i = 0; i < node.properties.length; i++) {
-    var prop = node.properties[i];
+  for (let i = 0; i < node.properties.length; i++) {
+    let prop = node.properties[i];
     if (prop.decorators) memoiseDecorators(prop.decorators, scope);
 
 
-    if (prop.kind === "init") {
+    if (prop.kind === "init" && !prop.method) {
       prop.kind = "";
       prop.value = t.functionExpression(null, [], t.blockStatement([
         t.returnStatement(prop.value)

src/babel/transformation/transformers/index.js

@@ -1,16 +1,21 @@
 export default {
-  //- builtin-setup
+  //- builtin-prepass
+  "minification.constantFolding":          require("./minification/constant-folding"),
+
+  //- builtin-pre
   strict:                                  require("./other/strict"),
+  eval:                                    require("./other/eval"),
   _explode:                                require("./internal/explode"),
   _validation:                             require("./internal/validation"),
   _hoistDirectives:                        require("./internal/hoist-directives"),
   "minification.removeDebugger":           require("./minification/remove-debugger"),
   "minification.removeConsole":            require("./minification/remove-console"),
   "utility.inlineEnvironmentVariables":    require("./utility/inline-environment-variables"),
-  "minification.inlineExpressions":        require("./minification/inline-expressions"),
   "minification.deadCodeElimination":      require("./minification/dead-code-elimination"),
   _modules:                                require("./internal/modules"),
   "spec.functionName":                     require("./spec/function-name"),
+  "es6.spec.templateLiterals":             require("./es6/spec.template-literals"),
+  "es6.templateLiterals":                  require("./es6/template-literals"),
 
   //- builtin-basic
   // this is where the bulk of the ES6 transformations take place, none of them require traversal state
@@ -32,8 +37,6 @@ export default {
   "es6.objectSuper":                       require("./es6/object-super"),
   "es7.objectRestSpread":                  require("./es7/object-rest-spread"),
   "es7.exponentiationOperator":            require("./es7/exponentiation-operator"),
-  "es6.spec.templateLiterals":             require("./es6/spec.template-literals"),
-  "es6.templateLiterals":                  require("./es6/template-literals"),
   "es5.properties.mutators":               require("./es5/properties.mutators"),
   "es6.properties.shorthand":              require("./es6/properties.shorthand"),
   "es6.properties.computed":               require("./es6/properties.computed"),
@@ -51,8 +54,6 @@ export default {
   "es6.spec.symbols":                      require("./es6/spec.symbols"),
   "es7.functionBind":                      require("./es7/function-bind"),
   "spec.undefinedToVoid":                  require("./spec/undefined-to-void"),
-  jscript:                                 require("./other/jscript"),
-  flow:                                    require("./other/flow"),
 
   //- builtin-advanced
   "es6.destructuring":                     require("./es6/destructuring"),
@@ -60,13 +61,11 @@ export default {
   "es6.spec.blockScoping":                 require("./es6/spec.block-scoping"),
   reactCompat:                             require("./other/react-compat"),
   react:                                   require("./other/react"),
+  regenerator:                             require("./other/regenerator"),
 
   // es6 syntax transformation is **forbidden** past this point since regenerator will chuck a massive
   // hissy fit
 
-  //- regenerator
-  regenerator:                             require("./other/regenerator"),
-
   //- builtin-modules
   runtime:                                 require("./other/runtime"),
   "es6.modules":                           require("./es6/modules"),
@@ -83,4 +82,6 @@ export default {
   "minification.memberExpressionLiterals": require("./minification/member-expression-literals"),
   "minification.propertyLiterals":         require("./minification/property-literals"),
   _blockHoist:                             require("./internal/block-hoist"),
+  jscript:                                 require("./other/jscript"),
+  flow:                                    require("./other/flow"),
 };

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

@@ -2,7 +2,7 @@ import clone from "lodash/lang/clone";
 import * as t from "../../../types";
 
 export var metadata = {
-  group: "builtin-setup"
+  group: "builtin-pre"
 };
 
 function buildClone(bindingKey, refKey, check?) {

src/babel/transformation/transformers/internal/hoist-directives.js

@@ -1,7 +1,7 @@
 import * as t from "../../../types";
 
 export var metadata = {
-  group: "builtin-setup"
+  group: "builtin-pre"
 };
 
 export var BlockStatement = {

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

@@ -1,19 +1,15 @@
-import * as strict from "../../helpers/strict";
-
 export var metadata = {
   group: "builtin-modules"
 };
 
 export var Program = {
   exit(program, parent, scope, file) {
-    strict.wrap(program, function () {
-      // ensure that these are at the top, just like normal imports
-      for (var node of (file.dynamicImports: Array)) {
-        node._blockHoist = 3;
-      }
+    // ensure that these are at the top, just like normal imports
+    for (var node of (file.dynamicImports: Array)) {
+      node._blockHoist = 3;
+    }
 
-      program.body = file.dynamicImports.concat(program.body);
-    });
+    program.body = file.dynamicImports.concat(program.body);
 
     if (!file.transformers["es6.modules"].canTransform()) return;
 

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

@@ -16,25 +16,15 @@ function getDeclar(node) {
 }
 
 export var metadata = {
-  group: "builtin-setup"
+  group: "builtin-pre"
 };
 
-export function ImportDeclaration(node, parent, scope, file) {
-  if (node.source) {
-    node.source.value = file.resolveModuleSource(node.source.value);
-  }
-}
-
-export { ImportDeclaration as ExportAllDeclaration };
-
 export function ExportDefaultDeclaration(node, parent, scope) {
-  ImportDeclaration.apply(this, arguments);
-
   var declar = node.declaration;
 
   if (t.isClassDeclaration(declar)) {
     // export default class Foo {};
-    var nodes = [getDeclar(node), node];
+    let nodes = [getDeclar(node), node];
     node.declaration = declar.id;
     return nodes;
   } else if (t.isClassExpression(declar)) {
@@ -44,14 +34,14 @@ export function ExportDefaultDeclaration(node, parent, scope) {
       t.variableDeclarator(temp, declar)
     ]);
 
-    var nodes = [getDeclar(node), node];
+    let nodes = [getDeclar(node), node];
     node.declaration = temp;
     return nodes;
   } else if (t.isFunctionDeclaration(declar)) {
     // export default function Foo() {}
     node._blockHoist = 2;
 
-    var nodes = [getDeclar(node), node];
+    let nodes = [getDeclar(node), node];
     node.declaration = declar.id;
     return nodes;
   }
@@ -62,14 +52,13 @@ function buildExportSpecifier(id) {
 }
 
 export function ExportNamedDeclaration(node, parent, scope) {
-  ImportDeclaration.apply(this, arguments);
-
   var declar = node.declaration;
 
   if (t.isClassDeclaration(declar)) {
     // export class Foo {}
     node.specifiers  = [buildExportSpecifier(declar.id)];
-    var nodes = [getDeclar(node), node];
+
+    let nodes = [getDeclar(node), node];
     node.declaration = null;
     return nodes;
   } else if (t.isFunctionDeclaration(declar)) {
@@ -77,7 +66,7 @@ export function ExportNamedDeclaration(node, parent, scope) {
     node.specifiers  = [buildExportSpecifier(declar.id)];
     node._blockHoist = 2;
 
-    var nodes = [getDeclar(node), node];
+    let nodes = [getDeclar(node), node];
     node.declaration = null;
     return nodes;
   } else if (t.isVariableDeclaration(declar)) {
@@ -94,7 +83,7 @@ export function ExportNamedDeclaration(node, parent, scope) {
 export var Program = {
   enter(node) {
     var imports = [];
-    var rest = [];
+    var rest    = [];
 
     for (var i = 0; i < node.body.length; i++) {
       var bodyNode = node.body[i];

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

@@ -8,7 +8,7 @@ function remap(path, key, create) {
   // ensure that we're shadowed
   if (!path.inShadow()) return;
 
-  var fnPath = path.findParent((node, path) => !node.shadow && (path.isFunction() || path.isProgram()));
+  var fnPath = path.findParent((path) => !path.is("shadow") && (path.isFunction() || path.isProgram()));
 
   var cached = fnPath.getData(key);
   if (cached) return cached;

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

@@ -2,7 +2,7 @@ import * as messages from "../../../messages";
 import * as t from "../../../types";
 
 export var metadata = {
-  group: "builtin-setup"
+  group: "builtin-pre"
 };
 
 export function ForOfStatement(node, parent, scope, file) {

src/babel/transformation/transformers/minification/constant-folding.js

@@ -0,0 +1,71 @@
+import * as t from "../../../types";
+
+export var metadata = {
+  optional: true,
+  group: "builtin-prepass",
+  experimental: true
+};
+
+export function AssignmentExpression() {
+  var left = this.get("left");
+  if (!left.isIdentifier()) return;
+
+  var binding = this.scope.getBinding(left.node.name);
+  if (!binding || binding.hasDeoptValue) return;
+
+  var evaluated = this.get("right").evaluate();
+  if (evaluated.confident) {
+    binding.setValue(evaluated.value);
+  } else {
+    binding.deoptValue();
+  }
+}
+
+export function IfStatement() {
+  var evaluated = this.get("test").evaluate();
+  if (!evaluated.confident) {
+    // todo: deopt binding values for constant violations inside
+    return this.skip();
+  }
+
+  if (evaluated.value) {
+    this.skipKey("alternate");
+  } else {
+    this.skipKey("consequent");
+  }
+}
+
+export var Scopable = {
+  enter() {
+    var funcScope = this.scope.getFunctionParent();
+
+    for (var name in this.scope.bindings) {
+      var binding = this.scope.bindings[name];
+      var deopt = false;
+
+      for (var path of (binding.constantViolations: Array)) {
+        var funcViolationScope = path.scope.getFunctionParent();
+        if (funcViolationScope !== funcScope) {
+          deopt = true;
+          break;
+        }
+      }
+
+      if (deopt) binding.deoptValue();
+    }
+  },
+
+  exit() {
+    for (var name in this.scope.bindings) {
+      var binding = this.scope.bindings[name];
+      binding.clearValue();
+    }
+  }
+};
+
+export var Expression = {
+  exit() {
+    var res = this.evaluate();
+    if (res.confident) return t.valueToNode(res.value);
+  }
+};