diff --git a/.jshintrc b/.jshintrc
index 9e68224789..f6a65273be 100644
--- a/.jshintrc
+++ b/.jshintrc
@@ -5,7 +5,6 @@
   "camelcase": true,
   "unused": true,
   "eqnull": true,
-  "proto": true,
   "newcap": true,
   "supernew": true,
   "noyield": true,
@@ -14,8 +13,6 @@
   "boss": true,
   "expr": true,
   "undef": true,
-  "loopfunc": true,
-  "white": true,
   "maxparams": 5,
   "maxdepth": 4,
 
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5106b0a3cb..45a18036b1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,6 +15,52 @@ _Note: Gaps between patch versions are faulty/broken releases._
 
  * **Breaking Change**
   * `allowImportExportEverywhere` acorn option has been disabled for spec compliancy so imports and exports can **only** be present at the top level.
+  * Caching is now always enabled for the require hook. It also now no longer caches require resolutions.
+
+## 2.12.0
+
+ * **Bug Fix**
+  * Support non-string JSX literals.
+ * **New Feature**
+  * Loose mode for some transformers that enables non-spec behaviour.
+ * **Internal**
+  * Uglify `--mangle sort` has been added to the build script, cutting minified scripts in half.
+
+## 2.11.4
+
+ * **Internal**
+  * Make all dependency versions fixed.
+
+## 2.11.3
+
+ * **Bug Fix**
+  * Allow a string to be passed as the `optional` option.
+
+## 2.11.2
+
+ * **Bug Fix**
+  * Support esprima-style catch clause handlers.
+ * **Polish**
+  * Don't print a stacktrace for syntax errors in the CLI.
+
+## 2.11.1
+
+ * **Bug Fix**
+  * Remove stray `console.log` outputting debug code.
+  * Remove `Dict` from `coreAliasing`.
+
+## 2.11.0
+
+ * **Bug Fix**
+  * Fix unnecessary IIFE in default parameters on method calls.
+  * Add support for supers inside of closures.
+ * **New Feature**
+  * Add `--keep-module-id-extensions`/`keepModuleIdExtensions` option to keep extensions in module ids.
+ * **Polish**
+  * Special case single argument spread properties in `super` inside classes.
+  * Don't use a variable declaration for class declaration IFFE.
+  * Rename `inherits` helper parameters.
+  * `coreAliasing` transformer now aliases `Promise`, `Set`, `Map` and more. Thanks [@AluisioASG](https://github.com/AluisioASG).
 
 ## 2.10.1
 
diff --git a/Makefile b/Makefile
index 120336e372..1acfc5281f 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 BROWSERIFY_CMD = node_modules/browserify/bin/cmd.js
 ISTANBUL_CMD = node_modules/istanbul/lib/cli.js cover
-UGLIFY_CMD = node_modules/uglify-js/bin/uglifyjs
+UGLIFY_CMD = node_modules/uglify-js/bin/uglifyjs --mangle sort
 JSHINT_CMD = node_modules/jshint/bin/jshint
 MOCHA_CMD = node_modules/mocha/bin/_mocha
 
@@ -71,7 +71,7 @@ publish:
 
 	make test
 
-	read -p "Version: "  version; \
+	read -p "Version: " version; \
 	npm version $$version --message "v%s"
 
 	make build
diff --git a/NOTES.md b/NOTES.md
index fcb68ebe86..a973eaafdf 100644
--- a/NOTES.md
+++ b/NOTES.md
@@ -10,4 +10,4 @@
  * Split up ES5 getter/setter transforming and ES6 property methods into separate transformers.
  * Add autoindentation.
  * Move `super` transformation from classes into a separate transformer that also supports object expressions.
- * Prefix all fast transformers with `fast`, make them declare that they're a fast transformer similar to optional transformers and add a `--fast` flag to enable them all.
+ * Remove fast transformer backwards compatibility.
diff --git a/bin/6to5/index.js b/bin/6to5/index.js
index 09d7925e43..955671555d 100755
--- a/bin/6to5/index.js
+++ b/bin/6to5/index.js
@@ -18,6 +18,7 @@ commander.option("-m, --modules [modules]", "Module formatter type to use [commo
 commander.option("-l, --whitelist [whitelist]", "Whitelist of transformers to ONLY use", util.list);
 commander.option("-b, --blacklist [blacklist]", "Blacklist of transformers to NOT use", util.list);
 commander.option("-i, --optional [list]", "List of optional transformers to enable", util.list);
+commander.option("--loose [list]", "List of transformers to enable their loose mode", util.list);
 commander.option("-o, --out-file [out]", "Compile all input files into a single file");
 commander.option("-d, --out-dir [out]", "Compile an input directory of modules into an output directory");
 commander.option("-c, --remove-comments", "Remove comments from the compiled code", false);
@@ -26,6 +27,7 @@ commander.option("-a, --amd-module-ids", "Insert module id in AMD modules", fals
 commander.option("-m, --module-ids", "Insert module id in modules", false);
 commander.option("-R, --react-compat", "Makes the react transformer produce pre-v0.12 code");
 commander.option("-E, --include-regenerator", "Include the regenerator runtime if necessary", false);
+commander.option("--keep-module-id-extensions", "Keep extensions when generating module ids", false);
 
 commander.on("--help", function(){
   var outKeys = function (title, obj) {
@@ -101,19 +103,21 @@ if (errors.length) {
 //
 
 exports.opts = {
-  includeRegenerator: commander.includeRegenerator,
-  sourceMapName:      commander.outFile,
-  experimental:       commander.experimental,
-  reactCompat:        commander.reactCompat,
-  playground:         commander.playground,
-  moduleIds:          commander.amdModuleIds || commander.moduleIds,
-  blacklist:          commander.blacklist,
-  whitelist:          commander.whitelist,
-  sourceMap:          commander.sourceMaps || commander.sourceMapsInline,
-  optional:           commander.optional,
-  comments:           !commander.removeComments,
-  runtime:            commander.runtime,
-  modules:            commander.modules,
+  keepModuleIdExtensions: commander.keepModuleIdExtensions,
+  includeRegenerator:     commander.includeRegenerator,
+  sourceMapName:          commander.outFile,
+  experimental:           commander.experimental,
+  reactCompat:            commander.reactCompat,
+  playground:             commander.playground,
+  moduleIds:              commander.amdModuleIds || commander.moduleIds,
+  blacklist:              commander.blacklist,
+  whitelist:              commander.whitelist,
+  sourceMap:              commander.sourceMaps || commander.sourceMapsInline,
+  optional:               commander.optional,
+  comments:               !commander.removeComments,
+  runtime:                commander.runtime,
+  modules:                commander.modules,
+  loose:                  commander.loose,
   format: {
     indent: {
       style:     util.repeat(parseInt(commander.indent))
diff --git a/bin/6to5/util.js b/bin/6to5/util.js
index 1adf6d5119..bd196c8fa0 100644
--- a/bin/6to5/util.js
+++ b/bin/6to5/util.js
@@ -20,7 +20,17 @@ exports.transform = function (filename, code, opts) {
   opts = _.extend(opts || {}, index.opts);
   opts.filename = filename;
 
-  var result = to5.transform(code, opts);
+  var result;
+  try {
+    result = to5.transform(code, opts);
+  } catch (e) {
+    if (e instanceof SyntaxError) {
+      console.error("SyntaxError:", e.message);
+      process.exit(1);
+    } else {
+      throw e;
+    }
+  }
   result.filename = filename;
   result.actual = code;
   return result;
diff --git a/lib/6to5/file.js b/lib/6to5/file.js
index 17d29b3e99..fa2967e3d2 100644
--- a/lib/6to5/file.js
+++ b/lib/6to5/file.js
@@ -24,6 +24,7 @@ File.helpers = [
   "prototype-properties",
   "apply-constructor",
   "tagged-template-literal",
+  "tagged-template-literal-loose",
   "interop-require",
   "to-array",
   "sliced-to-array",
@@ -41,29 +42,32 @@ File.helpers = [
 
 File.excludeHelpersFromRuntime = [
   "async-to-generator",
-  "typeof"
+  "typeof",
+  "tagged-template-literal-loose"
 ];
 
 File.normaliseOptions = function (opts) {
   opts = _.cloneDeep(opts || {});
 
   _.defaults(opts, {
-    includeRegenerator: false,
-    experimental:       false,
-    reactCompat:        false,
-    playground:         false,
-    whitespace:         true,
-    moduleIds:          opts.amdModuleIds || false,
-    blacklist:          [],
-    whitelist:          [],
-    sourceMap:          false,
-    optional:           [],
-    comments:           true,
-    filename:           "unknown",
-    modules:            "common",
-    runtime:            false,
-    code:               true,
-    ast:                true
+    keepModuleIdExtensions: false,
+    includeRegenerator:     false,
+    experimental:           false,
+    reactCompat:            false,
+    playground:             false,
+    whitespace:             true,
+    moduleIds:              opts.amdModuleIds || false,
+    blacklist:              [],
+    whitelist:              [],
+    sourceMap:              false,
+    optional:               [],
+    comments:               true,
+    filename:               "unknown",
+    modules:                "common",
+    runtime:                false,
+    loose:                  [],
+    code:                   true,
+    ast:                    true
   });
 
   // normalise windows path separators to unix
@@ -71,6 +75,19 @@ File.normaliseOptions = function (opts) {
 
   opts.blacklist = util.arrayify(opts.blacklist);
   opts.whitelist = util.arrayify(opts.whitelist);
+  opts.optional  = util.arrayify(opts.optional);
+  opts.loose     = util.arrayify(opts.loose);
+
+  // todo: remove in 3.0.0
+  _.each({
+    fastForOf: "forOf",
+    classesFastSuper: "classes"
+  }, function (newTransformer, oldTransformer) {
+    if (_.contains(opts.optional, oldTransformer)) {
+      _.pull(opts.optional, oldTransformer);
+      opts.loose.push(newTransformer);
+    }
+  });
 
   _.defaults(opts, {
     moduleRoot: opts.sourceRoot
@@ -100,10 +117,15 @@ File.normaliseOptions = function (opts) {
   transform._ensureTransformerNames("blacklist", opts.blacklist);
   transform._ensureTransformerNames("whitelist", opts.whitelist);
   transform._ensureTransformerNames("optional", opts.optional);
+  transform._ensureTransformerNames("loose", opts.loose);
 
   return opts;
 };
 
+File.prototype.isLoose = function (key) {
+  return _.contains(this.opts.loose, key);
+};
+
 File.prototype.getTransformers = function () {
   var file = this;
   var transformers = [];
diff --git a/lib/6to5/generation/generators/statements.js b/lib/6to5/generation/generators/statements.js
index 613fdcf630..f3a6babeab 100644
--- a/lib/6to5/generation/generators/statements.js
+++ b/lib/6to5/generation/generators/statements.js
@@ -107,7 +107,16 @@ exports.TryStatement = function (node, print) {
   this.keyword("try");
   print(node.block);
   this.space();
-  print(node.handler);
+
+  // 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]);
+  } else {
+    print(node.handler);
+  }
+
   if (node.finalizer) {
     this.space();
     this.push("finally ");
diff --git a/lib/6to5/generation/node/whitespace.js b/lib/6to5/generation/node/whitespace.js
index 03d17659eb..d1defd1cfe 100644
--- a/lib/6to5/generation/node/whitespace.js
+++ b/lib/6to5/generation/node/whitespace.js
@@ -72,5 +72,5 @@ _.each({
         return amount;
       };
     });
-  })
+  });
 });
diff --git a/lib/6to5/generation/whitespace.js b/lib/6to5/generation/whitespace.js
index aba4628493..c7dda860da 100644
--- a/lib/6to5/generation/whitespace.js
+++ b/lib/6to5/generation/whitespace.js
@@ -47,7 +47,13 @@ Whitespace.prototype.getNewlinesAfter = function (node) {
   if (endToken.type.type === "eof") {
     return 1;
   } else {
-    return this.getNewlinesBetween(startToken, endToken);
+    var lines = this.getNewlinesBetween(startToken, endToken);
+    if (node.type === "Line" && !lines) {
+      // line comment
+      return 1;
+    } else {
+      return lines;
+    }
   }
 };
 
diff --git a/lib/6to5/register-browser.js b/lib/6to5/register-browser.js
index 44ab2f5a39..7f7ab7a552 100644
--- a/lib/6to5/register-browser.js
+++ b/lib/6to5/register-browser.js
@@ -1,4 +1,5 @@
-// Required to safely use 6to5/register within a browserify codebase.
+// required to safely use 6to5/register within a browserify codebase
+
 module.exports = function () {};
 
 require("./polyfill");
diff --git a/lib/6to5/transformation/modules/_default.js b/lib/6to5/transformation/modules/_default.js
index a70db37f50..5e8ceb12a7 100644
--- a/lib/6to5/transformation/modules/_default.js
+++ b/lib/6to5/transformation/modules/_default.js
@@ -156,8 +156,10 @@ DefaultFormatter.prototype.getModuleName = function () {
     filenameRelative = filenameRelative.replace(sourceRootRegEx, "");
   }
 
-  // remove extension
-  filenameRelative = filenameRelative.replace(/\.(.*?)$/, "");
+  if (!opts.keepModuleIdExtensions) {
+    // remove extension
+    filenameRelative = filenameRelative.replace(/\.(.*?)$/, "");
+  }
 
   moduleName += filenameRelative;
 
diff --git a/lib/6to5/transformation/modules/umd.js b/lib/6to5/transformation/modules/umd.js
index 32dde9759a..d0122f4f68 100644
--- a/lib/6to5/transformation/modules/umd.js
+++ b/lib/6to5/transformation/modules/umd.js
@@ -31,15 +31,17 @@ UMDFormatter.prototype.transform = function (ast) {
 
   var factory = t.functionExpression(null, args, t.blockStatement(body));
 
-  // runner
+  // amd
 
   var defineArgs = [t.literal("exports")];
   if (this.passModuleArg) defineArgs.push(t.literal("module"));
   defineArgs = defineArgs.concat(names);
   defineArgs = [t.arrayExpression(defineArgs)];
 
+  // common
+
   var testExports = util.template("test-exports");
-  var testModule = util.template("test-module");
+  var testModule  = util.template("test-module");
   var commonTests = this.passModuleArg ? t.logicalExpression("&&", testExports, testModule) : testExports;
 
   var commonArgs = [t.identifier("exports")];
@@ -48,6 +50,12 @@ UMDFormatter.prototype.transform = function (ast) {
     return t.callExpression(t.identifier("require"), [name]);
   }));
 
+  // globals
+
+  //var umdArgs = [];
+
+  //
+
   var moduleName = this.getModuleName();
   if (moduleName) defineArgs.unshift(t.literal(moduleName));
 
diff --git a/lib/6to5/transformation/templates/class-super-constructor-call-fast.js b/lib/6to5/transformation/templates/class-super-constructor-call-fast.js
deleted file mode 100644
index dceab5e75b..0000000000
--- a/lib/6to5/transformation/templates/class-super-constructor-call-fast.js
+++ /dev/null
@@ -1,5 +0,0 @@
-(function () {
-  if (SUPER_NAME != null) {
-    SUPER_NAME.apply(this, arguments);
-  }
-});
diff --git a/lib/6to5/transformation/templates/class-super-constructor-call-loose.js b/lib/6to5/transformation/templates/class-super-constructor-call-loose.js
new file mode 100644
index 0000000000..ab957160f2
--- /dev/null
+++ b/lib/6to5/transformation/templates/class-super-constructor-call-loose.js
@@ -0,0 +1,3 @@
+if (SUPER_NAME != null) {
+  SUPER_NAME.apply(this, arguments);
+}
diff --git a/lib/6to5/transformation/templates/for-of-fast.js b/lib/6to5/transformation/templates/for-of-loose.js
similarity index 100%
rename from lib/6to5/transformation/templates/for-of-fast.js
rename to lib/6to5/transformation/templates/for-of-loose.js
diff --git a/lib/6to5/transformation/templates/tagged-template-literal-loose.js b/lib/6to5/transformation/templates/tagged-template-literal-loose.js
new file mode 100644
index 0000000000..d8dd44bb7a
--- /dev/null
+++ b/lib/6to5/transformation/templates/tagged-template-literal-loose.js
@@ -0,0 +1,4 @@
+(function (strings, raw) {
+  strings.raw = raw;
+  return strings;
+});
diff --git a/lib/6to5/transformation/transform.js b/lib/6to5/transformation/transform.js
index cd3a10669b..a3399e7b97 100644
--- a/lib/6to5/transformation/transform.js
+++ b/lib/6to5/transformation/transform.js
@@ -59,7 +59,6 @@ _.each({
   arrayComprehension:        require("./transformers/es7-array-comprehension"),
   generatorComprehension:    require("./transformers/es7-generator-comprehension"),
   arrowFunctions:            require("./transformers/es6-arrow-functions"),
-  classesFastSuper:          require("./transformers/optional-classes-fast-super"),
   classes:                   require("./transformers/es6-classes"),
 
   objectSpread:              require("./transformers/es7-object-spread"),
@@ -70,7 +69,6 @@ _.each({
   computedPropertyNames:     require("./transformers/es6-computed-property-names"),
   destructuring:             require("./transformers/es6-destructuring"),
   defaultParameters:         require("./transformers/es6-default-parameters"),
-  forOfFast:                 require("./transformers/optional-for-of-fast"),
   forOf:                     require("./transformers/es6-for-of"),
   unicodeRegex:              require("./transformers/es6-unicode-regex"),
   abstractReferences:        require("./transformers/es7-abstract-references"),
diff --git a/lib/6to5/transformation/transformers/es6-classes.js b/lib/6to5/transformation/transformers/es6-classes.js
index 55d09c3c60..c31d1787b9 100644
--- a/lib/6to5/transformation/transformers/es6-classes.js
+++ b/lib/6to5/transformation/transformers/es6-classes.js
@@ -33,6 +33,7 @@ function Class(node, file, scope, isStatement) {
   this.hasConstructor     = false;
   this.className          = node.id || file.generateUidIdentifier("class", scope);
   this.superName          = node.superClass;
+  this.isLoose            = file.isLoose("classes");
 }
 
 /**
@@ -62,8 +63,8 @@ Class.prototype.run = function () {
   }
   this.constructor = constructor;
 
-  var closureArgs = [];
   var closureParams = [];
+  var closureArgs = [];
 
   //
 
@@ -117,27 +118,31 @@ Class.prototype.buildBody = function () {
   var superName   = this.superName;
   var classBody   = this.node.body.body;
   var body        = this.body;
-  var self        = this;
 
   for (var i in classBody) {
     var node = classBody[i];
     if (t.isMethodDefinition(node)) {
-      self.replaceInstanceSuperReferences(node);
+      this.replaceInstanceSuperReferences(node);
 
       if (node.key.name === "constructor") {
-        self.pushConstructor(node);
+        this.pushConstructor(node);
       } else {
-        self.pushMethod(node);
+        this.pushMethod(node);
       }
     } else if (t.isPrivateDeclaration(node)) {
-      self.closure = true;
+      this.closure = true;
       body.unshift(node);
     }
   }
 
+  // we have no constructor, we have a super, and the super doesn't appear to be falsy
   if (!this.hasConstructor && superName && !t.isFalsyExpression(superName)) {
-    constructor.body.body.push(util.template("class-super-constructor-call", {
-      CLASS_NAME: className
+    var defaultConstructorTemplate = "class-super-constructor-call";
+    if (this.isLoose) defaultConstructorTemplate += "-loose";
+
+    constructor.body.body.push(util.template(defaultConstructorTemplate, {
+      CLASS_NAME: className,
+      SUPER_NAME: this.superName
     }, true));
   }
 
@@ -183,6 +188,19 @@ Class.prototype.pushMethod = function (node) {
   }
 
   if (kind === "") {
+    if (this.isLoose) {
+      // use assignments instead of define properties for loose classes
+
+      var className = this.className;
+      if (!node.static) className = t.memberExpression(className, t.identifier("prototype"));
+      methodName = t.memberExpression(className, methodName, node.computed);
+
+      var expr = t.expressionStatement(t.assignmentExpression("=", methodName, node.value));
+      t.inheritsComments(expr, node);
+      this.body.push(expr);
+      return;
+    }
+
     kind = "value";
   }
 
@@ -219,6 +237,47 @@ Class.prototype.superProperty = function (property, isStatic, isComputed, thisEx
   );
 };
 
+/**
+ * Description
+ *
+ * @param {Object} node
+ * @param {Object} id
+ * @param {Object} parent
+ * @returns {Object}
+ */
+
+Class.prototype.looseSuperProperty = function (methodNode, id, parent) {
+  var methodName = methodNode.key;
+  var superName  = this.superName || t.identifier("Function");
+
+  if (parent.property === id) {
+    return;
+  } else if (t.isCallExpression(parent, { callee: id })) {
+    // super(); -> ClassName.prototype.MethodName.call(this);
+    parent.arguments.unshift(t.thisExpression());
+
+    if (methodName.name === "constructor") {
+      // constructor() { super(); }
+      return t.memberExpression(superName, t.identifier("call"));
+    } else {
+      id = superName;
+
+      // foo() { super(); }
+      if (!methodNode.static) {
+        id = t.memberExpression(id, t.identifier("prototype"));
+      }
+
+      id = t.memberExpression(id, methodName, methodNode.computed);
+      return t.memberExpression(id, t.identifier("call"));
+    }
+  } else if (t.isMemberExpression(parent) && !methodNode.static) {
+    // super.test -> ClassName.prototype.test
+    return t.memberExpression(superName, t.identifier("prototype"));
+  } else {
+    return superName;
+  }
+};
+
 /**
  * Replace all `super` references with a reference to our `superClass`.
  *
@@ -229,54 +288,110 @@ Class.prototype.replaceInstanceSuperReferences = function (methodNode) {
   var method = methodNode.value;
   var self   = this;
 
-  traverse(method, {
-    enter: function (node, parent) {
-      var property;
-      var computed;
-      var args;
+  var topLevelThisReference;
 
-      if (t.isIdentifier(node, { name: "super" })) {
-        if (!(t.isMemberExpression(parent) && !parent.computed && parent.property === node)) {
-          throw self.file.errorWithNode(node, "illegal use of bare super");
+  traverseLevel(method, true);
+
+  if (topLevelThisReference) {
+    method.body.body.unshift(t.variableDeclaration("var", [
+      t.variableDeclarator(topLevelThisReference, t.thisExpression())
+    ]));
+  }
+
+  function traverseLevel(node, topLevel) {
+    traverse(node, {
+      enter: function (node, parent) {
+        if (t.isFunction(node) && !t.isArrowFunctionExpression(node)) {
+          // we need to call traverseLevel again so we're context aware
+          traverseLevel(node, false);
+          return this.skip();
         }
-      } else if (t.isCallExpression(node)) {
-        var callee = node.callee;
-        if (t.isIdentifier(callee, { name: "super" })) {
-          // super(); -> _get(Object.getPrototypeOf(ClassName), "MethodName", this).call(this);
-          property = methodNode.key;
-          computed = methodNode.computed;
-          args = node.arguments;
-        } else {
-          if (!t.isMemberExpression(callee)) return;
-          if (callee.object.name !== "super") return;
 
-          // super.test(); -> _get(Object.getPrototypeOf(ClassName.prototype), "test", this).call(this);
-          property = callee.property;
-          computed = callee.computed;
-          args = node.arguments;
-        }
-      } else if (t.isMemberExpression(node)) {
-        if (!t.isIdentifier(node.object, { name: "super" })) return;
+        var getThisReference = function () {
+          if (topLevel) {
+            // top level so `this` is the instance
+            return t.thisExpression();
+          } else {
+            // not in the top level so we need to create a reference
+            return topLevelThisReference = topLevelThisReference || self.file.generateUidIdentifier("this");
+          }
+        };
 
-        // super.name; -> _get(Object.getPrototypeOf(ClassName.prototype), "name", this);
-        property = node.property;
-        computed = node.computed;
+        var callback = specHandle;
+        if (self.isLoose) callback = looseHandle;
+        return callback(getThisReference, node, parent);
       }
+    });
+  }
 
-      if (property) {
-        var thisExpression = t.thisExpression();
-        var superProperty = self.superProperty(property, methodNode.static, computed, thisExpression);
-        if (args) {
-          return t.callExpression(
-            t.memberExpression(superProperty, t.identifier("call"), false),
-            [thisExpression].concat(args)
-          );
-        } else {
-          return superProperty;
-        }
-      }
+  function looseHandle(getThisReference, node, parent) {
+    if (t.isIdentifier(node, { name: "super" })) {
+      return self.looseSuperProperty(methodNode, node, parent);
+    } else if (t.isCallExpression(node)) {
+      var callee = node.callee;
+      if (!t.isMemberExpression(callee)) return;
+      if (callee.object.name !== "super") return;
+
+      // super.test(); -> ClassName.prototype.MethodName.call(this);
+      t.appendToMemberExpression(callee, t.identifier("call"));
+      node.arguments.unshift(getThisReference());
     }
-  });
+  }
+
+  function specHandle(getThisReference, node, parent) {
+    var property;
+    var computed;
+    var args;
+
+    if (t.isIdentifier(node, { name: "super" })) {
+      if (!(t.isMemberExpression(parent) && !parent.computed && parent.property === node)) {
+        throw self.file.errorWithNode(node, "illegal use of bare super");
+      }
+    } else if (t.isCallExpression(node)) {
+      var callee = node.callee;
+      if (t.isIdentifier(callee, { name: "super" })) {
+        // super(); -> _get(Object.getPrototypeOf(ClassName), "MethodName", this).call(this);
+        property = methodNode.key;
+        computed = methodNode.computed;
+        args = node.arguments;
+      } else {
+        if (!t.isMemberExpression(callee)) return;
+        if (callee.object.name !== "super") return;
+
+        // super.test(); -> _get(Object.getPrototypeOf(ClassName.prototype), "test", this).call(this);
+        property = callee.property;
+        computed = callee.computed;
+        args = node.arguments;
+      }
+    } else if (t.isMemberExpression(node)) {
+      if (!t.isIdentifier(node.object, { name: "super" })) return;
+
+      // super.name; -> _get(Object.getPrototypeOf(ClassName.prototype), "name", this);
+      property = node.property;
+      computed = node.computed;
+    }
+
+    if (!property) return;
+
+    var thisReference = getThisReference();
+    var superProperty = self.superProperty(property, methodNode.static, computed, thisReference);
+    if (args) {
+      if (args.length === 1 && t.isSpreadElement(args[0])) {
+        // super(...arguments);
+        return t.callExpression(
+          t.memberExpression(superProperty, t.identifier("apply")),
+          [thisReference, args[0].argument]
+        );
+      } else {
+        return t.callExpression(
+          t.memberExpression(superProperty, t.identifier("call")),
+          [thisReference].concat(args)
+        );
+      }
+    } else {
+      return superProperty;
+    }
+  }
 };
 
 /**
diff --git a/lib/6to5/transformation/transformers/es6-computed-property-names.js b/lib/6to5/transformation/transformers/es6-computed-property-names.js
index 3a559177df..94d4bd9e86 100644
--- a/lib/6to5/transformation/transformers/es6-computed-property-names.js
+++ b/lib/6to5/transformation/transformers/es6-computed-property-names.js
@@ -2,28 +2,63 @@ var t = require("../../types");
 
 exports.ObjectExpression = function (node, parent, file, scope) {
   var hasComputed = false;
-  var prop;
-  var key;
-  var i;
 
-  for (i in node.properties) {
+  for (var i in node.properties) {
     hasComputed = t.isProperty(node.properties[i], { computed: true, kind: "init" });
     if (hasComputed) break;
   }
 
   if (!hasComputed) return;
 
+  var initProps = [];
   var objId = scope.generateUidBasedOnNode(parent, file);
 
+  //
+
   var body = [];
   var container = t.functionExpression(null, [], t.blockStatement(body));
   container._aliasFunction = true;
 
+  //
+
+  var callback = spec;
+  if (file.isLoose("computedPropertyNames")) callback = loose;
+
+  var result = callback(node, body, objId, initProps, file);
+  if (result) return result;
+
+  //
+
+  body.unshift(t.variableDeclaration("var", [
+    t.variableDeclarator(objId, t.objectExpression(initProps))
+  ]));
+
+  body.push(t.returnStatement(objId));
+
+  return t.callExpression(container, []);
+};
+
+var loose = function (node, body, objId) {
+  for (var i in node.properties) {
+    var prop = node.properties[i];
+
+    body.push(t.expressionStatement(
+      t.assignmentExpression(
+        "=",
+        t.memberExpression(objId, prop.key, prop.computed),
+        prop.value
+      )
+    ));
+  }
+};
+
+var spec = function (node, body, objId, initProps, file) {
   var props = node.properties;
+  var prop, key;
 
   // normalise key
 
-  for (i in props) {
+  for (var i in props) {
     prop = props[i];
     if (prop.kind !== "init") continue;
 
@@ -36,7 +71,6 @@ exports.ObjectExpression = function (node, parent, file, scope) {
 
   // add all non-computed properties and `__proto__` properties to the initializer
 
-  var initProps = [];
   var broken = false;
 
   for (i in props) {
@@ -86,14 +120,4 @@ exports.ObjectExpression = function (node, parent, file, scope) {
       return first;
     }
   }
-
-  //
-
-  body.unshift(t.variableDeclaration("var", [
-    t.variableDeclarator(objId, t.objectExpression(initProps))
-  ]));
-
-  body.push(t.returnStatement(objId));
-
-  return t.callExpression(container, []);
 };
diff --git a/lib/6to5/transformation/transformers/es6-default-parameters.js b/lib/6to5/transformation/transformers/es6-default-parameters.js
index ba3c0ad631..db82d8e2d4 100644
--- a/lib/6to5/transformation/transformers/es6-default-parameters.js
+++ b/lib/6to5/transformation/transformers/es6-default-parameters.js
@@ -1,7 +1,6 @@
 var traverse = require("../../traverse");
 var util     = require("../../util");
 var t        = require("../../types");
-var _        = require("lodash");
 
 exports.Function = function (node, parent, file, scope) {
   if (!node.defaults || !node.defaults.length) return;
@@ -15,6 +14,23 @@ exports.Function = function (node, parent, file, scope) {
   var i;
   var def;
 
+  var checkTDZ = function (ids) {
+    var check = function (node, parent) {
+      if (!t.isIdentifier(node) || !t.isReferenced(node, parent)) return;
+
+      if (ids.indexOf(node.name) >= 0) {
+        throw file.errorWithNode(node, "Temporal dead zone - accessing a variable before it's initialized");
+      }
+
+      if (scope.has(node.name, true)) {
+        iife = true;
+      }
+    };
+
+    check(def, node);
+    traverse(def, { enter: check });
+  };
+
   for (i in node.defaults) {
     def = node.defaults[i];
     if (!def) continue;
@@ -23,22 +39,10 @@ exports.Function = function (node, parent, file, scope) {
 
     // temporal dead zone check - here we prevent accessing of params that
     // are to the right - ie. uninitialized parameters
-    _.each(ids.slice(i), function (ids) {
-      var check = function (node, parent) {
-        if (!t.isIdentifier(node) || !t.isReferenced(node, parent)) return;
-
-        if (ids.indexOf(node.name) >= 0) {
-          throw file.errorWithNode(node, "Temporal dead zone - accessing a variable before it's initialized");
-        }
-
-        if (scope.has(node.name)) {
-          iife = true;
-        }
-      };
-
-      check(def, node);
-      traverse(def, { enter: check });
-    });
+    var rightIds = ids.slice(i);
+    for (i in rightIds) {
+      checkTDZ(rightIds[i]);
+    }
 
     // we're accessing a variable that's already defined within this function
     var has = scope.get(param.name);
diff --git a/lib/6to5/transformation/transformers/es6-for-of.js b/lib/6to5/transformation/transformers/es6-for-of.js
index 737bf36b14..61357cfbad 100644
--- a/lib/6to5/transformation/transformers/es6-for-of.js
+++ b/lib/6to5/transformation/transformers/es6-for-of.js
@@ -2,6 +2,68 @@ var util = require("../../util");
 var t    = require("../../types");
 
 exports.ForOfStatement = function (node, parent, file, scope) {
+  var callback = spec;
+  if (file.isLoose("forOf")) callback = loose;
+
+  var build  = callback(node, parent, file, scope);
+  var declar = build.declar;
+  var loop   = build.loop;
+  var block  = loop.body;
+
+  // inherit comments from the original loop
+  t.inheritsComments(loop, node);
+
+  // ensure that it's a block so we can take all it's statemetns
+  t.ensureBlock(node);
+
+  // add the value declaration to the new loop body
+  if (declar){
+    if (build.shouldUnshift) {
+      block.body.unshift(declar);
+    } else {
+      block.body.push(declar);
+    }
+  }
+
+  // push the rest of the original loop body onto our new body
+  block.body = block.body.concat(node.body.body);
+
+  return loop;
+};
+
+var loose = function (node, parent, file, scope) {
+  var left = node.left;
+  var declar, id;
+
+  if (t.isIdentifier(left) || t.isPattern(left)) {
+    // for (i of test), for ({ i } of test)
+    id = left;
+  } else if (t.isVariableDeclaration(left)) {
+    // for (var i of test)
+    id = left.declarations[0].id;
+    declar = t.variableDeclaration(left.kind, [
+      t.variableDeclarator(id)
+    ]);
+  } else {
+    throw file.errorWithNode(left, "Unknown node type " + left.type + " in ForOfStatement");
+  }
+
+  var loop = util.template("for-of-loose", {
+    LOOP_OBJECT:  file.generateUidIdentifier("iterator", scope),
+    IS_ARRAY:     file.generateUidIdentifier("isArray", scope),
+    OBJECT:       node.right,
+    INDEX:        file.generateUidIdentifier("i", scope),
+    ID:           id
+  });
+
+  return {
+    shouldUnshift: true,
+    declar:        declar,
+    loop:          loop
+  };
+};
+
+var spec = function (node, parent, file, scope) {
   var left = node.left;
   var declar;
 
@@ -9,8 +71,10 @@ exports.ForOfStatement = function (node, parent, file, scope) {
   var stepValue = t.memberExpression(stepKey, t.identifier("value"));
 
   if (t.isIdentifier(left) || t.isPattern(left)) {
+    // for (i of test), for ({ i } of test)
     declar = t.expressionStatement(t.assignmentExpression("=", left, stepValue));
   } else if (t.isVariableDeclaration(left)) {
+    // for (var i of test)
     declar = t.variableDeclaration(left.kind, [
       t.variableDeclarator(left.declarations[0].id, stepValue)
     ]);
@@ -18,18 +82,14 @@ exports.ForOfStatement = function (node, parent, file, scope) {
     throw file.errorWithNode(left, "Unknown node type " + left.type + " in ForOfStatement");
   }
 
-  var node2 = util.template("for-of", {
+  var loop = util.template("for-of", {
     ITERATOR_KEY: file.generateUidIdentifier("iterator", scope),
     STEP_KEY:     stepKey,
     OBJECT:       node.right
   });
 
-  t.inheritsComments(node2, node);
-  t.ensureBlock(node);
-
-  var block = node2.body;
-  block.body.push(declar);
-  block.body = block.body.concat(node.body.body);
-
-  return node2;
+  return {
+    declar: declar,
+    loop:   loop
+  };
 };
diff --git a/lib/6to5/transformation/transformers/es6-let-scoping.js b/lib/6to5/transformation/transformers/es6-let-scoping.js
index 44151d58b8..a95c1b3a30 100644
--- a/lib/6to5/transformation/transformers/es6-let-scoping.js
+++ b/lib/6to5/transformation/transformers/es6-let-scoping.js
@@ -250,10 +250,11 @@ LetScoping.prototype.getInfo = function () {
     declar = block.body[i];
     if (!isLet(declar, block)) continue;
 
-    _.each(t.getIds(declar, true), function (id, key) {
-      duplicates(id, key);
+    var declars = t.getIds(declar, true);
+    for (var key in declars) {
+      duplicates(declars[key], key);
       opts.keys.push(key);
-    });
+    }
   }
 
   return opts;
diff --git a/lib/6to5/transformation/transformers/es6-template-literals.js b/lib/6to5/transformation/transformers/es6-template-literals.js
index 4be21d4269..5e4f824cf3 100644
--- a/lib/6to5/transformation/transformers/es6-template-literals.js
+++ b/lib/6to5/transformation/transformers/es6-template-literals.js
@@ -17,10 +17,12 @@ exports.TaggedTemplateExpression = function (node, parent, file) {
     raw.push(t.literal(elem.value.raw));
   }
 
-  args.push(t.callExpression(file.addHelper("tagged-template-literal"), [
-    t.arrayExpression(strings),
-    t.arrayExpression(raw)
-  ]));
+  strings = t.arrayExpression(strings);
+  raw = t.arrayExpression(raw);
+
+  var templateName = "tagged-template-literal";
+  if (file.isLoose("templateLiterals")) templateName += "-loose";
+  args.push(t.callExpression(file.addHelper(templateName), [strings, raw]));
 
   args = args.concat(quasi.expressions);
 
diff --git a/lib/6to5/transformation/transformers/optional-classes-fast-super.js b/lib/6to5/transformation/transformers/optional-classes-fast-super.js
deleted file mode 100644
index 7f65c08c93..0000000000
--- a/lib/6to5/transformation/transformers/optional-classes-fast-super.js
+++ /dev/null
@@ -1,74 +0,0 @@
-var traverse = require("../../traverse");
-var util     = require("../../util");
-var t        = require("../../types");
-
-exports.optional = true;
-
-exports.Class = function (node) {
-  var superClass = node.superClass || t.identifier("Function");
-
-  var hasConstructor = false;
-  var body = node.body.body;
-
-  for (var i in body) {
-    var methodNode = body[i];
-
-    hasConstructor = hasConstructor || methodNode.key.name === "constructor";
-
-    traverse(methodNode, {
-      enter: function (node, parent) {
-        if (t.isIdentifier(node, { name: "super" })) {
-          return superIdentifier(superClass, methodNode, node, parent);
-        } else if (t.isCallExpression(node)) {
-          var callee = node.callee;
-          if (!t.isMemberExpression(callee)) return;
-          if (callee.object.name !== "super") return;
-
-          // super.test(); -> ClassName.prototype.MethodName.call(this);
-          t.appendToMemberExpression(callee, t.identifier("call"));
-          node.arguments.unshift(t.thisExpression());
-        }
-      }
-    });
-  }
-
-  if (node.superClass && !hasConstructor) {
-    body.unshift(t.methodDefinition(
-      t.identifier("constructor"),
-      util.template("class-super-constructor-call-fast", {
-        SUPER_NAME: superClass
-      })
-    ));
-  }
-};
-
-var superIdentifier = function (superClass, methodNode, id, parent) {
-  var methodName = methodNode.key;
-
-  if (parent.property === id) {
-    return;
-  } else if (t.isCallExpression(parent, { callee: id })) {
-    // super(); -> ClassName.prototype.MethodName.call(this);
-    parent.arguments.unshift(t.thisExpression());
-
-    if (methodName.name === "constructor") {
-      // constructor() { super(); }
-      return t.memberExpression(superClass, t.identifier("call"));
-    } else {
-      id = superClass;
-
-      // foo() { super(); }
-      if (!methodNode.static) {
-        id = t.memberExpression(id, t.identifier("prototype"));
-      }
-
-      id = t.memberExpression(id, methodName, methodNode.computed);
-      return t.memberExpression(id, t.identifier("call"));
-    }
-  } else if (t.isMemberExpression(parent) && !methodNode.static) {
-    // super.test -> ClassName.prototype.test
-    return t.memberExpression(superClass, t.identifier("prototype"));
-  } else {
-    return superClass;
-  }
-};
diff --git a/lib/6to5/transformation/transformers/optional-core-aliasing.js b/lib/6to5/transformation/transformers/optional-core-aliasing.js
index 806ddb5cfb..3610ae8f62 100644
--- a/lib/6to5/transformation/transformers/optional-core-aliasing.js
+++ b/lib/6to5/transformation/transformers/optional-core-aliasing.js
@@ -8,6 +8,15 @@ var coreHas = function (node) {
   return node.name !== "_" && _.has(core, node.name);
 };
 
+var ALIASABLE_CONSTRUCTORS = [
+  "Symbol",
+  "Promise",
+  "Map",
+  "WeakMap",
+  "Set",
+  "WeakSet"
+];
+
 exports.optional = true;
 
 exports.ast = {
@@ -31,8 +40,8 @@ exports.ast = {
             this.skip();
             return t.prependToMemberExpression(node, file._coreId);
           }
-        } else if (t.isIdentifier(node) && !t.isMemberExpression(parent) && t.isReferenced(node, parent) && node.name === "Symbol") {
-          // new Symbol -> new _core.Symbol
+        } else if (t.isIdentifier(node) && !t.isMemberExpression(parent) && t.isReferenced(node, parent) && _.contains(ALIASABLE_CONSTRUCTORS, node.name)) {
+          // Symbol() -> _core.Symbol(); new Promise -> new _core.Promise
           return t.memberExpression(file._coreId, node);
         } else if (t.isCallExpression(node)) {
           // arr[Symbol.iterator]() -> _core.$for.getIterator(arr)
diff --git a/lib/6to5/transformation/transformers/optional-for-of-fast.js b/lib/6to5/transformation/transformers/optional-for-of-fast.js
deleted file mode 100644
index c2d0f1e148..0000000000
--- a/lib/6to5/transformation/transformers/optional-for-of-fast.js
+++ /dev/null
@@ -1,37 +0,0 @@
-var util = require("../../util");
-var t    = require("../../types");
-
-exports.optional = true;
-
-exports.ForOfStatement = function (node, parent, file, scope) {
-  var left = node.left;
-  var declar, id;
-
-  if (t.isIdentifier(left) || t.isPattern(left)) {
-    id = left;
-  } else if (t.isVariableDeclaration(left)) {
-    id = left.declarations[0].id;
-    declar = t.variableDeclaration(left.kind, [
-      t.variableDeclarator(id)
-    ]);
-  } else {
-    throw file.errorWithNode(left, "Unknown node type " + left.type + " in ForOfStatement");
-  }
-
-  var node2 = util.template("for-of-fast", {
-    LOOP_OBJECT:  file.generateUidIdentifier("loopObject", scope),
-    IS_ARRAY:     file.generateUidIdentifier("isArray", scope),
-    OBJECT:       node.right,
-    INDEX:        file.generateUidIdentifier("i", scope),
-    ID:           id
-  });
-
-  t.inheritsComments(node2, node);
-  t.ensureBlock(node);
-
-  var block = node2.body;
-  if (declar) block.body.unshift(declar);
-  block.body = block.body.concat(node.body.body);
-
-  return node2;
-};
diff --git a/lib/6to5/transformation/transformers/react.js b/lib/6to5/transformation/transformers/react.js
index fd0d7140ac..341d6b1492 100644
--- a/lib/6to5/transformation/transformers/react.js
+++ b/lib/6to5/transformation/transformers/react.js
@@ -5,6 +5,7 @@
 
 var esutils = require("esutils");
 var t       = require("../../types");
+var _       = require("lodash");
 
 exports.XJSIdentifier = function (node) {
   if (esutils.keyword.isIdentifierName(node.name)) {
@@ -61,11 +62,16 @@ exports.XJSOpeningElement = {
       }
     }
 
-    var props = node.attributes;
-    if (props.length) {
+    var attribs = node.attributes;
+    if (attribs.length) {
       var _props = [];
       var objs = [];
 
+      // so basically in order to support spread elements we
+      // loop over all the attributes, breaking on spreads
+      // we then push a new object containing all prior attributes
+      // to an array for later processing
+
       var pushProps = function () {
         if (!_props.length) return;
 
@@ -73,8 +79,8 @@ exports.XJSOpeningElement = {
         _props = [];
       };
 
-      while (props.length) {
-        var prop = props.shift();
+      while (attribs.length) {
+        var prop = attribs.shift();
         if (t.isXJSSpreadAttribute(prop)) {
           pushProps();
           objs.push(prop.argument);
@@ -86,22 +92,25 @@ exports.XJSOpeningElement = {
       pushProps();
 
       if (objs.length === 1) {
-        props = objs[0];
+        // only one object
+        attribs = objs[0];
       } else {
+        // looks like we have multiple objects
         if (!t.isObjectExpression(objs[0])) {
           objs.unshift(t.objectExpression([]));
         }
 
-        props = t.callExpression(
+        // spread it
+        attribs = t.callExpression(
           t.memberExpression(t.identifier("React"), t.identifier("__spread")),
           objs
         );
       }
     } else {
-      props = t.literal(null);
+      attribs = t.literal(null);
     }
 
-    args.push(props);
+    args.push(attribs);
 
     if (reactCompat) {
       if (tagName && isTag(tagName)) {
@@ -130,7 +139,7 @@ exports.XJSElement = {
     for (i in node.children) {
       var child = node.children[i];
 
-      if (t.isLiteral(child)) {
+      if (t.isLiteral(child) && _.isString(child.value)) {
         var lines = child.value.split(/\r\n|\n|\r/);
 
         for (i in lines) {
diff --git a/package.json b/package.json
index a81e4bf6c8..a76b3beabe 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "6to5",
   "description": "Turn ES6 code into readable vanilla ES5 with source maps",
-  "version": "2.10.1",
+  "version": "2.12.0",
   "author": "Sebastian McKenzie <sebmck@gmail.com>",
   "homepage": "https://github.com/6to5/6to5",
   "repository": {
@@ -39,35 +39,36 @@
     "test": "make test"
   },
   "dependencies": {
-    "acorn-6to5": "0.11.1-13",
+    "acorn-6to5": "0.11.1-14",
     "ast-types": "~0.6.1",
     "chokidar": "0.11.1",
     "commander": "2.5.0",
-    "core-js": "^0.4.4",
+    "core-js": "0.4.4",
     "estraverse": "1.8.0",
     "esutils": "1.1.6",
-    "esvalid": "^1.1.0",
+    "esvalid": "1.1.0",
     "fs-readdir-recursive": "0.1.0",
-    "jshint": "^2.5.10",
+    "jshint": "2.5.10",
     "lodash": "2.4.1",
     "mkdirp": "0.5.0",
     "private": "0.1.6",
-    "regenerator": "^0.8.3",
+    "regenerator": "0.8.3",
     "regexpu": "0.3.0",
+    "roadrunner": "1.0.4",
     "source-map": "0.1.40",
     "source-map-support": "0.2.8"
   },
   "devDependencies": {
     "browserify": "6.3.2",
-    "chai": "^1.9.2",
+    "chai": "1.9.2",
     "istanbul": "0.3.2",
-    "jshint-stylish": "^1.0.0",
+    "jshint-stylish": "1.0.0",
     "matcha": "0.6.0",
     "mocha": "1.21.4",
     "rimraf": "2.2.8",
     "uglify-js": "2.4.15"
   },
   "optionalDependencies": {
-    "kexec": "^0.2.0"
+    "kexec": "0.2.0"
   }
 }
diff --git a/test/bin.js b/test/bin.js
index 8930fdf05f..e8bd33b22e 100644
--- a/test/bin.js
+++ b/test/bin.js
@@ -1,5 +1,4 @@
-// skip these tests under instanbul since they're useless
-if (process.env.running_under_istanbul === '1') return;
+if (process.env.running_under_istanbul) return;
 
 var readdir = require("fs-readdir-recursive");
 var helper  = require("./_helper");
diff --git a/test/fixtures/transformation/optional-classes-fast-super/accessing-super-class/actual.js b/test/fixtures/transformation/es6-classes-loose/accessing-super-class/actual.js
similarity index 100%
rename from test/fixtures/transformation/optional-classes-fast-super/accessing-super-class/actual.js
rename to test/fixtures/transformation/es6-classes-loose/accessing-super-class/actual.js
diff --git a/test/fixtures/transformation/optional-classes-fast-super/accessing-super-class/expected.js b/test/fixtures/transformation/es6-classes-loose/accessing-super-class/expected.js
similarity index 60%
rename from test/fixtures/transformation/optional-classes-fast-super/accessing-super-class/expected.js
rename to test/fixtures/transformation/es6-classes-loose/accessing-super-class/expected.js
index a0dce8e571..6c9bd8d668 100644
--- a/test/fixtures/transformation/optional-classes-fast-super/accessing-super-class/expected.js
+++ b/test/fixtures/transformation/es6-classes-loose/accessing-super-class/expected.js
@@ -37,31 +37,21 @@ var Test = (function (Foo) {
 
   _inherits(Test, Foo);
 
-  _prototypeProperties(Test, {
-    foo: {
-      value: function () {
-        var _Foo$foo, _Foo$foo2;
-        Foo.foo.call(this);
-        (_Foo$foo = Foo.foo).call.apply(_Foo$foo, [this].concat(_slice.call(arguments)));
-        (_Foo$foo2 = Foo.foo).call.apply(_Foo$foo2, [this, "test"].concat(_slice.call(arguments)));
-      },
-      writable: true,
-      enumerable: true,
-      configurable: true
-    }
-  }, {
-    test: {
-      value: function () {
-        var _Foo$prototype$test3, _Foo$prototype$test4;
-        Foo.prototype.test.call(this);
-        (_Foo$prototype$test3 = Foo.prototype.test).call.apply(_Foo$prototype$test3, [this].concat(_slice.call(arguments)));
-        (_Foo$prototype$test4 = Foo.prototype.test).call.apply(_Foo$prototype$test4, [this, "test"].concat(_slice.call(arguments)));
-      },
-      writable: true,
-      enumerable: true,
-      configurable: true
-    }
-  });
+  Test.prototype.test = function () {
+    var _Foo$prototype$test3, _Foo$prototype$test4;
+    Foo.prototype.test.call(this);
+    (_Foo$prototype$test3 = Foo.prototype.test).call.apply(_Foo$prototype$test3, [this].concat(_slice.call(arguments)));
+    (_Foo$prototype$test4 = Foo.prototype.test).call.apply(_Foo$prototype$test4, [this, "test"].concat(_slice.call(arguments)));
+  };
+
+  Test.foo = function () {
+    var _Foo$foo, _Foo$foo2;
+    Foo.foo.call(this);
+    (_Foo$foo = Foo.foo).call.apply(_Foo$foo, [this].concat(_slice.call(arguments)));
+    (_Foo$foo2 = Foo.foo).call.apply(_Foo$foo2, [this, "test"].concat(_slice.call(arguments)));
+  };
+
+  _prototypeProperties(Test, {}, {});
 
   return Test;
 })(Foo);
diff --git a/test/fixtures/transformation/optional-classes-fast-super/accessing-super-properties/actual.js b/test/fixtures/transformation/es6-classes-loose/accessing-super-properties/actual.js
similarity index 100%
rename from test/fixtures/transformation/optional-classes-fast-super/accessing-super-properties/actual.js
rename to test/fixtures/transformation/es6-classes-loose/accessing-super-properties/actual.js
diff --git a/test/fixtures/transformation/optional-classes-fast-super/accessing-super-properties/expected.js b/test/fixtures/transformation/es6-classes-loose/accessing-super-properties/expected.js
similarity index 100%
rename from test/fixtures/transformation/optional-classes-fast-super/accessing-super-properties/expected.js
rename to test/fixtures/transformation/es6-classes-loose/accessing-super-properties/expected.js
diff --git a/test/fixtures/transformation/optional-classes-fast-super/calling-super-properties/actual.js b/test/fixtures/transformation/es6-classes-loose/calling-super-properties/actual.js
similarity index 100%
rename from test/fixtures/transformation/optional-classes-fast-super/calling-super-properties/actual.js
rename to test/fixtures/transformation/es6-classes-loose/calling-super-properties/actual.js
diff --git a/test/fixtures/transformation/optional-classes-fast-super/calling-super-properties/expected.js b/test/fixtures/transformation/es6-classes-loose/calling-super-properties/expected.js
similarity index 81%
rename from test/fixtures/transformation/optional-classes-fast-super/calling-super-properties/expected.js
rename to test/fixtures/transformation/es6-classes-loose/calling-super-properties/expected.js
index 7891b464e4..529795221c 100644
--- a/test/fixtures/transformation/optional-classes-fast-super/calling-super-properties/expected.js
+++ b/test/fixtures/transformation/es6-classes-loose/calling-super-properties/expected.js
@@ -28,16 +28,11 @@ var Test = (function (Foo) {
 
   _inherits(Test, Foo);
 
-  _prototypeProperties(Test, {
-    test: {
-      value: function () {
-        return Foo.wow.call(this);
-      },
-      writable: true,
-      enumerable: true,
-      configurable: true
-    }
-  });
+  Test.test = function () {
+    return Foo.wow.call(this);
+  };
+
+  _prototypeProperties(Test, {});
 
   return Test;
 })(Foo);
diff --git a/test/fixtures/transformation/es6-classes-loose/options.json b/test/fixtures/transformation/es6-classes-loose/options.json
new file mode 100644
index 0000000000..b928f940e6
--- /dev/null
+++ b/test/fixtures/transformation/es6-classes-loose/options.json
@@ -0,0 +1,3 @@
+{
+  "loose": ["classes"]
+}
diff --git a/test/fixtures/transformation/optional-classes-fast-super/super-class-id-member-expression/actual.js b/test/fixtures/transformation/es6-classes-loose/super-class-id-member-expression/actual.js
similarity index 100%
rename from test/fixtures/transformation/optional-classes-fast-super/super-class-id-member-expression/actual.js
rename to test/fixtures/transformation/es6-classes-loose/super-class-id-member-expression/actual.js
diff --git a/test/fixtures/transformation/optional-classes-fast-super/super-class-id-member-expression/expected.js b/test/fixtures/transformation/es6-classes-loose/super-class-id-member-expression/expected.js
similarity index 82%
rename from test/fixtures/transformation/optional-classes-fast-super/super-class-id-member-expression/expected.js
rename to test/fixtures/transformation/es6-classes-loose/super-class-id-member-expression/expected.js
index 0101e0778e..f8b4bc49e2 100644
--- a/test/fixtures/transformation/optional-classes-fast-super/super-class-id-member-expression/expected.js
+++ b/test/fixtures/transformation/es6-classes-loose/super-class-id-member-expression/expected.js
@@ -17,8 +17,8 @@ var _inherits = function (subClass, superClass) {
 
 var BaseController = (function (_Chaplin$Controller) {
   function BaseController() {
-    if (Chaplin.Controller != null) {
-      Chaplin.Controller.apply(this, arguments);
+    if (_Chaplin$Controller != null) {
+      _Chaplin$Controller.apply(this, arguments);
     }
   }
 
@@ -29,8 +29,8 @@ var BaseController = (function (_Chaplin$Controller) {
 
 var BaseController2 = (function (_Chaplin$Controller$Another) {
   function BaseController2() {
-    if (Chaplin.Controller.Another != null) {
-      Chaplin.Controller.Another.apply(this, arguments);
+    if (_Chaplin$Controller$Another != null) {
+      _Chaplin$Controller$Another.apply(this, arguments);
     }
   }
 
diff --git a/test/fixtures/transformation/optional-classes-fast-super/super-class/actual.js b/test/fixtures/transformation/es6-classes-loose/super-class/actual.js
similarity index 100%
rename from test/fixtures/transformation/optional-classes-fast-super/super-class/actual.js
rename to test/fixtures/transformation/es6-classes-loose/super-class/actual.js
diff --git a/test/fixtures/transformation/optional-classes-fast-super/super-class/expected.js b/test/fixtures/transformation/es6-classes-loose/super-class/expected.js
similarity index 100%
rename from test/fixtures/transformation/optional-classes-fast-super/super-class/expected.js
rename to test/fixtures/transformation/es6-classes-loose/super-class/expected.js
diff --git a/test/fixtures/transformation/optional-classes-fast-super/super-function-fallback/actual.js b/test/fixtures/transformation/es6-classes-loose/super-function-fallback/actual.js
similarity index 100%
rename from test/fixtures/transformation/optional-classes-fast-super/super-function-fallback/actual.js
rename to test/fixtures/transformation/es6-classes-loose/super-function-fallback/actual.js
diff --git a/test/fixtures/transformation/optional-classes-fast-super/super-function-fallback/expected.js b/test/fixtures/transformation/es6-classes-loose/super-function-fallback/expected.js
similarity index 100%
rename from test/fixtures/transformation/optional-classes-fast-super/super-function-fallback/expected.js
rename to test/fixtures/transformation/es6-classes-loose/super-function-fallback/expected.js
diff --git a/test/fixtures/transformation/es6-classes/accessing-super-class/expected.js b/test/fixtures/transformation/es6-classes/accessing-super-class/expected.js
index d467b433f5..a762c97203 100644
--- a/test/fixtures/transformation/es6-classes/accessing-super-class/expected.js
+++ b/test/fixtures/transformation/es6-classes/accessing-super-class/expected.js
@@ -45,16 +45,16 @@ var _inherits = function (subClass, superClass) {
 
 var Test = (function (Foo) {
   function Test() {
-    var _get2, _get3, _get4, _get5;
+    var _get2, _get3;
     woops["super"].test();
     _get(Object.getPrototypeOf(Test.prototype), "constructor", this).call(this);
     _get(Object.getPrototypeOf(Test.prototype), "test", this).call(this);
 
-    (_get2 = _get(Object.getPrototypeOf(Test.prototype), "constructor", this)).call.apply(_get2, [this].concat(_slice.call(arguments)));
-    (_get3 = _get(Object.getPrototypeOf(Test.prototype), "constructor", this)).call.apply(_get3, [this, "test"].concat(_slice.call(arguments)));
+    _get(Object.getPrototypeOf(Test.prototype), "constructor", this).apply(this, arguments);
+    (_get2 = _get(Object.getPrototypeOf(Test.prototype), "constructor", this)).call.apply(_get2, [this, "test"].concat(_slice.call(arguments)));
 
-    (_get4 = _get(Object.getPrototypeOf(Test.prototype), "test", this)).call.apply(_get4, [this].concat(_slice.call(arguments)));
-    (_get5 = _get(Object.getPrototypeOf(Test.prototype), "test", this)).call.apply(_get5, [this, "test"].concat(_slice.call(arguments)));
+    _get(Object.getPrototypeOf(Test.prototype), "test", this).apply(this, arguments);
+    (_get3 = _get(Object.getPrototypeOf(Test.prototype), "test", this)).call.apply(_get3, [this, "test"].concat(_slice.call(arguments)));
   }
 
   _inherits(Test, Foo);
@@ -62,10 +62,10 @@ var Test = (function (Foo) {
   _prototypeProperties(Test, {
     foo: {
       value: function () {
-        var _get6, _get7;
+        var _get4;
         _get(Object.getPrototypeOf(Test), "foo", this).call(this);
-        (_get6 = _get(Object.getPrototypeOf(Test), "foo", this)).call.apply(_get6, [this].concat(_slice.call(arguments)));
-        (_get7 = _get(Object.getPrototypeOf(Test), "foo", this)).call.apply(_get7, [this, "test"].concat(_slice.call(arguments)));
+        _get(Object.getPrototypeOf(Test), "foo", this).apply(this, arguments);
+        (_get4 = _get(Object.getPrototypeOf(Test), "foo", this)).call.apply(_get4, [this, "test"].concat(_slice.call(arguments)));
       },
       writable: true,
       enumerable: true,
@@ -74,10 +74,10 @@ var Test = (function (Foo) {
   }, {
     test: {
       value: function () {
-        var _get8, _get9;
+        var _get5;
         _get(Object.getPrototypeOf(Test.prototype), "test", this).call(this);
-        (_get8 = _get(Object.getPrototypeOf(Test.prototype), "test", this)).call.apply(_get8, [this].concat(_slice.call(arguments)));
-        (_get9 = _get(Object.getPrototypeOf(Test.prototype), "test", this)).call.apply(_get9, [this, "test"].concat(_slice.call(arguments)));
+        _get(Object.getPrototypeOf(Test.prototype), "test", this).apply(this, arguments);
+        (_get5 = _get(Object.getPrototypeOf(Test.prototype), "test", this)).call.apply(_get5, [this, "test"].concat(_slice.call(arguments)));
       },
       writable: true,
       enumerable: true,
diff --git a/test/fixtures/transformation/es6-computed-property-names-loose/argument/actual.js b/test/fixtures/transformation/es6-computed-property-names-loose/argument/actual.js
new file mode 100644
index 0000000000..fc50c41c49
--- /dev/null
+++ b/test/fixtures/transformation/es6-computed-property-names-loose/argument/actual.js
@@ -0,0 +1,3 @@
+foo({
+  [bar]: "foobar"
+});
diff --git a/test/fixtures/transformation/es6-computed-property-names-loose/argument/expected.js b/test/fixtures/transformation/es6-computed-property-names-loose/argument/expected.js
new file mode 100644
index 0000000000..8a544ec30e
--- /dev/null
+++ b/test/fixtures/transformation/es6-computed-property-names-loose/argument/expected.js
@@ -0,0 +1,8 @@
+"use strict";
+
+foo((function () {
+  var _foo = {};
+
+  _foo[bar] = "foobar";
+  return _foo;
+})());
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-computed-property-names-loose/assignment/actual.js b/test/fixtures/transformation/es6-computed-property-names-loose/assignment/actual.js
new file mode 100644
index 0000000000..dd74ed9f04
--- /dev/null
+++ b/test/fixtures/transformation/es6-computed-property-names-loose/assignment/actual.js
@@ -0,0 +1,3 @@
+foo = {
+  [bar]: "foobar"
+};
diff --git a/test/fixtures/transformation/es6-computed-property-names-loose/assignment/expected.js b/test/fixtures/transformation/es6-computed-property-names-loose/assignment/expected.js
new file mode 100644
index 0000000000..2b1f23d706
--- /dev/null
+++ b/test/fixtures/transformation/es6-computed-property-names-loose/assignment/expected.js
@@ -0,0 +1,8 @@
+"use strict";
+
+foo = (function () {
+  var _foo = {};
+
+  _foo[bar] = "foobar";
+  return _foo;
+})();
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-computed-property-names-loose/ignore-symbol/actual.js b/test/fixtures/transformation/es6-computed-property-names-loose/ignore-symbol/actual.js
new file mode 100644
index 0000000000..fce8293ed4
--- /dev/null
+++ b/test/fixtures/transformation/es6-computed-property-names-loose/ignore-symbol/actual.js
@@ -0,0 +1,3 @@
+var foo = {
+  [Symbol.iterator]: "foobar"
+};
diff --git a/test/fixtures/transformation/es6-computed-property-names-loose/ignore-symbol/expected.js b/test/fixtures/transformation/es6-computed-property-names-loose/ignore-symbol/expected.js
new file mode 100644
index 0000000000..852e2b4e6c
--- /dev/null
+++ b/test/fixtures/transformation/es6-computed-property-names-loose/ignore-symbol/expected.js
@@ -0,0 +1,8 @@
+"use strict";
+
+var foo = (function () {
+  var _foo = {};
+
+  _foo[Symbol.iterator] = "foobar";
+  return _foo;
+})();
diff --git a/test/fixtures/transformation/es6-computed-property-names-loose/method/actual.js b/test/fixtures/transformation/es6-computed-property-names-loose/method/actual.js
new file mode 100644
index 0000000000..068edebd55
--- /dev/null
+++ b/test/fixtures/transformation/es6-computed-property-names-loose/method/actual.js
@@ -0,0 +1,5 @@
+var obj = {
+  [foobar]() {
+    return "foobar";
+  }
+};
diff --git a/test/fixtures/transformation/es6-computed-property-names-loose/method/expected.js b/test/fixtures/transformation/es6-computed-property-names-loose/method/expected.js
new file mode 100644
index 0000000000..da3d3d08e2
--- /dev/null
+++ b/test/fixtures/transformation/es6-computed-property-names-loose/method/expected.js
@@ -0,0 +1,11 @@
+"use strict";
+
+var obj = (function () {
+  var _obj = {};
+
+  _obj[foobar] = function () {
+    return "foobar";
+  };
+
+  return _obj;
+})();
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-computed-property-names-loose/mixed/actual.js b/test/fixtures/transformation/es6-computed-property-names-loose/mixed/actual.js
new file mode 100644
index 0000000000..17e110ad3d
--- /dev/null
+++ b/test/fixtures/transformation/es6-computed-property-names-loose/mixed/actual.js
@@ -0,0 +1,6 @@
+var obj = {
+  ["x" + foo]: "heh",
+  ["y" + bar]: "noo",
+  foo: "foo",
+  bar: "bar"
+};
diff --git a/test/fixtures/transformation/es6-computed-property-names-loose/mixed/expected.js b/test/fixtures/transformation/es6-computed-property-names-loose/mixed/expected.js
new file mode 100644
index 0000000000..7728ebd72c
--- /dev/null
+++ b/test/fixtures/transformation/es6-computed-property-names-loose/mixed/expected.js
@@ -0,0 +1,11 @@
+"use strict";
+
+var obj = (function () {
+  var _obj = {};
+
+  _obj["x" + foo] = "heh";
+  _obj["y" + bar] = "noo";
+  _obj.foo = "foo";
+  _obj.bar = "bar";
+  return _obj;
+})();
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-computed-property-names-loose/multiple/actual.js b/test/fixtures/transformation/es6-computed-property-names-loose/multiple/actual.js
new file mode 100644
index 0000000000..02d4195fa7
--- /dev/null
+++ b/test/fixtures/transformation/es6-computed-property-names-loose/multiple/actual.js
@@ -0,0 +1,4 @@
+var obj = {
+  ["x" + foo]: "heh",
+  ["y" + bar]: "noo"
+};
diff --git a/test/fixtures/transformation/es6-computed-property-names-loose/multiple/expected.js b/test/fixtures/transformation/es6-computed-property-names-loose/multiple/expected.js
new file mode 100644
index 0000000000..fb1c4ceb31
--- /dev/null
+++ b/test/fixtures/transformation/es6-computed-property-names-loose/multiple/expected.js
@@ -0,0 +1,9 @@
+"use strict";
+
+var obj = (function () {
+  var _obj = {};
+
+  _obj["x" + foo] = "heh";
+  _obj["y" + bar] = "noo";
+  return _obj;
+})();
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-computed-property-names-loose/options.json b/test/fixtures/transformation/es6-computed-property-names-loose/options.json
new file mode 100644
index 0000000000..422293bd82
--- /dev/null
+++ b/test/fixtures/transformation/es6-computed-property-names-loose/options.json
@@ -0,0 +1,3 @@
+{
+  "loose": ["computedPropertyNames"]
+}
diff --git a/test/fixtures/transformation/es6-computed-property-names-loose/single/actual.js b/test/fixtures/transformation/es6-computed-property-names-loose/single/actual.js
new file mode 100644
index 0000000000..04ec89b5ce
--- /dev/null
+++ b/test/fixtures/transformation/es6-computed-property-names-loose/single/actual.js
@@ -0,0 +1,3 @@
+var obj = {
+  ["x" + foo]: "heh"
+};
diff --git a/test/fixtures/transformation/es6-computed-property-names-loose/single/expected.js b/test/fixtures/transformation/es6-computed-property-names-loose/single/expected.js
new file mode 100644
index 0000000000..627faff494
--- /dev/null
+++ b/test/fixtures/transformation/es6-computed-property-names-loose/single/expected.js
@@ -0,0 +1,8 @@
+"use strict";
+
+var obj = (function () {
+  var _obj = {};
+
+  _obj["x" + foo] = "heh";
+  return _obj;
+})();
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-computed-property-names-loose/this/actual.js b/test/fixtures/transformation/es6-computed-property-names-loose/this/actual.js
new file mode 100644
index 0000000000..3e3a34ef12
--- /dev/null
+++ b/test/fixtures/transformation/es6-computed-property-names-loose/this/actual.js
@@ -0,0 +1,3 @@
+var obj = {
+  ["x" + this.foo]: "heh"
+};
diff --git a/test/fixtures/transformation/es6-computed-property-names-loose/this/expected.js b/test/fixtures/transformation/es6-computed-property-names-loose/this/expected.js
new file mode 100644
index 0000000000..23b5ee17e4
--- /dev/null
+++ b/test/fixtures/transformation/es6-computed-property-names-loose/this/expected.js
@@ -0,0 +1,9 @@
+"use strict";
+
+var _this = this;
+var obj = (function () {
+  var _obj = {};
+
+  _obj["x" + _this.foo] = "heh";
+  return _obj;
+})();
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-computed-property-names-loose/two/actual.js b/test/fixtures/transformation/es6-computed-property-names-loose/two/actual.js
new file mode 100644
index 0000000000..c63046dd19
--- /dev/null
+++ b/test/fixtures/transformation/es6-computed-property-names-loose/two/actual.js
@@ -0,0 +1,4 @@
+var obj = {
+  first: "first",
+  ["second"]: "second",
+};
diff --git a/test/fixtures/transformation/es6-computed-property-names-loose/two/expected.js b/test/fixtures/transformation/es6-computed-property-names-loose/two/expected.js
new file mode 100644
index 0000000000..42ef0c1e64
--- /dev/null
+++ b/test/fixtures/transformation/es6-computed-property-names-loose/two/expected.js
@@ -0,0 +1,9 @@
+"use strict";
+
+var obj = (function () {
+  var _obj = {};
+
+  _obj.first = "first";
+  _obj.second = "second";
+  return _obj;
+})();
diff --git a/test/fixtures/transformation/es6-computed-property-names-loose/variable/actual.js b/test/fixtures/transformation/es6-computed-property-names-loose/variable/actual.js
new file mode 100644
index 0000000000..13d8e7f24a
--- /dev/null
+++ b/test/fixtures/transformation/es6-computed-property-names-loose/variable/actual.js
@@ -0,0 +1,3 @@
+var foo = {
+  [bar]: "foobar"
+};
diff --git a/test/fixtures/transformation/es6-computed-property-names-loose/variable/expected.js b/test/fixtures/transformation/es6-computed-property-names-loose/variable/expected.js
new file mode 100644
index 0000000000..6f691f0fd6
--- /dev/null
+++ b/test/fixtures/transformation/es6-computed-property-names-loose/variable/expected.js
@@ -0,0 +1,8 @@
+"use strict";
+
+var foo = (function () {
+  var _foo = {};
+
+  _foo[bar] = "foobar";
+  return _foo;
+})();
diff --git a/test/fixtures/transformation/es6-for-of-loose/identifier/actual.js b/test/fixtures/transformation/es6-for-of-loose/identifier/actual.js
new file mode 100644
index 0000000000..ddd15051ba
--- /dev/null
+++ b/test/fixtures/transformation/es6-for-of-loose/identifier/actual.js
@@ -0,0 +1,3 @@
+for (i of arr) {
+
+}
diff --git a/test/fixtures/transformation/es6-for-of-loose/identifier/expected.js b/test/fixtures/transformation/es6-for-of-loose/identifier/expected.js
new file mode 100644
index 0000000000..4a7ea3a6a5
--- /dev/null
+++ b/test/fixtures/transformation/es6-for-of-loose/identifier/expected.js
@@ -0,0 +1,15 @@
+"use strict";
+
+for (var _iterator = arr,
+    _isArray = Array.isArray(_iterator),
+    _i = 0,
+    _iterator = _isArray ? _iterator : _iterator[Symbol.iterator]();;) {
+  if (_isArray) {
+    if (_i >= _iterator.length) break;
+    i = _iterator[_i++];
+  } else {
+    _i = _iterator.next();
+    if (_i.done) break;
+    i = _i.value;
+  }
+}
diff --git a/test/fixtures/transformation/es6-for-of-loose/let/actual.js b/test/fixtures/transformation/es6-for-of-loose/let/actual.js
new file mode 100644
index 0000000000..f1e32392de
--- /dev/null
+++ b/test/fixtures/transformation/es6-for-of-loose/let/actual.js
@@ -0,0 +1,3 @@
+for (let i of arr) {
+
+}
diff --git a/test/fixtures/transformation/es6-for-of-loose/let/expected.js b/test/fixtures/transformation/es6-for-of-loose/let/expected.js
new file mode 100644
index 0000000000..94848fe0c1
--- /dev/null
+++ b/test/fixtures/transformation/es6-for-of-loose/let/expected.js
@@ -0,0 +1,16 @@
+"use strict";
+
+for (var _iterator = arr,
+    _isArray = Array.isArray(_iterator),
+    _i = 0,
+    _iterator = _isArray ? _iterator : _iterator[Symbol.iterator]();;) {
+  var i = undefined;
+  if (_isArray) {
+    if (_i >= _iterator.length) break;
+    i = _iterator[_i++];
+  } else {
+    _i = _iterator.next();
+    if (_i.done) break;
+    i = _i.value;
+  }
+}
diff --git a/test/fixtures/transformation/es6-for-of-loose/multiple/actual.js b/test/fixtures/transformation/es6-for-of-loose/multiple/actual.js
new file mode 100644
index 0000000000..d9c969b809
--- /dev/null
+++ b/test/fixtures/transformation/es6-for-of-loose/multiple/actual.js
@@ -0,0 +1,7 @@
+for (var i of arr) {
+
+}
+
+for (var i of numbers) {
+
+}
diff --git a/test/fixtures/transformation/es6-for-of-loose/multiple/expected.js b/test/fixtures/transformation/es6-for-of-loose/multiple/expected.js
new file mode 100644
index 0000000000..a20dee268b
--- /dev/null
+++ b/test/fixtures/transformation/es6-for-of-loose/multiple/expected.js
@@ -0,0 +1,31 @@
+"use strict";
+
+for (var _iterator = arr,
+    _isArray = Array.isArray(_iterator),
+    _i = 0,
+    _iterator = _isArray ? _iterator : _iterator[Symbol.iterator]();;) {
+  var i;
+  if (_isArray) {
+    if (_i >= _iterator.length) break;
+    i = _iterator[_i++];
+  } else {
+    _i = _iterator.next();
+    if (_i.done) break;
+    i = _i.value;
+  }
+}
+
+for (var _iterator2 = numbers,
+    _isArray2 = Array.isArray(_iterator2),
+    _i2 = 0,
+    _iterator2 = _isArray2 ? _iterator2 : _iterator2[Symbol.iterator]();;) {
+  var i;
+  if (_isArray2) {
+    if (_i2 >= _iterator2.length) break;
+    i = _iterator2[_i2++];
+  } else {
+    _i2 = _iterator2.next();
+    if (_i2.done) break;
+    i = _i2.value;
+  }
+}
diff --git a/test/fixtures/transformation/es6-for-of-loose/options.json b/test/fixtures/transformation/es6-for-of-loose/options.json
new file mode 100644
index 0000000000..c2821829bf
--- /dev/null
+++ b/test/fixtures/transformation/es6-for-of-loose/options.json
@@ -0,0 +1,3 @@
+{
+  "loose": ["forOf"]
+}
diff --git a/test/fixtures/transformation/es6-for-of-loose/var/actual.js b/test/fixtures/transformation/es6-for-of-loose/var/actual.js
new file mode 100644
index 0000000000..48e5f59b2c
--- /dev/null
+++ b/test/fixtures/transformation/es6-for-of-loose/var/actual.js
@@ -0,0 +1,3 @@
+for (var i of arr) {
+
+}
diff --git a/test/fixtures/transformation/es6-for-of-loose/var/expected.js b/test/fixtures/transformation/es6-for-of-loose/var/expected.js
new file mode 100644
index 0000000000..3695bf3454
--- /dev/null
+++ b/test/fixtures/transformation/es6-for-of-loose/var/expected.js
@@ -0,0 +1,16 @@
+"use strict";
+
+for (var _iterator = arr,
+    _isArray = Array.isArray(_iterator),
+    _i = 0,
+    _iterator = _isArray ? _iterator : _iterator[Symbol.iterator]();;) {
+  var i;
+  if (_isArray) {
+    if (_i >= _iterator.length) break;
+    i = _iterator[_i++];
+  } else {
+    _i = _iterator.next();
+    if (_i.done) break;
+    i = _i.value;
+  }
+}
diff --git a/test/fixtures/transformation/es6-generators/include-regenerator/actual.js b/test/fixtures/transformation/es6-generators/include-regenerator/actual.js
new file mode 100644
index 0000000000..d82da75f43
--- /dev/null
+++ b/test/fixtures/transformation/es6-generators/include-regenerator/actual.js
@@ -0,0 +1 @@
+function *x() {}
diff --git a/test/fixtures/transformation/es6-generators/include-regenerator/expected.js b/test/fixtures/transformation/es6-generators/include-regenerator/expected.js
new file mode 100644
index 0000000000..3b1d9b0960
--- /dev/null
+++ b/test/fixtures/transformation/es6-generators/include-regenerator/expected.js
@@ -0,0 +1,400 @@
+"use strict";
+
+!(function () {
+  var hasOwn = Object.prototype.hasOwnProperty;
+  var undefined;
+  var iteratorSymbol = typeof Symbol === "function" && Symbol.iterator || "@@iterator";
+  if (typeof regeneratorRuntime === "object") {
+    return;
+  }
+  var runtime = regeneratorRuntime = typeof exports === "undefined" ? {} : exports;
+  function wrap(innerFn, outerFn, self, tryList) {
+    return new Generator(innerFn, outerFn, self || null, tryList || []);
+  }
+
+  runtime.wrap = wrap;
+  var GenStateSuspendedStart = "suspendedStart";
+
+  var GenStateSuspendedYield = "suspendedYield";
+
+  var GenStateExecuting = "executing";
+
+  var GenStateCompleted = "completed";
+
+  var ContinueSentinel = {};
+
+  function GeneratorFunction() {}
+
+  function GeneratorFunctionPrototype() {}
+
+  var Gp = GeneratorFunctionPrototype.prototype = Generator.prototype;
+  GeneratorFunction.prototype = Gp.constructor = GeneratorFunctionPrototype;
+  GeneratorFunctionPrototype.constructor = GeneratorFunction;
+  GeneratorFunction.displayName = "GeneratorFunction";
+  runtime.isGeneratorFunction = function (genFun) {
+    var ctor = typeof genFun === "function" && genFun.constructor;
+    return ctor ? ctor === GeneratorFunction || (ctor.displayName || ctor.name) === "GeneratorFunction" : false;
+  };
+
+  runtime.mark = function (genFun) {
+    genFun.__proto__ = GeneratorFunctionPrototype;
+    genFun.prototype = Object.create(Gp);
+    return genFun;
+  };
+
+  runtime.async = function (innerFn, outerFn, self, tryList) {
+    return new Promise(function (resolve, reject) {
+      var generator = wrap(innerFn, outerFn, self, tryList);
+
+      var callNext = step.bind(generator.next);
+
+      var callThrow = step.bind(generator["throw"]);
+
+      function step(arg) {
+        try {
+          var info = this(arg);
+
+          var value = info.value;
+        } catch (error) {
+          return reject(error);
+        }
+        if (info.done) {
+          resolve(value);
+        } else {
+          Promise.resolve(value).then(callNext, callThrow);
+        }
+      }
+
+      callNext();
+    });
+  };
+
+  function Generator(innerFn, outerFn, self, tryList) {
+    var generator = outerFn ? Object.create(outerFn.prototype) : this;
+    var context = new Context(tryList);
+    var state = GenStateSuspendedStart;
+    function invoke(method, arg) {
+      if (state === GenStateExecuting) {
+        throw new Error("Generator is already running");
+      }
+      if (state === GenStateCompleted) {
+        return doneResult();
+      }
+      while (true) {
+        var delegate = context.delegate;
+        if (delegate) {
+          try {
+            var info = delegate.iterator[method](arg);
+
+            method = "next";
+            arg = undefined;
+          } catch (uncaught) {
+            context.delegate = null;
+            method = "throw";
+            arg = uncaught;
+            continue;
+          }
+          if (info.done) {
+            context[delegate.resultName] = info.value;
+            context.next = delegate.nextLoc;
+          } else {
+            state = GenStateSuspendedYield;
+            return info;
+          }
+          context.delegate = null;
+        }
+        if (method === "next") {
+          if (state === GenStateSuspendedStart && typeof arg !== "undefined") {
+            throw new TypeError("attempt to send " + JSON.stringify(arg) + " to newborn generator");
+          }
+          if (state === GenStateSuspendedYield) {
+            context.sent = arg;
+          } else {
+            delete context.sent;
+          }
+        } else if (method === "throw") {
+          if (state === GenStateSuspendedStart) {
+            state = GenStateCompleted;
+            throw arg;
+          }
+          if (context.dispatchException(arg)) {
+            method = "next";
+            arg = undefined;
+          }
+        } else if (method === "return") {
+          context.abrupt("return", arg);
+        }
+        state = GenStateExecuting;
+        try {
+          var value = innerFn.call(self, context);
+
+          state = context.done ? GenStateCompleted : GenStateSuspendedYield;
+          var info = {
+            value: value,
+            done: context.done
+          };
+
+          if (value === ContinueSentinel) {
+            if (context.delegate && method === "next") {
+              arg = undefined;
+            }
+          } else {
+            return info;
+          }
+        } catch (thrown) {
+          state = GenStateCompleted;
+          if (method === "next") {
+            context.dispatchException(thrown);
+          } else {
+            arg = thrown;
+          }
+        }
+      }
+    }
+
+    generator.next = invoke.bind(generator, "next");
+    generator["throw"] = invoke.bind(generator, "throw");
+    generator["return"] = invoke.bind(generator, "return");
+    return generator;
+  }
+
+  Gp[iteratorSymbol] = function () {
+    return this;
+  };
+
+  Gp.toString = function () {
+    return "[object Generator]";
+  };
+
+  function pushTryEntry(triple) {
+    var entry = {
+      tryLoc: triple[0]
+    };
+
+    if (1 in triple) {
+      entry.catchLoc = triple[1];
+    }
+    if (2 in triple) {
+      entry.finallyLoc = triple[2];
+    }
+    this.tryEntries.push(entry);
+  }
+
+  function resetTryEntry(entry, i) {
+    var record = entry.completion || {};
+    record.type = i === 0 ? "normal" : "return";
+    delete record.arg;
+    entry.completion = record;
+  }
+
+  function Context(tryList) {
+    this.tryEntries = [{
+      tryLoc: "root"
+    }];
+    tryList.forEach(pushTryEntry, this);
+
+    this.reset();
+  }
+
+  runtime.keys = function (object) {
+    var keys = [];
+
+    for (var key in object) {
+      keys.push(key);
+    }
+
+    keys.reverse();
+
+    return function next() {
+      while (keys.length) {
+        var key = keys.pop();
+
+        if (key in object) {
+          next.value = key;
+          next.done = false;
+          return next;
+        }
+      }
+      next.done = true;
+      return next;
+    };
+  };
+
+  function values(iterable) {
+    if (iterable) {
+      var iteratorMethod = iterable[iteratorSymbol];
+      if (iteratorMethod) {
+        return iteratorMethod.call(iterable);
+      }
+      if (typeof iterable.next === "function") {
+        return iterable;
+      }
+      if (!isNaN(iterable.length)) {
+        var i = -1;
+        function next() {
+          while (++i < iterable.length) {
+            if (hasOwn.call(iterable, i)) {
+              next.value = iterable[i];
+              next.done = false;
+              return next;
+            }
+          }
+          next.value = undefined;
+          next.done = true;
+          return next;
+        }
+
+        return next.next = next;
+      }
+    }
+    return {
+      next: doneResult
+    };
+  }
+
+  runtime.values = values;
+  function doneResult() {
+    return {
+      value: undefined,
+      done: true
+    };
+  }
+
+  Context.prototype = {
+    constructor: Context,
+    reset: function () {
+      this.prev = 0;
+      this.next = 0;
+      this.sent = undefined;
+      this.done = false;
+      this.delegate = null;
+      this.tryEntries.forEach(resetTryEntry);
+
+      for (var tempIndex = 0, tempName; hasOwn.call(this, tempName = "t" + tempIndex) || tempIndex < 20; ++tempIndex) {
+        this[tempName] = null;
+      }
+    },
+    stop: function () {
+      this.done = true;
+      var rootEntry = this.tryEntries[0];
+      var rootRecord = rootEntry.completion;
+      if (rootRecord.type === "throw") {
+        throw rootRecord.arg;
+      }
+      return this.rval;
+    },
+    dispatchException: function (exception) {
+      if (this.done) {
+        throw exception;
+      }
+      var context = this;
+      function handle(loc, caught) {
+        record.type = "throw";
+        record.arg = exception;
+        context.next = loc;
+        return !!caught;
+      }
+
+      for (var i = this.tryEntries.length - 1; i >= 0; --i) {
+        var entry = this.tryEntries[i];
+        var record = entry.completion;
+        if (entry.tryLoc === "root") {
+          return handle("end");
+        }
+        if (entry.tryLoc <= this.prev) {
+          var hasCatch = hasOwn.call(entry, "catchLoc");
+
+          var hasFinally = hasOwn.call(entry, "finallyLoc");
+
+          if (hasCatch && hasFinally) {
+            if (this.prev < entry.catchLoc) {
+              return handle(entry.catchLoc, true);
+            } else if (this.prev < entry.finallyLoc) {
+              return handle(entry.finallyLoc);
+            }
+          } else if (hasCatch) {
+            if (this.prev < entry.catchLoc) {
+              return handle(entry.catchLoc, true);
+            }
+          } else if (hasFinally) {
+            if (this.prev < entry.finallyLoc) {
+              return handle(entry.finallyLoc);
+            }
+          } else {
+            throw new Error("try statement without catch or finally");
+          }
+        }
+      }
+    },
+    _findFinallyEntry: function (finallyLoc) {
+      for (var i = this.tryEntries.length - 1; i >= 0; --i) {
+        var entry = this.tryEntries[i];
+        if (entry.tryLoc <= this.prev && hasOwn.call(entry, "finallyLoc") && (entry.finallyLoc === finallyLoc || this.prev < entry.finallyLoc)) {
+          return entry;
+        }
+      }
+    },
+    abrupt: function (type, arg) {
+      var entry = this._findFinallyEntry();
+
+      var record = entry ? entry.completion : {};
+      record.type = type;
+      record.arg = arg;
+      if (entry) {
+        this.next = entry.finallyLoc;
+      } else {
+        this.complete(record);
+      }
+      return ContinueSentinel;
+    },
+    complete: function (record) {
+      if (record.type === "throw") {
+        throw record.arg;
+      }
+      if (record.type === "break" || record.type === "continue") {
+        this.next = record.arg;
+      } else if (record.type === "return") {
+        this.rval = record.arg;
+        this.next = "end";
+      }
+      return ContinueSentinel;
+    },
+    finish: function (finallyLoc) {
+      var entry = this._findFinallyEntry(finallyLoc);
+
+      return this.complete(entry.completion);
+    },
+    "catch": function (tryLoc) {
+      for (var i = this.tryEntries.length - 1; i >= 0; --i) {
+        var entry = this.tryEntries[i];
+        if (entry.tryLoc === tryLoc) {
+          var record = entry.completion;
+          if (record.type === "throw") {
+            var thrown = record.arg;
+            resetTryEntry(entry, i);
+          }
+          return thrown;
+        }
+      }
+
+      throw new Error("illegal catch attempt");
+    },
+    delegateYield: function (iterable, resultName, nextLoc) {
+      this.delegate = {
+        iterator: values(iterable),
+        resultName: resultName,
+        nextLoc: nextLoc
+      };
+      return ContinueSentinel;
+    }
+  };
+})();
+var x = regeneratorRuntime.mark(function x() {
+  return regeneratorRuntime.wrap(function x$(context$1$0) {
+    while (1) switch (context$1$0.prev = context$1$0.next) {
+      case 0:
+      case "end":
+        return context$1$0.stop();
+    }
+  }, x, this);
+});
diff --git a/test/fixtures/transformation/es6-generators/include-regenerator/options.json b/test/fixtures/transformation/es6-generators/include-regenerator/options.json
new file mode 100644
index 0000000000..b61f12c5b9
--- /dev/null
+++ b/test/fixtures/transformation/es6-generators/include-regenerator/options.json
@@ -0,0 +1,4 @@
+{
+  "noCheckAst": true,
+  "includeRegenerator": true
+}
diff --git a/test/fixtures/transformation/es6-template-literals/tag-loose/actual.js b/test/fixtures/transformation/es6-template-literals/tag-loose/actual.js
new file mode 100644
index 0000000000..7fe1864736
--- /dev/null
+++ b/test/fixtures/transformation/es6-template-literals/tag-loose/actual.js
@@ -0,0 +1 @@
+var foo = bar`wow\na${ 42 }b ${_.foobar()}`;
diff --git a/test/fixtures/transformation/es6-template-literals/tag-loose/expected.js b/test/fixtures/transformation/es6-template-literals/tag-loose/expected.js
new file mode 100644
index 0000000000..7be77f1baa
--- /dev/null
+++ b/test/fixtures/transformation/es6-template-literals/tag-loose/expected.js
@@ -0,0 +1,8 @@
+"use strict";
+
+var _taggedTemplateLiteralLoose = function (strings, raw) {
+  strings.raw = raw;
+  return strings;
+};
+
+var foo = bar(_taggedTemplateLiteralLoose(["wow\na", "b ", ""], ["wow\\na", "b ", ""]), 42, _.foobar());
diff --git a/test/fixtures/transformation/es6-template-literals/tag-loose/options.json b/test/fixtures/transformation/es6-template-literals/tag-loose/options.json
new file mode 100644
index 0000000000..fe669cb1d4
--- /dev/null
+++ b/test/fixtures/transformation/es6-template-literals/tag-loose/options.json
@@ -0,0 +1,3 @@
+{
+  "loose": ["templateLiterals"]
+}
diff --git a/test/fixtures/transformation/optional-classes-fast-super/options.json b/test/fixtures/transformation/optional-classes-fast-super/options.json
deleted file mode 100644
index a1ebbb1755..0000000000
--- a/test/fixtures/transformation/optional-classes-fast-super/options.json
+++ /dev/null
@@ -1,3 +0,0 @@
-{
-  "optional": ["classesFastSuper"]
-}
diff --git a/test/fixtures/transformation/optional-core-aliasing/aliased-constructors/actual.js b/test/fixtures/transformation/optional-core-aliasing/aliased-constructors/actual.js
new file mode 100644
index 0000000000..b7c61b92b0
--- /dev/null
+++ b/test/fixtures/transformation/optional-core-aliasing/aliased-constructors/actual.js
@@ -0,0 +1,7 @@
+obj.constructor === Object;
+obj.constructor === Promise;
+
+Symbol();
+Symbol("test");
+
+new Map();
diff --git a/test/fixtures/transformation/optional-core-aliasing/map-symbol/expected.js b/test/fixtures/transformation/optional-core-aliasing/aliased-constructors/expected.js
similarity index 70%
rename from test/fixtures/transformation/optional-core-aliasing/map-symbol/expected.js
rename to test/fixtures/transformation/optional-core-aliasing/aliased-constructors/expected.js
index d67311567b..7c6e3f9ba2 100644
--- a/test/fixtures/transformation/optional-core-aliasing/map-symbol/expected.js
+++ b/test/fixtures/transformation/optional-core-aliasing/aliased-constructors/expected.js
@@ -6,5 +6,10 @@ var _interopRequire = function (obj) {
 
 var _core = _interopRequire(require("core-js/library"));
 
-_core.Symbol("test");
+obj.constructor === Object;
+obj.constructor === _core.Promise;
+
 _core.Symbol();
+_core.Symbol("test");
+
+new _core.Map();
diff --git a/test/fixtures/transformation/optional-core-aliasing/ignore-natives/actual.js b/test/fixtures/transformation/optional-core-aliasing/ignore-natives/actual.js
deleted file mode 100644
index 60fe1ccd57..0000000000
--- a/test/fixtures/transformation/optional-core-aliasing/ignore-natives/actual.js
+++ /dev/null
@@ -1 +0,0 @@
-obj.constructor === Object;
diff --git a/test/fixtures/transformation/optional-core-aliasing/ignore-natives/expected.js b/test/fixtures/transformation/optional-core-aliasing/ignore-natives/expected.js
deleted file mode 100644
index 9ce5ba07b1..0000000000
--- a/test/fixtures/transformation/optional-core-aliasing/ignore-natives/expected.js
+++ /dev/null
@@ -1,9 +0,0 @@
-"use strict";
-
-var _interopRequire = function (obj) {
-  return obj && (obj["default"] || obj);
-};
-
-var _core = _interopRequire(require("core-js/library"));
-
-obj.constructor === Object;
diff --git a/test/fixtures/transformation/optional-core-aliasing/map-symbol/actual.js b/test/fixtures/transformation/optional-core-aliasing/map-symbol/actual.js
deleted file mode 100644
index 5ebaadcd41..0000000000
--- a/test/fixtures/transformation/optional-core-aliasing/map-symbol/actual.js
+++ /dev/null
@@ -1,2 +0,0 @@
-Symbol("test");
-Symbol();
diff --git a/test/test262.js b/test/test262.js
index b8b8f8cb3d..12e31a8927 100644
--- a/test/test262.js
+++ b/test/test262.js
@@ -1,4 +1,4 @@
-if (process.env.SIMPLE_6TO5_TESTS) return;
+if (process.env.SIMPLE_6TO5_TESTS || process.env.running_under_istanbul) return;
 
 var transform = require("../lib/6to5/transformation/transform");
 var readdir   = require("fs-readdir-recursive");