v3.5.2

Since now we have runtime helper, we don't need
expression -> statement conversions anymore.

.editorconfig

@@ -6,6 +6,6 @@ charset = utf-8
 trim_trailing_whitespace = true
 insert_final_newline = true
 
-[*.js]
+[*.{js,json}]
 indent_style = space
 indent_size = 2

CHANGELOG.md

@@ -11,6 +11,32 @@
 
 _Note: Gaps between patch versions are faulty/broken releases._
 
+## 3.5.2
+
+ * Disable `es6.tailCall` temporairly after reports of it breaking.
+
+## 3.5.1
+
+ * **Polish**
+  * Allow tail calls to work across files without the runtime.
+ * **Internal**
+  * Upgrade `acorn-6to5`.
+
+## 3.5.0
+
+ * **Bug Fix**
+  * Destructuring patterns as the left operator in `ForInStatement`/`ForOfStatement`.
+ * **Polish**
+  * Make default parameter IIFE invocation smarter.
+  * Make `__esModule` flag non-enumerable. Thanks [@daliwali](https://github.com/daliwali)!
+ * **Internal**
+  * More performance improvements.
+  * Parsing is now ~30% faster thanks to [marijnh/acorn@7264bc0178e7e6af7cfe02e9e0c6b26ee0e6007f](https://github.com/marijnh/acorn/commit/7264bc0178e7e6af7cfe02e9e0c6b26ee0e6007f).
+ * **New Feature**
+  * Optional `es6.blockScopingTDZ` is now completely functional and handles all edgecases.
+  * `super` in object literals.
+  * Tail call optimisation. Thanks [@RReverser](https://github.com/RReverser)!
+
 ## 3.4.1
 
  * **Bug Fix**

lib/6to5/transformation/file.js

@@ -54,7 +54,10 @@ File.helpers = [
   "get",
   "set",
   "class-call-check",
-  "object-destructuring-empty"
+  "object-destructuring-empty",
+  "temporal-undefined",
+  "temporal-assert-defined",
+  "tail-call"
 ];
 
 File.validOptions = [
@@ -297,7 +300,7 @@ File.prototype.isConsequenceExpressionStatement = function (node) {
 
 File.prototype.addHelper = function (name) {
   if (!contains(File.helpers, name)) {
-    throw new ReferenceError("unknown declaration " + name);
+    throw new ReferenceError("Unknown helper " + name);
   }
 
   var program = this.ast.program;

lib/6to5/transformation/helpers/name-method.js

@@ -36,15 +36,18 @@ exports.property = function (node, file, scope) {
 
   scope.traverse(node, visitor, state);
 
+  var method = node.value;
+
   if (state.selfReference) {
-    // todo: support generators
-    node.value = util.template("property-method-assignment-wrapper", {
-      FUNCTION: node.value,
+    var templateName = "property-method-assignment-wrapper";
+    if (method.generator) templateName += "-generator";
+    node.value = util.template(templateName, {
+      FUNCTION: method,
       FUNCTION_ID: key,
       FUNCTION_KEY: scope.generateUidIdentifier(id),
       WRAPPER_KEY: scope.generateUidIdentifier(id + "Wrapper")
     });
   } else {
-    node.value.id = key;
+    method.id = key;
   }
 };

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

@@ -8,13 +8,17 @@ var t = require("../../types");
  * Description
  *
  * @param {Object} opts
+ * @param {Boolean} [inClass]
  */
 
-function ReplaceSupers(opts) {
-  this.topLevelThisReference = null;
+function ReplaceSupers(opts, inClass) {
+  this.topLevelThisReference = opts.topLevelThisReference;
   this.methodNode            = opts.methodNode;
   this.className             = opts.className;
   this.superName             = opts.superName;
+  this.isStatic              = opts.isStatic;
+  this.hasSuper              = false;
+  this.inClass               = inClass;
   this.isLoose               = opts.isLoose;
   this.scope                 = opts.scope;
   this.file                  = opts.file;
@@ -28,19 +32,21 @@ function ReplaceSupers(opts) {
  *   _set(Object.getPrototypeOf(CLASS.prototype), "METHOD", "VALUE", this)
  *
  * @param {Node} property
- * @param {boolean} isStatic
- * @param {boolean} isComputed
+ * @param {Node} value
+ * @param {Boolean} isComputed
+ * @param {Node} thisExpression
  *
  * @returns {Node}
  */
-ReplaceSupers.prototype.setSuperProperty = function (property, value, isStatic, isComputed, thisExpression) {
+
+ReplaceSupers.prototype.setSuperProperty = function (property, value, isComputed, thisExpression) {
   return t.callExpression(
     this.file.addHelper("set"),
     [
       t.callExpression(
         t.memberExpression(t.identifier("Object"), t.identifier("getPrototypeOf")),
         [
-          isStatic ? this.className : t.memberExpression(this.className, t.identifier("prototype"))
+          this.isStatic ? this.className : t.memberExpression(this.className, t.identifier("prototype"))
         ]
       ),
       isComputed ? property : t.literal(property.name),
@@ -58,20 +64,20 @@ ReplaceSupers.prototype.setSuperProperty = function (property, value, isStatic,
  *   _get(Object.getPrototypeOf(CLASS.prototype), "METHOD", this)
  *
  * @param {Node} property
- * @param {boolean} isStatic
- * @param {boolean} isComputed
+ * @param {Boolean} isComputed
+ * @param {Node} thisExpression
  *
  * @returns {Node}
  */
 
-ReplaceSupers.prototype.getSuperProperty = function (property, isStatic, isComputed, thisExpression) {
+ReplaceSupers.prototype.getSuperProperty = function (property, isComputed, thisExpression) {
   return t.callExpression(
     this.file.addHelper("get"),
     [
       t.callExpression(
         t.memberExpression(t.identifier("Object"), t.identifier("getPrototypeOf")),
         [
-          isStatic ? this.className : t.memberExpression(this.className, t.identifier("prototype"))
+          this.isStatic ? this.className : t.memberExpression(this.className, t.identifier("prototype"))
         ]
       ),
       isComputed ? property : t.literal(property.name),
@@ -153,7 +159,8 @@ ReplaceSupers.prototype.getThisReference = function () {
  * @returns {Object}
  */
 
-ReplaceSupers.prototype.getLooseSuperProperty = function (methodNode, id, parent) {
+ReplaceSupers.prototype.getLooseSuperProperty = function (id, parent) {
+  var methodNode = this.methodNode;
   var methodName = methodNode.key;
   var superName  = this.superName || t.identifier("Function");
 
@@ -195,13 +202,15 @@ ReplaceSupers.prototype.getLooseSuperProperty = function (methodNode, id, parent
 
 ReplaceSupers.prototype.looseHandle = function (getThisReference, node, parent) {
   if (t.isIdentifier(node, { name: "super" })) {
-    return this.getLooseSuperProperty(this.methodNode, node, parent);
+    this.hasSuper = true;
+    return this.getLooseSuperProperty(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);
+    this.hasSuper = true;
     t.appendToMemberExpression(callee, t.identifier("call"));
     node.arguments.unshift(getThisReference());
   }
@@ -237,7 +246,7 @@ ReplaceSupers.prototype.specHandle = function (getThisReference, node, parent) {
       // bare `super` call is illegal inside non-constructors
       //  - https://esdiscuss.org/topic/super-call-in-methods
       //  - https://twitter.com/wycats/status/544553184396836864
-      if (methodNode.key.name !== "constructor") {
+      if (methodNode.key.name !== "constructor" || !this.inClass) {
         var methodName = methodNode.key.name || "METHOD_NAME";
         throw this.file.errorWithNode(node, "Direct super call is illegal in non-constructor, use super." + methodName + "() instead");
       }
@@ -253,13 +262,16 @@ ReplaceSupers.prototype.specHandle = function (getThisReference, node, parent) {
     computed = node.computed;
   } else if (t.isAssignmentExpression(node) && isSuper(node.left.object, node.left) && methodNode.kind === "set") {
     // super.name = "val"; -> _set(Object.getPrototypeOf(ClassName.prototype), "name", this);
-    return this.setSuperProperty(node.left.property, node.right, methodNode.static, node.left.computed, getThisReference());
+    this.hasSuper = true;
+    return this.setSuperProperty(node.left.property, node.right, node.left.computed, getThisReference());
   }
 
   if (!property) return;
 
+  this.hasSuper = true;
+
   thisReference = getThisReference();
-  var superProperty = this.getSuperProperty(property, methodNode.static, computed, thisReference);
+  var superProperty = this.getSuperProperty(property, computed, thisReference);
   if (args) {
     if (args.length === 1 && t.isSpreadElement(args[0])) {
       // super(...arguments);

lib/6to5/transformation/templates/default-parameter.js

@@ -1 +1 @@
-var VARIABLE_NAME = ARGUMENTS[ARGUMENT_KEY] === undefined ? DEFAULT_VALUE : ARGUMENTS[ARGUMENT_KEY];
+let VARIABLE_NAME = ARGUMENTS[ARGUMENT_KEY] === undefined ? DEFAULT_VALUE : ARGUMENTS[ARGUMENT_KEY];

lib/6to5/transformation/templates/exports-module-declaration.js

@@ -1 +1,3 @@
-exports.__esModule = true;
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});

lib/6to5/transformation/templates/property-method-assignment-wrapper-generator.js

@@ -0,0 +1,11 @@
+(function (FUNCTION_KEY) {
+  var WRAPPER_KEY = function* FUNCTION_ID() {
+    return yield* FUNCTION_KEY.apply(this, arguments);
+  };
+
+  WRAPPER_KEY.toString = function () {
+    return FUNCTION_KEY.toString();
+  };
+
+  return WRAPPER_KEY;
+})(FUNCTION)

lib/6to5/transformation/templates/set.js

@@ -4,21 +4,16 @@
   if (desc === undefined) {
     var parent = Object.getPrototypeOf(object);
 
-    if (parent === null) {
-      return;
-    } else {
+    if (parent !== null) {
       return set(parent, property, value, receiver);
     }
   } else if ("value" in desc && desc.writable) {
-    desc.value = value;
-    return;
+    return desc.value = value;
   } else {
     var setter = desc.set;
 
-    if (setter === undefined) {
-      return;
+    if (setter !== undefined) {
+      return setter.call(receiver, value);
     }
-
-    return setter.call(receiver, value);
   }
 });

lib/6to5/transformation/templates/tail-call.js

@@ -0,0 +1,23 @@
+(function () {
+  function Tail(func, args, context) {
+    this.func = func;
+    this.args = args;
+    this.context = context;
+  }
+
+  Tail.prototype._isTailDescriptor = true;
+
+  var isRunning = false;
+
+  return function (func, args, context) {
+    var result = new Tail(func, args, context);
+    if (!isRunning) {
+      isRunning = true;
+      do {
+        result = result.func.apply(result.context, result.args);
+      } while (result instanceof Tail || (result && result._isTailDescriptor));
+      isRunning = false;
+    }
+    return result;
+  };
+})()

lib/6to5/transformation/templates/temporal-assert-defined.js

@@ -0,0 +1,6 @@
+(function (val, name, undef) {
+  if (val === undef) {
+    throw new ReferenceError(name + " is not defined - temporal dead zone");
+  }
+  return true;
+})

lib/6to5/transformation/templates/temporal-undefined.js

@@ -0,0 +1 @@
+({})

lib/6to5/transformation/transformer-pass.js

@@ -29,7 +29,7 @@ TransformerPass.prototype.canRun = function () {
 
   // whitelist
   var whitelist = opts.whitelist;
-  if (whitelist.length && !contains(whitelist, key)) return false;
+  if (whitelist.length) return contains(whitelist, key);
 
   // optional
   if (transformer.optional && !contains(opts.optional, key)) return false;

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

@@ -12,22 +12,18 @@ var visitor = {
     // declared node is different in this scope
     if (scope.getBinding(node.name) !== declared) return;
 
-    var declaredLoc  = declared.loc;
-    var referenceLoc = node.loc;
+    var assert = t.callExpression(
+      state.file.addHelper("temporal-assert-defined"),
+      [node, t.literal(node.name), state.file.addHelper("temporal-undefined")]
+    );
 
-    if (!declaredLoc || !referenceLoc) return;
+    this.skip();
 
-    // does this reference appear on a line before the declaration?
-    var before = referenceLoc.start.line < declaredLoc.start.line;
-
-    if (referenceLoc.start.line === declaredLoc.start.line) {
-      // this reference appears on the same line
-      // check it appears before the declaration
-      before = referenceLoc.start.col < declaredLoc.start.col;
-    }
-
-    if (before) {
-      throw state.file.errorWithNode(node, "Temporal dead zone - accessing a variable before it's initialized");
+    if (t.isAssignmentExpression(parent) || t.isUpdateExpression(parent)) {
+      if (parent._ignoreBlockScopingTDZ) return;
+      this.parentPath.replaceNode(t.sequenceExpression([assert, parent]));
+    } else {
+      return t.logicalExpression("&&", assert, node);
     }
   }
 };

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

@@ -17,7 +17,7 @@ var isLet = function (node, parent) {
   if (node.kind !== "let") return false;
 
   // https://github.com/6to5/6to5/issues/255
-  if (!t.isFor(parent) || t.isFor(parent) && parent.left !== node) {
+  if (isLetInitable(node, parent)) {
     for (var i = 0; i < node.declarations.length; i++) {
       var declar = node.declarations[i];
       declar.init = declar.init || t.identifier("undefined");
@@ -29,6 +29,10 @@ var isLet = function (node, parent) {
   return true;
 };
 
+var isLetInitable = function (node, parent) {
+  return !t.isFor(parent) || t.isFor(parent) && parent.left !== node;
+};
+
 var isVar = function (node, parent) {
   return t.isVariableDeclaration(node, { kind: "var" }) && !isLet(node, parent);
 };
@@ -39,8 +43,26 @@ var standardizeLets = function (declars) {
   }
 };
 
-exports.VariableDeclaration = function (node, parent) {
-  isLet(node, parent);
+exports.VariableDeclaration = function (node, parent, scope, file) {
+  if (!isLet(node, parent)) return;
+
+  if (isLetInitable(node) && file.transformers["es6.blockScopingTDZ"].canRun()) {
+    var nodes = [node];
+
+    for (var i = 0; i < node.declarations.length; i++) {
+      var decl = node.declarations[i];
+      if (decl.init) {
+        var assign = t.assignmentExpression("=", decl.id, decl.init);
+        assign._ignoreBlockScopingTDZ = true;
+        nodes.push(t.expressionStatement(assign));
+      }
+      decl.init = file.addHelper("temporal-undefined");
+    }
+
+    node._blockHoist = 2;
+
+    return nodes;
+  }
 };
 
 exports.Loop = function (node, parent, scope, file) {

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

@@ -152,10 +152,11 @@ Class.prototype.buildBody = function () {
         methodNode: node,
         className:  this.className,
         superName:  this.superName,
+        isStatic:   node.static,
         isLoose:    this.isLoose,
         scope:      this.scope,
         file:       this.file
-      });
+      }, true);
       replaceSupers.replace();
 
       if (node.key.name === "constructor") {

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

@@ -112,6 +112,12 @@ Destructuring.prototype.pushObjectPattern = function (pattern, parentId) {
     ));
   }
 
+  if (pattern.properties.length > 1 && t.isMemberExpression(parentId)) {
+    var temp = this.scope.generateUidBasedOnNode(parentId, this.file);
+    this.nodes.push(this.buildVariableDeclaration(temp, parentId));
+    parentId = temp;
+  }
+
   for (var i = 0; i < pattern.properties.length; i++) {
     var prop = pattern.properties[i];
     if (t.isSpreadProperty(prop)) {
@@ -179,21 +185,40 @@ Destructuring.prototype.init = function (pattern, parentId) {
 
 exports.ForInStatement =
 exports.ForOfStatement = function (node, parent, scope, file) {
-  var declar = node.left;
-  if (!t.isVariableDeclaration(declar)) return;
+  var left = node.left;
 
-  var pattern = declar.declarations[0].id;
+  if (t.isPattern(left)) {
+    // for ({ length: k } in { abc: 3 });
+
+    var temp = scope.generateUidIdentifier("ref");
+
+    node.left = t.variableDeclaration("var", [
+      t.variableDeclarator(temp)
+    ]);
+
+    t.ensureBlock(node);
+
+    node.body.body.unshift(t.variableDeclaration("var", [
+      t.variableDeclarator(left, temp)
+    ]));
+
+    return;
+  }
+
+  if (!t.isVariableDeclaration(left)) return;
+
+  var pattern = left.declarations[0].id;
   if (!t.isPattern(pattern)) return;
 
   var key = scope.generateUidIdentifier("ref");
-  node.left = t.variableDeclaration(declar.kind, [
+  node.left = t.variableDeclaration(left.kind, [
     t.variableDeclarator(key, null)
   ]);
 
   var nodes = [];
 
   var destructuring = new Destructuring({
-    kind: declar.kind,
+    kind: left.kind,
     file: file,
     scope: scope,
     nodes: nodes
@@ -248,7 +273,7 @@ exports.CatchClause = function (node, parent, scope, file) {
   var nodes = [];
 
   var destructuring = new Destructuring({
-    kind: "var",
+    kind: "let",
     file: file,
     scope: scope,
     nodes: nodes
@@ -256,6 +281,8 @@ exports.CatchClause = function (node, parent, scope, file) {
   destructuring.init(pattern, ref);
 
   node.body.body = nodes.concat(node.body.body);
+
+  return node;
 };
 
 exports.ExpressionStatement = function (node, parent, scope, file) {

lib/6to5/transformation/transformers/es6/for-of.js

@@ -28,6 +28,8 @@ exports.ForOfStatement = function (node, parent, scope, file) {
   // push the rest of the original loop body onto our new body
   block.body = block.body.concat(node.body.body);
 
+  t.inherits(loop, node);
+
   // todo: find out why this is necessary? #538
   loop._scopeInfo = node._scopeInfo;
 

lib/6to5/transformation/transformers/es6/object-super.js

@@ -0,0 +1,34 @@
+"use strict";
+
+var ReplaceSupers = require("../../helpers/replace-supers");
+var t             = require("../../../types");
+
+exports.check = function (node) {
+  return t.isIdentifier(node, { name: "super" });
+};
+
+exports.Property = function (node, parent, scope, file) {
+  if (!node.method) return;
+
+  var value = node.value;
+  var thisExpr = scope.generateUidIdentifier("this");
+
+  var replaceSupers = new ReplaceSupers({
+    topLevelThisReference: thisExpr,
+    methodNode:            node,
+    className:             thisExpr,
+    isStatic:              true,
+    scope:                 scope,
+    file:                  file
+  });
+
+  replaceSupers.replace();
+
+  if (replaceSupers.hasSuper) {
+    value.body.body.unshift(
+      t.variableDeclaration("var", [
+        t.variableDeclarator(thisExpr, t.thisExpression())
+      ])
+    );
+  }
+};

lib/6to5/transformation/transformers/es6/parameters.default.js

@@ -9,21 +9,23 @@ exports.check = function (node) {
 
 var hasDefaults = function (node) {
   for (var i = 0; i < node.params.length; i++) {
-    if (t.isAssignmentPattern(node.params[i])) return true;
+    if (!t.isIdentifier(node.params[i])) return true;
   }
   return false;
 };
 
 var iifeVisitor = {
   enter: function (node, parent, scope, state) {
-    if (t.isReferencedIdentifier(node, parent) && state.scope.hasOwnReference(node.name)) {
-      state.iife = true;
-      this.stop();
-    }
+    if (!t.isReferencedIdentifier(node, parent)) return;
+    if (!state.scope.hasOwnBinding(node.name)) return;
+    if (state.scope.bindingEquals(node.name, node)) return;
+
+    state.iife = true;
+    this.stop();
   }
 };
 
-exports.Function = function (node, parent, scope) {
+exports.Function = function (node, parent, scope, file) {
   if (!hasDefaults(node)) return;
 
   t.ensureBlock(node);
@@ -37,11 +39,32 @@ exports.Function = function (node, parent, scope) {
 
   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);
+    file.checkNode(defNode);
+    defNode._blockHoist = node.params.length - i;
+    body.push(defNode);
+  };
+
   for (var i = 0; i < node.params.length; i++) {
     var param = node.params[i];
 
     if (!t.isAssignmentPattern(param)) {
-      lastNonDefaultParam = +i + 1;
+      lastNonDefaultParam = i + 1;
+
+      if (!t.isIdentifier(param)) {
+        scope.traverse(param, iifeVisitor, state);
+      }
+
+      if (file.transformers["es6.blockScopingTDZ"].canRun()) {
+        pushDefNode(param, t.identifier("undefined"), i);
+      }
+
       continue;
     }
 
@@ -58,14 +81,7 @@ exports.Function = function (node, parent, scope) {
       }
     }
 
-    var defNode = util.template("default-parameter", {
-      VARIABLE_NAME: left,
-      DEFAULT_VALUE: right,
-      ARGUMENT_KEY:  t.literal(+i),
-      ARGUMENTS:     argsIdentifier
-    }, true);
-    defNode._blockHoist = node.params.length - i;
-    body.push(defNode);
+    pushDefNode(left, right, i);
   }
 
   // we need to cut off all trailing default parameters

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

@@ -73,8 +73,8 @@ exports.CallExpression = function (node, parent, scope, file) {
   } else {
     nodes = build(args, file);
   }
-  var first = nodes.shift();
 
+  var first = nodes.shift();
   if (nodes.length) {
     node.arguments.push(t.callExpression(t.memberExpression(first, t.identifier("concat")), nodes));
   } else {

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

@@ -0,0 +1,118 @@
+"use strict";
+
+/*
+var t    = require("../../../types");
+
+function transformExpression(node, scope, state) {
+  if (!node) return;
+
+  return (function subTransform(node) {
+    switch (node.type) {
+      case "ConditionalExpression":
+        // any value of ternary operator can be final one
+        subTransform(node.consequent);
+        subTransform(node.alternate);
+        break;
+
+      case "LogicalExpression":
+        // only right expression can be final and so optimized
+        subTransform(node.right);
+        break;
+
+      case "SequenceExpression":
+        // only last element of sequence can be optimized
+        var seq = node.expressions;
+        subTransform(seq[seq.length - 1]);
+        break;
+
+      case "CallExpression":
+        var callee = node.callee, thisBinding;
+        var args = [callee];
+
+        // bind `this` to object in member expressions
+        if (t.isMemberExpression(callee)) {
+          var object = state.wrapSideEffect(callee.object);
+          callee.object = object.expr;
+          thisBinding = object.ref;
+        }
+
+        if (node.arguments.length > 0 || thisBinding) {
+          args.push(t.arrayExpression(node.arguments));
+        }
+
+        if (thisBinding) {
+          args.push(thisBinding);
+        }
+
+        node.callee = state.getHelperRef();
+        node.arguments = args;
+        break;
+    }
+  })(node);
+}
+
+var functionChildrenVisitor = {
+  enter: function (node, parent, scope, state) {
+    if (t.isReturnStatement(node)) {
+      // prevent entrance by current visitor
+      this.skip();
+      // transform return argument into statement if
+      // it contains tail recursion
+      transformExpression(node.argument, scope, state);
+    } else if (t.isFunction(node)) {
+      // inner function's bodies are irrelevant
+      this.skip();
+    } else if (t.isTryStatement(parent)) {
+      if (node === parent.block) {
+        // `try`-blocks can't be optimized
+        this.skip();
+      } else if (parent.finalizer && node !== parent.finalizer) {
+        // `catch` clause followed by `finally` can't be optimized
+        this.skip();
+      }
+    }
+  }
+};
+
+var functionVisitor = {
+  enter: function (node, parent, scope, state) {
+    // traverse all child nodes of this function and find `arguments` and `this`
+    scope.traverse(node, functionChildrenVisitor, state);
+
+    return this.skip();
+  }
+};
+
+exports.FunctionDeclaration =
+exports.FunctionExpression = function (node, parent, scope, file) {
+  var tempId, helperRef;
+
+  var state = {
+    ownerId: node.id,
+
+    getHelperRef: function () {
+      return helperRef = helperRef || file.addHelper("tail-call");
+    },
+
+    wrapSideEffect: function (node) {
+      if (t.isIdentifier(node) || t.isLiteral(node)) {
+        return {expr: node, ref: node};
+      }
+      tempId = tempId || scope.generateUidIdentifier("temp");
+      return {
+        expr: t.assignmentExpression("=", tempId, node),
+        ref: tempId
+      };
+    }
+  };
+
+  // traverse the function and look for tail recursion
+  scope.traverse(node, functionVisitor, state);
+
+  if (tempId) {
+    t.ensureBlock(node).body.unshift(t.variableDeclaration("var", [
+      t.variableDeclarator(tempId)
+    ]));
+  }
+};
+*/

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

@@ -28,6 +28,7 @@ module.exports = {
   asyncToGenerator:                        require("./other/async-to-generator"),
   bluebirdCoroutines:                      require("./other/bluebird-coroutines"),
 
+  "es6.objectSuper":                       require("./es6/object-super"),
   "es7.objectRestSpread":                  require("./es7/object-rest-spread"),
   "es7.exponentiationOperator":            require("./es7/exponentiation-operator"),
   "es6.spread":                            require("./es6/spread"),
@@ -46,6 +47,14 @@ module.exports = {
 
   "es6.constants":                         require("./es6/constants"),
 
+  // needs to be before `es6.blockScoping` as default parameters have a TDZ
+  "es6.parameters.default":                require("./es6/parameters.default"),
+
+  "es6.parameters.rest":                   require("./es6/parameters.rest"),
+
+  // needs to be before `es6.blockScoping` as let variables may be produced
+  "es6.destructuring":                     require("./es6/destructuring"),
+
   // needs to be before `_aliasFunction` due to block scopes sometimes being wrapped in a
   // closure
   "es6.blockScoping":                      require("./es6/block-scoping"),
@@ -53,10 +62,7 @@ module.exports = {
   // needs to be after `es6.blockScoping` due to needing `letReferences` set on blocks
   "es6.blockScopingTDZ":                   require("./es6/block-scoping-tdz"),
 
-  "es6.parameters.default":                require("./es6/parameters.default"),
-  "es6.parameters.rest":                   require("./es6/parameters.rest"),
-
-  "es6.destructuring":                     require("./es6/destructuring"),
+  "es6.tailCall":                          require("./es6/tail-call"),
 
   regenerator:                             require("./other/regenerator"),
 
@@ -86,5 +92,7 @@ module.exports = {
   "minification.removeDebugger":           require("./minification/remove-debugger"),
   "minification.removeConsoleCalls":       require("./minification/remove-console-calls"),
   "minification.deadCodeElimination":      require("./minification/dead-code-elimination"),
-  "minification.renameLocalVariables":     require("./minification/rename-local-variables")
+  "minification.renameLocalVariables":     require("./minification/rename-local-variables"),
+
+  _cleanUp:                                require("./internal/cleanup")
 };

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

@@ -0,0 +1,5 @@
+exports.SequenceExpression = function (node) {
+  if (node.expressions.length === 1) {
+    return node.expressions[0];
+  }
+};

lib/6to5/transformation/transformers/spec/block-scoped-functions.js

@@ -2,7 +2,7 @@
 
 var t = require("../../../types");
 
-exports.BlockStatement = function (node, parent) {
+exports.BlockStatement = function (node, parent, scope, file) {
   if ((t.isFunction(parent) && parent.body === node) || t.isExportDeclaration(parent)) {
     return;
   }
@@ -22,5 +22,7 @@ exports.BlockStatement = function (node, parent) {
     func.id = null;
 
     node.body[i] = declar;
+
+    file.checkNode(declar);
   }
 };

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

@@ -2,6 +2,8 @@
 
 var t = require("../../../types");
 
+exports.check = t.isFor;
+
 exports.ForInStatement =
 exports.ForOfStatement = function (node, parent, scope, file) {
   var left = node.left;

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

@@ -1,5 +1,9 @@
 "use strict";
 
+exports.check = function (node) {
+  return node.kind === "set";
+};
+
 exports.MethodDefinition =
 exports.Property = function (node, parent, scope, file) {
   if (node.kind === "set" && node.value.params.length !== 1) {

lib/6to5/traversal/context.js

@@ -8,42 +8,20 @@ var TraversalPath = require("./path");
 var flatten       = require("lodash/array/flatten");
 var compact       = require("lodash/array/compact");
 
-function TraversalContext(scope, opts, state) {
+function TraversalContext(scope, opts, state, parentPath) {
   this.shouldFlatten = false;
+  this.parentPath    = parentPath;
 
   this.scope = scope;
   this.state = state;
   this.opts  = opts;
-
-  this.reset();
 }
 
 TraversalContext.prototype.flatten = function () {
   this.shouldFlatten = true;
 };
 
-TraversalContext.prototype.remove = function () {
-  this.shouldRemove = true;
-  this.shouldSkip   = true;
-};
-
-TraversalContext.prototype.skip = function () {
-  this.shouldSkip = true;
-};
-
-TraversalContext.prototype.stop = function () {
-  this.shouldStop = true;
-  this.shouldSkip = true;
-};
-
-TraversalContext.prototype.reset = function () {
-  this.shouldRemove = false;
-  this.shouldSkip   = false;
-  this.shouldStop   = false;
-};
-
 TraversalContext.prototype.visitNode = function (node, obj, key) {
-  this.reset();
   var iteration = new TraversalPath(this, node, obj, key);
   return iteration.visit();
 };

lib/6to5/traversal/index.js

@@ -29,11 +29,11 @@ function traverse(parent, opts, scope, state) {
   }
 }
 
-traverse.node = function (node, opts, scope, state) {
+traverse.node = function (node, opts, scope, state, parentPath) {
   var keys = t.VISITOR_KEYS[node.type];
   if (!keys) return;
 
-  var context = new TraversalContext(scope, opts, state);
+  var context = new TraversalContext(scope, opts, state, parentPath);
   for (var i = 0; i < keys.length; i++) {
     if (context.visit(node, keys[i])) {
       return;

lib/6to5/traversal/path.js

@@ -14,16 +14,17 @@ function TraversalPath(context, parent, obj, key) {
   this.shouldSkip   = false;
   this.shouldStop   = false;
 
-  this.context = context;
-  this.state   = this.context.state;
-  this.opts    = this.context.opts;
+  this.parentPath = context.parentPath;
+  this.context    = context;
+  this.state      = this.context.state;
+  this.opts       = this.context.opts;
 
   this.key     = key;
   this.obj     = obj;
 
-  this.parent  = parent;
-  this.scope   = TraversalPath.getScope(this.getNode(), parent, context.scope);
-  this.state   = context.state;
+  this.parent = parent;
+  this.scope  = TraversalPath.getScope(this.getNode(), parent, context.scope);
+  this.state  = context.state;
 }
 
 TraversalPath.prototype.remove = function () {
@@ -70,7 +71,7 @@ TraversalPath.prototype.getNode = function () {
   return this.obj[this.key];
 };
 
-TraversalPath.prototype.replaceNode = function (replacement, scope) {
+TraversalPath.prototype.replaceNode = function (replacement) {
   var isArray = Array.isArray(replacement);
 
   // inherit comments from original node to the first replacement node
@@ -85,10 +86,10 @@ TraversalPath.prototype.replaceNode = function (replacement, scope) {
   if (file) {
     if (isArray) {
       for (var i = 0; i < replacement.length; i++) {
-        file.checkNode(replacement[i], scope);
+        file.checkNode(replacement[i], this.scope);
       }
     } else {
-      file.checkNode(replacement, scope);
+      file.checkNode(replacement, this.scope);
     }
   }
 
@@ -144,10 +145,10 @@ TraversalPath.prototype.visit = function () {
     // traverse over these replacement nodes we purposely don't call exitNode
     // as the original node has been destroyed
     for (var i = 0; i < node.length; i++) {
-      traverse.node(node[i], opts, this.scope, this.state);
+      traverse.node(node[i], opts, this.scope, this.state, this);
     }
   } else {
-    traverse.node(node, opts, this.scope, this.state);
+    traverse.node(node, opts, this.scope, this.state, this);
     this.call("exit");
   }
 

lib/6to5/traversal/scope.js

@@ -320,11 +320,12 @@ Scope.prototype.crawl = function () {
     for (i = 0; i < block.params.length; i++) {
       this.register(block.params[i]);
     }
+    this.traverse(block.body, blockVariableVisitor, this);
   }
 
   // Program, BlockStatement, Function - let variables
 
-  if (t.isBlockStatement(block) || t.isProgram(block) || t.isFunction(block)) {
+  if (t.isBlockStatement(block) || t.isProgram(block)) {
     this.traverse(block, blockVariableVisitor, this);
   }
 

lib/6to5/types/index.js

@@ -340,8 +340,8 @@ t.isReferenced = function (node, parent) {
  * @returns {Boolean}
  */
 
-t.isReferencedIdentifier = function (node, parent) {
-  return t.isIdentifier(node) && t.isReferenced(node, parent);
+t.isReferencedIdentifier = function (node, parent, opts) {
+  return t.isIdentifier(node, opts) && t.isReferenced(node, parent);
 };
 
 /**
@@ -395,7 +395,7 @@ t.toIdentifier = function (name) {
 
 t.ensureBlock = function (node, key) {
   key = key || "body";
-  node[key] = t.toBlock(node[key], node);
+  return node[key] = t.toBlock(node[key], node);
 };
 
 /**
@@ -690,10 +690,12 @@ t.inheritsComments = function (child, parent) {
  */
 
 t.inherits = function (child, parent) {
-  child.range = parent.range;
-  child.start = parent.start;
-  child.loc   = parent.loc;
-  child.end   = parent.end;
+  child._declarations = parent._declarations;
+  child._scopeInfo    = parent._scopeInfo;
+  child.range         = parent.range;
+  child.start         = parent.start;
+  child.loc           = parent.loc;
+  child.end           = parent.end;
   t.inheritsComments(child, parent);
   return child;
 };

package.json

@@ -1,7 +1,7 @@
 {
   "name": "6to5",
   "description": "Turn ES6 code into readable vanilla ES5 with source maps",
-  "version": "3.4.1",
+  "version": "3.5.2",
   "author": "Sebastian McKenzie <sebmck@gmail.com>",
   "homepage": "https://6to5.org/",
   "repository": "6to5/6to5",
@@ -33,7 +33,7 @@
     "test": "make test"
   },
   "dependencies": {
-    "acorn-6to5": "0.11.1-25",
+    "acorn-6to5": "0.11.1-28",
     "ast-types": "~0.6.1",
     "chalk": "^0.5.1",
     "chokidar": "0.12.6",

packages/6to5-runtime/package.json

@@ -1,7 +1,7 @@
 {
   "name": "6to5-runtime",
   "description": "6to5 selfContained runtime",
-  "version": "3.4.0",
+  "version": "3.5.1",
   "repository": "6to5/6to5",
   "author": "Sebastian McKenzie <sebmck@gmail.com>"
 }

test/_browser.js

@@ -1,5 +1,5 @@
 if (process.browser) {
-  require("../lib/6to5/browser");
+  require("../lib/6to5/api/browser");
   require("./generation");
   require("./transformation");
   require("./traverse");

test/_helper.js

@@ -19,14 +19,14 @@ var readFile = exports.readFile = function (filename) {
   }
 };
 
-exports.esvalid = function (ast, loc) {
+exports.esvalid = function (ast, code, loc) {
   var errors = esvalid.errors(ast);
   if (errors.length) {
     var msg = [];
     _.each(errors, function (err) {
       msg.push(err.message + " - " + JSON.stringify(err.node));
     });
-    throw new Error(loc + ": " + msg.join(". "));
+    throw new Error(loc + ": " + msg.join(". ") + "\n" + code);
   }
 };
 

test/_transformation-helper.js

@@ -16,6 +16,14 @@ global.assertNoOwnProperties = function (obj) {
   assert.equal(Object.getOwnPropertyNames(obj).length, 0);
 };
 
+global.assertHasOwnProperty = function () {
+
+};
+
+global.assertLacksOwnProperty = function () {
+
+};
+
 global.assertArrayEquals = assert.deepEqual;
 global.assert = chai.assert;
 global.chai = chai;
@@ -29,6 +37,8 @@ chai.assert.throw = function (fn, msg) {
     msg = "Generator is already running";
   } else if (msg === "Sent value to newborn generator") {
     msg = /^attempt to send (.*?) to newborn generator$/;
+  } else if (msg === "super prototype must be an Object or null") {
+    msg = "Object prototype may only be an Object or null";
   }
 
   return chai.assert._throw(fn, msg);
@@ -54,7 +64,7 @@ var run = function (task, done) {
 
   var checkAst = function (result, opts) {
     if (noCheckAst) return;
-    helper.esvalid(result.ast.program, opts.loc);
+    helper.esvalid(result.ast.program, result.code, opts.loc);
   };
 
   if (execCode) {
@@ -129,12 +139,7 @@ module.exports = function (suiteOpts, taskOpts, dynamicOpts) {
 
         var runTest = function (done) {
           var runTask = function () {
-            try {
-              run(task, done);
-            } catch (err) {
-              if (task.options.after) task.options.after();
-              throw err;
-            }
+            run(task, done);
           };
 
           _.extend(task.options, taskOpts);

test/api.js

@@ -17,6 +17,6 @@ suite("api", function () {
     var file = new File;
     assert.throws(function () {
       file.addHelper("foob");
-    }, /unknown declaration foob/);
+    }, /Unknown helper foob/);
   });
 });

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

test/fixtures/transformation/es6-arrow-functions/options.json

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

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

@@ -0,0 +1,3 @@
+a = 1;
+
+let a = 2;

test/fixtures/transformation/es6-block-scoping-tdz-fail/call-2.js

@@ -0,0 +1,7 @@
+function b() {
+  assert.equals(a, 1);
+}
+
+let a = 1;
+
+b();

test/fixtures/transformation/es6-block-scoping-tdz-fail/call-3.js

@@ -0,0 +1,7 @@
+function b() {
+  assert.equals(a, 1);
+}
+
+b();
+
+let a = 1;

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

@@ -0,0 +1,3 @@
+a;
+
+let a = 1;

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

@@ -0,0 +1,3 @@
+function foo(bar = bar2, bar2) {}
+
+foo();

test/fixtures/transformation/es6-block-scoping-tdz-fail/options.json

@@ -0,0 +1,4 @@
+{
+  "optional": "es6.blockScopingTDZ",
+  "throws": "is not defined - temporal dead zone"
+}

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

@@ -0,0 +1,3 @@
+a++;
+
+let a = 1;

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

@@ -0,0 +1,3 @@
+let a = 1;
+a = 2;
+assert.equal(a, 2);

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

@@ -0,0 +1,7 @@
+let a = 1;
+
+function b() {
+  return a + 1;
+}
+
+assert.equal(b(), 2);

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

@@ -0,0 +1,3 @@
+function foo(bar, bar2 = bar) {}
+
+foo();

test/fixtures/transformation/es6-block-scoping-tdz-pass/options.json

@@ -0,0 +1,3 @@
+{
+  "optional": "es6.blockScopingTDZ"
+}

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

@@ -0,0 +1,3 @@
+let a = 1;
+a++;
+assert.equal(a, 2);

test/fixtures/transformation/es6-block-scoping/temporal-dead-zone/actual.js

@@ -1,2 +0,0 @@
-qux;
-let qux = 456;

test/fixtures/transformation/es6-block-scoping/temporal-dead-zone/options.json

@@ -1,4 +0,0 @@
-{
-  "throws": "Temporal dead zone - accessing a variable before it's initialized",
-  "optional": ["es6.blockScopingTDZ"]
-}

test/fixtures/transformation/es6-classes-loose/options.json

@@ -1,3 +1,4 @@
 {
-  "loose": ["es6.classes"]
+  "loose": ["es6.classes"],
+  "blacklist": ["es6.tailCall"]
 }

test/fixtures/transformation/es6-classes/calling-super-properties/options.json

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

test/fixtures/transformation/es6-destructuring/object-advanced/expected.js

@@ -1,6 +1,8 @@
 "use strict";
 
-var x1 = rect.topLeft.x;
-var y1 = rect.topLeft.y;
-var x2 = rect.bottomRight.x;
-var y2 = rect.bottomRight.y;
+var _rect$topLeft = rect.topLeft;
+var x1 = _rect$topLeft.x;
+var y1 = _rect$topLeft.y;
+var _rect$bottomRight = rect.bottomRight;
+var x2 = _rect$bottomRight.x;
+var y2 = _rect$bottomRight.y;

test/fixtures/transformation/es6-destructuring/parameters/expected.js

@@ -3,10 +3,12 @@
 var _slicedToArray = function (arr, i) { if (Array.isArray(arr)) { return arr; } else { var _arr = []; for (var _iterator = arr[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) { _arr.push(_step.value); if (i && _arr.length === i) break; } return _arr; } };
 
 function somethingAdvanced(_ref) {
-  var x1 = _ref.topLeft.x;
-  var y1 = _ref.topLeft.y;
-  var x2 = _ref.bottomRight.x;
-  var y2 = _ref.bottomRight.y;
+  var _ref$topLeft = _ref.topLeft;
+  var x1 = _ref$topLeft.x;
+  var y1 = _ref$topLeft.y;
+  var _ref$bottomRight = _ref.bottomRight;
+  var x2 = _ref$bottomRight.x;
+  var y2 = _ref$bottomRight.y;
 }
 
 function unpackObject(_ref) {

test/fixtures/transformation/es6-destructuring/spread/options.json

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

test/fixtures/transformation/es6-modules-amd/exports-from/expected.js

@@ -14,5 +14,7 @@ define(["exports", "foo"], function (exports, _foo) {
   exports["default"] = _foo.foo;
   exports["default"] = _foo.foo;
   exports.bar = _foo.bar;
-  exports.__esModule = true;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
 });

test/fixtures/transformation/es6-modules-amd/exports-named/expected.js

@@ -8,5 +8,7 @@ define(["exports"], function (exports) {
   exports["default"] = foo;
   exports["default"] = foo;
   exports.bar = bar;
-  exports.__esModule = true;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
 });

test/fixtures/transformation/es6-modules-amd/exports-variable/expected.js

@@ -17,5 +17,7 @@ define(["exports"], function (exports) {
     _classCallCheck(this, foo8);
   };
 
-  exports.__esModule = true;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
 });

test/fixtures/transformation/es6-modules-amd/hoist-function-exports/expected.js

@@ -12,5 +12,7 @@ define(["exports", "./evens"], function (exports, _evens) {
       return !isEven(n);
     };
   })(isEven);
-  exports.__esModule = true;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
 });

test/fixtures/transformation/es6-modules-amd/overview/expected.js

@@ -12,5 +12,7 @@ define(["exports", "foo", "foo-bar", "./directory/foo-bar"], function (exports,
   var test2 = exports.test2 = 5;
 
   exports["default"] = test;
-  exports.__esModule = true;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
 });

test/fixtures/transformation/es6-modules-amd/remap/expected.js

@@ -10,5 +10,7 @@ define(["exports"], function (exports) {
     test = 3;
     test++;
   })();
-  exports.__esModule = true;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
 });

test/fixtures/transformation/es6-modules-common/exports-default-non-function/expected.js

@@ -3,4 +3,6 @@
 exports.Cachier = Cachier;
 exports["default"] = new Cachier();
 function Cachier(databaseName) {}
-exports.__esModule = true;
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});

test/fixtures/transformation/es6-modules-common/exports-from/expected.js

@@ -15,4 +15,6 @@ exports.bar = _foo.foo;
 exports["default"] = _foo.foo;
 exports["default"] = _foo.foo;
 exports.bar = _foo.bar;
-exports.__esModule = true;
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});

test/fixtures/transformation/es6-modules-common/exports-named/expected.js

@@ -7,4 +7,6 @@ exports.bar = foo;
 exports["default"] = foo;
 exports["default"] = foo;
 exports.bar = bar;
-exports.__esModule = true;
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});

test/fixtures/transformation/es6-modules-common/exports-variable/expected.js

@@ -16,4 +16,6 @@ var foo8 = exports.foo8 = function foo8() {
   _classCallCheck(this, foo8);
 };
 
-exports.__esModule = true;
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});

test/fixtures/transformation/es6-modules-common/hoist-function-exports/expected.js

@@ -11,4 +11,6 @@ var isOdd = exports.isOdd = (function (isEven) {
     return !isEven(n);
   };
 })(isEven);
-exports.__esModule = true;
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});

test/fixtures/transformation/es6-modules-common/overview/expected.js

@@ -18,4 +18,6 @@ var bar = require("foo4").bar;
 var bar2 = require("foo5").foo;
 exports.test = test;
 var test = exports.test = 5;
-exports.__esModule = true;
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});

test/fixtures/transformation/es6-modules-common/remap/expected.js

@@ -9,4 +9,6 @@ test = exports.test += 1;
   test = 3;
   test++;
 })();
-exports.__esModule = true;
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});

test/fixtures/transformation/es6-modules-system/hoist-function-exports/options.json

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

test/fixtures/transformation/es6-modules-umd/exports-from/expected.js

@@ -20,5 +20,7 @@
   exports["default"] = _foo.foo;
   exports["default"] = _foo.foo;
   exports.bar = _foo.bar;
-  exports.__esModule = true;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
 });

test/fixtures/transformation/es6-modules-umd/exports-named/expected.js

@@ -14,5 +14,7 @@
   exports["default"] = foo;
   exports["default"] = foo;
   exports.bar = bar;
-  exports.__esModule = true;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
 });

test/fixtures/transformation/es6-modules-umd/exports-variable/expected.js

@@ -23,5 +23,7 @@
     _classCallCheck(this, foo8);
   };
 
-  exports.__esModule = true;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
 });

test/fixtures/transformation/es6-modules-umd/hoist-function-exports/expected.js

@@ -18,5 +18,7 @@
       return !isEven(n);
     };
   })(isEven);
-  exports.__esModule = true;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
 });

test/fixtures/transformation/es6-modules-umd/overview/expected.js

@@ -18,5 +18,7 @@
   var test2 = exports.test2 = 5;
 
   exports["default"] = test;
-  exports.__esModule = true;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
 });

test/fixtures/transformation/es6-modules-umd/remap/expected.js

@@ -16,5 +16,7 @@
     test = 3;
     test++;
   })();
-  exports.__esModule = true;
+  Object.defineProperty(exports, "__esModule", {
+    value: true
+  });
 });

test/fixtures/transformation/es6-object-super/simple.js

@@ -0,0 +1,15 @@
+var a = {
+  name() {
+    return "Suyash";
+  }
+};
+
+var b = {
+  name() {
+    return super.name() + " Verma";
+  }
+};
+
+Object.setPrototypeOf(b, a);
+
+assert.equal(b.name(), "Suyash Verma");

test/fixtures/transformation/es6-properties.shorthand/method-self-reference/options.json

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

test/fixtures/transformation/es6-spread/options.json

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

test/fixtures/transformation/es7-comprehensions/options.json

@@ -1,3 +1,4 @@
 {
-  "experimental": true
+  "experimental": true,
+  "blacklist": ["es6.tailCall"]
 }

test/fixtures/transformation/playground/method-binding/options.json

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

test/fixtures/transformation/react/arrow-functions/options.json

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

test/fixtures/transformation/self-contained/full/expected.js

@@ -27,4 +27,6 @@ var foo = _to5Helpers.interopRequire(_someModule);
 var bar = _to5Helpers.interopRequireWildcard(_someModule);
 
 var myWord = exports.myWord = _core.Symbol("abc");
-exports.__esModule = true;
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});

test/traceur.js

@@ -1,5 +1,3 @@
-if (!process.env.ALL_6TO5_TESTS) return;
-
 require("./_helper").assertVendor("traceur");
 
 var fs = require("fs");
@@ -10,6 +8,18 @@ require("./_transformation-helper")({
   loc: __dirname + "/../vendor/traceur/test/feature",
 
   ignoreSuites: [
+    // weird environmental issue make these hard to test
+    "Modules",
+
+    // these are the responsibility of regenerator
+    "AsyncFunctions",
+    "Yield",
+
+    // these are the responsibility of core-js
+    "StringExtras",
+    "ArrayExtras",
+    "Collections",
+
     // these are all internal traceur tests or non-standard features
     "ObjectMixin",
     "Annotations",
@@ -24,34 +34,56 @@ require("./_transformation-helper")({
   ],
 
   ignoreTasks: [
-    // core.js doesn't support due to a perf hit and having to override a lot
-    // of native methods
+    // TODO: #426
+    "Classes/SuperUnary",
+    "Classes/SuperPostfix",
+
+    // TODO: investigate
+    "Classes/SuperSet",
+    "Classes/PrototypeDescriptor",
+    "Classes/ExtendStrange",
+    "Classes/ClassNameBinding",
+
+    // these are the responsibility of core-js
     "Symbol/GetOwnPropertySymbols",
+    "Spread/Type",
+    "Symbol/ObjectModel",
+    "Symbol/Object",
+    "Spread/NoIterator",
+    "Destructuring/Rest",
+    "Destructuring/Empty",
+
+    // traceur uses an old version of regexpu
+    "RegularExpression/Simple",
+
+    // class methods are still enumerable in traceur
+    "NumericLiteral/Simple",
+    "Classes/Method",
+
+    // Object.mixin didn't make it into ES6
+    "ObjectMixin",
 
     // traceur doesn't name methods and has an incorrect test asserting that
     // they have no names
     "PropertyMethodAssignment/PropertyMethodAssignment",
 
-    // 6to5 assumes that all code transformed is a module
+    // 6to5 assumes that all code transformed is a module so this isn't necessary
     "Strict",
     "Syntax/UseStrictEscapeSequence",
     "Syntax/UseStrictLineContinuation",
 
     // experimental es7 - the spec hasn't been finalized yet
-    // these both fail because of filter between blocks
+    // these both fail because of filters between blocks
     "ArrayComprehension/Simple",
     "GeneratorComprehension/Simple",
 
-    // yield has been added as a keyword in ES6 so this test is actually incorrect
-    "Yield/YieldIdentifier"
+    // yield has been added as a keyword in ES6
+    "Yield/YieldIdentifier",
+    "Syntax/StrictKeywords"
   ]
 }, {
-  optional: ["typeofSymbol"],
-  experimental: true,
-  after: function () {
-    // StringExtras/StarsWith
-    delete Object.prototype[1];
-  }
+  optional: ["spec.typeofSymbol"],
+  experimental: true
 }, function (opts, task) {
   if (!_.contains(task.exec.loc, "module.js")) {
     opts.blacklist = ["useStrict"];