add util.object that we'll use to construct objects to avoid prototype collisions

lib/6to5/transformation/modules/_default.js

@@ -28,7 +28,7 @@ var exportsVisitor = {
 };
 
 DefaultFormatter.prototype.getLocalExports = function () {
-  var localExports = {};
+  var localExports = util.object();
   traverse(this.file.ast, exportsVisitor, this.file.scope, localExports);
   return localExports;
 };
@@ -42,7 +42,7 @@ var importsVisitor = {
 };
 
 DefaultFormatter.prototype.getLocalImports = function () {
-  var localImports = {};
+  var localImports = util.object();
   traverse(this.file.ast, importsVisitor, this.file.scope, localImports);
   return localImports;
 };

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

@@ -82,9 +82,9 @@ function LetScoping(loopParent, block, parent, scope, file) {
   this.block      = block;
   this.file       = file;
 
-  this.outsideLetReferences = {};
+  this.outsideLetReferences = util.object();
   this.hasLetReferences     = false;
-  this.letReferences        = block._letReferences = {};
+  this.letReferences        = block._letReferences = util.object();
   this.body                 = [];
 }
 
@@ -150,7 +150,7 @@ LetScoping.prototype.remap = function () {
   // we have to check if any of our let variables collide with
   // those in upper scopes and then if they do, generate a uid
   // for them and replace all references with it
-  var remaps = {};
+  var remaps = util.object();
 
   for (var key in letRefs) {
     // just an Identifier node we collected in `getLetReferences`

lib/6to5/util.js

@@ -25,6 +25,10 @@ exports.isInteger = function (i) {
   return _.isNumber(i) && i % 1 === 0;
 };
 
+exports.object = function () {
+  return Object.create(null);
+};
+
 exports.resolve = function (loc) {
   try {
     return require.resolve(loc);