Use toFastProperties to speed up t.* method access

lib/6to5/to-fast-properties.js

@@ -0,0 +1,14 @@
+/**
+ * A trick from Bluebird to force V8 to use fast properties for an object.
+ * Read more: http://stackoverflow.com/questions/24987896/
+ *
+ * Use %HasFastProperties(obj) and --allow-natives-syntax to check whether
+ * a particular object already has fast properties.
+ */
+module.exports = function toFastProperties(obj) {
+  /*jshint -W027*/
+  function f() {}
+  f.prototype = obj;
+  return f;
+  eval(obj);
+};

lib/6to5/types/index.js

@@ -1,5 +1,6 @@
-var esutils = require("esutils");
-var _       = require("lodash");
+var esutils          = require("esutils");
+var _                = require("lodash");
+var toFastProperties = require("../to-fast-properties");
 
 var t = exports;
 
@@ -573,3 +574,5 @@ t.getSpecifierName = function (specifier) {
 t.isSpecifierDefault = function (specifier) {
   return t.isIdentifier(specifier.id) && specifier.id.name === "default";
 };
+
+toFastProperties(t);