switch to core-js from es6-symbol and es6-shim

Conflicts:
	lib/6to5/polyfill.js

doc/polyfill.md

@@ -1,12 +1,11 @@
 # Polyfill
 
-6to5 includes a polyfill that includes the
-[regenerator runtime](https://github.com/facebook/regenerator/blob/master/runtime.js) and the
-[es6-shim](https://github.com/paulmillr/es6-shim) and
-[es6-symbol](https://github.com/medikoo/es6-symbol) polyfills.
+6to5 includes a polyfill that includes a custom
+[regenerator runtime](https://github.com/facebook/regenerator/blob/master/runtime.js) and
+[core.js](https://github.com/zloirock/core-js).
 
 This will emulate a full ES6 environment. This polyfill is automatically loaded
-when using [6to5-node](usage.md#node).
+when using [6to5-node](usage.md#node) and [6to5/register](usage.md#register-hook).
 
 ## Usage
 

lib/6to5/polyfill.js

@@ -1,37 +1,16 @@
 /* jshint newcap: false */
 
+require("core-js/shim");
+require("./transformation/transformers/es6-generators/runtime");
+
 var ensureSymbol = function (key) {
   Symbol[key] = Symbol[key] || Symbol();
 };
 
-var ensureProto = function (Constructor, key, val) {
-  var proto = Constructor.prototype;
-  proto[key] = proto[key] || val;
-};
-
-//
-
-if (typeof Symbol === "undefined") {
-  require("es6-symbol/implement");
-}
-
-require("es6-shim");
-require("./transformation/transformers/es6-generators/runtime");
-
-// Abstract references
-
-ensureSymbol("referenceGet");
-ensureSymbol("referenceSet");
-ensureSymbol("referenceDelete");
-
-ensureProto(Function, Symbol.referenceGet, function () { return this; });
-
-ensureProto(Map, Symbol.referenceGet, Map.prototype.get);
-ensureProto(Map, Symbol.referenceSet, Map.prototype.set);
-ensureProto(Map, Symbol.referenceDelete, Map.prototype.delete);
-
-if (global.WeakMap) {
-  ensureProto(WeakMap, Symbol.referenceGet, WeakMap.prototype.get);
-  ensureProto(WeakMap, Symbol.referenceSet, WeakMap.prototype.set);
-  ensureProto(WeakMap, Symbol.referenceDelete, WeakMap.prototype.delete);
-}
+ensureSymbol("species");
+ensureSymbol("hasInstance");
+ensureSymbol("isConcatSpreadable");
+ensureSymbol("isRegExp");
+ensureSymbol("toPrimitive");
+ensureSymbol("toStringTag");
+ensureSymbol("unscopables");

package.json

@@ -39,8 +39,7 @@
     "ast-types": "0.6.5",
     "chokidar": "0.11.1",
     "commander": "2.5.0",
-    "es6-shim": "0.21.0",
-    "es6-symbol": "0.1.1",
+    "core-js": "^0.2.2",
     "estraverse": "1.8.0",
     "esutils": "1.1.6",
     "fs-readdir-recursive": "0.1.0",

test/transformation.js

@@ -7,6 +7,8 @@ var chai       = require("chai");
 var util       = require("../lib/6to5/util");
 var _          = require("lodash");
 
+require("../lib/6to5/polyfill");
+
 var run = function (task, done) {
   var actual = task.actual;
   var expect = task.expect;
@@ -27,8 +29,6 @@ var run = function (task, done) {
     result = transform(execCode, getOpts(exec));
     execCode = result.code;
 
-    require("../lib/6to5/polyfill");
-
     try {
       var fn = new Function("assert", "done", "genHelpers", execCode);
       fn(assert, done, genHelpers);