add a workaround for IE11 crash, fix #485

modules/_function-to-string.js

@@ -0,0 +1 @@
+module.exports = require('./_shared')('native-function-to-string', Function.toString);

modules/_native-weak-map.js

@@ -0,0 +1,4 @@
+var nativeFunctionToString = require('./_function-to-string');
+var WeakMap = require('./_global').WeakMap;
+
+module.exports = typeof WeakMap === 'function' && /native code/.test(nativeFunctionToString.call(WeakMap));

modules/_redefine.js

@@ -2,8 +2,8 @@ var global = require('./_global');
 var hide = require('./_hide');
 var has = require('./_has');
 var SRC = require('./_uid')('src');
+var $toString = require('./_function-to-string');
 var TO_STRING = 'toString';
-var $toString = Function[TO_STRING];
 var TPL = ('' + $toString).split(TO_STRING);
 
 require('./_core').inspectSource = function (it) {

modules/es6.weak-map.js

@@ -1,17 +1,18 @@
 'use strict';
+var global = require('./_global');
 var each = require('./_array-methods')(0);
 var redefine = require('./_redefine');
 var meta = require('./_meta');
 var assign = require('./_object-assign');
 var weak = require('./_collection-weak');
 var isObject = require('./_is-object');
-var fails = require('./_fails');
 var validate = require('./_validate-collection');
+var NATIVE_WEAK_MAP = require('./_validate-collection');
+var IS_IE11 = !global.ActiveXObject && 'ActiveXObject' in global;
 var WEAK_MAP = 'WeakMap';
 var getWeak = meta.getWeak;
 var isExtensible = Object.isExtensible;
 var uncaughtFrozenStore = weak.ufstore;
-var tmp = {};
 var InternalMap;
 
 var wrapper = function (get) {
@@ -39,7 +40,7 @@ var methods = {
 var $WeakMap = module.exports = require('./_collection')(WEAK_MAP, wrapper, methods, weak, true, true);
 
 // IE11 WeakMap frozen keys fix
-if (fails(function () { return new $WeakMap().set((Object.freeze || Object)(tmp), 7).get(tmp) != 7; })) {
+if (NATIVE_WEAK_MAP && IS_IE11) {
   InternalMap = weak.getConstructor(wrapper, WEAK_MAP);
   assign(InternalMap.prototype, methods);
   meta.NEED = true;