--- /dev/null
+var coreJsData = require('./_coreJsData');
+
+/** Used to detect methods masquerading as native. */
+var maskSrcKey = (function() {
+ var uid = /[^.]+$/.exec(coreJsData && coreJsData.keys && coreJsData.keys.IE_PROTO || '');
+ return uid ? ('Symbol(src)_1.' + uid) : '';
+}());
+
+/**
+ * Checks if `func` has its source masked.
+ *
+ * @private
+ * @param {Function} func The function to check.
+ * @returns {boolean} Returns `true` if `func` is masked, else `false`.
+ */
+function isMasked(func) {
+ return !!maskSrcKey && (maskSrcKey in func);
+}
+
+module.exports = isMasked;