babel: transform-es2015-typeof-symbol causes cross-domain error in IE

transform-es2015-typeof-symbol converts typeof foo to _typeof(foo) when typeof Symbol.iterator !== "symbol". _typeof is implemented as follows:

function(obj) {
        return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj;
}

That obj.constructor property lookup throws an error when it’s applied to a cross-domain window object. For example, typeof window.frames[0] transpiles to _typeof(window.frames[0]) which ends up calling window.frames[0].constructor, which triggers a cross-domain permission error.

Input Code

typeof window.frames[0];

"use strict";

var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };

_typeof(window.frames[0]);

Babel Configuration (.babelrc, package.json, cli command)

{
    "presets": [ "es2015" ]
}

Expected Behavior

_typeof should not try to access privileged properties on a cross-domain window object.

Current Behavior

_typeof tries to access privileged properties on a cross-domain window object.

Possible Solution

try/catch and fall-back to typeof?

Context

Broke the following addition to post-robot, which allows sending messages to remote windows. We validate the passed window using typeof to ensure it’s at least an "object"

Your Environment

software	version
Babel	6
node	4
npm	3
Operating System	Windows 7 / IE9-11