ShadyDOM polyfill incompatible when MooTools loaded in IE 11

[petermikitsh]

Description

If you load a "compat" version of MooTools on a webpage, ShadyDOM will throw exceptions in these locations:

https://github.com/webcomponents/polyfills/blob/c6021490e0fa172dc389de2e806b83ef0ffb11bf/packages/shadydom/src/patches/Node.js#L200

https://github.com/webcomponents/polyfills/blob/c6021490e0fa172dc389de2e806b83ef0ffb11bf/packages/shadydom/src/patches/Node.js#L207

This is because MooTools mutates Document in a way that breaks instanceof checks.

Example

Visit the example in Internet Explorer 11 to see the runtime exceptions:

https://petermikitsh.github.io/cheatsheets-web/?path=/story/demos--web-components-moo-tools-ie-11

Source code: https://github.com/petermikitsh/cheatsheets-web/blob/b6ef632ba45631e5a04bf0ed30860b190eb0ca88/static/WebComponentsIE11.html#L1

Steps to reproduce

1. Load a "compat" version of MooTools
2. Add the webcomponents polyfills
3. Use a web component and see the exception

Invalid operand to 'instanceof': Function expected

Expected behavior

No runtime exception: the correct webpage looks like this (shown in Chrome for example purposes):

Actual behavior

Runtime exception

Version

Latest

Browsers affected

• [ ] Chrome
• [ ] Firefox
• [ ] Edge
• [ ] Safari
• [x] IE 11 (tested in Windows 7)

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