eactions]: https://html.spec.whatwg.org/multipage/scripting.html#invoke-custom-element-reactions
[report the exception]: https://html.spec.whatwg.org/multipage/webappapis.html#report-the-exception
-->
<template id="constructor-throws">
  <script>
'use strict';
window.errors = [];
// https://html.spec.whatwg.org/multipage/webappapis.html#event-handler-attributes:handler-onerror
window.onerror = function (event, source, lineno, colno, error) {
  errors.push({
    event: event,
    source: source,
    lineno: 