Current Kibana master doesn't load in IE due to some react-intl related error

6.7, 7.0 and 7.x do work though.
@Bamieh
cc @elastic/kibana-qa and @elastic/kibana-design so they are aware.
I reproduced in IE11 locally against master
packages/kbn-i18n/node_modules/react-intl/lib/index.js
Line 165, Column: 5
maps to the 2nd line of
if (typeof Symbol === "function" && Symbol.asyncIterator) {
AsyncGenerator.prototype[Symbol.asyncIterator] = function () {
return this;
};
}
Running this in the IE11 console creates the same error:
thing = function() {};
thing.prototype[Symbol.asyncIterator]
Pinging @elastic/kibana-platform
bisecting commits through git, appears to be 3727b5355a7680888c5a05a156fe52a21204108e https://github.com/elastic/kibana/pull/29072 which introduces the change breaking IE11.
Moving before that commit there is an existing error in IE11 about a SyntaxError: Expected ';' from ./node_modules/vega-lib/build/vega.js in _vendors.bundle.dll.js_, so there may be a few issues to resolve for IE support.
@chandlerprall The vega issue gets resolved with https://github.com/elastic/kibana/commit/562edd6578fdfa831628fa0189d8dbfb9349bb3d
so that shouldn't pop up again if the problem with 3727b53 #29072 gets resolved (at least it works in the PR branch flash1293:fix/vega-version which was based on a commit prior to 3727b53). If this shouldn't be the case, please ping me.
For testing: Cherry-picking https://github.com/elastic/kibana/commit/562edd6578fdfa831628fa0189d8dbfb9349bb3d on top of the commit before 3727b53 should work if there isn't a third IE breaking change at the same time.
Specifically, adding "@storybook/react": "^4.0.7", to x-pack's package.json triggers the error. There is a release note on 4.1.6 that it includes an IE11 fix, bumping to that version removes the error but still no pageload happens (stays on a blank screen).
Adding the @storybook/react dependency duplicates or triplicates a number of babel-related packages in yarn.lock (all with miniscule version differences) so that's where I'm looking now. It might be best to remove the storybook dependencies for now to get master working again. @clintandrewhall
I talked to @mistic about this while trying to fix the vega problem, and it might be possible to resolve this by configuring webpack to correctly compile this stuff down to IE supported syntax (packages/kbn-babel-preset). If we find a reliable way to prevent this, https://github.com/elastic/kibana/issues/31413 should get a lot easier.
For now it makes more sense to just revert though IMHO, no idea how easy it is to resolve this once and for all without unwanted side effects (like killing compile performance)
馃帀 @chandlerprall !!