Stark autocomplete fields busted

Autocomplete is busted because the invisible autocomplete elements does not get into the page in Stark (but it gets on the page and works with phptemplate).

No. False alarm. Twig engine receives it correct.

I have tracked the issue to twig's doDisplay(). It receives the necessary data. Somewhere during the rendering, it's lost.

How I can I debug it from here?

Further update: input.html.twig seems to be the culprit.

Update: input.html.twig receives the rendered element already without it's hidden autocomplete counterpart.

Update: the autocomplete is filtered out at theme() in common_inc line 5494 (render())

Attaching a fix for autocomplete.

The issue is this: common.inc drupal_render() seems to have broken logic. There is an element and there are elements children. It tries to render an element into it children's key, and then twig template input.html.twig prints out {{ children }}. But it's not healthy to merge it like this. Current solution makes it work, but it needs to be reworked, probably.

tested the patch, fixed the issue with no errors. committing to sandbox.