twig loop.parent.loop not there for nested loops

[marionnewlevant]

Description

This used to work, and does work in twigfiddle:

{% for x in 1..2 %}
  {% for y in 1..2 %}
    [{{loop.parent.loop.index}} {{loop.index}}]
  {% endfor %}
{% endfor %}

Steps to reproduce

1. Brand new Craft install (3.1.27)
2. Create a twig template with that content
3. Error is:

Key "loop" for array with keys "view, devMode, SORT_ASC, SORT_DESC, SORT_REGULAR, SORT_NUMERIC, SORT_STRING, SORT_LOCALE_STRING, SORT_NATURAL, SORT_FLAG_CASE, POS_HEAD, POS_BEGIN, POS_END, POS_READY, POS_LOAD, isInstalled, loginUrl, logoutUrl, now, craft, currentUser, systemName, currentSite, siteName, siteUrl, _parent, _seq, x, _key" does not exist.

Additional info

• Craft version: 3.1.27
• PHP version: 7.0.13
• Twig version: 2.8.1
• Plugins & versions: none

Looking at the compiled template, and comparing it to the compiled template from twigfiddle it is pretty clear what is going wrong.
compiledTemplateComparison.zip

[brandonkelly]

Sorry for the delay Marion! Just fixed this for the next release.

To get the fix early, change your craftcms/cms requirement in composer.json to:

"require": {
  "craftcms/cms": "dev-develop#c77cb93ba9c0a448abee7bf5ce263a84431517f8 as 3.1.28",
  "...": "..."
}

Then run composer update.