Update for.rst

[marilenaRM]

Add context and explanation about loop.parent.

[homersimpsons]

For the record, this is not only on nested loop:

• (v3.x)
  

  Twig/src/Node/ForNode.php

  Line 56 in da8bd40

  ->write("\$context['_parent'] = \$context;\n")

• (v4.x)
  

  Twig/src/Runtime/LoopContext.php

  Lines 34 to 37 in 66cb19f

  	public function getParent(): mixed
  	{
  	return $this->parent;
  	}

One use-case I found when documenting this in #4865 is about variable shadowing:

{% set users = [{"name": "Homer"}] %}
{% set user = {'name': 'Fabien'} %}
{% for user in users %}
    {{ loop.parent.user.name }} - {{ user.name }}
{% endfor %}

I do not have a proper wording to document this.

[marilenaRM]

Good point — loop.parent is indeed the whole enclosing context, not just nested loops. I've reworded the intro and added your variable-shadowing example. Thanks!

[fabpot]

Thank you @marilenaRM.