Twig extract FOR loop variables

Say I have a collection of items

$collection = array(
      'item1' => array(
            'post' => $post,
            'category' => $category,
            // ...
  ),
  'item2' => array(...)
);

And I have a template:

{% for item in collection %}

    Now I can use item data
       - {{ item.post.title }}
       - {{ item.category.id }}
       - {{ item.var1 }}
       - {{ item.var2 }}
       - and another 20 vars

    I want to extract those vars into more global FOR context, and use them as:

        {{ post.title }}
        {{ category.id }}
        {{ var1 }}
         ... etc

{% endfor %}

Is this possible?

I was thining of defining the loop as a template block and then iterating it with Twig_Template::renderBlock(). But the docs say renderBlock is for 'internal' use only :) So not sure.

EDIT:

Another idea I had:

{% for item in collection %}

    {% do extract(item) %}
    // extract() would work similar to extract function from php

{% endfor %}

However, it seems that context is passed to twig functions by value, so this would not work.

Lastly I could write a TokenParser and do:

{% for item in collection %}

    {% extract item %}
    // would probably get direct access to the context, but haven't tried it

{% endfor %}

But this is quite a bit of work.. I am just hoping that twig can already do this natively :)