--TEST--
"block" function with undefined block
--TEMPLATE--
{% extends "base.twig" %}
{% block foo %}
    {{ parent() }}
    {{ block('unknown') }}
    {{ block('bar') }}
{% endblock %}
--TEMPLATE(base.twig)--
{% block foo %}Foo{% endblock %}
{% block bar %}Bar{% endblock %}
--DATA--
return []
--EXCEPTION--
Twig\Error\RuntimeError: Block "unknown" on template "base.twig" does not exist in "index.twig" at line 5.