lib/Twig/lib/Twig/Template.php
public function hasBlock($name, array $context = null, array $blocks = array())
    {
        if (null === $context) {
            @trigger_error('The '.__METHOD__.' method is internal and should never be called; calling it directly is deprecated since version 1.28 and won\'t be possible anymore in 2.0.', E_USER_DEPRECATED);

            return isset($this->blocks[(string) $name]);
        }

        if (isset($blocks[$name])) {
            return $blocks[$name][0] instanceof self;
        }

        if (isset($this->blocks[$name])) {
            return true;
        }

        if (false !== $parent = $this->getParent($context)) {
            return $parent->hasBlock($name, $context);
        }

        return false;
    }
public function hasBlock($name, array $context = null, array $blocks = array())
    {
        if (null === $context) {
            @trigger_error('The '.__METHOD__.' method is internal and should never be called; calling it directly is deprecated since version 1.28 and won\'t be possible anymore in 2.0.', E_USER_DEPRECATED);

            return isset($this->blocks[(string) $name]);
        }

        if (isset($blocks[$name])) {
            return $blocks[$name][0] instanceof self;
        }

        if (isset($this->blocks[$name])) {
            return true;
        }

        if (false !== $parent = $this->getParent($context)) {
            return $parent->hasBlock($name, $context);
        }

        return false;
    }
Returns whether a block exists or not in the current context of the template.

This method checks blocks defined in the current template
or defined in "used" traits or defined in parent templates.

@param string $name    The block name
@param array  $context The context
@param array  $blocks  The current set of blocks

@return bool true if the block exists, false otherwise

@internal