BlockReferenceExpression example

if (!$this->parser->getParent() && !$this->parser->hasTraits()) {
                    throw new SyntaxError('Calling "parent" on a template that does not extend nor "use" another template is forbidden.', $line, $this->parser->getStream()->getSourceContext());
                }

                return new ParentExpression($this->parser->peekBlockStack(), $line);
            case 'block':
                $args = $this->parseArguments();
                if (\count($args) < 1) {
                    throw new SyntaxError('The "block" function takes one argument (the block name).', $line, $this->parser->getStream()->getSourceContext());
                }

                return new BlockReferenceExpression($args->getNode(0), \count($args) > 1 ? $args->getNode(1) : null, $line);
            case 'attribute':
                $args = $this->parseArguments();
                if (\count($args) < 2) {
                    throw new SyntaxError('The "attribute" function takes at least two arguments (the variable and the attributes).', $line, $this->parser->getStream()->getSourceContext());
                }

                return new GetAttrExpression($args->getNode(0), $args->getNode(1), \count($args) > 2 ? $args->getNode(2) : null, Template::ANY_CALL, $line);
            default:
                if (null !== $alias = $this->parser->getImportedSymbol('function', $name)) {
                    $arguments = new ArrayExpression([], $line);
                    foreach ($this->parseArguments() as $n) {