lib/Twig/lib/Twig/Environment.php
public function parse(Twig_TokenStream $stream)
    {
        if (null === $this->parser) {
            $this->parser = new Twig_Parser($this);
        }

        return $this->parser->parse($stream);
    }
public function parse(Twig_TokenStream $stream)
    {
        if (null === $this->parser) {
            $this->parser = new Twig_Parser($this);
        }

        return $this->parser->parse($stream);
    }
Converts a token stream to a node tree.

@return Twig_Node_Module

@throws Twig_Error_Syntax When the token stream is syntactically or semantically wrong