interface NodeVisitorInterface

interface NodeVisitorInterface {
    
    /**
     * Called before child nodes are visited.
     *
     * @return Node The modified node
     */
    public function enterNode(Node $node, Environment $env) : Node;
    
    /**
     * Called after child nodes are visited.
     *
     * @return Node|null The modified node or null if the node must be removed
     */
    public function leaveNode(Node $node, Environment $env) : ?Node;
    
    /**
     * Returns the priority for this visitor.
     *
     * Priority should be between -10 and 10 (0 is the default).
     *
     * @return int The priority level
     */
    public function getPriority();

}