protected function append($statement, $pos = null)
    {
        if ($pos !== null) {
            list($line, $column) = $this->getSourcePosition($pos);

            $statement[static::SOURCE_LINE]   = $line;
            $statement[static::SOURCE_COLUMN] = $column;
            $statement[static::SOURCE_INDEX]  = $this->sourceIndex;
        }

        $this->env->children[] = $statement;

        $comments = $this->env->comments;

        if (count($comments)) {
            $this->env->children = array_merge($this->env->children, $comments);
            $this->env->comments = [];
        }
    }