private function parsing() : void
    {
        $lines = explode("\n", $this->raw);

        foreach ($lines as $line) {
            // check "at" mark
            if (false === strpos($line, '@')) {
                continue;
            }

            // check inline annotation
            if ($anp = strpos($line, '//')) {
                $line = substr($line, 0, $anp);
            }

            // trim blanks
            $line = trim(ltrim($line, ' *'));

            // analyze expr
            if (false === $fws = strpos($line, ' ')) {
                // @some-key
                $key = substr($line, 1);
                $val = true;
            } else {
                // @some-key some-val
                $key = substr($line, 1, $fws - 1);
                $val = trim(substr($line, $fws));
            }

            $this->lines[] = [$key, $val];

            $this->declares[$key][] = $val;
        }
    }