performDomainStartChecks example

    protected $label = '';

    public function parse(): Result
    {
        $this->lexer->clearRecorded();
        $this->lexer->startRecording();

        $this->lexer->moveNext();

        $domainChecks = $this->performDomainStartChecks();
        if ($domainChecks->isInvalid()) {
            return $domainChecks;
        }

        if ($this->lexer->current->isA(EmailLexer::S_AT)) {
            return new InvalidEmail(new ConsecutiveAt(), $this->lexer->current->value);
        }

        $result = $this->doParseDomainPart();
        if ($result->isInvalid()) {
            return $result;
        }