这里有一个解决方案来实现你想要做的事情：
在FormType中，在PRE_SUBMIT上添加一个事件侦听器，并像这样添加约束：

use Symfony\Component\Form\FormEvent;
use Symfony\Component\Form\FormEvents;
use Symfony\Component\Validator\Constraints\EqualTo;

// ...

$builder->addEventListener(FormEvents::PRE_SUBMIT, function (FormEvent $event) {
    $data = $event->getData();
    $form = $event->getForm();

    if (isset($data['cityA'])) {
        $form->add('cityB', TextType::class, [
            'constraints' => [
                new EqualTo([
                    'value' => $data['cityA'],
                    'message' => 'Must be the same as cityA',
                ]),
            ],
        ]);
    }

    // Here other constraints
});

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