test.php

<?php
/* composer.json
{
    "require": {
        "symfony/security-core": ">=3.4"
    }
}
*/

require 'vendor/autoload.php';

use Symfony\Component\Security\Core\Authentication\Token\UsernamePasswordToken;
use Symfony\Component\Security\Core\User\UserInterface;

class User implements UserInterface
{
    private const USERNAME = 'dummy';
    private const ROLE_DUMMY = 'ROLE_DUMMY';

    public function getUsername()
    {
        return self::USERNAME;
    }

    public function getRoles()
    {
        return [self::ROLE_DUMMY];
    }

    public function getPassword()
    {
        return null;
    }

    public function getSalt()
    {
        return null;
    }

    public function eraseCredentials()
    {
        return;
    }
}

$user = new User();
$token = new UsernamePasswordToken($user, null, uniqid(), ['ROLE_EXTRA']);

assert($token->isAuthenticated());
echo 'Token is authenticated.' . PHP_EOL;

$token->setUser($user);

echo 'After setting the same user instance into the token,' . PHP_EOL;
echo '  the token should be still authenticated;' . PHP_EOL;

if ($token->isAuthenticated()) {
    echo '  and token is still authenticated.' . PHP_EOL;
    echo 'So you are using symfony/symfony <= 4.3' . PHP_EOL;
} else {
    echo '  but token is not authenticated anymore.' . PHP_EOL;
    echo 'So you are using symfony/symfony >= 4.4' . PHP_EOL;
}

assert($token->isAuthenticated());