complex-enum.php

<?php

enum Token {
    case identifier(string $name) = self(true);
    case whitespace = self(true);
    case comment(string $comment) = self(false);

    public function __construct(public bool $isSignificant);
}

de-sugared.php

<?php

abstract class Token {
    public function __construct(public bool $isSignificant);
}

class identifier extends Token {
    public function __construct(public string $name) {
       parent::__construct(true);
    }
}
class whitespace extends Token {
    public function __construct() {
       parent::__construct(true);
    }
}
class comment extends Token {
    public function __construct(public string $comment) {
       parent::__construct(false);
    }
}