Asymmetric Visibility v2

I don't have any arguments to add other than: It adds a lot of complexity and potential confusion for (IMO) negligible gain.

I would really like to see actual use cases (and less foobar) because I truely can't think of valid ones.. For mutable constructs I would just use methods to change the state and for immutable constructs readonly does the trick for me.

clone with would be nice, but this works reasonably fine for me:

final readonly class SomeClass
{
    public function __construct(
        public string $prop1,
        public bool $prop2,
    ) {}

    public function with(
        string $prop1 = null,
        bool $prop2 = null,
    ): self {
        return new self(
            $prop1 ?? $this->prop1,
            $prop2 ?? $this->prop2,
        );
    }
}

to be used with named arguments like

$someClass->with(
  prop1: 'changed',
);

Let us rather remove the writeonce behavior from readonly and add a separate writeonce keyword.

The private(set) syntax is also ugly.

I like the idea behind this RFC, maybe the syntax is not my favourite, but it's ok.