PHP readonly class with constructor promotion and named arguments

<?php

final readonly class Point
{
    public function __construct(public int $x = 0, public int $y = 0) {}

    public function withX(int $x): static
    {
        return new static($x, $this->y);
    }
}

$p = new Point(y: 5);
$q = $p->withX(10);
echo "$p->x,$p->y -> $q->x,$q->y", PHP_EOL; // 0,5 -> 10,5

try {
    $p->x = 99;
} catch (Error $e) {
    echo $e->getMessage(), PHP_EOL; // Cannot modify readonly property Point::$x
}