Description

The following code:

https://3v4l.org/DdVMXM#v8.3.3

<?php

class A
{
    private readonly array $matches;
    
    public function __construct()
    {
        \preg_match('/t/', '', $this->matches);
    }
}

new A();

Resulted in this output:

Uncaught Error: Cannot indirectly modify readonly property A::$matches

But I expected this output instead:
The same-scope uninitialised readonly property is initialised by preg_match matches. Such by-reference initialisation of core method arguments works for local variables and untyped writable properties. I did not find anything in the documentation regarding readonly in combination with by-reference.
Even empty array (no matches) initialisation (which definitley would be a write-once operation) triggers the error.
Is this intended, a bug or an overlooked case?

If it actually is intended shouldn't it throw the following Error instead, however?

Uncaught Error: Cannot access uninitialized non-nullable property A::$matches by reference

PHP Version

PHP 8.3

Operating System

Ubuntu 23.10