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Date: Tue, 29 Jun 2021 08:44:39 -0500
To: "php internals" <internals@lists.php.net>
Content-Type: text/plain
Subject: Re: [PHP-DEV] Re: [RFC] Readonly properties
From: larry@garfieldtech.com ("Larry Garfield")

On Tue, Jun 29, 2021, at 8:08 AM, Nikita Popov wrote:

> > You might not like the boilerplate, but that just works.
> >
> > Can this be considered Nikita?
> >
> 
> Well, it's a nifty hack :) I don't think this is the solution we want to
> encourage though. It requires you pass extra information through a
> side-channel -- I think I'd rather not use readonly than write that code.
> 
> Continuing along the same line, one could extend that to "clone with
> argument" and do something like this:
> 
> public function __clone(self $original, array $replacements = []) {
>     foreach ($original as $k => $v) {
>         $this->$k = $replacements[$k] ?? $original->$k;
>     }
> }
> 
> and then do "clone $this(['bar' => $bar])".
> 
> In any case, I don't want to include changes to cloning in this proposal --
> the topic is related, but also orthogonal to readonly properties.
> Unfortunately, it will not be possible to get cloning changes into PHP 8.1
> anymore, due to feature freeze.
> 
> It's okay to vote against this if cloning is a deal breaker. In that case
> I'll probably either work on cloning before re-proposing this, or pivot to
> asymmetric visibility -- it's not my first preference, but it may be the
> more pragmatic choice. Cloning is definitely the weak point of this
> proposal.
> 
> Regards,
> Nikita

I already went through the clone-arguments mental exercise in my earlier analysis, and the code it produces is totally disgusting. :-)  clone-with is a considerably better approach if you're starting from readonly.  (It's also better if you start from asymmetric visibility, although that version needs a clone-help feature far less.)

--Larry Garfield