Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:128054
Precedence: bulk
MIME-Version: 1.0
References: <d603f372-5f58-4308-aba1-151c35f3aa94@app.fastmail.com>
 <0D6532F3-6E95-48B9-B394-E9CC1EC00B56@gmail.com> <d4da4b69-7f13-4e8f-a043-d610d178479b@app.fastmail.com>
In-Reply-To: <d4da4b69-7f13-4e8f-a043-d610d178479b@app.fastmail.com>
Date: Tue, 15 Jul 2025 19:05:13 +0200
Message-ID: <CAOWwgpk2YqoDaC4O9wqCSJxRcsZKT=R0B6XLPA1PboFo=MMMkA@mail.gmail.com>
Subject: Re: [PHP-DEV] RFC: Records
To: Rob Landers <rob@bottled.codes>
Cc: Dmitry Derepko <xepozzd@gmail.com>, internals@lists.php.net
Content-Type: multipart/alternative; boundary="0000000000004efe7a0639fac851"
From: nicolas.grekas+php@gmail.com (Nicolas Grekas)

--0000000000004efe7a0639fac851
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

Le lun. 14 juil. 2025 =C3=A0 20:26, Rob Landers <rob@bottled.codes> a =C3=
=A9crit :

> Hey Dmitry,
>
> Please remember to bottom post!
>
> On Mon, Jul 14, 2025, at 11:16, Dmitry Derepko wrote:
>
> Hi, Rob!
>
> I'm just wondering, why the implementation differs from a regular class?
>
> Record makes a "class" immutable and unique, using field value comparison
> instead of object refs. It has a custom `with` method which is similar to
> the new `clone` operator accepted recently. I'd suggest not introducing a
> new keyword "record" and new syntax to create records, but use regular
> `class` and `new Class`. Class should have a modifier "data" like readonl=
y,
> so it should be:
>
> data class Record {
>     public function __construct(public $a){} // $a is mutable, because wh=
y
> not?
> }
>
> Data class will compare with others using field value comparison.
> Moreover, if you want to make it readonly, use the existing keyword to
> achieve this:
>
> readonly data class Record {
>     public function __construct(public $a){} // $a is immutable, because
> of "readonly" class modifier
> }
>
>
> Data classes are basically structs (as we collectively discovered last
> December when I tried implementing exactly that). Records are implemented
> completely differently than structs, even though they seem very similar.
> This is largely why they=E2=80=99re completely different keywords. Furthe=
r, records
> were meant to be nested inside other classes, and I did try to actually
> pull that off with regular classes =E2=80=94 and it was declined. This ne=
gates the
> short-syntax and nested aspect of records.
>
>
> 1. So record Record {} becomes readonly data class Record {}
>
>
> A record is not a class just like an enum is not a class. :) Though, it i=
s
> class-like semantics.
>
> 2. We introduce data classes, which are similar to records and are mutabl=
e
> by default
>
>
> You=E2=80=99re referring to structs, not records.
>
> 3. No new constructions to create the new type of classes, no adjustments
> for autoloading and other things internally
>
>
> Records aren=E2=80=99t created (aka, "new'd"); that=E2=80=99s an intentio=
nal design
> choice. Whether or not it is a good one is still up for debate.
>
> 4. Eliminate with method, replace `with` method with the new `clone`
>
>
> The new clone is not compatible with records or any other type defined vi=
a
> a constructor (including regular classes). This was a deliberate choice o=
f
> that implementation. Here's some examples run on that branch:
>
> <?php
>
> final readonly class Response {
>     public function __construct(
>         public int $statusCode,
>         public string $reasonPhrase,
>         // ...
>     ) {
>         if($this->statusCode >=3D 600) {
>             throw new LogicException();
>         }
>     }
> }
>
> $test =3D new Response(404, "Not Found");
> var_dump($test);
> $test =3D clone($test, ['statusCode' =3D> 900]);
> var_dump($test);
>
> --- output ---
>
> PHP Fatal error:  Uncaught Error: Cannot modify protected(set) readonly
> property Response::$statusCode from global scope in
> /home/withinboredom/code/php-src/test.php:28
> Stack trace:
> #0 /home/withinboredom/code/php-src/test.php(28): clone()
> #1 {main}
>   thrown in /home/withinboredom/code/php-src/test.php on line 28
> Fatal error: Uncaught Error: Cannot modify protected(set) readonly
> property Response::$statusCode from global scope in
> /home/withinboredom/code/php-src/test.php:28
> Stack trace:
> #0 /home/withinboredom/code/php-src/test.php(28): clone()
> #1 {main}
>   thrown in /home/withinboredom/code/php-src/test.php on line 28
>
> Then removing the readonly distinction:
>
> object(Response)#1 (2) {
>   ["statusCode"]=3D>
>   int(404)
>   ["reasonPhrase"]=3D>
>   string(9) "Not Found"
> }
> object(Response)#2 (2) {
>   ["statusCode"]=3D>
>   int(900)
>   ["reasonPhrase"]=3D>
>   string(9) "Not Found"
> }
>
> ---
>
> As you can see, it doesn't work for readonly classes and allows invalid
> mutable objects to be created, requiring devs to rethink how validation
> will be structured as this will make any constructor validations entirely
> bypassable in PHP 8.5+. Previously, you needed to use reflection to do
> this, but now it is going to be incredibly easy and a footgun. I think th=
is
> will be another weird quirk of PHP from now on and it is by design.
>

Not sure it's really a contribution to the discussion but in case you
missed it, you can make public properties "public(set)":

final readonly class Response {
    public function __construct(
        public public(set) int $statusCode,
        public public(set) string $reasonPhrase,
        // ...
    ) {
        if($this->statusCode >=3D 600) {
            throw new LogicException();
        }
    }
}

Then your example works.
That's ugly, but that doesn't have to stay that way.
And I'm now wondering why is that not the default?

Nicolas

--0000000000004efe7a0639fac851
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr"><div dir=3D"ltr"><br></div><br><div class=3D"gmail_quote g=
mail_quote_container"><div dir=3D"ltr" class=3D"gmail_attr">Le=C2=A0lun. 14=
 juil. 2025 =C3=A0=C2=A020:26, Rob Landers &lt;rob@bottled.codes&gt; a =C3=
=A9crit=C2=A0:<br></div><blockquote class=3D"gmail_quote" style=3D"margin:0=
px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><=
u></u><div><div>Hey Dmitry,</div><div><br></div><div>Please remember to bot=
tom post!<br></div><div><br></div><div>On Mon, Jul 14, 2025, at 11:16, Dmit=
ry Derepko wrote:</div><blockquote type=3D"cite" id=3D"m_-81707005554836210=
51qt"><div>Hi, Rob!</div><div><br></div><div>I&#39;m just wondering, why th=
e implementation differs from a regular class?=C2=A0</div><div><br></div><d=
iv>Record makes a &quot;class&quot; immutable and unique, using field value=
 comparison instead of object refs. It has a custom `with` method which is =
similar to the new `clone` operator accepted recently. I&#39;d suggest not =
introducing a new keyword &quot;record&quot; and new syntax to create recor=
ds, but use regular `class` and `new Class`. Class should have a modifier &=
quot;data&quot; like readonly, so it should be:</div><div><br></div><div>da=
ta class Record {</div><div>=C2=A0 =C2=A0 public function __construct(publi=
c $a){} // $a is mutable, because why not?</div><div>}</div><div><br></div>=
<div>Data class will compare with others using field value comparison. More=
over, if you want to make it readonly, use the existing keyword to achieve =
this:</div><div><br></div><div>readonly data class Record {</div><div>=C2=
=A0 =C2=A0 public function __construct(public $a){} // $a is immutable, bec=
ause of &quot;readonly&quot; class modifier</div><div>}</div></blockquote><=
div><br></div><div>Data classes are basically structs (as we collectively d=
iscovered last December when I tried implementing exactly that). Records ar=
e implemented completely differently than structs, even though they seem ve=
ry similar. This is largely why they=E2=80=99re completely different keywor=
ds. Further, records were meant to be nested inside other classes, and I di=
d try to actually pull that off with regular classes =E2=80=94 and it was d=
eclined. This negates the short-syntax and nested aspect of records.</div><=
div><br></div><blockquote type=3D"cite" id=3D"m_-8170700555483621051qt"><di=
v><br></div><div>1. So record Record {} becomes readonly data class Record =
{}</div></blockquote><div><br></div><div>A record is not a class just like =
an enum is not a class. :) Though, it is class-like semantics.</div><div><b=
r></div><blockquote type=3D"cite" id=3D"m_-8170700555483621051qt"><div>2. W=
e introduce data classes, which are similar to records and are mutable by d=
efault</div></blockquote><div><br></div><div>You=E2=80=99re referring to st=
ructs, not records.</div><div><br></div><blockquote type=3D"cite" id=3D"m_-=
8170700555483621051qt"><div>3. No new constructions to create the new type =
of classes, no adjustments for autoloading and other things internally</div=
></blockquote><div><br></div><div>Records aren=E2=80=99t created (aka, &quo=
t;new&#39;d&quot;); that=E2=80=99s an intentional design choice. Whether or=
 not it is a good one is still up for debate.</div><div><br></div><blockquo=
te type=3D"cite" id=3D"m_-8170700555483621051qt"><div>4. Eliminate with met=
hod, replace `with` method with the new `clone`</div></blockquote><div><br>=
</div><div>The new clone is not compatible with records or any other type d=
efined via a constructor (including regular classes). This was a deliberate=
 choice of that implementation. Here&#39;s some examples run on that branch=
:</div><div><br></div><div>&lt;?php</div><div><br></div><div>final readonly=
 class Response {</div><div>=C2=A0=C2=A0=C2=A0 public function __construct(=
</div><div>=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 public int $statusCod=
e,</div><div>=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 public string $reas=
onPhrase,</div><div>=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 // ...</div>=
<div>=C2=A0=C2=A0=C2=A0 ) {</div><div>=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0 if($this-&gt;statusCode &gt;=3D 600) {</div><div>=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 throw new LogicException()=
;</div><div>=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 }</div><div>=C2=A0=
=C2=A0=C2=A0 }<br></div><div>}</div><div><br></div><div>$test =3D new Respo=
nse(404, &quot;Not Found&quot;);</div><div>var_dump($test);</div><div>$test=
 =3D clone($test, [&#39;statusCode&#39; =3D&gt; 900]);</div><div>var_dump($=
test);</div><div><br></div><div>--- output ---</div><div><br></div><div>PHP=
 Fatal error:=C2=A0 Uncaught Error: Cannot modify protected(set) readonly p=
roperty Response::$statusCode from global scope in /home/withinboredom/code=
/php-src/test.php:28</div><div>Stack trace:</div><div>#0 /home/withinboredo=
m/code/php-src/test.php(28): clone()</div><div>#1 {main}</div><div>=C2=A0 t=
hrown in /home/withinboredom/code/php-src/test.php on line 28</div><div>Fat=
al error: Uncaught Error: Cannot modify protected(set) readonly property Re=
sponse::$statusCode from global scope in /home/withinboredom/code/php-src/t=
est.php:28</div><div>Stack trace:</div><div>#0 /home/withinboredom/code/php=
-src/test.php(28): clone()</div><div>#1 {main}</div><div>=C2=A0 thrown in /=
home/withinboredom/code/php-src/test.php on line 28</div><div><br></div><di=
v>Then removing the readonly distinction:</div><div><br></div><div>object(R=
esponse)#1 (2) {</div><div>=C2=A0 [&quot;statusCode&quot;]=3D&gt;</div><div=
>=C2=A0 int(404)</div><div>=C2=A0 [&quot;reasonPhrase&quot;]=3D&gt;</div><d=
iv>=C2=A0 string(9) &quot;Not Found&quot;</div><div>}</div><div>object(Resp=
onse)#2 (2) {</div><div>=C2=A0 [&quot;statusCode&quot;]=3D&gt;</div><div>=
=C2=A0 int(900)</div><div>=C2=A0 [&quot;reasonPhrase&quot;]=3D&gt;</div><di=
v>=C2=A0 string(9) &quot;Not Found&quot;</div><div>}</div><div><br></div><d=
iv>---</div><div><br></div><div>As you can see, it doesn&#39;t work for rea=
donly classes and allows invalid mutable objects to be created, requiring d=
evs to rethink how validation will be structured as this will make any cons=
tructor validations entirely bypassable in PHP 8.5+. Previously, you needed=
 to use reflection to do this, but now it is going to be incredibly easy an=
d a footgun. I think this will be another weird quirk of PHP from now on an=
d it is by design.</div></div></blockquote><div><br></div><div>Not sure it&=
#39;s really a contribution to the discussion but in case you missed it, yo=
u can make public properties &quot;public(set)&quot;:</div><div><br></div><=
div>final readonly class Response {<br>=C2=A0 =C2=A0 public function __cons=
truct(<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 public public(set) int $statusCode,<b=
r>=C2=A0 =C2=A0 =C2=A0 =C2=A0 public public(set) string $reasonPhrase,<br>=
=C2=A0 =C2=A0 =C2=A0 =C2=A0 // ...<br>=C2=A0 =C2=A0 ) {<br>=C2=A0 =C2=A0 =
=C2=A0 =C2=A0 if($this-&gt;statusCode &gt;=3D 600) {<br>=C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 throw new LogicException();<br>=C2=A0 =C2=A0 =C2=
=A0 =C2=A0 }<br>=C2=A0 =C2=A0 }<br>}<br></div><div><br></div><div>Then your=
 example works.</div><div>That&#39;s ugly, but that doesn&#39;t have to sta=
y that way.</div><div>And I&#39;m now wondering why is that not the default=
?</div></div><div class=3D"gmail_quote gmail_quote_container"><br></div><di=
v class=3D"gmail_quote gmail_quote_container">Nicolas</div></div>

--0000000000004efe7a0639fac851--