Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:126935
Precedence: bulk
MIME-Version: 1.0
References: <CALaXqqRWL8ygMGoA5xnMtt7w6rE-5WJJZ5P9oiO3vHgqvod=Fw@mail.gmail.com>
 <CAJF_ukXsyh9k+JTOiuJvYJ5Brq41vYBb-8+Cg6rfH9yE459Pbg@mail.gmail.com>
 <CALaXqqQDMKju=TmSR4hruG1dr4qb4MTKrmcyQdXqGa2j5B_joQ@mail.gmail.com>
 <CAJF_ukVCV-rP7XfK7BCWkb28M4DPAdWCF-J5_WAHhfP6SPS3oA@mail.gmail.com>
 <ab983707b9845d5288305017205f27a1@bastelstu.be> <f598da71-abc9-4ad7-8480-00fca53ef4f8@rwec.co.uk>
In-Reply-To: <f598da71-abc9-4ad7-8480-00fca53ef4f8@rwec.co.uk>
Date: Tue, 25 Mar 2025 11:14:21 -0700
Message-ID: <CALaXqqRyLPw_6U0KOhH6VPzf-1NMdSe0037iV+rUcyAoxG0=dA@mail.gmail.com>
Subject: Re: [PHP-DEV] [RFC] [Discussion] Never parameters
To: "Rowan Tommins [IMSoP]" <imsop.php@rwec.co.uk>
Cc: internals@lists.php.net
Content-Type: multipart/alternative; boundary="000000000000ccd72d06312eb2d7"
From: daniel.e.scherzer@gmail.com (Daniel Scherzer)

--000000000000ccd72d06312eb2d7
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

On Tue, Mar 25, 2025 at 11:01=E2=80=AFAM Rowan Tommins [IMSoP] <imsop.php@r=
wec.co.uk>
wrote:

>
> I don't think the language should pretend to support something that it
> doesn't
>

I don't see what the pretending is here - the engine supports declaring
that a method must accept a parameter but makes no promises about the type
of that parameter, which is what we claim it supports. If people want to
use this for generics, then great, but I don't think this should be blocked
on the expectation that it is only useful for userland generics (e.g.
the Serde use case isn't really generics).


> - if the contract is actually enforced by a third-party tool reading
> docblocks, put the contract in a docblock:
>
>     /**
>        * @template T
>        * @method compareTo(T $other): int;
>        */
>     interface Comparable {
>     }
>
>     /** @implements Comparable<Number> */
>     final class Number implements Comparable {
>         public function compareTo(Number $other): int { return $this <=3D=
>
> $other; }
>     }
>
>
> What happens if there is a bigger contract than just the never parameter,
and we want the engine to enforce the rest? For example, the Serde use case
given previously. Or, if you had an object store that might occasionally
clean up expired items:

     /** @template T */
     interface ObjectStore {
         /** @param T $object */
         public function storeObject(never $object, bool $alsoDoCleanup):
void;
     }

If we move the entire contract to the docblock, then the engine cannot be
used to enforce the non-never-related parts.

--Daniel

--000000000000ccd72d06312eb2d7
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr"><div dir=3D"ltr">On Tue, Mar 25, 2025 at 11:01=E2=80=AFAM =
Rowan Tommins [IMSoP] &lt;<a href=3D"mailto:imsop.php@rwec.co.uk">imsop.php=
@rwec.co.uk</a>&gt; wrote:</div><div class=3D"gmail_quote gmail_quote_conta=
iner"><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;b=
order-left:1px solid rgb(204,204,204);padding-left:1ex"><u></u>

 =20
   =20
 =20
  <div>
    <div><br></div>
    <p>I don&#39;t think the language should pretend to support something
      that it
      doesn&#39;t</p></div></blockquote><div><br></div><div>I don&#39;t see=
 what the pretending is here - the engine supports declaring that a method =
must accept a parameter but makes no promises about the type of that parame=
ter, which is what we claim it supports. If people want to use this for gen=
erics, then great, but I don&#39;t think this should=C2=A0be blocked on the=
 expectation that it is only useful for userland generics (e.g. the=C2=A0Se=
rde use case isn&#39;t really generics).</div><div>=C2=A0</div><blockquote =
class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px sol=
id rgb(204,204,204);padding-left:1ex"><div><p> - if the contract is actuall=
y enforced by a third-party
      tool reading docblocks, put the contract in a docblock:</p>
    <p>=C2=A0=C2=A0=C2=A0 /** <br>
      =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * @template T<br>
      =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * @method compareTo(T $other): i=
nt;
      <br>
      =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 */
      <br>
      =C2=A0=C2=A0=C2=A0 interface Comparable {<br>
      =C2=A0=C2=A0=C2=A0 } <br>
    </p>
    <p>=C2=A0=C2=A0=C2=A0 /** @implements Comparable&lt;Number&gt; */
      <br>
      =C2=A0=C2=A0=C2=A0 final class Number implements Comparable {
      <br>
      =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 public function compareTo(=
Number $other): int { return
      $this &lt;=3D&gt; $other; }
      <br>
      =C2=A0=C2=A0=C2=A0 }
    </p>
    <p><br></p></div></blockquote><div>What happens if there is a bigger co=
ntract than just the never parameter, and we want the engine to enforce the=
 rest? For example, the Serde use case given previously. Or, if you had an =
object store that might occasionally clean up expired items:</div><div><br>=
=C2=A0 =C2=A0 =C2=A0/** @template T */<br>=C2=A0 =C2=A0 =C2=A0interface Obj=
ectStore {<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0/** @param T $object */<br>=
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0public function storeObject(never $object=
, bool $alsoDoCleanup): void;<br>=C2=A0 =C2=A0 =C2=A0}</div><div><br></div>=
<div>If we move the entire contract to the docblock, then the engine cannot=
 be used to enforce the non-never-related parts.</div><div><br></div><div>-=
-Daniel</div><div>=C2=A0</div></div></div>

--000000000000ccd72d06312eb2d7--