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Date: Thu, 20 Mar 2025 09:50:37 -0700
Message-ID: <CALaXqqQDMKju=TmSR4hruG1dr4qb4MTKrmcyQdXqGa2j5B_joQ@mail.gmail.com>
Subject: Re: [PHP-DEV] [RFC] [Discussion] Never parameters
To: Matt Fonda <matthewfonda@gmail.com>
Cc: internals@lists.php.net
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From: daniel.e.scherzer@gmail.com (Daniel Scherzer)

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On Sun, Mar 16, 2025 at 12:31=E2=80=AFPM Matt Fonda <matthewfonda@gmail.com=
> wrote:

> Hi Daniel,
>
> I believe this feature essentially amounts to "add methods which can neve=
r
> be called", which in my mind makes no sense. If a method types against an
> interface, and that interface uses a method with a never parameter type,
> then we cannot actually call that method. We'd need to know the specific
> concrete type, which defeats the purpose of using an interface in the fir=
st
> place.
>

First, I would point out that I tried to make this limited to methods that
already cannot be called - only to interfaces and abstract methods. You
already can't call those directly, you need to have a subclass. And you can
always type against the implementation with the actual methods that are not
never-typed.

So I would ask - if not `never` parameters, then what should users do? It
seems like, for the use case of "the interface adds a method but there are
no promises about what parameters it accepts", the options would otherwise
be
* documenting that the method should exist, and checking for it, but not
adding it to the interface directly so that PHP doesn't complain
* having implementations "accept" parameters that they then manually throw
errors for, c.f. https://3v4l.org/pTdMg

The original inspiration which I discussed in the RFC is fixing the
signature of the BackedEnum methods, which currently use the second option.


>
> See note from Nikita [1] from previous discussion which expands on this
> idea more, and shows that generics is really what we need here.
>
> [1] https://externals.io/message/115712#115719
>
> Best regards,
> --Matthew
>

I agree that generics would be great and really useful, but should that
stop never parameters? There has also been some discussion about generics
on the inner classes RFC thread - should the dream of generics eventually
stand in the way of independently-useful and smaller-scoped features now?

-Daniel

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<div dir=3D"ltr"><div dir=3D"ltr">On Sun, Mar 16, 2025 at 12:31=E2=80=AFPM =
Matt Fonda &lt;<a href=3D"mailto:matthewfonda@gmail.com">matthewfonda@gmail=
.com</a>&gt; wrote:</div><div class=3D"gmail_quote gmail_quote_container"><=
blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-l=
eft:1px solid rgb(204,204,204);padding-left:1ex"><div dir=3D"ltr"><div><div=
><div dir=3D"ltr"></div></div><div><div dir=3D"ltr"><div dir=3D"ltr">Hi Dan=
iel,</div></div></div></div><div><div><div dir=3D"ltr"><div class=3D"gmail_=
quote"><div><br></div><div>I believe this feature essentially amounts to &q=
uot;add methods which can never be called&quot;, which in my mind makes no =
sense. If a method types against an interface, and that interface uses a me=
thod with a never parameter type, then we cannot actually call that method.=
 We&#39;d need to know the specific concrete type, which defeats the purpos=
e of using an interface in the first place.</div></div></div></div></div></=
div></blockquote><div><br></div><div>First, I would point out that I tried =
to make this limited to methods that already cannot be called - only to int=
erfaces and abstract methods. You already can&#39;t call those directly, yo=
u need to have a subclass. And you can always type against the implementati=
on with the actual methods that are not never-typed.</div><div><br></div><d=
iv>So I would ask - if not `never` parameters, then what should users do? I=
t seems like, for the use case of &quot;the interface adds a method but the=
re are no promises about what parameters it accepts&quot;, the options woul=
d otherwise be</div><div>* documenting that the method should exist, and ch=
ecking for it, but not adding it to the interface directly so that PHP does=
n&#39;t complain</div><div>* having implementations &quot;accept&quot; para=
meters that they then manually throw errors for, c.f.=C2=A0<a href=3D"https=
://3v4l.org/pTdMg">https://3v4l.org/pTdMg</a></div><div><br></div><div>The =
original inspiration which I discussed in the RFC is fixing the signature o=
f the BackedEnum methods, which currently use the second option.</div><div>=
=C2=A0</div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0=
.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir=3D"l=
tr"><div><div><div dir=3D"ltr"><div class=3D"gmail_quote"><div><br></div><d=
iv dir=3D"auto">See note from Nikita [1] from previous discussion which exp=
ands on this idea more, and shows that generics is really what we need here=
.</div><div><br></div><div>[1] <a href=3D"https://externals.io/message/1157=
12#115719" target=3D"_blank">https://externals.io/message/115712#115719</a>=
</div><div><br></div><div>Best regards,</div><div>--Matthew</div></div></di=
v></div></div></div></blockquote><div><br></div><div>I agree that generics =
would be great and really useful, but should that stop never parameters? Th=
ere has also been some discussion about generics on the inner classes RFC t=
hread - should the dream of generics eventually stand in the way of indepen=
dently-useful and smaller-scoped features now?</div><div><br></div><div>-Da=
niel</div><div>=C2=A0</div></div></div>

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