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Date: Thu, 22 Jan 2026 10:41:51 -0600
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Subject: Re: [PHP-DEV] [RFC] Partial Function Application for instance of non-static
 methods ("$this")
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From: larry@garfieldtech.com ("Larry Garfield")

On Thu, Jan 22, 2026, at 10:26 AM, Rowan Tommins [IMSoP] wrote:
> On 22/01/2026 16:08, Tim D=C3=BCsterhus wrote:
>> Yes, it certainly requires some getting used to it. It's the best we=20
>> could come up with, but if there are any better suggestions, we're=20
>> open to hearing those. I'd like to note the =E2=80=9CRejected Feature=
s=E2=80=9D=20
>> section, since it lists some non-workable alternatives we considered.=20
>
>
> Looking at this:
>
>  >=C2=A0PHP itself already has "ALGOL-style" declarations, for "const"=
,=20
> "global", and "static".
>
> I'm reminded of placeholders in PostgreSQL; the type is needed to choo=
se=20
> overloaded functions and operators, so this doesn't compile (without=20
> extra metadata):
>
> Select do_something(?) as result
>
> Instead, you can insert a dummy cast to indicate the type:
>
> Select=C2=A0do_something(?::int) as result
>
>
> The PHP equivalent would be something like this:
>
> $f =3D (DateTimeImmutable)?->format('c');
>
> Or, slightly more readable but less consistent with casts:
>
> $f =3D (? as=C2=A0DateTimeImmutable)->format('c');
>
>
> That doesn't solve the second part of the problem though:
>
>  >=C2=A0It would also not allow to reorder the parameters in the resul=
ting=20
> Closure, which is an explicit feature of Partial Function Application.
>
>
> I thought I'd throw it out there anyway in case it stimulates any othe=
r=20
> ideas.

More spitballing on my previous reply:

class Test {
  public function stuff(int $a) {}
}

(Test)?->stuff(?);

Translates to:

fn(Test $__this, int $a) =3D> $__this->stuff($a);

But if there's no partialing on the method side, it could get abbreviate=
d to:

(?)->stuff(4);

Translates to:

fn(object $__this) =3D> $__this->stuff(4);

Because we don't need to know the type at compile time, and a method-not=
-found error would still happen at runtime anyway if necessary.  That wo=
uld then be a lot easier to write in cases where you're just dropping a =
$this->stuff() call into a pipe chain but want to receive $this.

I'm not sure if that would also allow for reading properties with the sa=
me syntax?

--Larry Garfield