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Date: Thu, 10 Jun 2021 19:32:21 +0200
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To: Larry Garfield <larry@garfieldtech.com>
Cc: php internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [RFC] Partial Function Application, take 2
From: guilliam.xavier@gmail.com (Guilliam Xavier)

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On Thu, Jun 10, 2021 at 4:34 PM Larry Garfield <larry@garfieldtech.com>
wrote:

> On Thu, Jun 10, 2021, at 3:17 AM, Guilliam Xavier wrote:
> > On Wed, Jun 2, 2021 at 7:47 PM Larry Garfield <larry@garfieldtech.com>
> > wrote:
> >
> > > https://wiki.php.net/rfc/partial_function_application
> >
> > for `$null === null`, is `$c = $null->bar(?);` / `$c =
> > $null::baz(?);` an immediate error, or only later when calling
> `$c($arg)`?
>
> That dies with "call to member function on null" when trying to create the
> partial:
>
> https://3v4l.org/E6MgK/rfc#focus=rfc.partials
>

That makes sense (eager evaluation of non-placeholder "arguments",
including the called-on object).


> > does it
> > support nullsafe calls, e.g. `$foo?->bar(?)`? and if yes, what is the
> > signature of the Closure when `$foo === null`?
>
> I just checked, and it... sort of supports nullsafe.  Rather, if you try
> to partial a method on a null object, you get null back for your closure.
> Then when you try to call it, you get a "cannot invoke null" error.
> Which... I think makes sense.
>
> cf: https://3v4l.org/4XeB3/rfc#focus=rfc.partials


Well I find that unexpected :/


> As a cute side effect, Joe pointed out you could do this:
>
> https://3v4l.org/ERRdY/rfc#focus=rfc.partials


So there's a "workaround", although I wouldn't call it precisely "cute"...


> I wouldn't really call that a feature, but more of a side effect of the
> implementation.  Please don't count on that behavior.
>

I'd rather not indeed ;)  Since `$null?->whatever(1, 'a')` currently always
returns null without error, shouldn't `$null?->whatever(?, 'a')` return a
closure (with a signature built from the placeholders only) that will
return null when called (i.e. equivalent to `fn (mixed $arg1) => null`
here)?

Thanks,

-- 
Guilliam Xavier

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