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Date: Thu, 10 Jun 2021 09:33:57 -0500
To: "php internals" <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [RFC] Partial Function Application, take 2
From: larry@garfieldtech.com ("Larry Garfield")

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:
> 
> > Hi folks.  After much off-list discussion, iteration, and consideration,
> > we have a new draft of PFA ready for review.
> >
> > The URL is the same:
> >
> > https://wiki.php.net/rfc/partial_function_application
> >
> 
> Hi, thanks all for the reworks!  I just thought to something: does it
> support nullsafe calls, e.g. `$foo?->bar(?)`? and if yes, what is the
> signature of the Closure when `$foo === null` (and does it make a
> difference if, inside a function, it was created as a local variable `$foo
> = null;` vs received as a typed parameter `?Foo $foo`)?

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

As a cute side effect, Joe pointed out you could do this:

https://3v4l.org/ERRdY/rfc#focus=rfc.partials

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 also discovered while checking that nullsafe differentiates between null and undefined.  That was unexpected, but not related to the topic at hand. :-)

> Related, 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

--Larry Garfield