[RFC] Callable Types

hi!

From: Mathieu Rochette mathieu@texthtml.net

Date: 2016-04-23 12:44 GMT-04:00
Subject: Re: [PHP-DEV][RFC] Callable Types

Hello everyone,

We just completed the draft for the "Callable Types" RFC. This RFC has been
recently mentioned during other type related threads on this mailing list,
so it feels to be the right time to put the proposal in context:

The proposal is at https://wiki.php.net/rfc/callable-types

It looks very nice overall :) and would be, imho, a great addition to PHP

I have a few comments, first about the optional arguments, the example in
the rfc says :

// That means that foo() could call $cb and pass anything as a first
argument and if it would be something that is not an instance of A the call
would fail.
I don't get why foo would be declared as

function foo(callable() $cb) { }

instead of

function foo(callable($any) $cb) { }

if foo intends to call $cb with an argument.

what about optional arguments, eg:

class Foo
{
private $logger;
public __construct(Logger $logger = null) {$this->logger = $logger;}
public doSomething(callable(int $done, int $remaining, Logger = null)
$progressCb) {
// ...
for($i = 0; $i < $n; $i++) {
// ...
$progressCb($i, $n - $i, $this->logger);
}
}
}

should that be supported ?

Currently you can nullify or skip the Logger argument upon implementation
of the callable. Rendering your example:

https://3v4l.org/qb5QR/rfc#tabs

Admittedly, the expectation for default values to work seems legit and we
are currently discussing whether to support
default values on callable types signatures or not (inclined to do not
support). But honestly I haven't seen a legit use
case when we already have the ability to satisfy the callback with a
smaller type. Perhaps you may have one use case
where a default value would be indispensable?
I wouldn't say it's indispensable. it's just that in the previous
example, the class Foo cannot say that the #rd argument of the callable
is either a Logger or null.
that means that giving function(int $done, int
$remaining){var_dump($remaining);} works but function(int $done, int
$remaining, Logger $logger){$logger->debug($remaining);} does
not even though it is compatible with the callable signature. and
afaikt, I cannot make a signature without a default null value or one of
the rfc about union types or nullable types

and last one, will instanceof supports this new syntax?

Yes, please expect to see this on the next minor version of the RFC :)
great !

I've seen someone mentioning variadics so I made a few small tests, I
think those two should work (they currently don't):

https://3v4l.org/eZgR9/rfc#rfc-callable_typehint
https://3v4l.org/N7i0u/rfc#rfc-callable_typehint

and this one should not:

https://3v4l.org/fcRlT/rfc#rfc-callable_typehint

thank you

The W.I.P patch is available for testing through http://3v4l.org under the
RFC tab.

We count with your detailed feedback and insights. Let's have a nice,
respectful and
constructive conversation about the RFC and work on possible improvements!

Thanks
Nikita Nefedov
Márcio Almada

--
Mathieu Rochette

Cheers.

--
Mathieu Rochette