Newsgroups: php.internals
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Xref: news.php.net php.internals:113988
Date: Wed, 07 Apr 2021 13:25:30 +0000
To: Hamza Ahmad <office.hamzaahmad@gmail.com>
Cc: "internals@lists.php.net" <internals@lists.php.net>
Reply-To: Saif Eddin Gmati <azjezz@protonmail.com>
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Subject: Re: [PHP-DEV] Empower Callables with Function Signature Hints
From: azjezz@protonmail.com (Saif Eddin Gmati)

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Hello Hamza,

I think this is something that has been discussed here before.

function types already exist in HackLang: https://docs.hhvm.com/hack/funct=
ions/introduction#function-types,

And, if we would follow the same syntax `(function(T, T): T)` or `(callabl=
e(T, T): T)`, PHP needs to first support parentheses in
type declaration ( grouping ), which currently it doesn't ( i.e: `function=
 baz((string|bar) $foo): void {}` becomes valid ).

And just to note, function types are also supported by static analysis too=
ls such as Psalm ( https://psalm.dev/docs/annotating_code/type_syntax/call=
able_types/ ) and PHPStan ( https://phpstan.org/writing-php-code/phpdoc-ty=
pes#callables ), so i suppose if PHP is to support typed callables, it sho=
uld take inspiration from these tools.

There's also an alternative syntax that was proposed back in 2016 for PHP =
7.1, but it seems like the RFC was abandoned: https://wiki.php.net/rfc/typ=
esafe-callable

Cheers,

Saif.

=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90 Original M=
essage =E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90=E2=80=90
On Wednesday, April 7, 2021 11:58 AM, Hamza Ahmad <office.hamzaahmad@gmail=
.com> wrote:

> Hello Internals,
> I want to request making possible to catch functions with wrong signatur=
e
> when passed as callable. In other words, when a function or a method is
> passed as callable value, PHP will first confirm whether the function is=
 of
> the write callable type that the function being executed requires. It wi=
ll
> help catch silent errors.
> Currently, PHP does following:
> =


> 1.  Confirms whether a callable is valid.
> 2.  Passes the callable value to a function, and the execution starts.
> 3.  If the passed function receives values which's type is different tha=
n
>     function signature, PHP throws an error.
>     =


> 4.  If passed function returns nothing, the variable that wanted a value=
 from
>     the passed function receives null.
>     =


> 5.  As a result, the unexpected results emerge.
>     To resolve this issue, I propose to introduce a mechanism that allow=
s to
>     hint callable signatures. To understand the spirit of this request, =
look at
>     the similar functionality that Angel Script Project provides with.
>     =


> 6.  One defines a function definition.
> 7.  Use its name to hint the same signature.
> 8.  The compiler alerts about the incorrect signature before passing thi=
s to
>     a function.
>     If I could do this in PHP, I would write like following:
>     `funcdef preg_replace_callback_hint(array $matches) : string;`
>     If I accidently pass a callable which's signature is different than =
desired
>     function call, the error is caught earlier.
>     This message does not suggests syntax; it only points to a problem a=
nd
>     suggests a solution. Any volunteers that would love to come up with =
syntax
>     and implement this?
>     I am curious to see the feedback.
>     Regards
>     Hamza Ahmad
>     =


>     --
>     PHP Internals - PHP Runtime Development Mailing List
>     To unsubscribe, visit: https://www.php.net/unsub.php
>


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