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Date: Thu, 25 Jan 2024 00:15:20 +0100
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To: Larry Garfield <larry@garfieldtech.com>
Cc: Jorg Sowa <jorg.sowa@gmail.com>, php internals <internals@lists.php.net>
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Subject: Re: Basic Type Alias
From: oladoyinbov@gmail.com (Oladoyinbo Vincent)

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I have been so busy lately, which gave me no time to work on the type alias
implementation. but I will be happy if anyone can volunteer/help in
implementing this feature so that it can be introduced in PHP 8.4 or 9.0,
as this will help optimise a lot of people and codebase out there.


On Monday, October 30, 2023, Larry Garfield <larry@garfieldtech.com> wrote:

> On Sun, Oct 29, 2023, at 9:52 PM, Jorg Sowa wrote:
> > I really like the idea and I would love to see it in PHP. I'm wondering
> > however, what would be the scope of the feature and how complex would be
> > designed type system. Examples I saw in this thread could be easily
> > replaced with union and intersection types (i.e. numeric as int|float).
> In
> > my opinion, there is a little benefit implementing in this shape making
> the
> > PHP core more complex.
> >
> > The two use cases of user defined types in PHP which would benefit a lot
> > IMO, would be:
> > 1. Typed arrays similar to Typescript.
> > 2. Semantic types which would increase the security of systems. Example:
> > type UserId = int;
> >
> > function setUserId_1(int $userId){}
> >
> > function setUserId_2(UserId $userId){}
> >
> > setUserId_1(5); // OK
> > setUserId_2(5); // TypeError
> >
> > setUserId_1(UserId(5)); // OK
> > setUserId_2(UserId(5)); // OK
> >
> > Kind regards,
> > Jorg
>
> Simple unions are the easiest to talk about in quick examples, but the
> real benefit of type aliases is in other cases, some of which they would
> enable.
>
> Example:
>
> I have a real parameter defined in my attributes library like this:
>
> \ReflectionProperty|\ReflectionMethod|\ReflectionClassConstant $subject
>
> And it appears several times, I believe.  That would definitely be nicer
> if simplified to an alias.
>
> Example:
>
> There's general consensus that callable types would be beneficial:
> callable(RequestInterface, string): string or similar.  But inline, that
> gets long and complicated fast.  Type aliases would allow simplifying that
> to
>
> type callable(RequestInterface, string): string as PropertyRetriever
>
> function foo(PropertyRetriever $c) { ... }
>
> Example:
>
> As in the above example, type aliases serve as documentation for callables
> or complex types, explaining what that complex ruleset actually means,
> semantically.
>
> Example:
>
> If generics or typed arrays ever happen, they'd probably be useful here,
> too.
>
> Note that using type aliases in a required-fashion is a different matter,
> and potentially not feasible.  Free standing variables are untyped, which
> means setUserId(UserId $id) could not require a UserId, because there's no
> way to define a variable as being a UserId, not an int.  While I can
> definitely see a value in that kind of restriction, in practice I don't
> think PHP is capable of it without vastly larger changes.
>
> --Larry Garfield
>


-- 
Best Regards,
O. Vincent

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