Re: Basic Type Alias

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