Hey!
Using the "never" type to require that downstream libs specify a type does
not make intuitive sense to me, because the same is not true the other way
(covariantly) for return types.
The existence of a "never" type on an overriding method does not require
that upstream libs specify a return type — this is perfectly valid:
class A {
public function foo() {}
}
class AChild extends A {
public function foo():never { exit; }
}
Best wishes,
Matt
On Fri, 13 Aug 2021 at 19:27, Jordan LeDoux <jordan.led...@gmail.com> wrote:
> Hey internals,
>
> I've been working on the draft for my operator overloading RFC, and in
> doing so I encountered a separate change that I would like to see.
>
> That is, the use of `never` as an argument type for interfaces. Since
> arguments in PHP are contravariant to preserve Liskov substitution, `never`
> as the bottom type should indicate that implementing classes can require
> any type combination they want. This is in fact consistent with type theory
> and set theory, and is how the bottom type is treated in several other
> languages.
>
> In this case, the bottom type would be used to indicate covariant parameter
> polymorphism while not conflicting with LSP.
>
> This would provide a sort of minimal form of generics to PHP without the
> issues that actual generics present from an implementation perspective. It
> would not, however, restrict or hinder any future RFC for generics.
>
> This is at the first draft stage, and I currently have the RFC on a github
> repo to allow for easy contribution and collaboration.
>
> Any feedback is greatly appreciated.
>
> https://github.com/JordanRL/never-argument-type
>
> Jordan
>
