Re: [RFC] Never For Argument Types

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.ledoux@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 >