On Mon, Jun 15, 2026, at 20:27, Rob Landers wrote: > > > On Mon, Jun 15, 2026, at 20:22, Matthew Brown wrote: >> On Mon, 15 Jun 2026 at 12:28, Levi Morrison <[email protected]> >> wrote: >>> > Voting is now open on the Bound-Erased Generic Types RFC, as announced >>> > in the Intent to Vote message earlier this week. >>> > >>> > The vote started on 2026-06-14 at 16:50 UTC and ends on 2026-06-28 at >>> > 17:00 UTC. >>> > >>> > RFC: https://wiki.php.net/rfc/bound_erased_generic_types >>> > Discussion thread: https://news-web.php.net/php.internals/130816 >>> > Implementation: https://github.com/php/php-src/pull/21969 >>> >>> To my own surprise, I am voting yes on this proposal. >>> >>> I still believe that refied generics should be the goal. To that end, >>> I think we should be able to merge this and in minor versions, fix >>> "soundness" and implementation holes as "bug" fixes on that route. If >>> internals can agree on this, and then the community can communicate >>> this through education, promotion, documentation, etc, then this RFC >>> is simply a useful stepping stone. >>> >>> This is based on my own experience playing with the RFC, which >>> included reporting 2 bugs in the implementation on the RFC. To be >>> honest, it's not too useful to me. I very quickly run up against some >>> limitation when trying to build useful things. Most notably, we need >>> to be able to define lower bounds (syntax pending, obviously): >>> >>> class Option<+A> >>> { >>> // B >: A means B is an ancestor of A >>> // Since all As are Bs, you can return the A here >>> function get_or_default<B >: A>(Option $option, B $default): B >>> { >>> return $option->has_some() >>> ? $option->get() >>> : $default; >>> } >>> // todo: the rest of the implementation >>> } >>> >>> You can't take `A $default` and return `A` because this violates the >>> variance laws: a covariant type A cannot be used in parameter >>> position. So alternatively you could solve this with `inout A >>> $default` or similar. >> >> Presumably this would work with the current proposal: >> >> class Option<+A> { >> public function getOrDefault<B>(B $default): A|B { >> return $this->hasSome() ? $this->get() : $default; >> } >> } >> >> Hack also has `super` type constraints: >> https://hhvm.com/blog/9215/covariance-contravariance-and-super-type-constraints > > It wouldn’t actually do anything though… > > — Rob
Sorry. Sent before I was finished writing. It wouldn’t actually do anything though… Both are “correct” in erased generics. You’d receive no error or feedback what you’d written was “wrong” or “broken”. In both examples, types reduce to mixed. — Rob
