2022-10-07-planning-meeting.md

2022-10-07 planning meeting

Zulip discussion link: https://rust-lang.zulipchat.com/#narrow/stream/326132-t-types.2Fmeetings/topic/2022-10-07.20Planning.20meeting/near/302846151 Previous planning meeting: https://hackmd.io/BN-RofYeTZKKc_5Iu3sPFg

Proposed meetings

Status updates

RPIT refactor

• PR got closed :(
• Changing to RPIT/RPITIT cleanup

TAITs

• landed rust-lang/rust#95474
• opened rust-lang/rust#102417
• opened rust-lang/rust#102700
• Status tracked here: https://github.com/orgs/rust-lang/projects/22/views/1

GATs

• Stable now ? !
• TODO: blog post for 1.65 release
• Issues tracked here: https://github.com/orgs/rust-lang/projects/17
  • Some, at least
• Adding PredicateTy to rustc: https://github.com/jackh726/rust/tree/a-whole-new-world

a-mir-formality

voidc landed some improvements to the type checker.

Currently working on adding a version of the borrow checker (modeling NLL, to start). This has led me to realize that we may be able to make a lightweight change to rustc that would help us with "problem case #3":

if let Some(v) = self.map.get() {
    return v;
}
self.map.insert();

Currently investigating if this is true. :)

Going to be giving a talk on mir-formality next week at HILT '22. Will share slides when they're worth looking at.

Subtyping refactor

mostly distracted by opaque types in ctfe. annoying 😠

Trait object upcasting

Blocked on the need to author an RFC. Should do that.

Negative impls

Did preliminary integration into a-mir-formality and uncovered a problem, filed at #102678, concerning cyclic reasoning. The basic idea is that, before we rely on (T: !Foo) => (T: Foo), we need to establish that. The planned fix is to refactor coherence and leverage query system to avoid cycles.

Polonius

We are planning a series of hackathons to get oriented, starting Oct 26. We will be adding these to the compiler team calendar.

chalk-ty

• No TypeFoldable for EarlyBinder: rust-lang/rust#101901