triage-2019-03-11.md

Triage meeting on 2019-03-11

Info

Zulip thread

Help wanted!

• nikomatsakis is looking for someone to help with investigating lazy normatlization. The task would be to experimentally modify rustc and is best suited to someone already vaguely familiar with the Rust query system etc. See below.

Summary

We followed up on the goals from last time.

Lazy normalization and const generics

Link

Last week, nikomatsakis did more investigation, taking notes in this dropbox paper document. In general, it's still not entirely clear if the "cycle" that gives rise to the need for lazy normalization is something we can easily circumvent. One thing is that the generics_of and other queries for "anonymous constants" currently use the incorrect parent def-id precisely to avoid a cycle, so it's hard to see how the cycle would manifest.

Next step: re-establish the cycle in those queries so it can be observed.

GATs

Link

centril + aturon drew up a paper document containing GAT use casts and there are some notes from the conversation in this Zulip thread.

Next step: unclear, but probably to investigate the use cases and make some comments.

Integrating into RLS 2.0

Link

We had a chat (with video) about how the RLS 2.0 type checker works. We decided we'd rather try to do the chalk integration into RLS 2.0 "correct", meaning that we can share a lot more code with chalk.

Next step: nikomatsakis to schedule some time to sketch out what chalk integration would look like.

Other chalk improvements

Maybe discuss other chalk improvements? (e.g., benchmarking harness) (nikomatsakis)

This didn't happen and we'll probably shelve it for now in favor of the previous point.

"lifetime capture"

Maybe discuss the "lifetime capture" problem in impl Trait?

This didn't happen and we'll probably shelve it for now in favor of the next point.

Draft RFCs

centril plans to (at minimum) upload some draft RFCs to a new wg-traits repository.

Associated type bounds

alexreg has been working on associated type bounds in this Zulip thread and will likely continue to do so.

Plans for the coming week

• Try to correct the generics_of query etc for constants so we can observe what results.
  • Help wanted! nikomatsakis is looking for someone to help with investigating lazy normatlization. The task would be to experimentally modify rustc and is best suited to someone already vaguely familiar with the Rust query system etc.
• Read-over GAT use cases and try to theorize about what it would take to support them in rustc etc (nikomatsakis)
• Schedule a call to talk over what chalk integration into RLS 2.0 might look like (nikomatsakis)
• Create a wg-traits repository to house draft RFCs and the like. (nikomatsakis)
• Upload drafts of various traits-related RFCs to wg-traits (centril)
• Continue work on associated type bounds (alexreg)