Remove chalk support from Rust

[compiler-errors]

Proposal

As far as I'm aware, the Chalk compiler is deprecated^1. My understanding is that T-types will continue maintaining it for rust-analyzer, but we have no plans to continue integrating it into rustc and it's a bit of a burden on the compiler due to the interning layer from chalk <=> rustc and the specific workarounds that live in the compiler to accomodate for the chalk solver.

Mentors or Reviewers

I can implement the removal. The code should be very easy to review since it's just a bunch of code going away.

Process

The main points of the Major Change Process are as follows:

• [x] File an issue describing the proposal.
• [ ] A types team member or contributor who is knowledgeable in the area can second by writing @rustbot second.
  • Finding a "second" suffices for internal changes. If however, you are proposing a new public-facing feature, such as a -C flag, then full team check-off is required.
  • Types team members can initiate a check-off via @rfcbot fcp merge on either the MCP or the PR.
• [ ] Once an MCP is seconded, the Final Comment Period begins. If no objections are raised after 10 days, the MCP is considered approved.

You can read more about Major Change Proposals on forge.

Comments

Not sure if this should be a full-fledged FCP. If so, I can open one on the removal PR.

[rustbot]

This issue is not meant to be used for technical discussion. There is a Zulip stream for that. Use this issue to leave procedural comments, such as volunteering to review, indicating that you second the proposal (or third, etc), or raising a concern that you would like to be addressed.

cc @rust-lang/types

[BoxyUwU]

@rustbot second

[jackh726]

/concern

As I mentioned on zulip I do think the Chalk integration is still useful, particularly with my experimentation with associated types.

Can you say more about exactly how it's a burden to maintain? New features and such don't need to be implemented in the Chalk integration code. Is there some specific changes or refactoring that we can't do because of the chalk integration code? (That can't simply just be unimplemented!()?

[lcnr]

closing as accepted https://rust-lang.zulipchat.com/#narrow/stream/326132-t-types.2Fmeetings/topic/2023-07-03.20planning.20meeting/near/372030757