move hir typeck into separate crate

[lcnr]

Proposal

With https://github.com/rust-lang/rust/pull/99015 landing, the typeck query is the only place using an FnCtxt and this should stay this way. HIR typeck is a fairly complex and self contained part of rustc and moving all of that in a separate, common place should make refactorings and cleanups easier. It should also be easier to understand and more difficult to misuse, as you would have to add a dependency on a new crate to use the FnCtxt now.

We should move the typeck queries, FnCtxt and anything else exclusively used by HIR typeck to a new crate rustc_hir_typeck.

At the same time I also suggest renaming rustc_typeck to rustc_hir_analysis as that crate is responsible for so much more than simply "checking types".

Mentors or Reviewers

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Process

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

• [x] File an issue describing the proposal.
• [ ] A compiler 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.
  • Compiler 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.

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Comments

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.

[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/compiler @rust-lang/compiler-contributors

[compiler-errors]

Since this change will be mostly moving things around and name changing, I don't think this is particularly controversial. Things under rustc_typeck/src/check/fn_ctxt are already somewhat self-contained.

@rustbot second

[apiraino]

@rustbot label -final-comment-period +major-change-accepted