Combine ty::Projection and ty::Opaque into ty::Alias

[compiler-errors]

Implements rust-lang/types-team#79.

This PR consolidates ty::Projection and ty::Opaque into a single ty::Alias, with an AliasKind and AliasTy type (renamed from ty::ProjectionTy, which is the inner data of ty::Projection) defined as so:

enum AliasKind {
  Projection,
  Opaque,
}

struct AliasTy<'tcx> {
  def_id: DefId,
  substs: SubstsRef<'tcx>,
}

Since we don't have access to TyCtxt in type flags computation, and because repeatedly calling DefKind on the def-id is expensive, these two types are distinguished with ty::AliasKind, conveniently glob-imported into ty::{Projection, Opaque}. For example:

  match ty.kind() {
-   ty::Opaque(..) => 
+   ty::Alias(ty::Opaque, ..) => {}
    _ => {}
  }

This PR also consolidates match arms that treated ty::Opaque and ty::Projection identically.

r? @ghost

[cjgillot]

I wonder what are the next steps. Can this be used to integrate in-trait opaques as a variant of AliasKind?

[bors]

☔ The latest upstream changes (presumably #105008) made this pull request unmergeable. Please resolve the merge conflicts.

[rustbot]

Some changes occurred to the CTFE / Miri engine

cc @rust-lang/miri

Some changes occurred in need_type_info.rs

cc @lcnr

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

[compiler-errors]

I think this is ready

r? types

[bors]

☔ The latest upstream changes (presumably #105348) made this pull request unmergeable. Please resolve the merge conflicts.

[oli-obk]

r=me with some nits and a clean perf run

[oli-obk]

@bors p=1 bitrotty

[bors]

⌛ Trying commit 99417d5 with merge ad35b8e377db9f8fa1364750ed99d283bc52b2f2...

[bors]

☀️ Try build successful - checks-actions
Build commit: ad35b8e377db9f8fa1364750ed99d283bc52b2f2 (ad35b8e377db9f8fa1364750ed99d283bc52b2f2)

[rust-timer]

Finished benchmarking commit (ad35b8e377db9f8fa1364750ed99d283bc52b2f2): comparison URL.

Overall result: ❌ regressions - ACTION NEEDED

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	1.1%	[1.0%, 1.1%]	2
Regressions ❌ (secondary)	2.1%	[0.9%, 2.7%]	7
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.1%	[1.0%, 1.1%]	2

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.2%	[-2.2%, -2.2%]	1
All ❌✅ (primary)	-	-	0

Cycles

This benchmark run did not return any relevant results for this metric.

[compiler-errors]

This looks like the same exact noisy crates that we saw in #105350 (comment)

[oli-obk]

@bors r+

[bors]

📌 Commit 99417d5 has been approved by oli-obk

It is now in the queue for this repository.

[bors]

⌛ Testing commit 99417d5 with merge 918d0ac...

[bors]

☀️ Test successful - checks-actions
Approved by: oli-obk
Pushing 918d0ac to master...

[rust-timer]

Finished benchmarking commit (918d0ac): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	3.6%	[3.3%, 3.9%]	2
Regressions ❌ (secondary)	1.6%	[1.6%, 1.6%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	3.6%	[3.3%, 3.9%]	2

Cycles

This benchmark run did not return any relevant results for this metric.