Revert "Stabilize -Znext-solver=coherence"

[compiler-errors]

This is a clean revert of #121848, prepared by running:

$ git revert 17b322fa69eed7216dccc9f097eb68237cf62234 -m1

Which effectively reverts:

• a138a92, 69fdd14, d93e047, 1a893ac

see: https://rust-lang.zulipchat.com/#narrow/stream/364551-t-types.2Ftrait-system-refactor/topic/nalgebra.20hang

Closes #130056

r? lcnr

[rustbot]

Some changes occurred in engine.rs, potentially modifying the public API of ObligationCtxt.

cc @lcnr, @compiler-errors

[lcnr]

r=me after CI is green

@bors rollup=never

[lcnr]

Thanks for opening this PR!

@bors r+

[bors]

📌 Commit e866f8a has been approved by lcnr

It is now in the queue for this repository.

[bors]

⌛ Testing commit e866f8a with merge f753bc7...

[bors]

☀️ Test successful - checks-actions
Approved by: lcnr
Pushing f753bc7 to master...

[rust-timer]

Finished benchmarking commit (f753bc7): comparison URL.

Overall result: ❌✅ regressions and improvements - ACTION NEEDED

Next Steps: If you can justify the regressions found in this perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please open an issue or create a new PR that fixes the regressions, add a comment linking to the newly created issue or PR, and then add the perf-regression-triaged label to this PR.

@rustbot label: +perf-regression
cc @rust-lang/wg-compiler-performance

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)	3.7%	[2.9%, 4.5%]	7
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.5%	[-0.9%, -0.2%]	13
Improvements ✅ (secondary)	-0.5%	[-0.7%, -0.1%]	9
All ❌✅ (primary)	1.0%	[-0.9%, 4.5%]	20

Max RSS (memory usage)

Results (primary -0.5%)

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)	-0.5%	[-0.5%, -0.5%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.5%	[-0.5%, -0.5%]	1

Cycles

Results (primary 3.7%, secondary 2.4%)

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)	3.7%	[2.9%, 4.7%]	6
Regressions ❌ (secondary)	2.4%	[2.1%, 2.6%]	4
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	3.7%	[2.9%, 4.7%]	6

Binary size

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

Bootstrap: 758.873s -> 759.185s (0.04%)
Artifact size: 341.30 MiB -> 341.20 MiB (-0.03%)