Get rid of HIR const checker

[compiler-errors]

As far as I can tell, the HIR const checker was implemented in #66170 because we were not able to issue useful const error messages in the MIR const checker.

This seems to have changed in the last 5 years, probably due to work like #90532. I've tweaked the diagnostics slightly and think the error messages have gotten better in fact.

Thus I think the HIR const checker has reached the end of its usefulness, and we can retire it.

cc @RalfJung

[rustbot]

r? @wesleywiser

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[rustbot]

Some changes occurred to the CTFE machinery

cc @rust-lang/wg-const-eval

[RalfJung]

I didn't even know we had another const checker...
Cc @rust-lang/wg-const-eval

[compiler-errors]

@wesleywiser, do you have a chance to review this? Otherwise, should I re-roll? (Unless @RalfJung would like to r+ this instead 😸)

[wesleywiser]

This is a really nice cleanup! 🏅

I agree, on average it feels to me like diagnostics are slightly better than before even with the couple notable regressions.

[wesleywiser]

@bors r+ rollup=never

in case removing this pass changes compiler perf any

[bors]

📌 Commit 01ff36a has been approved by wesleywiser

It is now in the queue for this repository.

[bors]

⌛ Testing commit 01ff36a with merge efdd9e8...

[bors]

☀️ Test successful - checks-actions
Approved by: wesleywiser
Pushing efdd9e8 to master...

[rust-timer]

Finished benchmarking commit (efdd9e8): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -perf-regression

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.2%	[0.2%, 0.2%]	1
Improvements ✅ (primary)	-0.2%	[-0.3%, -0.1%]	12
Improvements ✅ (secondary)	-0.2%	[-0.4%, -0.1%]	28
All ❌✅ (primary)	-0.2%	[-0.3%, -0.1%]	12

Max RSS (memory usage)

Results (primary 1.9%, secondary 1.9%)

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)	1.9%	[1.9%, 1.9%]	1
Regressions ❌ (secondary)	3.3%	[2.5%, 4.4%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.4%	[-2.4%, -2.4%]	1
All ❌✅ (primary)	1.9%	[1.9%, 1.9%]	1

Cycles

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

Binary size

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

Bootstrap: 767.847s -> 767.333s (-0.07%)
Artifact size: 332.18 MiB -> 332.08 MiB (-0.03%)