mark ty::Const::Error when meet unsupport ty for const generic params

[bvanjoi]

Close #116796

[rustbot]

r? @wesleywiser

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[compiler-errors]

Why can't we just delay a bug? Or is there a way we could do the ConstParamTy trait check earlier?

[bvanjoi]

Or is there a way we could do the ConstParamTy trait check earlier?

The function type_allowed_to_implement_const_param_ty is executed within check_param_wf which follows check_item , wherein the internals of check_item trigger a panic.

Can we reorder it and halt the process as follows? I'm concerned that it may not be feasible because it could lead to unsoundness

let mut res = None;
if let Some(generics) = node.generics() {
    for param in generics.params {
        res = res.and(check_param_wf(tcx, param));
    }
}
if res.is_error() {
    return res
}
return res.and(check_item(xxxx));

Why can't we just delay a bug?

How might we postpone this? The exact value is retrieved using the c.expect, but there doesn't appear to be an error fallback for ValTree.

[bors]

☔ The latest upstream changes (presumably #116930) made this pull request unmergeable. Please resolve the merge conflicts.

[wesleywiser]

r? @jackh726

[jackh726]

I'll take this review, but it'll be this weekend

r? @jackh726

[jackh726]

Okay, this errors cleanly since beta 1.76. So, I'll mark the issue as needs-test. @bvanjoi sorry for the review delay here - would you like to just update the PR to add the test as a regression test?

[bvanjoi]

Pleased to see the issue being jointly addressed. And I will add a test case.

[jackh726]

Can you put the test under const-generics? And rename to something descriptive, referencing the issue in a comment?

[jackh726]

Thanks!

@bors r+ rollup

[bors]

📌 Commit 0f814e3 has been approved by jackh726

It is now in the queue for this repository.

[bors]

⌛ Testing commit 0f814e3 with merge 08cc634...

[bors]

☀️ Test successful - checks-actions
Approved by: jackh726
Pushing 08cc634 to master...

[rust-timer]

Finished benchmarking commit (08cc634): comparison URL.

Overall result: ❌ regressions - 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)	0.7%	[0.6%, 0.7%]	4
Regressions ❌ (secondary)	0.4%	[0.2%, 0.6%]	19
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.7%	[0.6%, 0.7%]	4

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)	-3.6%	[-5.0%, -2.1%]	2
All ❌✅ (primary)	-	-	0

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: 670.535s -> 669.722s (-0.12%)
Artifact size: 312.63 MiB -> 312.65 MiB (0.01%)

[jackh726]

This is only a test, so must be noise.