don't point at nonexisting code beyond EOF when warning about delims

[matthiaskrgr]

Previously we would show this:

warning: unnecessary braces around block return value
 --> /tmp/bad.rs:1:8
  |
1 | fn a(){{{
  |        ^  ^
  |
  = note: `#[warn(unused_braces)]` on by default
help: remove these braces
  |
1 - fn a(){{{
1 + fn a(){{
  |

which is now hidden in this case.
We would create a span spanning between the pair of redundant {}s but there is only EOF instead of the } so we would previously point at nothing. This would cause the debug assertion ice to trigger. I would have loved to just only point at the second delim and say "you can remove that" but I'm not sure how to do that without refactoring the entire diagnostic which seems tricky. :( But given that this does not seem to regress any other tests we have, I think this edge-casey enough be acceptable.

Fixes #107423

r? @compiler-errors

[compiler-errors]

@bors r+ rollup

[bors]

📌 Commit ed58c01 has been approved by compiler-errors

It is now in the queue for this repository.

[bors]

⌛ Testing commit ed58c01 with merge a676496...

[bors]

☀️ Test successful - checks-actions
Approved by: compiler-errors
Pushing a676496 to master...

[rust-timer]

Finished benchmarking commit (a676496): 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)	0.2%	[0.2%, 0.2%]	1
Regressions ❌ (secondary)	0.9%	[0.2%, 1.3%]	9
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.2%	[0.2%, 0.2%]	1

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)	2.2%	[2.2%, 2.2%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.9%	[-1.9%, -1.9%]	1
All ❌✅ (primary)	-	-	0

Cycles

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

[lqd]

The tt-muncher, serde-derive benchmarks here are currently noisy, and have since then swung back with #107526 (comment)

Some of the deep-vector use cases are currently in an upward trend that's unrelated to this PR, but are also currently being bimodal.

@rustbot label: +perf-regression-triaged