Add some additional warnings for duplicated diagnostic items

[weiznich]

This commit adds warnings if a user supplies several diagnostic options where we can only apply one of them. We explicitly warn about ignored options here. In addition a small test for these warnings is added.

r? @compiler-errors

For now that's the last PR to improve the warnings generated by misused #[diagnostic::on_unimplemented] attributes. I'm not sure what needs to be done next to move this closer to stabilization.

[weiznich]

@compiler-errors Is there anything I can do to move this forward?

[bors]

☔ The latest upstream changes (presumably #117875) made this pull request unmergeable. Please resolve the merge conflicts.

[compiler-errors]

r=me once it's rebased, sorry for the review delay

[weiznich]

@bors r+

[bors]

@weiznich: 🔑 Insufficient privileges: Not in reviewers

[weiznich]

No worries for taking time to review changes. It was just meant to be a little reminder

[compiler-errors]

@weiznich: the syntax is @bors r=compiler-errors or something, since you're not approving the PR. But also, you need bors rights, so if I say "r=me when...", it's code for "I will approve it when", not "please invoke bors".

@bors r+

[compiler-errors]

@bors r+

[bors]

📌 Commit 10538d4 has been approved by compiler-errors

It is now in the queue for this repository.

[bors]

⌛ Testing commit 10538d4 with merge 547ace8...

[bors]

☀️ Test successful - checks-actions
Approved by: compiler-errors
Pushing 547ace8 to master...

[rust-timer]

Finished benchmarking commit (547ace8): 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)	-	-	0
Regressions ❌ (secondary)	3.1%	[1.0%, 5.4%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.4%	[-1.4%, -1.4%]	1
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: 675.978s -> 676.499s (0.08%)
Artifact size: 313.80 MiB -> 313.81 MiB (0.00%)