Add diagnostic arg 'current_crate'

[jannic]

With this fix, I get almost the same error message as on stable, again.

However, I expected to get the new error message std is required by {$current_crate} because it does not declare #![no_std], but I didn't. Instead, I got a new line help: consider building the standard library from source with cargo build -Zbuild-std. So I obviously do not fully understand what is going on.

In any case, the bug itself seems to be fixed by this patch.

Closes #101640

[rust-highfive]

r? @compiler-errors

(rust-highfive has picked a reviewer for you, use r? to override)

[jyn514]

@jannic "std is required" is only triggered if you've built core but not std: https://github.com/rust-lang/rust/pull/101678/files#diff-087de0fff21942e14f7f0d8c532ad2e4b0a7468734d934f3a5ac4ed82586e601R583-R586
You might be able to trigger it with -Zbuild-std=core.

@bors r+ rollup p=1 (fixes nightly breakage)

[bors]

📌 Commit 156717d has been approved by jyn514

It is now in the queue for this repository.

[bors]

⌛ Testing commit 156717d with merge 0d56e34...

[bors]

☀️ Test successful - checks-actions
Approved by: jyn514
Pushing 0d56e34 to master...

[rust-timer]

Finished benchmarking commit (0d56e34): 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.

	mean1	range	count2
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.9%	[0.6%, 1.1%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-5.4%	[-5.4%, -5.4%]	1
All ❌✅ (primary)	-	-	0

Cycles

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.

	mean1	range	count2
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	3.0%	[3.0%, 3.0%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Footnotes

1. the arithmetic mean of the percent change ↩ ↩²

2. number of relevant changes ↩ ↩²