Fix lint scoping for let-else.

[cjgillot]

The scoping for let-else is inconsistent with HIR nesting. This creates cases, in ui/let-else/let-else-allow-unused.rs for instance, where an allow lint attribute does not apply to the bindings created by let-else.

This PR is an attempt to correct this.

As there is no lint that currently relies on this, the test for this behaviour is #101500.

cc @dingxiangfei2009 as you filed #101894

[rust-highfive]

r? @compiler-errors

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[dingxiangfei2009]

This looks quite right. Sorry for the confusion!

[compiler-errors]

@bors r=dingxiangfei2009

[bors]

📌 Commit 73c52bc has been approved by dingxiangfei2009

It is now in the queue for this repository.

[bors]

⌛ Testing commit 73c52bc with merge 1d1f142...

[bors]

☀️ Test successful - checks-actions
Approved by: dingxiangfei2009
Pushing 1d1f142 to master...

[rust-timer]

Finished benchmarking commit (1d1f142): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean1	range	count2
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.7%	[-0.7%, -0.7%]	1
Improvements ✅ (secondary)	-1.4%	[-1.6%, -1.2%]	6
All ❌✅ (primary)	-0.7%	[-0.7%, -0.7%]	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.

	mean1	range	count2
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	4.5%	[4.5%, 4.5%]	1
Improvements ✅ (primary)	-3.6%	[-3.6%, -3.6%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-3.6%	[-3.6%, -3.6%]	1

Cycles

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

Footnotes

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

2. number of relevant changes ↩ ↩²