Fix capacity overflow issue during transmutability check

[chenyukang]

Fixes #103751

[rustbot]

r? @nagisa

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[nagisa]

FWIW it is useful to name regression tests after the issues they come from. This has couple purposes:

• It is easy to see this is a regression test;
• Resolving to the original issue report takes a single dereference (rather than having to go through git log, looking at the commit message and only then finding the issue number to load up.)

Not a huge deal either way though.

[nagisa]

@bors r+ thanks!

[bors]

📌 Commit 749afe5 has been approved by nagisa

It is now in the queue for this repository.

[bors]

⌛ Testing commit 749afe5 with merge 6b8d9dd...

[bors]

☀️ Test successful - checks-actions
Approved by: nagisa
Pushing 6b8d9dd to master...

[rust-timer]

Finished benchmarking commit (6b8d9dd): 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.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.4%	[-0.4%, -0.4%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.4%	[-0.4%, -0.4%]	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)	-	-	0
Improvements ✅ (primary)	-0.4%	[-0.4%, -0.4%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.4%	[-0.4%, -0.4%]	1

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.

	mean	range	count
Regressions ❌ (primary)	0.9%	[0.9%, 0.9%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.5%	[-0.5%, -0.5%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.2%	[-0.5%, 0.9%]	2