Remove arena_cache modifier from associated_item query & copy ty::AssocItem instead of passing by ref

[WaffleLapkin]

r? @ghost

[WaffleLapkin]

@bors try @rust-timer queue

[bors]

⌛ Trying commit 1a5355fb820b5b154f1fc32bd756fb2d91fe9c2b with merge f0e0e22d1bd065156a940e921ea502d230ae5a7f...

[bors]

☀️ Try build successful - checks-actions
Build commit: f0e0e22d1bd065156a940e921ea502d230ae5a7f (f0e0e22d1bd065156a940e921ea502d230ae5a7f)

[rust-timer]

Finished benchmarking commit (f0e0e22d1bd065156a940e921ea502d230ae5a7f): comparison URL.

Overall result: no relevant changes - no action needed

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

@bors rollup=never
@rustbot label: -S-waiting-on-perf -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)	2.9%	[1.0%, 4.6%]	5
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Cycles

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

[Noratrieb]

r? Nilstrieb
Looks good, it's just 24 bytes so this should be fine, perf is neutral as well.
Are there any usages in clippy? If yes, you should adjust them as well probably since you also changed rustdoc.
There's an internal lint about passing things by value that are #[rustc_pass_by_value]. Does it make sense to also add it here? It's generally used for IDs and other tiny things, I'm not sure whether it's worth bothering here, having a reference to an assoc item shouldn't hurt anyone.

[WaffleLapkin]

@Nilstrieb clippy seems to be fine (x c clippy passes locally for me), #[rustc_pass_by_value] doesn't seem necessary to me.

[Noratrieb]

r=me after rebase

[WaffleLapkin]

@bors r=Nilstrieb

[bors]

📌 Commit dce666b has been approved by Nilstrieb

It is now in the queue for this repository.

[bors]

⌛ Testing commit dce666b with merge 9aa5c24...

[bors]

☀️ Test successful - checks-actions
Approved by: Nilstrieb
Pushing 9aa5c24 to master...

[bors]

☀️ Test successful - checks-actions
Approved by: Nilstrieb
Pushing 9aa5c24 to master...

[rust-timer]

Finished benchmarking commit (9aa5c24): 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)	-	-	0
Improvements ✅ (primary)	-3.7%	[-3.7%, -3.7%]	1
Improvements ✅ (secondary)	-2.9%	[-2.9%, -2.9%]	1
All ❌✅ (primary)	-3.7%	[-3.7%, -3.7%]	1

Cycles

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