Use as_lang_item instead of repeatedly matching

[oli-obk]

drive-by fix I noticed while reviewing https://github.com/rust-lang/rust/pull/157489/changes#r3550851573

[rustbot]

r? @khyperia

rustbot has assigned @khyperia.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

Why was this reviewer chosen?

The reviewer was selected based on:

• Owners of files modified in this PR: compiler, types
• compiler, types expanded to 75 candidates
• Random selection from 17 candidates

[lqd]

r? me

Looks good and simple, r=me when green

[oli-obk]

@bors r=lqd rollup

[rust-bors]

📌 Commit 79b7231 has been approved by lqd

It is now in the queue for this repository.

[Kobzol]

@bors try @rust-timer queue

Racing the queue, just to check if it had any potential perf. effect.

[rust-bors]

☀️ Try build successful (CI)
Build commit: 5eef5c6 (5eef5c65e9a624f737a13c8fc22ca68d359f4656)
Base parent: 561ea2b (561ea2bfa3022226082e2db39d6ccb241e9e34bc)

[rust-timer]

Finished benchmarking commit (5eef5c6): comparison URL.

Overall result: ❌ regressions - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	0.2%	[0.2%, 0.3%]	2
Regressions ❌ (secondary)	0.3%	[0.2%, 0.3%]	9
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.2%	[0.2%, 0.3%]	2

Max RSS (memory usage)

Results (secondary 4.7%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	4.7%	[3.2%, 6.2%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Cycles

Results (primary -3.1%, secondary -2.5%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-3.1%	[-3.1%, -3.1%]	1
Improvements ✅ (secondary)	-2.5%	[-2.6%, -2.3%]	2
All ❌✅ (primary)	-3.1%	[-3.1%, -3.1%]	1

Binary size

Results (primary -0.1%, secondary -0.1%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.1%	[-0.1%, -0.0%]	56
Improvements ✅ (secondary)	-0.1%	[-0.1%, -0.0%]	22
All ❌✅ (primary)	-0.1%	[-0.1%, -0.0%]	56

Bootstrap: 489.147s -> 489.653s (0.10%)
Artifact size: 388.47 MiB -> 388.36 MiB (-0.03%)

[JonathanBrouwer]

Perf is quite negative but I'm convinced this is all noise
@bors rollup=iffy

[JonathanBrouwer]

@rust-timer build 0fde074

[rust-timer]

Finished benchmarking commit (0fde074): comparison URL.

Overall result: ❌✅ regressions and improvements - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.1%	[0.0%, 0.1%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.1%	[-0.2%, -0.0%]	7
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (secondary 3.2%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	3.2%	[3.2%, 3.2%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Cycles

Results (primary -2.1%, secondary 5.4%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	8.2%	[1.8%, 23.5%]	9
Improvements ✅ (primary)	-2.1%	[-2.1%, -2.1%]	1
Improvements ✅ (secondary)	-3.2%	[-4.2%, -2.6%]	3
All ❌✅ (primary)	-2.1%	[-2.1%, -2.1%]	1

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 490.729s -> 488.618s (-0.43%)
Artifact size: 389.29 MiB -> 389.89 MiB (0.15%)

[JonathanBrouwer]

@rustbot label: +perf-regression-triaged
Noise