various small rustc_expand cleanups

[cyrgani]

Each commit should be reviewable on its own.

[rustbot]

rust-analyzer is developed in its own repository. If possible, consider making this change to rust-lang/rust-analyzer instead.

cc @rust-lang/rust-analyzer

[rustbot]

r? @BoxyUwU

rustbot has assigned @BoxyUwU.
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
• compiler expanded to 69 candidates
• Random selection from 14 candidates

[Kivooeo]

r? me

just wondering about how much this affects perf

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: dc646e9 (dc646e9b0338941cd2c6068cc00555cebac17041, parent: a5c825cd824ee0ef9463021078a2f464b4cc1a0d)

[rust-timer]

Finished benchmarking commit (dc646e9): comparison URL.

Overall result: ✅ improvements - no action needed

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.

@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
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.3%	[-0.3%, -0.3%]	3
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (secondary 1.0%)

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)	6.3%	[6.3%, 6.3%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-4.4%	[-4.4%, -4.4%]	1
All ❌✅ (primary)	-	-	0

Cycles

Results (primary 4.9%, secondary 0.2%)

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

	mean	range	count
Regressions ❌ (primary)	6.3%	[1.1%, 15.4%]	6
Regressions ❌ (secondary)	2.9%	[2.6%, 3.8%]	4
Improvements ✅ (primary)	-3.4%	[-3.4%, -3.4%]	1
Improvements ✅ (secondary)	-5.2%	[-6.6%, -3.9%]	2
All ❌✅ (primary)	4.9%	[-3.4%, 15.4%]	7

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)	0.1%	[0.0%, 0.1%]	15
Regressions ❌ (secondary)	0.1%	[0.0%, 0.1%]	20
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.1%	[0.0%, 0.1%]	15

Bootstrap: 489.296s -> 491.084s (0.37%)
Artifact size: 394.04 MiB -> 394.21 MiB (0.04%)

[Kivooeo]

@bors r=Kivooeo,petrochenkov rollup

[rust-bors]

📌 Commit 2e3036d has been approved by Kivooeo,petrochenkov

It is now in the queue for this repository.