Do not modify resolver outputs during lowering

[cjgillot]

Split from #142830

I believe this achieves the same thing as #153656 but in a much simpler way.

This PR forces AST->HIR lowering to stop mutating resolver outputs. Instead, it manages a few override maps that only live during lowering and are dropped afterwards.

r? @petrochenkov
cc @aerooneqq

[rustbot]

Some changes occurred in compiler/rustc_ast_lowering/src/format.rs

cc @m-ou-se

[cjgillot]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: fd1275a (fd1275a2d0718b26a05018665073cb854870b511, parent: f29256dd1420dc681bf4956e3012ffe9eccdc7e7)

[rust-timer]

Finished benchmarking commit (fd1275a): 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%]	5
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.1%	[-0.2%, -0.0%]	4
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary 2.8%, 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)	2.8%	[0.9%, 7.3%]	123
Regressions ❌ (secondary)	3.2%	[0.9%, 8.0%]	48
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.8%	[0.9%, 7.3%]	123

Cycles

Results (secondary -3.7%)

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)	2.0%	[2.0%, 2.0%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-5.1%	[-8.0%, -2.3%]	4
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 490.91s -> 488.306s (-0.53%)
Artifact size: 394.18 MiB -> 395.94 MiB (0.45%)

[petrochenkov]

This is a bit suspicious, why are we using partial_res_map directly instead of get_partial_res here?

View changes since the review

[rustbot]

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

[cjgillot]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

@rustbot label: +S-waiting-on-perf

[rust-bors]

⌛ Trying commit a9cee38 with merge 1c6d6e2…

To cancel the try build, run the command @bors try cancel.

Workflow: https://github.com/rust-lang/rust/actions/runs/24752555469