Audit Symbols by camsteffen · Pull Request #152624 · rust-lang/rust

camsteffen · 2026-02-14T17:22:49Z

Remove unused symbols and hoist some symbols to Clippy.

rustbot · 2026-02-14T17:22:52Z

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

rustbot · 2026-02-14T17:22:55Z

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

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camsteffen · 2026-02-14T17:29:36Z

compiler/rustc_span/src/symbol.rs

-        new_v1,
-        new_v1_formatted,
        next,
-        niko,


@nikomatsakis sorry

samueltardieu

With the removal of the slice duplicate, you can r=me for the Clippy part.

View changes since this review

src/tools/clippy/clippy_utils/src/sym.rs

bjorn3 · 2026-02-14T22:53:58Z

Some of these symbols were added as a perf optimization to avoid having to allocate for identifiers that are commonly used. And pre-interned symbols are represented with less bytes in the crate metadata.

bjorn3 · 2026-02-14T23:02:11Z

compiler/rustc_span/src/symbol.rs

-        BTreeEntry,
        BTreeMap,
-        BTreeSet,
-        BinaryHeap,


These were added in camsteffen@eada4d1 They are still diagnostics items.

Since then, #138682 gave Clippy the ability to define their own Symbols. Many diagnostic items exist only for Clippy, so I figured only Clippy benefits from the pre-defined Symbols.

bjorn3 · 2026-02-14T23:03:46Z

compiler/rustc_span/src/symbol.rs

        SymbolIntern,
        Sync,
        SyncUnsafeCell,
-        T,


This is a very common identifier.

I'd rather try to pre-intern all ASCII letters a-zA-Z, similarly to sym::integer, and see if it makes any difference. Many of them are common.
(Not as a part of this PR.)

Makes sense. I wonder if there should be a special place for pre-interned symbols that are not sym::_ consts, just to ensure that silly people like me won't spend time auditing them.

Mark-Simulacrum · 2026-02-14T23:42:16Z

@bors try @rust-timer queue

Audit Symbols

camsteffen · 2026-02-14T23:46:35Z

Some of these symbols were added as a perf optimization to avoid having to allocate for identifiers that are commonly used. And pre-interned symbols are represented with less bytes in the crate metadata.

Hmm, I didn't realize that. I can look for names that are common and add those back. So IIUC we may want to keep as_str since that is a common method name, but not necessarily keep String since most crates don't define a String.

I'll wait for the perf run for now.

bjorn3 · 2026-02-15T00:19:01Z

but not necessarily keep String since most crates don't define a String

But they do reference it. Each crate has an independent symbol interner. There is no cross-crate importing of symbols.

adwinwhite · 2026-02-15T01:20:50Z

@bjorn3 I'm not familiar with this part and won't have much time looking into it either. Would you like to take over the review since you're already reviewing it?

rust-bors · 2026-02-15T01:53:26Z

☀️ Try build successful (CI)
Build commit: 6f9923e (6f9923e5e0a6b621aa74d57d64d3ff834b60a8cc, parent: a33907a7a5381473eec8bcfa0c56e05a856a911c)

rust-timer · 2026-02-15T02:33:44Z

Finished benchmarking commit (6f9923e): comparison URL.

Overall result: ❌✅ regressions and improvements - no action needed

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in 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)	0.3%	[0.3%, 0.3%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.3%	[-0.5%, -0.2%]	3
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary 3.0%, secondary 0.0%)

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

	mean	range	count
Regressions ❌ (primary)	3.0%	[3.0%, 3.0%]	1
Regressions ❌ (secondary)	2.3%	[1.3%, 2.8%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-6.8%	[-6.8%, -6.8%]	1
All ❌✅ (primary)	3.0%	[3.0%, 3.0%]	1

Cycles

Results (secondary -3.9%)

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
Improvements ✅ (secondary)	-3.9%	[-3.9%, -3.9%]	1
All ❌✅ (primary)	-	-	0

Binary size

Results (primary -0.0%, secondary -0.0%)

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)	0.0%	[0.0%, 0.0%]	1
Improvements ✅ (primary)	-0.0%	[-0.0%, -0.0%]	4
Improvements ✅ (secondary)	-0.0%	[-0.0%, -0.0%]	14
All ❌✅ (primary)	-0.0%	[-0.0%, -0.0%]	4

Bootstrap: 483.617s -> 479.802s (-0.79%)
Artifact size: 397.94 MiB -> 397.91 MiB (-0.01%)

camsteffen · 2026-02-20T01:28:52Z

@rustbot ready

petrochenkov · 2026-02-20T04:59:29Z

@bors r+

rust-bors · 2026-02-20T04:59:32Z

📌 Commit 0f9b166 has been approved by petrochenkov

It is now in the queue for this repository.

JonathanBrouwer · 2026-02-20T15:23:48Z

@bors p=2
Scheduling this in front of the p=1 iffy job in case the rollup fails

Audit Symbols *[View all comments](https://triagebot.infra.rust-lang.org/gh-comments/rust-lang/rust/pull/152624)* Remove unused symbols and hoist some symbols to Clippy.

jhpratt · 2026-02-21T02:51:45Z

CI appears stuck (x86_64-gnu-aux specifically)

@bors yield

rust-bors · 2026-02-21T02:51:49Z

Auto build cancelled. Cancelled workflows:

https://github.com/rust-lang/rust/actions/runs/22244490978

The next pull request likely to be tested is #152624.

Audit Symbols *[View all comments](https://triagebot.infra.rust-lang.org/gh-comments/rust-lang/rust/pull/152624)* Remove unused symbols and hoist some symbols to Clippy.

jhpratt · 2026-02-21T02:52:35Z

@bors yield

Let's give a rollup a chance first

rust-bors · 2026-02-21T02:52:38Z

Auto build cancelled. Cancelled workflows:

https://github.com/rust-lang/rust/actions/runs/22248970210

The next pull request likely to be tested is #152924.

JonathanBrouwer · 2026-02-21T10:10:46Z

The last job is aarch64-apple which tends to finish if you just give it time, so this time I'm not worried about it being stuck :)

rust-bors · 2026-02-21T10:15:30Z

☀️ Test successful - CI
Approved by: petrochenkov
Duration: 3h 31m 2s
Pushing 3fc3732 to main...

github-actions · 2026-02-21T10:19:06Z

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing 1c00e98 (parent) -> 3fc3732 (this PR)

Test differences

Show 1 test diff

1 doctest diff were found. These are ignored, as they are noisy.

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 3fc37321c49cb8aed32da426de6145e6d57105da --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

dist-aarch64-linux: 2h 32m -> 1h 54m (-25.0%)
dist-x86_64-apple: 2h 36m -> 2h 8m (-17.8%)
aarch64-msvc-2: 1h 40m -> 1h 52m (+12.6%)
dist-apple-various: 1h 51m -> 1h 38m (-11.8%)
x86_64-msvc-ext1: 2h 3m -> 2h 14m (+9.2%)
aarch64-apple: 3h 44m -> 3h 23m (-9.2%)
x86_64-gnu-llvm-21-1: 1h 13m -> 1h 7m (-8.9%)
dist-aarch64-msvc: 1h 38m -> 1h 46m (+8.4%)
dist-ohos-aarch64: 1h 16m -> 1h 22m (+7.9%)
dist-various-1: 1h 6m -> 1h 11m (+7.1%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

rust-timer · 2026-02-21T10:55:35Z

Finished benchmarking commit (3fc3732): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Our benchmarks found a performance regression caused by this PR.
This might be an actual regression, but it can also be just noise.

Next Steps:

If the regression was expected or you think it can be justified,
please write a comment with sufficient written justification, and add
@rustbot label: +perf-regression-triaged to it, to mark the regression as triaged.
If you think that you know of a way to resolve the regression, try to create
a new PR with a fix for the regression.
If you do not understand the regression or you think that it is just noise,
you can ask the @rust-lang/wg-compiler-performance working group for help (members of this group
were already notified of this PR).

@rustbot label: +perf-regression
cc @rust-lang/wg-compiler-performance

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%, 0.2%]	1
Regressions ❌ (secondary)	0.2%	[0.1%, 0.2%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.5%	[-0.7%, -0.3%]	4
All ❌✅ (primary)	0.2%	[0.2%, 0.2%]	1

Max RSS (memory usage)

Results (secondary 1.9%)

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)	1.9%	[0.9%, 3.5%]	8
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Cycles

Results (secondary -4.1%)

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
Improvements ✅ (secondary)	-4.1%	[-4.1%, -4.1%]	1
All ❌✅ (primary)	-	-	0

Binary size

Results (primary -0.0%, secondary -0.0%)

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)	-	-	0
Improvements ✅ (primary)	-0.0%	[-0.0%, -0.0%]	1
Improvements ✅ (secondary)	-0.0%	[-0.0%, -0.0%]	14
All ❌✅ (primary)	-0.0%	[-0.0%, -0.0%]	1

Bootstrap: 480.967s -> 482.367s (0.29%)
Artifact size: 397.91 MiB -> 397.92 MiB (0.00%)

rustbot assigned adwinwhite Feb 14, 2026

camsteffen commented Feb 14, 2026

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samueltardieu reviewed Feb 14, 2026

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camsteffen force-pushed the symbols-audit branch from 14ad4f5 to f35741a Compare February 14, 2026 18:08

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camsteffen force-pushed the symbols-audit branch from f35741a to dc753d0 Compare February 14, 2026 19:08

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rust-bors bot pushed a commit that referenced this pull request Feb 14, 2026

Auto merge of #152624 - camsteffen:symbols-audit, r=<try>

6f9923e

Audit Symbols

rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Feb 14, 2026

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rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Feb 20, 2026

rust-bors bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Feb 20, 2026

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rust-bors bot added merged-by-bors This PR was explicitly merged by bors. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Feb 21, 2026

rust-bors bot merged commit 3fc3732 into rust-lang:main Feb 21, 2026
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rustbot added this to the 1.95.0 milestone Feb 21, 2026

rustbot added the perf-regression Performance regression. label Feb 21, 2026

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Overall result: ❌✅ regressions and improvements - no action needed

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Test differences

Job duration changes

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