rustdoc: Fix trait impl ordering by nnethercote · Pull Request #157233 · rust-lang/rust

nnethercote · 2026-06-01T05:58:59Z

For types, rustdoc produces different impl orderings in the sidebar vs. the main section.

E.g. for std::cell::UnsafeCell the "Trait Implementations" sidebar order is this:

!Freeze
!RefUnwindSafe
!Sync
CoerceUnsized<UnsafeCell<U>>
Debug
Default
DispatchFromDyn<UnsafeCell<U>>
From<T>

The primary sort is on polarity, and the secondary sort is alphabetical. Makes sense.

The main section order is this:

impl<T> Debug for UnsafeCell<T>
impl<T> Default for UnsafeCell<T>
impl<T> From<T> for UnsafeCell<T>
impl<T, U> CoerceUnsized<UnsafeCell<U>> for UnsafeCell<T>
impl<T, U> DispatchFromDyn<UnsafeCell<U>> for UnsafeCell<T>
impl<T> !Freeze for UnsafeCell<T>
impl<T> !RefUnwindSafe for UnsafeCell<T>
impl<T> !Sync for UnsafeCell<T>

This strange ordering occurs because the entries are sorted on the generated HTML. Impls with methods (the first three) come first because they start with a <details> tag while the others start with a <section> tag. After that, the order depends on a section id of the form impl-{trait}-for-{type} that doesn't include the polarity, which is why the secondary ordering is alphabetical but ignores the !.

The sidebar ordering is the better of the two. This commit changes the main section to use the same ordering as the sidebar. This involves creating a new function impl_trait_key shared between the two parts.

r? @GuillaumeGomez

nnethercote · 2026-06-01T07:05:08Z

It's not ideal that this change didn't require any test changes. I know very little about rustdoc testing so I'm not sure where/how to add tests for this.

GuillaumeGomez · 2026-06-01T15:14:52Z

The tool we use for XPaths in tests/rustdoc-html doesn't allow to specify which nth item we want, so we'll be forced to add a test in tests/rustdoc-gui. The selector for the trait implementations in the sidebar would be .sidebar .trait-implementation li:nth-child(3) a (where you change the integer of nth-child) to check its text with assert-text.

For the main section, the selector is #trait-implementations-list details:nth-child(3) .code-header and same as described previously. Don't hesitate if you need help.

rustbot · 2026-06-02T01:44:11Z

Some changes occurred in GUI tests.

cc @GuillaumeGomez

nnethercote · 2026-06-02T01:45:01Z

I have added a new test. Thanks for the rustdoc-gui tips, they were very helpful.

This shows how the ordering in the sidebar and the main section differ. The next commit will fix this inconsistency.

For types, rustdoc produces different impl orderings in the sidebar vs. the main section. E.g. for `std::cell::UnsafeCell` the "Trait Implementations" sidebar order is this: ``` !Freeze !RefUnwindSafe !Sync CoerceUnsized<UnsafeCell<U>> Debug Default DispatchFromDyn<UnsafeCell<U>> From<T> ``` The primary sort is on polarity, and the secondary sort is alphabetical. Makes sense. The main section order is this: ``` impl<T> Debug for UnsafeCell<T> impl<T> Default for UnsafeCell<T> impl<T> From<T> for UnsafeCell<T> impl<T, U> CoerceUnsized<UnsafeCell<U>> for UnsafeCell<T> impl<T, U> DispatchFromDyn<UnsafeCell<U>> for UnsafeCell<T> impl<T> !Freeze for UnsafeCell<T> impl<T> !RefUnwindSafe for UnsafeCell<T> impl<T> !Sync for UnsafeCell<T> ``` This strange ordering occurs because the entries are sorted on the generated HTML. Impls with methods (the first three) come first because they start with a `<details>` tag while the others start with a `<section>` tag. After that, the order depends on a section id of the form `impl-{trait}-for-{type}` that doesn't include the polarity, which is why the secondary ordering is alphabetical but ignores the `!`. The sidebar ordering is the better of the two. This commit changes the main section to use the same ordering as the sidebar. This involves creating a new function `impl_trait_key` shared between the two parts.

GuillaumeGomez · 2026-06-02T08:48:06Z

Thanks!

@bors r+ rollup

rust-bors · 2026-06-02T08:48:09Z

📌 Commit eef3ae7 has been approved by GuillaumeGomez

It is now in the queue for this repository.

…uwer Rollup of 14 pull requests Successful merges: - #156467 (mark the 'import linkage' statics as unnamed_addr) - #156923 (Couple of diagnostics improvements for EII) - #157240 (Enable Enzyme for aarch64-apple-darwin) - #157244 (Privacy: tweak macros + more tests) - #157276 (miri subtree update) - #157130 (Use a `ArrayVec` in `CastTarget`) - #157131 (Add regression test for issue #144888) - #157195 (Move feature gating to the new attr parsing infrastructure) - #157233 (rustdoc: Fix trait impl ordering) - #157256 (tests: adapt for LLVM codegen change) - #157265 (Update books) - #157277 (triagebot.toml: add LawnGnome to libs reviewers) - #157291 (Clean up attribute target checking diagnostics) - #157301 (Remove unused import from a test)

@GuillaumeGomez

Rollup merge of #157233 - nnethercote:rustdoc-impl-order, r=GuillaumeGomez rustdoc: Fix trait impl ordering For types, rustdoc produces different impl orderings in the sidebar vs. the main section. E.g. for `std::cell::UnsafeCell` the "Trait Implementations" sidebar order is this: ``` !Freeze !RefUnwindSafe !Sync CoerceUnsized<UnsafeCell<U>> Debug Default DispatchFromDyn<UnsafeCell<U>> From<T> ``` The primary sort is on polarity, and the secondary sort is alphabetical. Makes sense. The main section order is this: ``` impl<T> Debug for UnsafeCell<T> impl<T> Default for UnsafeCell<T> impl<T> From<T> for UnsafeCell<T> impl<T, U> CoerceUnsized<UnsafeCell<U>> for UnsafeCell<T> impl<T, U> DispatchFromDyn<UnsafeCell<U>> for UnsafeCell<T> impl<T> !Freeze for UnsafeCell<T> impl<T> !RefUnwindSafe for UnsafeCell<T> impl<T> !Sync for UnsafeCell<T> ``` This strange ordering occurs because the entries are sorted on the generated HTML. Impls with methods (the first three) come first because they start with a `<details>` tag while the others start with a `<section>` tag. After that, the order depends on a section id of the form `impl-{trait}-for-{type}` that doesn't include the polarity, which is why the secondary ordering is alphabetical but ignores the `!`. The sidebar ordering is the better of the two. This commit changes the main section to use the same ordering as the sidebar. This involves creating a new function `impl_trait_key` shared between the two parts. r? @GuillaumeGomez

JonathanBrouwer · 2026-06-03T08:02:22Z

@rust-timer build 0f41b4a

rust-timer · 2026-06-03T10:43:37Z

Finished benchmarking commit (0f41b4a): 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%	[0.1%, 0.3%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.2%	[0.1%, 0.3%]	2

Max RSS (memory usage)

Results (secondary 5.5%)

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)	5.5%	[5.5%, 5.5%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Cycles

Results (primary 2.1%, secondary -1.6%)

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

	mean	range	count
Regressions ❌ (primary)	2.1%	[2.1%, 2.1%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.6%	[-1.6%, -1.6%]	1
All ❌✅ (primary)	2.1%	[2.1%, 2.1%]	1

Binary size

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

Bootstrap: 510.625s -> 511.417s (0.16%)
Artifact size: 400.75 MiB -> 400.78 MiB (0.01%)

JonathanBrouwer · 2026-06-03T11:58:55Z

This PR caused the regression in #157303

rustbot assigned GuillaumeGomez Jun 1, 2026

nnethercote mentioned this pull request Jun 1, 2026

rustdoc: optimize impl sorting #157179

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nnethercote force-pushed the rustdoc-impl-order branch from 2665e2a to a43bb36 Compare June 2, 2026 01:44

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rustdoc: Fix comment in sidebar-foreign-impl-sort.goml

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nnethercote force-pushed the rustdoc-impl-order branch from a43bb36 to 7a6efc5 Compare June 2, 2026 03:04

nnethercote added 2 commits June 2, 2026 13:04

rustdoc: Add a test for trait impl ordering

9119e3c

This shows how the ordering in the sidebar and the main section differ. The next commit will fix this inconsistency.

nnethercote force-pushed the rustdoc-impl-order branch from 7a6efc5 to eef3ae7 Compare June 2, 2026 03:04

nnethercote changed the title ~~Fix impl ordering~~ rustdoc: Fix trait impl ordering Jun 2, 2026

GuillaumeGomez approved these changes Jun 2, 2026

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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 Jun 2, 2026

JonathanBrouwer mentioned this pull request Jun 2, 2026

Rollup of 14 pull requests #157303

Merged

rust-bors Bot merged commit 181ccb1 into rust-lang:main Jun 2, 2026
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rustbot added this to the 1.98.0 milestone Jun 2, 2026

nnethercote deleted the rustdoc-impl-order branch June 3, 2026 00:25

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rustbot added the perf-regression Performance regression. label Jun 3, 2026

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rustdoc: Fix trait impl ordering#157233

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Overall result: ❌ regressions - please read:

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