rustdoc: Only synthesize auto/blanket impls for documented items by camelid · Pull Request #159779 · rust-lang/rust

camelid · 2026-07-23T16:20:14Z

Previously, the code would skip synthesizing impls if the trait was
not documented, but it would still synthesize even if the type was not
documented. This is wasted work.

camelid · 2026-07-23T16:20:45Z

This is based on #159721, so this should be rebased and get a perf run once that PR lands.

Previously, the code would skip synthesizing impls if the *trait* was not documented, but it would still synthesize even if the *type* was not documented. This is wasted work.

rustbot · 2026-07-23T19:13:09Z

r? @GuillaumeGomez

rustbot has assigned @GuillaumeGomez.
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camelid · 2026-07-23T19:13:12Z

@bors try @rust-timer queue

rustdoc: Only synthesize auto/blanket impls for documented items

rust-bors · 2026-07-23T21:19:02Z

☀️ Try build successful (CI)
Build commit: 8d0c82f (8d0c82f4399e40d56ef07de43fedf554ddb93e9f)
Base parent: 2d8fa67 (2d8fa67781953811835f7ae45f670afbb7f44285)

rust-timer · 2026-07-23T21:59:23Z

Finished benchmarking commit (8d0c82f): 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 rustc-perf
@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)	-6.5%	[-19.1%, -0.8%]	11
Improvements ✅ (secondary)	-5.4%	[-13.7%, -0.3%]	3
All ❌✅ (primary)	-6.5%	[-19.1%, -0.8%]	11

Max RSS (memory usage)

Results (primary -1.6%, secondary -2.2%)

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)	2.6%	[2.6%, 2.6%]	1
Improvements ✅ (primary)	-1.6%	[-2.0%, -1.3%]	4
Improvements ✅ (secondary)	-3.8%	[-4.9%, -1.6%]	3
All ❌✅ (primary)	-1.6%	[-2.0%, -1.3%]	4

Cycles

Results (primary -7.4%, secondary -6.5%)

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)	3.3%	[3.3%, 3.3%]	1
Improvements ✅ (primary)	-7.4%	[-16.2%, -2.7%]	8
Improvements ✅ (secondary)	-9.8%	[-15.4%, -2.1%]	3
All ❌✅ (primary)	-7.4%	[-16.2%, -2.7%]	8

Binary size

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

Bootstrap: 488.662s -> 489.706s (0.21%)
Artifact size: 387.62 MiB -> 387.61 MiB (-0.00%)

GuillaumeGomez · 2026-07-23T22:01:54Z

Another great improvement, thanks a lot!

@bors r+ p=6 rollup=never

rust-bors · 2026-07-23T22:01:56Z

📌 Commit ab70c36 has been approved by GuillaumeGomez

It is now in the queue for this repository.

rust-bors · 2026-07-24T01:48:40Z

☀️ Test successful - CI
Approved by: GuillaumeGomez
Duration: 3h 10m 42s
Pushing 76c35a1 to main...

github-actions · 2026-07-24T01:51:37Z

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 89c61a7 (parent) -> 76c35a1 (this PR)

Test differences

Show 2 test diffs

2 doctest diffs were found. These are ignored, as they are noisy.

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 76c35a14a45897a366c11657ecbbe9ec4153ad17 --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

x86_64-gnu-gcc-core-tests: 14m 30s -> 8m 30s (-41.4%)
x86_64-gnu-tools: 43m 2s -> 55m 54s (+29.9%)
x86_64-gnu-llvm-21: 55m 27s -> 1h 11m (+29.6%)
optional-x86_64-gnu-parallel-frontend: 2h 9m -> 1h 31m (-29.2%)
dist-i686-msvc: 1h 29m -> 1h 55m (+28.7%)
x86_64-rust-for-linux: 36m 54s -> 47m 21s (+28.3%)
dist-powerpc64le-linux-musl: 1h 15m -> 1h 32m (+23.0%)
dist-arm-linux-gnueabi: 1h 9m -> 1h 24m (+21.6%)
arm-android: 1h 21m -> 1h 39m (+21.6%)
dist-armhf-linux: 1h 26m -> 1h 7m (-21.5%)

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 · 2026-07-24T02:30:22Z

Finished benchmarking commit (76c35a1): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -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)	-6.5%	[-19.1%, -0.8%]	11
Improvements ✅ (secondary)	-5.4%	[-13.8%, -0.3%]	3
All ❌✅ (primary)	-6.5%	[-19.1%, -0.8%]	11

Max RSS (memory usage)

Results (primary -1.8%, secondary -1.2%)

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)	2.8%	[2.8%, 2.8%]	1
Improvements ✅ (primary)	-1.8%	[-2.0%, -1.5%]	4
Improvements ✅ (secondary)	-3.1%	[-4.8%, -1.4%]	2
All ❌✅ (primary)	-1.8%	[-2.0%, -1.5%]	4

Cycles

Results (primary -7.4%, secondary -3.8%)

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)	2.5%	[2.5%, 2.5%]	1
Improvements ✅ (primary)	-7.4%	[-16.3%, -2.1%]	9
Improvements ✅ (secondary)	-5.9%	[-11.9%, -2.6%]	3
All ❌✅ (primary)	-7.4%	[-16.3%, -2.1%]	9

Binary size

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

Bootstrap: 487.226s -> 488.274s (0.22%)
Artifact size: 387.62 MiB -> 387.66 MiB (0.01%)

Pkgsrc changes: * Adapt to changes in vendored crate versions. * Version & checksum changes. Upstream changes: Version 1.99.0 (2026-10-01) ========================== Language -------- - [Add allow-by-default `raw_borrows_via_references` lint that checks for references that decay immediately into raw borrows](rust-lang/rust#138230) - [Extend `unconditional_panic` lint to function calls that panic when the chunks/windows size is zero] (rust-lang/rust#153563) - [Stabilize C-variadic function definitions] (rust-lang/rust#155697) - [Stabilize the ability to use `#[unsafe(naked)]` functions to define C-variadic functions (`#![feature(c_variadic_naked_functions)]`).] (rust-lang/rust#159746) - [Trait methods are now resolved on an adjusted never type (producing a FCW)] (rust-lang/rust#156047) - [Coerce from inference variables to trait objects if the inference variable is related via subtyping to a type that is known to be `Sized`] (rust-lang/rust#157820) - [Stabilize `#[my_macro] mod foo;`] (rust-lang/rust#157857). This allows outlined modules (`mod foo;`) anywhere in the body of a custom attribute or derive macro. - [Fix the `overflowing_literals` lint with repeated negation] (rust-lang/rust#158302). For instance, it will now no longer lint on `--128_i8`, which is already detected by the `arithmetic_overflow` lint. - [Add POSIX symbols to the `invalid_runtime_symbol_definitions` and `suspicious_runtime_symbol_definitions` lints] (rust-lang/rust#158522) - [Lint unused `#[path]` attributes on inline modules] (rust-lang/rust#158835) - [Enable `unreachable_cfg_select_predicates` lint as part of `unused` lint group] (rust-lang/rust#159179) - [Stabilize passing 128-bit integers via vector registers with `asm!` on x86] (rust-lang/rust#159525) - [Explicitly document that some allocations are allowed to grow in-place (but none are allowed to shrink)] (rust-lang/rust#159729) - We now [guarantee] (rust-lang/rust#159730) that the contents of an `UnsafeCell` can be accessed without going through `get` - [The `invalid_reference_casting` lint was adjusted accordingly] (rust-lang/rust#159960) - [Account for globally enabled target features in `global_asm!`] (rust-lang/rust#160594) - [Warn if an invalid `doc` attribute is used on a macro invocation] (rust-lang/rust#161003) Compiler -------- - [Convert `-Ctarget-cpu` into a target-modifier for AVR, AMDGCN and NVPTX] (rust-lang/rust#150732) - [Enable `static_position_independent_executables` on all gnu and musl targets] (rust-lang/rust#158510) - When providing a suggestion about a missing method, rustc now prefers an exactly matching name from a [doc alias attribute] (https://doc.rust-lang.org/rustdoc/advanced-features.html#add-aliases-for-an-item-in-documentation-search) over a similarity search from other method names. If your new users sometimes expect a method under a different name, adding a doc alias will now help them find it via rustc suggestions, in addition to helping them find it via rustdoc search: [When suggesting method names, prefer *exact* doc aliases over similar names](rust-lang/rust#160369) Platform Support ---------------- - [Promote `riscv64-unknown-linux-musl` to Tier 2 with host tools] (rust-lang/rust#158766) Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support. [platform-support-doc]: https://doc.rust-lang.org/rustc/platform-support.html Libraries --------- - Iteration on `RangeInclusive` (`a..=b` ranges) is now [optimized better in some circumstances] (rust-lang/rust#155114). As a side effect of this, the behavior of `RangeInclusive` values that has already been exhausted (as an iterator) has changed. For example, the return values of `start()` and `end()` on such ranges may return different values, and using such ranges as slice indexes may have different behavior. These behaviors were not guaranteed to be stable, so these changes are considered to not be breaking changes. - [Relax `transmute_copy` to accept `?Sized` types] (rust-lang/rust#155989) - [Update `transmute_copy` to use a non-unwinding panic] (rust-lang/rust#155989) - [Don't escape U+FF9E and U+FF9F in `escape_debug_ext`] (rust-lang/rust#158057) - [Re-export `core::fmt::NumBuffer` in `alloc` (and `std`)] (rust-lang/rust#161430) Stabilized APIs --------------- - [`IntoIterator` for `Box<[T; N]>`] (https://doc.rust-lang.org/stable/std/iter/trait.IntoIterator.html#impl-IntoIterator-for-Box%3C%5BT;+N%5D,+A%3E) - [`IntoIterator` for `&Box<[T; N]>`] (https://doc.rust-lang.org/stable/std/iter/trait.IntoIterator.html#impl-IntoIterator-for-%26Box%3C%5BT;+N%5D,+A%3E) - [`IntoIterator` for `&mut Box<[T; N]>`] (https://doc.rust-lang.org/stable/std/iter/trait.IntoIterator.html#impl-IntoIterator-for-%26mut+Box%3C%5BT;+N%5D,+A%3E) - [`VecDeque::retain_back`] (https://doc.rust-lang.org/stable/std/collections/struct.VecDeque.html#method.retain_back) - [`core::ffi::VaList`] (https://doc.rust-lang.org/stable/core/ffi/struct.VaList.html) - [`Box::into_non_null`] (https://doc.rust-lang.org/stable/std/boxed/struct.Box.html#method.into_non_null) - [`Box::from_non_null`] (https://doc.rust-lang.org/stable/std/boxed/struct.Box.html#method.from_non_null) - [`Vec::into_parts`] (https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#method.into_parts) - [`Vec::from_parts`] (https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#method.from_parts) - [`core::mem::size_of_val_raw`] (https://doc.rust-lang.org/stable/core/mem/fn.size_of_val_raw.html) - [`core::mem::align_of_val_raw`] (https://doc.rust-lang.org/stable/core/mem/fn.align_of_val_raw.html) - [`core::alloc::Layout::for_value_raw`] (https://doc.rust-lang.org/stable/core/alloc/struct.Layout.html#method.for_value_raw) - [`String::from_utf8_lossy_owned`] (https://doc.rust-lang.org/stable/std/string/struct.String.html#method.from_utf8_lossy_owned) - [`string::FromUtf8Error::into_utf8_lossy`] (https://doc.rust-lang.org/stable/std/string/struct.FromUtf8Error.html#method.into_utf8_lossy) - [`FusedIterator for StepBy<I>`] (https://doc.rust-lang.org/stable/std/iter/struct.StepBy.html#impl-FusedIterator-for-StepBy%3CI%3E) - [`std::fs::set_times`] (https://doc.rust-lang.org/stable/std/fs/fn.set_times.html) - [`std::fs::set_times_nofollow`] (https://doc.rust-lang.org/stable/std/fs/fn.set_times_nofollow.html) Cargo ----- - Add a new built-in profile `debug`. This is a preparation for transitioning the `dev` profile away from debugging to give a saner default for faster development iterations. Currently there is no difference between `dev` and `debug` profiles. [docs] (https://doc.rust-lang.org/nightly/cargo/reference/profiles.html#debug-1) [#17214] (rust-lang/cargo#17214) - Workspace members on edition 2024 or later can now override an inherited workspace dependency's `default-features` field. For example, `serde = { workspace = true, default-features = false }` now turns off default features even when the workspace definition enables them. On earlier editions, `default-features = false` is ignored with a warning. ([RFC 3945] (rust-lang/rfcs#3945)) [#17126](rust-lang/cargo#17126) - Incremental compilation is now disabled by default when running in CI. CI is detected via the CI environment variable. [#17220] (rust-lang/cargo#17220) See also the [full Cargo changelog] (https://doc.rust-lang.org/nightly/cargo/CHANGELOG.html#cargo-199-2026-10-01) Rustdoc ----- - [Add new `unused_footnote_definition` rustdoc lint] (rust-lang/rust#137858) - Smarter filtering of trait impls yields performance improvements of 20% on average and up to 40% on some real-world crates. ([1] (rust-lang/rust#159623), [2](rust-lang/rust#159721), [3](rust-lang/rust#159779), [4](rust-lang/rust#159854), [5](rust-lang/rust#159091)) Compatibility Notes ------------------- - [Fully deprecate the legacy integral modules] (rust-lang/rust#146882). For example, `std::i32::MAX` should be accessed via `i32::MAX` instead. - [Upgrade `no_mangle_generic_items` into hard error] (rust-lang/rust#154585) - [The `Pin::new_unchecked` has had its safety invariants changed slightly] (rust-lang/rust#156935) - [Do not promote references to extern statics] (rust-lang/rust#157641) - [Ensure that the inferred types of `let` patterns typecheck] (rust-lang/rust#157841) - [hermit/fs: Return `unsupported()` instead of `from_raw_os_error(22)`] (rust-lang/rust#158247) - [Fixed a bug where `#[repr(simd)]` was accidentally allowed on macro invocations on stable Rust] (rust-lang/rust#158523) - [Abort const-eval when there are generics in the type of the value being produced] (rust-lang/rust#159504) - [Attributes not applying to anything are now an error in code blocks in doc comments] (rust-lang/rust#159849) - [`Box::leak`: tell people to avoid unleaking] (rust-lang/rust#160323) - [PowerPC inline ASM: Fix scalar floats being in the wrong vector lane on little endian] (rust-lang/rust#160441) - [Do not take `doc(cfg())` into account when filtering doctests] (rust-lang/rust#159014) - [Infer anonymous lifetimes in the types of associated consts as `'static`] (rust-lang/rust#156508) - Macros that expand to a semicolon now produce a warning lint (`semicolon_in_expressions_from_non_local_macros`) even when the macro comes from another crate. Previously, such warnings only appeared for macros from the same crate, to avoid showing warnings that can't be fixed locally; however, this masked problems, as integration tests from the crate providing the macro get compiled as a separate crate, so tests often wouldn't reveal this issue. If you encounter a lint like this, please make sure to report it to the crate providing the macro so they can fix it; don't just silence it in your own crate. - [`semicolon_in_expressions_from_macros`: Lint on non-local macros too] (rust-lang/rust#159222) - [Split non-local `semicolon_in_expressions_from_macros` into a separate lint] (rust-lang/rust#159700) Internal Changes ---------------- These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools. - [Update to LLVM 23] (rust-lang/rust#158734)

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-rustdoc Relevant to the rustdoc team, which will review and decide on the PR/issue. labels Jul 23, 2026

rustdoc: Only synthesize auto/blanket impls for documented items

ab70c36

Previously, the code would skip synthesizing impls if the *trait* was not documented, but it would still synthesize even if the *type* was not documented. This is wasted work.

camelid force-pushed the even-better-impls branch from b240756 to ab70c36 Compare July 23, 2026 19:12

camelid marked this pull request as ready for review July 23, 2026 19:13

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rust-bors Bot pushed a commit that referenced this pull request Jul 23, 2026

Auto merge of #159779 - camelid:even-better-impls, r=<try>

8d0c82f

rustdoc: Only synthesize auto/blanket impls for documented items

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 23, 2026

GuillaumeGomez approved these changes Jul 23, 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 Jul 24, 2026

rust-bors Bot merged commit 76c35a1 into rust-lang:main Jul 24, 2026
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camelid deleted the even-better-impls branch July 24, 2026 19:04

camelid mentioned this pull request Jul 30, 2026

Tracking issue for release notes of #159623: rustdoc: Only build extern trait impls if needed #159674

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rustdoc: Only synthesize auto/blanket impls for documented items - #159779

rustdoc: Only synthesize auto/blanket impls for documented items#159779
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Overall result: ✅ improvements - no action needed

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Test differences

Job duration changes

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