rustdoc: hide `#[repr(transparent)]` if it isn't part of the public ABI #115439

fmease · 2023-09-01T13:34:00Z

This hides #[repr(transparent)] when the non-1-ZST field the struct is "transparent" over is private.

Tentatively nominating it for the release notes, feel free to remove the nomination.
@rustbot label needs-fcp relnotes A-rustdoc-ui

rustbot · 2023-09-01T13:34:06Z

r? @oli-obk

(rustbot has picked a reviewer for you, use r? to override)

rustbot · 2023-09-01T13:34:09Z

Some changes occurred in src/librustdoc/clean/types.rs

cc @camelid

fmease · 2023-09-01T13:34:17Z

r? rustdoc

fmease · 2023-09-01T13:38:31Z

src/doc/rustdoc/src/advanced-features.md

@@ -110,3 +110,23 @@ https://doc.rust-lang.org/stable/std/?search=%s&go_to_first=true

 This URL adds the `go_to_first=true` query parameter which can be appended to any `rustdoc` search URL
 to automatically go to the first result.
+
+## `#[repr(transparent)]`: Documenting the transparent representation


I wasn't sure where to place this section, open to suggestions

This is probably the best place to put it right now.

fmease · 2023-09-01T13:40:12Z

src/librustdoc/clean/types.rs

@@ -770,10 +791,9 @@ impl Item {
                };
                out.push(&int_s);
            }
-            if out.is_empty() {
-                return Vec::new();


The early return wasn't correct. It resulted in us not rendering some attributes like #[non_exhaustive] in cross-crate re-export scenarios. I've added a regression test for this: tests/rustdoc/inline_cross/attributes.rs.

fmease · 2023-09-01T13:43:12Z

src/doc/rustdoc/src/advanced-features.md

+You can read more about `#[repr(transparent)]` itself in the [Rust Reference][repr-trans-ref] and
+in the [Rustonomicon][repr-trans-nomicon].
+
+Since this representation is only considered part of the public ABI if the single field with non-trivial
+size or alignment is public and if the documentation does not say otherwise, Rustdoc displays the
+attribute if and only if the non-1-ZST field is public or at least one field is public in case all
+fields are 1-ZST fields. The term *1-ZST* refers to types that are one-aligned and zero-sized.
+
+If you would like to declare the representation as private even if the non-1-ZST field is public,
+document it in prose. It would seem that you can manually hide the attribute with
+`#[cfg_attr(not(doc), repr(transparent))]`. However, due to [current limitations][cross-crate-cfg-doc],
+this does not work for types re-exported from another crate. Therefore, you should always additionally
+explicitly write down the layout guarantees in such a case.


Update: I've slightly tweaked this section, please see the latest revision.
I'm pretty sure that the phrasing in this section can be improved upon, it feels a bit awkward in some places.

Edit: And it's longer than one sentence, notriddle :P

fmease · 2023-09-01T13:48:53Z

src/librustdoc/json/conversions.rs

@@ -41,7 +42,7 @@ impl JsonRenderer<'_> {
            })
            .collect();
        let docs = item.opt_doc_value();
-        let attrs = item.attributes(self.tcx, true);
+        let attrs = item.attributes(self.tcx, self.cache(), true);


Note that my patch doesn't affect Rustdoc JSON. We still pass through every inert attribute. Let me know if I that needs changing.

GuillaumeGomez · 2023-09-01T14:16:13Z

Changes look good to me overall (didn't go into details yet). It'll need to go through FCP and to have someone from the compiler team to take a look as well. But otherwise, nice work! 👍

bors · 2023-09-07T18:09:14Z

☔ The latest upstream changes (presumably #114855) made this pull request unmergeable. Please resolve the merge conflicts.

rfcbot · 2023-10-02T20:06:19Z

🔔 This is now entering its final comment period, as per the review above. 🔔

rfcbot · 2023-10-12T20:09:27Z

The final comment period, with a disposition to merge, as per the review above, is now complete.

As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed.

This will be merged soon.

GuillaumeGomez · 2023-10-14T14:53:16Z

Thanks everyone!

@bors r+ rollup

bors · 2023-10-14T14:53:18Z

📌 Commit 64fa12a has been approved by GuillaumeGomez

It is now in the queue for this repository.

…iaskrgr Rollup of 6 pull requests Successful merges: - rust-lang#115439 (rustdoc: hide `#[repr(transparent)]` if it isn't part of the public ABI) - rust-lang#116591 (Don't accidentally detect the commit hash as an `fadd` instruction) - rust-lang#116603 (Reorganize `bootstrap/Cargo.toml`) - rust-lang#116715 (Prevent more spurious unreachable pattern lints) - rust-lang#116723 (Fix broken build on ESP-IDF caused by rust-lang#115108) - rust-lang#116730 (Add some unsoundness tests for opaques capturing hidden regions not in substs) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of rust-lang#115439 - fmease:rustdoc-priv-repr-transparent-heuristic, r=GuillaumeGomez rustdoc: hide `#[repr(transparent)]` if it isn't part of the public ABI Fixes rust-lang#90435. This hides `#[repr(transparent)]` when the non-1-ZST field the struct is "transparent" over is private. CC `@RalfJung` Tentatively nominating it for the release notes, feel free to remove the nomination. `@rustbot` label needs-fcp relnotes A-rustdoc-ui

dtolnay · 2023-10-14T21:06:55Z

Thank you!

I created #116743 to follow up by deleting cfg_attr(not(doc), repr(...))-based workarounds from the standard library.

Pkgsrc changes: * Adjust patches and cargo checksums to new versions. * For an external LLVM, set dependency of llvm >= 16, in accordance with the upstream changes. * Mark that on NetBSD we now need >= 9.0, so 8.x is no longer supported. * On NetBSD/sparc64 10.x, we now need GCC 12 to build the embedded LLVM, which is version 17; apparently GCC 10.4 or 10.5 mis-compiles it, resulting in an illegal instruction fault during the build. Ref. rust-lang/rust#117231 Upstream changes: Version 1.75.0 (2023-12-28) ========================== - [Stabilize `async fn` and return-position `impl Trait` in traits.] (rust-lang/rust#115822) - [Allow function pointer signatures containing `&mut T` in `const` contexts.] (rust-lang/rust#116015) - [Match `usize`/`isize` exhaustively with half-open ranges.] (rust-lang/rust#116692) - [Guarantee that `char` has the same size and alignment as `u32`.] (rust-lang/rust#116894) - [Document that the null pointer has the 0 address.] (rust-lang/rust#116988) - [Allow partially moved values in `match`.] (rust-lang/rust#103208) - [Add notes about non-compliant FP behavior on 32bit x86 targets.] (rust-lang/rust#113053) - [Stabilize ratified RISC-V target features.] (rust-lang/rust#116485) Compiler -------- - [Rework negative coherence to properly consider impls that only partly overlap.] (rust-lang/rust#112875) - [Bump `COINDUCTIVE_OVERLAP_IN_COHERENCE` to deny, and warn in dependencies.] (rust-lang/rust#116493) - [Consider alias bounds when computing liveness in NLL.] (rust-lang/rust#116733) - [Add the V (vector) extension to the `riscv64-linux-android` target spec.] (rust-lang/rust#116618) - [Automatically enable cross-crate inlining for small functions] (rust-lang/rust#116505) - Add several new tier 3 targets: - [`csky-unknown-linux-gnuabiv2hf`] (rust-lang/rust#117049) - [`i586-unknown-netbsd`] (rust-lang/rust#117170) - [`mipsel-unknown-netbsd`] (rust-lang/rust#117356) Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support. Libraries --------- - [Override `Waker::clone_from` to avoid cloning `Waker`s unnecessarily.] (rust-lang/rust#96979) - [Implement `BufRead` for `VecDeque<u8>`.] (rust-lang/rust#110604) - [Implement `FusedIterator` for `DecodeUtf16` when the inner iterator does.] (rust-lang/rust#110729) - [Implement `Not, Bit{And,Or}{,Assign}` for IP addresses.] (rust-lang/rust#113747) - [Implement `Default` for `ExitCode`.] (rust-lang/rust#114589) - [Guarantee representation of None in NPO] (rust-lang/rust#115333) - [Document when atomic loads are guaranteed read-only.] (rust-lang/rust#115577) - [Broaden the consequences of recursive TLS initialization.] (rust-lang/rust#116172) - [Windows: Support sub-millisecond sleep.] (rust-lang/rust#116461) - [Fix generic bound of `str::SplitInclusive`'s `DoubleEndedIterator` impl] (rust-lang/rust#100806) - [Fix exit status / wait status on non-Unix `cfg(unix)` platforms.] (rust-lang/rust#115108) Stabilized APIs --------------- - [`Atomic*::from_ptr`] (https://doc.rust-lang.org/stable/core/sync/atomic/struct.AtomicUsize.html#method.from_ptr) - [`FileTimes`] (https://doc.rust-lang.org/stable/std/fs/struct.FileTimes.html) - [`FileTimesExt`] (https://doc.rust-lang.org/stable/std/os/windows/fs/trait.FileTimesExt.html) - [`File::set_modified`] (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.set_modified) - [`File::set_times`] (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.set_times) - [`IpAddr::to_canonical`] (https://doc.rust-lang.org/stable/core/net/enum.IpAddr.html#method.to_canonical) - [`Ipv6Addr::to_canonical`] (https://doc.rust-lang.org/stable/core/net/struct.Ipv6Addr.html#method.to_canonical) - [`Option::as_slice`] (https://doc.rust-lang.org/stable/core/option/enum.Option.html#method.as_slice) - [`Option::as_mut_slice`] (https://doc.rust-lang.org/stable/core/option/enum.Option.html#method.as_mut_slice) - [`pointer::byte_add`] (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.byte_add) - [`pointer::byte_offset`] (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.byte_offset) - [`pointer::byte_offset_from`] (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.byte_offset_from) - [`pointer::byte_sub`] (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.byte_sub) - [`pointer::wrapping_byte_add`] (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.wrapping_byte_add) - [`pointer::wrapping_byte_offset`] (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.wrapping_byte_offset) - [`pointer::wrapping_byte_sub`] (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.wrapping_byte_sub) These APIs are now stable in const contexts: - [`Ipv6Addr::to_ipv4_mapped`] (https://doc.rust-lang.org/stable/core/net/struct.Ipv6Addr.html#method.to_ipv4_mapped) - [`MaybeUninit::assume_init_read`] (https://doc.rust-lang.org/stable/core/mem/union.MaybeUninit.html#method.assume_init_read) - [`MaybeUninit::zeroed`] (https://doc.rust-lang.org/stable/core/mem/union.MaybeUninit.html#method.zeroed) - [`mem::discriminant`] (https://doc.rust-lang.org/stable/core/mem/fn.discriminant.html) - [`mem::zeroed`] (https://doc.rust-lang.org/stable/core/mem/fn.zeroed.html) Cargo ----- - [Add new packages to `[workspace.members]` automatically.] (rust-lang/cargo#12779) - [Allow version-less `Cargo.toml` manifests.] (rust-lang/cargo#12786) - [Make browser links out of HTML file paths.] (rust-lang/cargo#12889) Rustdoc ------- - [Accept less invalid Rust in rustdoc.] (rust-lang/rust#117450) - [Document lack of object safety on affected traits.] (rust-lang/rust#113241) - [Hide `#[repr(transparent)]` if it isn't part of the public ABI.] (rust-lang/rust#115439) - [Show enum discriminant if it is a C-like variant.] (rust-lang/rust#116142) Compatibility Notes ------------------- - [FreeBSD targets now require at least version 12.] (rust-lang/rust#114521) - [Formally demote tier 2 MIPS targets to tier 3.] (rust-lang/rust#115238) - [Make misalignment a hard error in `const` contexts.] (rust-lang/rust#115524) - [Fix detecting references to packed unsized fields.] (rust-lang/rust#115583) - [Remove support for compiler plugins.] (rust-lang/rust#116412)

rustbot assigned oli-obk Sep 1, 2023

rustbot assigned notriddle and unassigned oli-obk Sep 1, 2023

fmease mentioned this pull request Sep 1, 2023

repr(transparent): it's fine if the one non-1-ZST field is a ZST #115334

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fmease commented Sep 1, 2023

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fmease mentioned this pull request Sep 1, 2023

Hide #[repr(transparent)] where the field is non-public #90435

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fmease force-pushed the rustdoc-priv-repr-transparent-heuristic branch 3 times, most recently from a32b08d to a7c9170 Compare September 2, 2023 13:48

rustbot added A-rustdoc-ui Area: Rustdoc UI (generated HTML) needs-fcp This change is insta-stable, so needs a completed FCP to proceed. relnotes Marks issues that should be documented in the release notes of the next release. labels Sep 2, 2023

fmease removed the A-rustdoc-json Area: Rustdoc JSON backend label Sep 6, 2023

fmease force-pushed the rustdoc-priv-repr-transparent-heuristic branch from a7c9170 to f797064 Compare September 8, 2023 17:28

rustbot added the A-rustdoc-json Area: Rustdoc JSON backend label Sep 8, 2023

fmease added S-blocked Status: Marked as blocked ❌ on something else such as an RFC or other implementation work. and removed A-rustdoc-json Area: Rustdoc JSON backend labels Sep 8, 2023

rfcbot removed the proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. label Oct 2, 2023

fmease removed the needs-fcp This change is insta-stable, so needs a completed FCP to proceed. label Oct 13, 2023

bors 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 Oct 14, 2023

matthiaskrgr mentioned this pull request Oct 14, 2023

Rollup of 6 pull requests #116737

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bors merged commit 4dd4d9b into rust-lang:master Oct 14, 2023
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rustbot added this to the 1.75.0 milestone Oct 14, 2023

fmease deleted the rustdoc-priv-repr-transparent-heuristic branch October 14, 2023 20:37

dtolnay mentioned this pull request Oct 14, 2023

Eliminate use of #[cfg_attr(not(doc), repr(...))] #116743

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Veykril mentioned this pull request Oct 17, 2023

Pull upstream master 2023 10 17 ferrocene/ferrocene#54

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fmease mentioned this pull request Oct 18, 2023

rustdoc: hide #[repr] if it isn't part of the public ABI #116882

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apiraino removed the to-announce Announce this issue on triage meeting label Oct 19, 2023

This was referenced Mar 22, 2024

Remove conditional on repr(transparent) serde-rs/bytes#49

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Remove conditional on repr(transparent) serde-rs/json#1118

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Remove conditional on repr(transparent) dtolnay/anyhow#357

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scottmcm mentioned this pull request Apr 9, 2024

Add an expression for direct access to an enum's discriminant rust-lang/rfcs#3607

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fmease mentioned this pull request Jul 22, 2024

Fix some #[cfg_attr(not(doc), repr(..))] #128046

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dtolnay mentioned this pull request Jul 29, 2024

Repr is incorrectly documented for structs with hidden field #128364

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rustdoc: hide `#[repr(transparent)]` if it isn't part of the public ABI #115439

rustdoc: hide `#[repr(transparent)]` if it isn't part of the public ABI #115439

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rustdoc: hide #[repr(transparent)] if it isn't part of the public ABI #115439

rustdoc: hide #[repr(transparent)] if it isn't part of the public ABI #115439

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rustdoc: hide `#[repr(transparent)]` if it isn't part of the public ABI #115439

rustdoc: hide `#[repr(transparent)]` if it isn't part of the public ABI #115439

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