[rustdoc] Retrieve `cfg_attr` information for derived impls for `doc_cfg` feature by GuillaumeGomez · Pull Request #159722 · rust-lang/rust

GuillaumeGomez · 2026-07-22T15:04:50Z

After long last, this PR finally allows the derive proc-macro cfg_attr cfg predicates information to be kept so rustdoc can use it for its doc_cfg feature (cc #43781).

It works as follows: for impl generated by macro expansion, we then look for the attributes on the type for which the impl block is implemented. Then, to know which cfg_attr attribute we want to look at, we use expn_that_defined on the impl's DefId which returns the Span where the macro was expanded. If it's part of a cfg_attr, then the cfg_attr's Span will contain the derive's, so from then, we just need to add the cfg information.

This PR also adds the cfg predicates into the AttributeKind::CfgAttrTrace variant so it can be reused by rustdoc (hence the compiler/* changes).

Thanks a lot @petrochenkov for the pointers here!

r? @petrochenkov

rustbot · 2026-07-22T15:04:53Z

Some changes occurred in compiler/rustc_attr_parsing

cc @jdonszelmann, @JonathanBrouwer

Some changes occurred in compiler/rustc_hir/src/attrs

cc @jdonszelmann, @JonathanBrouwer

clippy is developed in its own repository. If possible, consider making this change to rust-lang/rust-clippy instead.

cc @rust-lang/clippy

Some changes occurred in compiler/rustc_passes/src/check_attr.rs

cc @jdonszelmann, @JonathanBrouwer

GuillaumeGomez · 2026-07-22T15:07:01Z

@bors try @rust-timer queue

[rustdoc] Retrieve `cfg_attr` information for derived impls for `doc_cfg` feature

GuillaumeGomez · 2026-07-22T15:24:19Z

@bors try-

rust-bors · 2026-07-22T15:24:22Z

Unknown command "try-". Run @bors help or go to https://bors.rust-lang.org/help to see available commands.

GuillaumeGomez · 2026-07-22T15:24:47Z

@bors try cancel

rust-bors · 2026-07-22T15:24:50Z

Try build cancelled. Cancelled workflows:

https://github.com/rust-lang/rust/actions/runs/29931853548

GuillaumeGomez · 2026-07-22T15:25:02Z

@bors try @rust-timer queue

[rustdoc] Retrieve `cfg_attr` information for derived impls for `doc_cfg` feature

petrochenkov · 2026-07-22T15:29:37Z

LGTM, r=me when CI and perf are green, unless you want an additional rustdoc review from someone else.
@rustbot author

rust-bors · 2026-07-22T17:31:12Z

☀️ Try build successful (CI)
Build commit: 29dd1b5 (29dd1b5c141ed5381e32c07666d6e757a32cfab2)
Base parent: c188565 (c188565812a9b414ddf02f3c7d89e84f1ba53f7d)

rust-bors · 2026-07-23T17:31:48Z

📌 Commit 7e294a5 has been approved by petrochenkov,mejrs,Urgau

It is now in the queue for this repository.

@petrochenkov

…=petrochenkov,mejrs,Urgau [rustdoc] Retrieve `cfg_attr` information for derived impls for `doc_cfg` feature Fixes rust-lang#103300. After long last, this PR finally allows the derive proc-macro `cfg_attr` cfg predicates information to be kept so rustdoc can use it for its `doc_cfg` feature (cc rust-lang#43781). It works as follows: for `impl` generated by macro expansion, we then look for the attributes on the type for which the `impl` block is implemented. Then, to know which `cfg_attr` attribute we want to look at, we use `expn_that_defined` on the impl's `DefId` which returns the `Span` where the macro was expanded. If it's part of a `cfg_attr`, then the `cfg_attr`'s `Span` will contain the derive's, so from then, we just need to add the `cfg` information. This PR also adds the cfg predicates into the `AttributeKind::CfgAttrTrace` variant so it can be reused by rustdoc (hence the `compiler/*` changes). Thanks a lot @petrochenkov for the pointers here! r? @petrochenkov

@petrochenkov

…=petrochenkov,mejrs,Urgau [rustdoc] Retrieve `cfg_attr` information for derived impls for `doc_cfg` feature Fixes rust-lang#103300. After long last, this PR finally allows the derive proc-macro `cfg_attr` cfg predicates information to be kept so rustdoc can use it for its `doc_cfg` feature (cc rust-lang#43781). It works as follows: for `impl` generated by macro expansion, we then look for the attributes on the type for which the `impl` block is implemented. Then, to know which `cfg_attr` attribute we want to look at, we use `expn_that_defined` on the impl's `DefId` which returns the `Span` where the macro was expanded. If it's part of a `cfg_attr`, then the `cfg_attr`'s `Span` will contain the derive's, so from then, we just need to add the `cfg` information. This PR also adds the cfg predicates into the `AttributeKind::CfgAttrTrace` variant so it can be reused by rustdoc (hence the `compiler/*` changes). Thanks a lot @petrochenkov for the pointers here! r? @petrochenkov

@petrochenkov

…=petrochenkov,mejrs,Urgau [rustdoc] Retrieve `cfg_attr` information for derived impls for `doc_cfg` feature Fixes rust-lang#103300. After long last, this PR finally allows the derive proc-macro `cfg_attr` cfg predicates information to be kept so rustdoc can use it for its `doc_cfg` feature (cc rust-lang#43781). It works as follows: for `impl` generated by macro expansion, we then look for the attributes on the type for which the `impl` block is implemented. Then, to know which `cfg_attr` attribute we want to look at, we use `expn_that_defined` on the impl's `DefId` which returns the `Span` where the macro was expanded. If it's part of a `cfg_attr`, then the `cfg_attr`'s `Span` will contain the derive's, so from then, we just need to add the `cfg` information. This PR also adds the cfg predicates into the `AttributeKind::CfgAttrTrace` variant so it can be reused by rustdoc (hence the `compiler/*` changes). Thanks a lot @petrochenkov for the pointers here! r? @petrochenkov

Rollup of 12 pull requests Successful merges: - #159765 (Avoid spurious rebuilds of JSON docs in bootstrap) - #159781 (Update bootstrap to use -Zembed-metadata=no instead of -Zno-embed-metadata) - #158362 (trait solver: account for universes from replace_bound_vars) - #159173 (Add allowed list check on EII implementations attributes) - #159718 (Make `DocLinkResMap` an `FxIndexMap`) - #159722 ( [rustdoc] Retrieve `cfg_attr` information for derived impls for `doc_cfg` feature) - #155795 (constify `vec![1, 2, 3]` macro) - #157776 (ci: Enable autodiff tests on x86_64 linux) - #158766 (Promote riscv64-unknown-linux-musl to tier 2 with host tools) - #159271 (str: add ASCII fast path to word_to_titlecase) - #159666 (fix(ld64.lld): route version mismatch warnings to linker_info on macOS) - #159667 (Make some parser structured suggestions verbose and tweak their wording)

Rollup of 14 pull requests Successful merges: - #159765 (Avoid spurious rebuilds of JSON docs in bootstrap) - #159781 (Update bootstrap to use -Zembed-metadata=no instead of -Zno-embed-metadata) - #158362 (trait solver: account for universes from replace_bound_vars) - #158372 (rustfmt: Discover modules via `cfg_select!`) - #159173 (Add allowed list check on EII implementations attributes) - #159718 (Make `DocLinkResMap` an `FxIndexMap`) - #159722 ( [rustdoc] Retrieve `cfg_attr` information for derived impls for `doc_cfg` feature) - #159731 (std: Implement futex on wasip3 targets, update target spec) - #159755 (Improve consistency of attribute error messages) - #155795 (constify `vec![1, 2, 3]` macro) - #157776 (ci: Enable autodiff tests on x86_64 linux) - #158766 (Promote riscv64-unknown-linux-musl to tier 2 with host tools) - #159271 (str: add ASCII fast path to word_to_titlecase) - #159667 (Make some parser structured suggestions verbose and tweak their wording)

@petrochenkov

Rollup merge of #159722 - GuillaumeGomez:cfg_attr-doc_cfg, r=petrochenkov,mejrs,Urgau [rustdoc] Retrieve `cfg_attr` information for derived impls for `doc_cfg` feature Fixes #103300. After long last, this PR finally allows the derive proc-macro `cfg_attr` cfg predicates information to be kept so rustdoc can use it for its `doc_cfg` feature (cc #43781). It works as follows: for `impl` generated by macro expansion, we then look for the attributes on the type for which the `impl` block is implemented. Then, to know which `cfg_attr` attribute we want to look at, we use `expn_that_defined` on the impl's `DefId` which returns the `Span` where the macro was expanded. If it's part of a `cfg_attr`, then the `cfg_attr`'s `Span` will contain the derive's, so from then, we just need to add the `cfg` information. This PR also adds the cfg predicates into the `AttributeKind::CfgAttrTrace` variant so it can be reused by rustdoc (hence the `compiler/*` changes). Thanks a lot @petrochenkov for the pointers here! r? @petrochenkov

Rollup of 14 pull requests Successful merges: - rust-lang/rust#159765 (Avoid spurious rebuilds of JSON docs in bootstrap) - rust-lang/rust#159781 (Update bootstrap to use -Zembed-metadata=no instead of -Zno-embed-metadata) - rust-lang/rust#158362 (trait solver: account for universes from replace_bound_vars) - rust-lang/rust#158372 (rustfmt: Discover modules via `cfg_select!`) - rust-lang/rust#159173 (Add allowed list check on EII implementations attributes) - rust-lang/rust#159718 (Make `DocLinkResMap` an `FxIndexMap`) - rust-lang/rust#159722 ( [rustdoc] Retrieve `cfg_attr` information for derived impls for `doc_cfg` feature) - rust-lang/rust#159731 (std: Implement futex on wasip3 targets, update target spec) - rust-lang/rust#159755 (Improve consistency of attribute error messages) - rust-lang/rust#155795 (constify `vec![1, 2, 3]` macro) - rust-lang/rust#157776 (ci: Enable autodiff tests on x86_64 linux) - rust-lang/rust#158766 (Promote riscv64-unknown-linux-musl to tier 2 with host tools) - rust-lang/rust#159271 (str: add ASCII fast path to word_to_titlecase) - rust-lang/rust#159667 (Make some parser structured suggestions verbose and tweak their wording)

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