Attribute documentation for cfg_attr, path, feature, doc, should_panic, expect, ignore, and used

[kantnero]

Documents the cfg_attr, path, feature, doc, should_panic, expect, ignore, and used

Part of #157604

r? @GuillaumeGomez
cc @fmease @traviscross

[rustbot]

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

[rust-log-analyzer]

The job aarch64-gnu-llvm-21-2 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

##[endgroup]
[TIMING:end] tool::ToolBuild { build_compiler: Compiler { stage: 0, host: aarch64-unknown-linux-gnu, forced_compiler: false }, target: aarch64-unknown-linux-gnu, tool: "linkchecker", path: "src/tools/linkchecker", mode: ToolBootstrap, source_type: InTree, extra_features: [], allow_features: "", cargo_args: [], artifact_kind: Binary } -- 0.135
[TIMING:end] tool::Linkchecker { compiler: Compiler { stage: 0, host: aarch64-unknown-linux-gnu, forced_compiler: false }, target: aarch64-unknown-linux-gnu } -- 0.000
##[group]Testing stage1 Linkcheck (aarch64-unknown-linux-gnu)
core/attribute.feature.html:9: broken link - `/checkout/obj/build/aarch64-unknown-linux-gnu/unstable-book/the-unstable-book.html`
core/attribute.doc.html:21: broken link - `/checkout/obj/build/aarch64-unknown-linux-gnu/rustdoc/write-documentation/the-doc-attribute.html`
std/attribute.feature.html:9: broken link - `/checkout/obj/build/aarch64-unknown-linux-gnu/unstable-book/the-unstable-book.html`
std/attribute.doc.html:21: broken link - `/checkout/obj/build/aarch64-unknown-linux-gnu/rustdoc/write-documentation/the-doc-attribute.html`
checked links in: 25.0s
number of HTML files scanned: 62485
number of HTML redirects found: 22210
number of links checked: 2982686
number of links ignored due to external: 184493
number of links ignored due to exceptions: 31
number of intra doc links ignored: 9
errors found: 4
found some broken links
NOTE: if you are adding or renaming a markdown file in a mdBook, don't forget to register the page in SUMMARY.md
Command `/checkout/obj/build/aarch64-unknown-linux-gnu/stage1-tools-bin/linkchecker /checkout/obj/build/aarch64-unknown-linux-gnu/doc` failed with exit code 1
Created at: src/bootstrap/src/core/build_steps/tool.rs:1637:23
Executed at: src/bootstrap/src/core/build_steps/test.rs:202:77

Command has failed. Rerun with -v to see more details.
Bootstrap failed while executing `--stage 2 test --skip tidy --skip library/stdarch/crates/intrinsic-test --skip src/tools/rust-analyzer --skip tests --skip library --skip tidyselftest`
Currently active steps:
test::Linkcheck { host: aarch64-unknown-linux-gnu } at src/bootstrap/src/core/build_steps/test.rs:139
Build completed unsuccessfully in 0:32:44
  local time: Fri Jul 24 14:09:34 UTC 2026

[fmease]

Meta note:

Instead of trying to add docs for more and more attributes at once in one PR, I think it would be more helpful & generally better to split your efforts into several smaller PRs going forward which each contain a small set of related attributes / just one attribute instead of a large mixed bag.

That would make it a lot easier for reviewers since they wouldn't have to wade through 100 comments like in #158664 and context-switch constantly within the same PR. Consequently, it would mean your PRs can get merged a lot faster.

Re. you closing #158664 I guess that was due to git / GitHub issues? In case it wasn't though, I want to say that it makes it harder to follow the progress & discussions for specific attributes since they're now spread across several PRs (one has 100 comments as I've already mentioned), esp. since there's no link from the old to the new PR.

---

In any case, thanks for working on this!

[kantnero]

@fmease
Thanks, makes sense I'll split future PRs into smaller ones.

Initially sent the PR in twos, but I created each one before the last had merged, every new PR ended up showing the previous PR's changes too, not just its own. Diffs got confusing, so I just merged them into one PR against main instead.

Going forward I'll wait for each one to merge before opening the next.