… r=Manishearth

Warn on `#![doc(test(...))]` on items other than the crate root and use future incompatible lint

Part of rust-lang#82672.

This PR does multiple things:
 * Create a new `INVALID_DOC_ATTRIBUTE` lint which is also "future incompatible", allowing us to use it as a warning for the moment until it turns (eventually) into a hard error.
 * Use this link when `#![doc(test(...))]` isn't used at the crate level.
 * Make rust-lang#82702 use this new lint as well.

r? `@jyn514`

…laumeGomez

Rollup of 7 pull requests

Successful merges:

 - rust-lang#80845 (Make ItemKind::ExternCrate looks like hir::ItemKind::ExternCrate to make transition over hir::ItemKind simpler)
 - rust-lang#82708 (Warn on `#![doc(test(...))]` on items other than the crate root and use future incompatible lint)
 - rust-lang#82714 (Detect match arm body without braces)
 - rust-lang#82736 (Bump optimization from mir_opt_level 2 to 3 and 3 to 4 and make "release" be level 2 by default)
 - rust-lang#82782 (Make rustc shim's verbose output include crate_name being compiled.)
 - rust-lang#82797 (Update tests names to start with `issue-`)
 - rust-lang#82809 (rustdoc: Use substrings instead of split to grab enum variant paths)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

…s-attr, r=GuillaumeGomez

rustdoc: Erase `#![doc(document_private_items)]`

I just found out about the existence of `#![doc(document_private_items)]`. Apparently it was added by PR rust-lang#50669 back in 2018 without any tests or docs as a replacement for some specific forms of the removed `#![doc(passes)]` / `#![doc(no_default_passes)]`.

However, rustc and rustdoc actually emit the deny-by-default lint `invalid_doc_attributes` for it (but if you allow it, the attribute does function)! To be more precise since PR rust-lang#82708 (1.52, May 2021) which introduced lint `invalid_doc_attributes`, rust{,do}c has emitted a future-incompat warning for this attribute. And since PR rust-lang#111505 (1.78, May 2024) that lint is deny by default. I presume nobody knew this attribute existed and thus it was never allowlisted.

Given the fact that since 2021 nobody has ever opened a ticket ([via](https://github.com/rust-lang/rust/issues?q=is%3Aissue+document_private_items)) complaining about the lint emission and the fact that GitHub code search doesn't yield any actual uses ([via](https://github.com/search?q=%2F%23%21%5C%5Bdoc%5C%28.*%3Fdocument_private_items%2F+language%3ARust&type=code&ref=advsearch)), I'm led to believe that nobody knows about and uses this attribute.

I don't find the existence of this attribute to be justified since in my view the flag `--document-private-items` is strictly superior: In most if not all cases, you don't want to "couple" your crate with this "mode" even if you gate it behind a cfg; instead, you most likely want to set this manually at invocation time, via a build config file like `.cargo/config.toml` or via a command runner like `just` I'd say.

Because of this I propose to wipe this attribute from existence. I don't believe it's worth cratering this (i.e., temporarily emitting a hard error for this attribute and running crater) given the fact that it's been undocumented since forever and led to a warning for years.

…s-attr, r=GuillaumeGomez

rustdoc: Erase `#![doc(document_private_items)]`

I just found out about the existence of `#![doc(document_private_items)]`. Apparently it was added by PR rust-lang#50669 back in 2018 without any tests or docs as a replacement for some specific forms of the removed `#![doc(passes)]` / `#![doc(no_default_passes)]`.

However, rustc and rustdoc actually emit the deny-by-default lint `invalid_doc_attributes` for it (but if you allow it, the attribute does function)! To be more precise since PR rust-lang#82708 (1.52, May 2021) which introduced lint `invalid_doc_attributes`, rust{,do}c has emitted a future-incompat warning for this attribute. And since PR rust-lang#111505 (1.78, May 2024) that lint is deny by default. I presume nobody knew this attribute existed and thus it was never allowlisted.

Given the fact that since 2021 nobody has ever opened a ticket ([via](https://github.com/rust-lang/rust/issues?q=is%3Aissue+document_private_items)) complaining about the lint emission and the fact that GitHub code search doesn't yield any actual uses ([via](https://github.com/search?q=%2F%23%21%5C%5Bdoc%5C%28.*%3Fdocument_private_items%2F+language%3ARust&type=code&ref=advsearch)), I'm led to believe that nobody knows about and uses this attribute.

I don't find the existence of this attribute to be justified since in my view the flag `--document-private-items` is strictly superior: In most if not all cases, you don't want to "couple" your crate with this "mode" even if you gate it behind a cfg; instead, you most likely want to set this manually at invocation time, via a build config file like `.cargo/config.toml` or via a command runner like `just` I'd say.

Because of this I propose to wipe this attribute from existence. I don't believe it's worth cratering this (i.e., temporarily emitting a hard error for this attribute and running crater) given the fact that it's been undocumented since forever and led to a warning for years.

…s-attr, r=GuillaumeGomez

rustdoc: Erase `#![doc(document_private_items)]`

I just found out about the existence of `#![doc(document_private_items)]`. Apparently it was added by PR rust-lang#50669 back in 2018 without any tests or docs as a replacement for some specific forms of the removed `#![doc(passes)]` / `#![doc(no_default_passes)]`.

However, rustc and rustdoc actually emit the deny-by-default lint `invalid_doc_attributes` for it (but if you allow it, the attribute does function)! To be more precise since PR rust-lang#82708 (1.52, May 2021) which introduced lint `invalid_doc_attributes`, rust{,do}c has emitted a future-incompat warning for this attribute. And since PR rust-lang#111505 (1.78, May 2024) that lint is deny by default. I presume nobody knew this attribute existed and thus it was never allowlisted.

Given the fact that since 2021 nobody has ever opened a ticket ([via](https://github.com/rust-lang/rust/issues?q=is%3Aissue+document_private_items)) complaining about the lint emission and the fact that GitHub code search doesn't yield any actual uses ([via](https://github.com/search?q=%2F%23%21%5C%5Bdoc%5C%28.*%3Fdocument_private_items%2F+language%3ARust&type=code&ref=advsearch)), I'm led to believe that nobody knows about and uses this attribute.

I don't find the existence of this attribute to be justified since in my view the flag `--document-private-items` is strictly superior: In most if not all cases, you don't want to "couple" your crate with this "mode" even if you gate it behind a cfg; instead, you most likely want to set this manually at invocation time, via a build config file like `.cargo/config.toml` or via a command runner like `just` I'd say.

Because of this I propose to wipe this attribute from existence. I don't believe it's worth cratering this (i.e., temporarily emitting a hard error for this attribute and running crater) given the fact that it's been undocumented since forever and led to a warning for years.

…s-attr, r=GuillaumeGomez

rustdoc: Erase `#![doc(document_private_items)]`

I just found out about the existence of `#![doc(document_private_items)]`. Apparently it was added by PR rust-lang#50669 back in 2018 without any tests or docs as a replacement for some specific forms of the removed `#![doc(passes)]` / `#![doc(no_default_passes)]`.

However, rustc and rustdoc actually emit the deny-by-default lint `invalid_doc_attributes` for it (but if you allow it, the attribute does function)! To be more precise since PR rust-lang#82708 (1.52, May 2021) which introduced lint `invalid_doc_attributes`, rust{,do}c has emitted a future-incompat warning for this attribute. And since PR rust-lang#111505 (1.78, May 2024) that lint is deny by default. I presume nobody knew this attribute existed and thus it was never allowlisted.

Given the fact that since 2021 nobody has ever opened a ticket ([via](https://github.com/rust-lang/rust/issues?q=is%3Aissue+document_private_items)) complaining about the lint emission and the fact that GitHub code search doesn't yield any actual uses ([via](https://github.com/search?q=%2F%23%21%5C%5Bdoc%5C%28.*%3Fdocument_private_items%2F+language%3ARust&type=code&ref=advsearch)), I'm led to believe that nobody knows about and uses this attribute.

I don't find the existence of this attribute to be justified since in my view the flag `--document-private-items` is strictly superior: In most if not all cases, you don't want to "couple" your crate with this "mode" even if you gate it behind a cfg; instead, you most likely want to set this manually at invocation time, via a build config file like `.cargo/config.toml` or via a command runner like `just` I'd say.

Because of this I propose to wipe this attribute from existence. I don't believe it's worth cratering this (i.e., temporarily emitting a hard error for this attribute and running crater) given the fact that it's been undocumented since forever and led to a warning for years.

Rollup merge of #146495 - fmease:rustdoc-erase-doc-priv-items-attr, r=GuillaumeGomez

rustdoc: Erase `#![doc(document_private_items)]`

I just found out about the existence of `#![doc(document_private_items)]`. Apparently it was added by PR #50669 back in 2018 without any tests or docs as a replacement for some specific forms of the removed `#![doc(passes)]` / `#![doc(no_default_passes)]`.

However, rustc and rustdoc actually emit the deny-by-default lint `invalid_doc_attributes` for it (but if you allow it, the attribute does function)! To be more precise since PR #82708 (1.52, May 2021) which introduced lint `invalid_doc_attributes`, rust{,do}c has emitted a future-incompat warning for this attribute. And since PR #111505 (1.78, May 2024) that lint is deny by default. I presume nobody knew this attribute existed and thus it was never allowlisted.

Given the fact that since 2021 nobody has ever opened a ticket ([via](https://github.com/rust-lang/rust/issues?q=is%3Aissue+document_private_items)) complaining about the lint emission and the fact that GitHub code search doesn't yield any actual uses ([via](https://github.com/search?q=%2F%23%21%5C%5Bdoc%5C%28.*%3Fdocument_private_items%2F+language%3ARust&type=code&ref=advsearch)), I'm led to believe that nobody knows about and uses this attribute.

I don't find the existence of this attribute to be justified since in my view the flag `--document-private-items` is strictly superior: In most if not all cases, you don't want to "couple" your crate with this "mode" even if you gate it behind a cfg; instead, you most likely want to set this manually at invocation time, via a build config file like `.cargo/config.toml` or via a command runner like `just` I'd say.

Because of this I propose to wipe this attribute from existence. I don't believe it's worth cratering this (i.e., temporarily emitting a hard error for this attribute and running crater) given the fact that it's been undocumented since forever and led to a warning for years.

…=GuillaumeGomez

rustdoc: Erase `#![doc(document_private_items)]`

I just found out about the existence of `#![doc(document_private_items)]`. Apparently it was added by PR rust-lang/rust#50669 back in 2018 without any tests or docs as a replacement for some specific forms of the removed `#![doc(passes)]` / `#![doc(no_default_passes)]`.

However, rustc and rustdoc actually emit the deny-by-default lint `invalid_doc_attributes` for it (but if you allow it, the attribute does function)! To be more precise since PR rust-lang/rust#82708 (1.52, May 2021) which introduced lint `invalid_doc_attributes`, rust{,do}c has emitted a future-incompat warning for this attribute. And since PR rust-lang/rust#111505 (1.78, May 2024) that lint is deny by default. I presume nobody knew this attribute existed and thus it was never allowlisted.

Given the fact that since 2021 nobody has ever opened a ticket ([via](https://github.com/rust-lang/rust/issues?q=is%3Aissue+document_private_items)) complaining about the lint emission and the fact that GitHub code search doesn't yield any actual uses ([via](https://github.com/search?q=%2F%23%21%5C%5Bdoc%5C%28.*%3Fdocument_private_items%2F+language%3ARust&type=code&ref=advsearch)), I'm led to believe that nobody knows about and uses this attribute.

I don't find the existence of this attribute to be justified since in my view the flag `--document-private-items` is strictly superior: In most if not all cases, you don't want to "couple" your crate with this "mode" even if you gate it behind a cfg; instead, you most likely want to set this manually at invocation time, via a build config file like `.cargo/config.toml` or via a command runner like `just` I'd say.

Because of this I propose to wipe this attribute from existence. I don't believe it's worth cratering this (i.e., temporarily emitting a hard error for this attribute and running crater) given the fact that it's been undocumented since forever and led to a warning for years.