Co-authored-by: Ralf Jung <post@ralfj.de>

General improvements, and also aims to better encourage the reader
to actually check out Arc::try_unwrap.

Currently, when building with `build-std`, some library build scripts
check properties of the target by inspecting the target triple at
`env::TARGET`, which is simply set to the filename of the JSON file
when using JSON target files.

This patch alters these build scripts to use `env::CARGO_CFG_*` to
fetch target information instead, allowing JSON target files
describing platforms without `restricted_std` to build correctly when
using `-Z build-std`.

Fixes wg-cargo-std-aware/rust-lang#60.

This refactors run.sh to never override an explicit $CODEGEN_BACKENDS if
set in the build.

This includes a change to the upstream build_fuchsia_from_rust_ci script
that builds a minimal set of tests, to improve coverage on this builder.

For consistency with normal functions.

…e def id

References refer to allocated objects

Partially addresses rust-lang/unsafe-code-guidelines#465

Add support for custom JSON targets when using build-std.

Currently, when building with `build-std`, some library build scripts check properties of the target by inspecting the target triple at `env::TARGET`, which is simply set to the filename of the JSON file when using JSON target files.

This patch alters these build scripts to use `env::CARGO_CFG_*` to fetch target information instead, allowing JSON target files describing platforms without `restricted_std` to build correctly when using `-Z build-std`. There are some weak assertions here (for example, `nintendo && newlib`), however this seems at least a marginal improvement on the existing solution.

Fixes rust-lang/wg-cargo-std-aware#60.

…ark-Simulacrum

Improve documentation for [A]Rc::into_inner

General improvements, and also aims to better encourage the reader to actually check out Arc::try_unwrap.

This addresses concerns from rust-lang#106894 (comment).

Rendered:

![Screenshot_20240123_114436](https://github.com/rust-lang/rust/assets/3986214/68896d62-13e0-4f3a-8073-91d8e77c5554)
![Screenshot_20240123_114455](https://github.com/rust-lang/rust/assets/3986214/dc58e4bd-dd7f-40b1-bc50-fd6200dde593)

…ark-Simulacrum

Bump Fuchsia, build tests, and use 8 core bots

- Build Fuchsia on 8 cores instead of 16
- Skip building cranelift for Fuchsia
- Bump Fuchsia (includes building tests)

This includes a change to the upstream build_fuchsia_from_rust_ci script that builds a minimal set of tests, to improve coverage on this builder. This would have caught rust-lang/rust-clippy#11952 and rust-lang#119593.

See prior discussion on rust-lang#119400 about building on 8 cores instead of 16. This PR combines changes from that and rust-lang#119399, plus clean up.

r? ```@Mark-Simulacrum```

…120040, r=ChrisDenton

Adjust Behaviour of `read_dir` and `ReadDir` in Windows Implementation: Check Whether Path to Search In Exists

This pull request changes the `read_dir` function's and the `ReadDir` structure's internal implementations for the Windows operating system to make its behaviour more accurate.

It should be noted that `ERROR_FILE_NOT_FOUND` is returned by the `FindFirstFileW` function when *no matching files can be found*, not necessarily that the path to search in does not exist in the first place. Therefore, directly returning the "The system cannot find the file specified." may not be accurate.

An extra check for whether the path to search in exists is added, returning a constructed `ReadDir` iterator with its handle being an `INVALID_HANDLE_VALUE` returned by the `FindFirstFileW` function if `ERROR_FILE_NOT_FOUND` is indeed the last OS error. The `ReadDir` implementation for the Windows operating system is correspondingly updated to always return `None` if the handle it has is an `INVALID_HANDLE_VALUE` which can only be the case if and only if specifically constructed by the `read_dir` function in the aforementioned conditions.

It should also be noted that `FindFirstFileW` would have returned `ERROR_PATH_NOT_FOUND` if the path to search in does not exist in the first place.

Presumably fixes rust-lang#120040.

…tree, r=cjgillot

Make the coroutine def id of an async closure the child of the closure def id

Adjust def collection to make the (inner) coroutine returned by an async closure be a def id child of the (outer) closure. This makes it easy to map from coroutine -> closure by using `tcx.parent`, since currently it's not trivial to do this.

…tive, r=Nilstrieb

Stop using derivative in rustc_pattern_analysis

CC rust-lang#109302, rust-lang/rust-analyzer#16420 (comment)

r? ``@Nadrieril``

…Nilstrieb

Remove unnecessary unit returns in query declarations

For consistency with normal functions.