Co-authored-by: Tomoaki Kawada <kawada@kmckk.co.jp>

Using typed identifiers instead of strings with the Fluent identifier
enables the diagnostic derive to benefit from the compile-time
validation that comes with typed identifiers - use of a non-existent
Fluent identifier will not compile.

Signed-off-by: David Wood <david.wood@huawei.com>

As in the diagnostic derive, using typed identifiers in the
subdiagnostic derive improves the diagnostics of using the subdiagnostic
derive as Fluent messages will be confirmed to exist at compile-time.

Signed-off-by: David Wood <david.wood@huawei.com>

Now that typed identifiers are used in both derives, constructors for
the `DiagnosticMessage` and `SubdiagnosticMessage` types are not
required.

Signed-off-by: David Wood <david.wood@huawei.com>

Add `struct FileTimes` to contain the relevant file timestamps, since
most platforms require setting all of them at once. (This also allows
for future platform-specific extensions such as setting creation time.)

Add `File::set_file_time` to set the timestamps for a `File`.

Implement the `sys` backends for UNIX, macOS (which needs to fall back
to `futimes` before macOS 10.13 because it lacks `futimens`), Windows,
and WASI.

This would otherwise silently ignore the attempt, since 0 serves as a
flag to not set a timestamp.

std: use an event-flag-based thread parker on SOLID

`Mutex` and `Condvar` are being replaced by more efficient implementations, which need thread parking themselves (see rust-lang#93740). Therefore, the generic `Parker` needs to be replaced on all platforms where the new lock implementation will be used, which, after rust-lang#96393, are SOLID, SGX and Hermit (more PRs coming soon).

SOLID, conforming to the [μITRON specification](http://www.ertl.jp/ITRON/SPEC/FILE/mitron-400e.pdf), has event flags, which are a thread parking primitive very similar to `Parker`. However, they do not make any atomic ordering guarantees (even though those can probably be assumed) and necessitate a system call even when the thread token is already available. Hence, this `Parker`, like the Windows parker, uses an extra atomic state variable.

I future-proofed the code by wrapping the event flag in a `WaitFlag` structure, as both SGX and Hermit can share the Parker implementation, they just have slightly different primitives (SGX uses signals and Hermit has a thread blocking API).

```@kawadakk``` I assume you are the target maintainer? Could you test this for me?

…ompiler-errors

[rustc_parse] Forbid `let`s in certain places

Currently only forbids in locals to resolve rust-lang#94927 (comment) but feel free to point any other places.

… r=estebank

make const_err show up in future breakage reports

As tracked in rust-lang#71800, const_err should become a hard error Any Day Now (TM). I'd love to move forward with that sooner rather than later; it has been deny-by-default for many years and a future incompat lint since rust-lang#80394 (landed more than a year ago). Some CTFE errors are already hard errors since rust-lang#86194. But before we truly make it a hard error in all cases, we now have one more intermediate step we can take -- to make it show up in future breakage reports.

Cc ```@rust-lang/wg-const-eval```

…_ops_constness, r=scottmcm

Stabilize NonZero* checked operations constness.

Partial stabilization for rust-lang#97547 (continued).

Support setting file accessed/modified timestamps

Add `struct FileTimes` to contain the relevant file timestamps, since
most platforms require setting all of them at once. (This also allows
for future platform-specific extensions such as setting creation time.)

Add `File::set_file_time` to set the timestamps for a `File`.

Implement the `sys` backends for UNIX, macOS (which needs to fall back
to `futimes` before macOS 10.13 because it lacks `futimens`), Windows,
and WASI.

…notriddle

Transform help popup into a pocket menu

Just like we moved the settings menu into a "pocket menu", it's doing the same to the help popup.

You can test it [here](https://rustdoc.crud.net/imperio/help-pocket-menu/doc/foo/index.html) and here is a screenshot:

![Screenshot from 2022-06-20 20-58-29](https://user-images.githubusercontent.com/3050060/174663718-538e9d11-3bf9-48b2-8909-f9bfe75af135.png)

r? ````````@jsha````````

…identifiers, r=oli-obk

macros: use typed identifiers in diag and subdiag derive

Using typed identifiers instead of strings with the Fluent identifiers in the diagnostic and subdiagnostic derives - this enables the diagnostic derive to benefit from the compile-time validation that comes with typed identifiers, namely that use of a non-existent Fluent identifier will not compile.

r? ```@oli-obk```

…9, r=lcnr

Add regression test for generic const in rustdoc

Fixes rust-lang#92859.

r? `@lcnr`