Fix a bug in `x.py fmt` that prevents some files being formatted.

If you have a file in the repository root with the same name as a file
somewhere within a directory, the latter currently won't get formatted.

I have experienced this multiple times and not understood what was
happening; I finally figured out the problem today. This commit fixes
the problem.

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

CTFE SwitchInt: update comment

I just wondered why this doesn't use `binary_op`.

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

Use `HandleOrNull` and `HandleOrInvalid` in the Windows FFI bindings.

Use the new `HandleOrNull` and `HandleOrInvalid` types that were introduced
as part of [I/O safety] in a few functions in the Windows FFI bindings.

This factors out an `unsafe` block and two `unsafe` function calls in the
Windows implementation code.

And, it helps test `HandleOrNull` and `HandleOrInvalid`, and indeed, it
turned up a bug: `OwnedHandle` also needs to be `#[repr(transparent)]`,
as it's used inside of `HandleOrNull` and `HandleOrInvalid` which are also
`#[repr(transparent)]`.

r? ```@joshtriplett```

[I/O safety]: https://github.com/rust-lang/rust/issues/87074

bootstrap: correct reading of flags for llvm

First, this reverts the `CFLAGS`/`CXXFLAGS` of #93918. Those flags are
already read by `cc` and populated into `Build` earlier on in the
process. We shouldn't be overriding that based on `CFLAGS`, since `cc`
also respects overrides like `CFLAGS_{TARGET}` and `HOST_CFLAGS`, which
we want to take into account.

Second, this adds the same capability to specify target-specific
versions of `LDFLAGS` as we have through `cc` for the `C*` flags:
https://github.com/alexcrichton/cc-rs#external-configuration-via-environment-variables

Make Ord and PartialOrd opt-out in `newtype_index`

Part of work on #90317. This will allow us to do

```diff
rustc_index::newtype_index! {
    /// A unique ID associated with a macro invocation and expansion.
    pub struct LocalExpnId {
        ENCODABLE = custom
        DEBUG_FORMAT = "expn{}"
+       ORD_IMPL = off
    }
}
```

ARM: Only allow using d16-d31 with asm! when supported by the target

Support can be determined by checking for the "d32" LLVM feature.

r? ```````````````@nagisa```````````````

Make regular stdio lock() return 'static handles

This also deletes the unstable API surface area previously added to expose this
functionality on new methods rather than built into the current set.

Closes #86845 (tracking issue for unstable API needed without this)

r? ``````@dtolnay`````` to kick off T-libs-api FCP

Remove the everybody loops pass

It isn't used anymore by rustdoc.

Split out of https://github.com/rust-lang/rust/pull/92895. There has been some previous discussion there.

rustdoc & doc: no `shortcut` for `rel="icon"`

According to https://html.spec.whatwg.org/multipage/links.html#rel-icon:

> For historical reasons, the `icon` keyword may be preceded by the keyword "`shortcut`".

And to https://developer.mozilla.org/en-US/docs/Web/HTML/Link_types:

> **Warning:** The `shortcut` link type is often seen before `icon`, but this link type is non-conforming, ignored and **web authors must not use it anymore.**

While it was removed from the Rust logo case a while ago in commit 085679c8 ("Use theme-adaptive SVG favicon from other Rust sites"), it is still there for the custom logo case.

Also updated a few other instances.
Signed-off-by: NMiguel Ojeda <ojeda@kernel.org>

Clarification of default socket flags

This PR outlines the decision to disable inheritance of socket objects when possible to child processes in the documentation.

If you have a file in the repository root with the same name as a file
somewhere within a directory, the latter currently won't get formatted.

I have experienced this multiple times and not understood what was
happening; I finally figured out the problem today. This commit fixes
the problem.

Rollup of 8 pull requests

Successful merges:

 - #92697 (Use cgroup quotas for calculating `available_parallelism`)
 - #94057 (improve comments for `simplify_type`)
 - #94547 (`parse_tt` cleanups)
 - #94550 (rustdoc: Add test for higher kinded functions generated by macros)
 - #94551 (Doc: Fix use of quote instead of backstick in Adapter::map.)
 - #94554 (Fix invalid lint_node_id being put on a removed stmt)
 - #94555 (all: fix some typos)
 - #94563 (Remove a unnecessary `..` pattern)

Failed merges:

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

Use the new `HandleOrNull` and `HandleOrInvalid` types that were introduced
as part of [I/O safety] in a few functions in the Windows FFI bindings.

This factors out an `unsafe` block and two `unsafe` function calls in the
Windows implementation code.

And, it helps test `HandleOrNull` and `HandleOrInvalid`, which indeed turned
up a bug: `OwnedHandle` also needs to be `#[repr(transparent)]`, as it's
used inside of `HandleOrNull` and `HandleOrInvalid` which are also
`#[repr(transparent)]`.

[I/O safety]: https://github.com/rust-lang/rust/issues/87074

Rollup merge of #94563 - TaKO8Ki:remove-unnecessary-patten-for-ignoring-remaining-parts, r=Dylan-DPC

Remove a unnecessary `..` pattern

all: fix some typos
Signed-off-by: Ncuishuang <imcusg@gmail.com>

Fix invalid lint_node_id being put on a removed stmt

This pull-request remove a invalid `assign_id!` being put on an stmt node.

The problem is that this node is being removed away by a cfg making it unreachable when triggering a buffered lint.
The comment in the other match arm already tell to not assign a id because it could have a `#[cfg()]` so this is just respecting the comment.

Fixes https://github.com/rust-lang/rust/issues/94523
r? ```````@petrochenkov```````

Doc: Fix use of quote instead of backstick in Adapter::map.

A little commit to fix documentation rendering and semantics in https://doc.rust-lang.org/std/iter/struct.Map.html#notes-about-side-effects `"` where used around an expression instead \`.

Screenshot on doc.rust-lang.org:
![2022-03-03 11-21-43_backstick](https://user-images.githubusercontent.com/2827553/156546536-569b7692-7ac4-4388-8e93-c1628ddc6a0f.png)

Looking forward: Maybe reworking the doc to use assert_eq like the upper paragraph:
```
let v: Vec<i32> = vec![1, 2, 3].into_iter().map(|x| x + 1).rev().collect();

assert_eq!(v, [4, 3, 2]);
```

rustdoc: Add test for higher kinded functions generated by macros

Fixes #75564.

The problem has been solved apparently so adding a test to prevent a regression.

r? ```@notriddle```

`parse_tt` cleanups

I've been looking closely at this code, and saw some opportunities to improve its readability.

r? ```````@petrochenkov```````

improve comments for `simplify_type`

Should now correctly describe what's going on. Experimented with checking the invariant for projections
but that ended up requiring fairly involved changes. I assume that it is not possible to get unsoundness here,
at least for now and I can pretty much guarantee that it's impossible to trigger it by accident.

r? `````@nikomatsakis````` cc #92721

Use cgroup quotas for calculating `available_parallelism`

Automated tests for this are possible but would require a bunch of assumptions. It requires root + a recent kernel, systemd and maybe docker. And even then it would need a helper binary since the test has to run in a separate process.

Limitations

* only supports cgroup v2 and assumes it's mounted under `/sys/fs/cgroup`
* procfs must be available
* the quota gets mixed into `sched_getaffinity`, so if the latter doesn't work then quota information gets ignored too

Manually tested via

```
// spawn a new cgroup scope for the current user
$ sudo systemd-run -p CPUQuota="300%" --uid=$(id -u) -tdS

// quota.rs
#![feature(available_parallelism)]
fn main() {
    println!("{:?}", std::thread::available_parallelism()); // prints Ok(3)
}
```

strace:

```
sched_getaffinity(3041643, 32, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47]) = 32
openat(AT_FDCWD, "/proc/self/cgroup", O_RDONLY|O_CLOEXEC) = 3
statx(0, NULL, AT_STATX_SYNC_AS_STAT, STATX_ALL, NULL) = -1 EFAULT (Bad address)
statx(3, "", AT_STATX_SYNC_AS_STAT|AT_EMPTY_PATH, STATX_ALL, {stx_mask=STATX_BASIC_STATS|STATX_MNT_ID, stx_attributes=0, stx_mode=S_IFREG|0444, stx_size=0, ...}) = 0
lseek(3, 0, SEEK_CUR)                   = 0
read(3, "0::/system.slice/run-u31477.serv"..., 128) = 36
read(3, "", 92)                         = 0
close(3)                                = 0
statx(AT_FDCWD, "/sys/fs/cgroup/system.slice/run-u31477.service/cgroup.controllers", AT_STATX_SYNC_AS_STAT, STATX_ALL, {stx_mask=STATX_BASIC_STATS|STATX_MNT_ID, stx_attributes=0, stx_mode=S_IFREG|0444, stx_size=0, ...}) = 0
openat(AT_FDCWD, "/sys/fs/cgroup/system.slice/run-u31477.service/cpu.max", O_RDONLY|O_CLOEXEC) = 3
statx(3, "", AT_STATX_SYNC_AS_STAT|AT_EMPTY_PATH, STATX_ALL, {stx_mask=STATX_BASIC_STATS|STATX_MNT_ID, stx_attributes=0, stx_mode=S_IFREG|0644, stx_size=0, ...}) = 0
lseek(3, 0, SEEK_CUR)                   = 0
read(3, "300000 100000\n", 20)          = 14
read(3, "", 6)                          = 0
close(3)                                = 0
openat(AT_FDCWD, "/sys/fs/cgroup/system.slice/cpu.max", O_RDONLY|O_CLOEXEC) = 3
statx(3, "", AT_STATX_SYNC_AS_STAT|AT_EMPTY_PATH, STATX_ALL, {stx_mask=STATX_BASIC_STATS|STATX_MNT_ID, stx_attributes=0, stx_mode=S_IFREG|0644, stx_size=0, ...}) = 0
lseek(3, 0, SEEK_CUR)                   = 0
read(3, "max 100000\n", 20)             = 11
read(3, "", 9)                          = 0
close(3)                                = 0
openat(AT_FDCWD, "/sys/fs/cgroup/cpu.max", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
sched_getaffinity(0, 128, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47]) = 40
```

r? ```````@joshtriplett```````
cc ```````@yoshuawuyts```````

Tracking issue and previous discussion: #74479

Implementation of the `expect` attribute (RFC 2383)

This is an implementation of the `expect` attribute as described in [RFC-2383](https://rust-lang.github.io/rfcs/2383-lint-reasons.html). The attribute allows the suppression of lint message by expecting them. Unfulfilled lint expectations (meaning no expected lint was caught) will emit the `unfulfilled_lint_expectations` lint at the `expect` attribute.

### Example
#### input
```rs
// required feature flag
#![feature(lint_reasons)]

#[expect(unused_mut)] // Will warn about an unfulfilled expectation
#[expect(unused_variables)] // Will be fulfilled by x
fn main() {
    let x = 0;
}
```

#### output

```txt
warning: this lint expectation is unfulfilled
  --> $DIR/trigger_lint.rs:3:1
   |
LL | #[expect(unused_mut)] // Will warn about an unfulfilled expectation
   |          ^^^^^^^^^^
   |
   = note: `#[warn(unfulfilled_lint_expectations)]` on by default
```

### Implementation

This implementation introduces `Expect` as a new lint level for diagnostics, which have been expected. All lint expectations marked via the `expect` attribute are collected in the [`LintLevelsBuilder`] and assigned an ID that is stored in the new lint level. The `LintLevelsBuilder` stores all found expectations and the data needed to emit the `unfulfilled_lint_expectations` in the [`LintLevelsMap`] which is the result of the [`lint_levels()`] query.

The [`rustc_errors::HandlerInner`] is the central error handler in rustc and handles the emission of all diagnostics. Lint message with the level `Expect` are suppressed during this emission, while the expectation ID is stored in a set which marks them as fulfilled. The last step is then so simply check if all expectations collected by the [`LintLevelsBuilder`] in the [`LintLevelsMap`] have been marked as fulfilled in the [`rustc_errors::HandlerInner`]. Otherwise, a new lint message will be emitted.

The implementation of the `LintExpectationId` required some special handling to make it stable between sessions. Lints can be emitted during [`EarlyLintPass`]es. At this stage, it's not possible to create a stable identifier. The level instead stores an unstable identifier, which is later converted to a stable `LintExpectationId`.

### Followup TO-DOs
All open TO-DOs have been marked with `FIXME` comments in the code. This is the combined list of them:

* [ ] The current implementation doesn't cover cases where the `unfulfilled_lint_expectations` lint is actually expected by another `expect` attribute.
   * This should be easily possible, but I wanted to get some feedback before putting more work into this.
   * This could also be done in a new PR to not add to much more code to this one
* [ ] Update unstable documentation to reflect this change.
* [ ] Update unstable expectation ids in [`HandlerInner::stashed_diagnostics`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_errors/struct.HandlerInner.html#structfield.stashed_diagnostics)

### Open questions
I also have a few open questions where I would like to get feedback on:
1. The RFC discussion included a suggestion to change the `expect` attribute to something else. (Initiated by `@Ixrec` [here](https://github.com/rust-lang/rfcs/pull/2383#issuecomment-378424091), suggestion from `@scottmcm` to use `#[should_lint(...)]` [here](https://github.com/rust-lang/rfcs/pull/2383#issuecomment-378648877)). No real conclusion was drawn on that point from my understanding. Is this still open for discussion, or was this discarded with the merge of the RFC?
2. How should the expect attribute deal with the new `force-warn` lint level?

---

This approach was inspired by a discussion with `@LeSeulArtichaut.`

RFC tracking issue: #54503

Mentoring/Implementation issue: #85549

[`LintLevelsBuilder`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_lint/levels/struct.LintLevelsBuilder.html
[`LintLevelsMap`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/lint/struct.LintLevelMap.html
[`lint_levels()`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty/context/struct.TyCtxt.html#method.lint_levels
[`rustc_errors::HandlerInner`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_errors/struct.HandlerInner.html
[`EarlyLintPass`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_lint/trait.EarlyLintPass.html

Also remove `step` impl if `ORD_IMPL = off`

First, this reverts the `CFLAGS`/`CXXFLAGS` of #93918. Those flags are
already read by `cc` and populated into `Build` earlier on in the
process. We shouldn't be overriding that based on `CFLAGS`, since `cc`
also respects overrides like `CFLAGS_{TARGET}` and `HOST_CFLAGS`, which
we want to take into account.

Second, this adds the same capability to specify target-specific
versions of `LDFLAGS` as we have through `cc` for the `C*` flags:
https://github.com/alexcrichton/cc-rs#external-configuration-via-environment-variables

Note that this also necessitated an update to compiletest to treat
CXXFLAGS separately from CFLAGS.

It isn't used anymore by rustdoc

remove obligation dedup from `impl_or_trait_obligations`

Looking at the examples from #38528 they all seem to compile fine even without this and it seems like this might be unnecessary effort

Miri/CTFE: properly treat overflow in (signed) division/rem as UB

To my surprise, it looks like LLVM treats overflow of signed div/rem as UB. From what I can tell, MIR `Div`/`Rem` directly lowers to the corresponding LLVM operation, so to make that correct we also have to consider these overflows UB in the CTFE/Miri interpreter engine.

r? `@oli-obk`

Signed-off-by: Ncuishuang <imcusg@gmail.com>

Because `inner_parse_loop` has only one way to not succeed, not three.

There are three `Option` fields in `MatcherPos` that are only used in
tandem. This commit combines them, making the code slightly easier to
read. (It also makes clear that the `sep` field arguably should have
been `Option<Option<Token>>`!)

To avoid the strange style where comments force `else` onto its own
line.

The commit also removes several else-after-return constructs, which can
be hard to read.

Rollup of 8 pull requests

Successful merges:

 - #93562 (Update the documentation for `{As,Into,From}Raw{Fd,Handle,Socket}`.)
 - #94101 (rustdoc: add test cases for hidden enum variants)
 - #94484 (8 - Make more use of `let_chains`)
 - #94522 (Remove out-of-context line at end of E0284 message)
 - #94534 (Re-export (unstable) core::ffi types from std::ffi)
 - #94536 (Move transmute_undefined_repr back to nursery again)
 - #94537 (Use ? operator in one instance instead of manual match)
 - #94544 (Add some examples to comments in mbe code)

Failed merges:

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

Add some examples to comments in mbe code

I found these things non-obvious when re-familiarizing myself with the code.

r? `@petrochenkov`