Rollup of 10 pull requests

Successful merges:

 - #92611 (Add links to the reference and rust by example for asm! docs and lints)
 - #93158 (wasi: implement `sock_accept` and enable networking)
 - #93239 (Add os::unix::net::SocketAddr::from_path)
 - #93261 (Some unwinding related cg_ssa cleanups)
 - #93295 (Avoid double panics when using `TempDir` in tests)
 - #93353 (Unimpl {Add,Sub,Mul,Div,Rem,BitXor,BitOr,BitAnd}<$t> for Saturating<$t>)
 - #93356 (Edit docs introduction for `std::cmp::PartialOrd`)
 - #93375 (fix typo `documenation`)
 - #93399 (rustbuild: Fix compiletest warning when building outside of root.)
 - #93404 (Fix a typo from #92899)

Failed merges:

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

backport llvm fix for issue 91671.

fix #91671

Fix a typo from #92899

Just happened to notice this in passing

rustbuild: Fix compiletest warning when building outside of root.

This fixes a warning that would happen when passing arguments to compiletest (like `x.py test src/test/ui`) when running `x.py` outside of the root source directory. For example, the CI builders do this, which causes a confusing warning message. This also fixes it so that passing a full path works (like `x.py test src/test/ui/hello.rs`) in the same scenario (previously it would just ignore the `hello.rs` part).

fix typo `documenation`

Edit docs introduction for `std::cmp::PartialOrd`

This makes `PartialOrd` consistent with the other three traits in this module, which all include links to their corresponding mathematical concepts on Wikipedia.

<img width="500" alt="Screen Shot 2022-01-26 at 10 24 23 PM" src="https://user-images.githubusercontent.com/19642016/151291720-decd85ed-cd6e-4be0-84a9-619b98ceb386.png">

Unimpl {Add,Sub,Mul,Div,Rem,BitXor,BitOr,BitAnd}<$t> for Saturating<$t>

Tracking issue #92354

Analog to 9648b313 #93208 reduce `saturating_int_assign_impl` (#93208) to:

```rust
let mut value = Saturating(2u8);
value += 3u8;
value -= 1u8;
value *= 2u8;
value /= 2u8;
value %= 2u8;
value ^= 255u8;
value |= 123u8;
value &= 2u8;
```

See https://github.com/rust-lang/rust/pull/93208#issuecomment-1022564429

Avoid double panics when using `TempDir` in tests

`TempDir` could panic on drop if `remove_dir_all` returns an error. If this happens while already panicking, the test process would abort and therefore not show the test results.

This PR tries to avoid such double panics.

Some unwinding related cg_ssa cleanups

These should make it a bit easier for alternative codegen backends to implement unwinding.

Add os::unix::net::SocketAddr::from_path

Creates a new SocketAddr from a path, supports both regular paths and
abstract namespaces.

Note that `SocketAddr::from_abstract_namespace` could be removed after this as `SocketAddr::unix` also supports abstract namespaces.

Updates #65275
Unblocks https://github.com/tokio-rs/mio/issues/1527

r? `@m-ou-se`

wasi: implement `sock_accept` and enable networking

With the addition of `sock_accept()` to snapshot1, simple networking via a passed `TcpListener` is possible. This PR implements the basics to make a simple server work.

See also:
* [wasmtime tracking issue](https://github.com/bytecodealliance/wasmtime/issues/3730)
* [wasmtime PR](https://github.com/bytecodealliance/wasmtime/pull/3711)

TODO:
* [ ] Discussion of `SocketAddr` return value for `::accept()`

```rust
        Ok((
            TcpStream::from_inner(unsafe { Socket::from_raw_fd(fd as _) }),
            // WASI has no concept of SocketAddr yet
            // return an unspecified IPv4Addr
            SocketAddr::new(Ipv4Addr::UNSPECIFIED.into(), 0),
        ))
```

Add links to the reference and rust by example for asm! docs and lints

These were previously removed in #91728 due to broken links.

cc ``@ehuss`` since this updates the rust-by-example submodule

Fix debuginfo for pointers/references to unsized types

This PR makes the compiler emit fat pointer debuginfo in all cases. Before, we sometimes got thin-pointer debuginfo, making it impossible to fully interpret the pointed to memory in debuggers. The code is actually cleaner now, especially around generation of trait object pointer debuginfo.

Fixes https://github.com/rust-lang/rust/issues/92718

~~Blocked on https://github.com/rust-lang/rust/pull/92729.~~

With the addition of `sock_accept()` to snapshot1, simple networking via
a passed `TcpListener` is possible. This patch implements the basics to
make a simple server work.
Signed-off-by: NHarald Hoyer <harald@profian.com>

To make use of `sock_accept()`, update the wasi crate to `0.11.0`.
Signed-off-by: NHarald Hoyer <harald@profian.com>

Suggest tuple-parentheses for enum variants

This follows on from #86493 / #86481, making the parentheses suggestion. To summarise, given the following code:

```rust
fn f() -> Option<(i32, i8)> {
    Some(1, 2)
}
```

The current output is:

```
error[E0061]: this enum variant takes 1 argument but 2 arguments were supplied
 --> b.rs:2:5
  |
2 |     Some(1, 2)
  |     ^^^^ -  - supplied 2 arguments
  |     |
  |     expected 1 argument

error: aborting due to previous error

For more information about this error, try `rustc --explain E0061`.
```

With this change, `rustc` will now suggest parentheses when:
- The callee is expecting a single tuple argument
- The number of arguments passed matches the element count in the above tuple
- The arguments' types match the tuple's fields

```
error[E0061]: this enum variant takes 1 argument but 2 arguments were supplied
 --> b.rs:2:5
  |
2 |     Some(1, 2)
  |     ^^^^ -  - supplied 2 arguments
  |
help: use parentheses to construct a tuple
  |
2 |     Some((1, 2))
  |          +    +
```

[debuginfo] Fix and unify handling of fat pointers in debuginfo: Don't mark fat pointer fields as artificial.

LLDB does not seem to see fields if they are marked with DW_AT_artificial
which breaks pretty printers that use these fields for decoding fat pointers.

This makes `PartialOrd` consistent with the other three traits in this
module, which all include links to their respective mathematical concepts
on Wikipedia.

Only traverse attrs once while checking for coherence override attributes

In coherence, while checking for negative impls override attributes: only traverse the `DefId`s' attributes once.

This PR is an easy way to get back some of the small perf loss in #93175

Just happened to notice this in passing

Update Clippy

r? `@Manishearth`

Rollup of 8 pull requests

Successful merges:

 - #91641 (Define c_char using cfg_if rather than repeating 40-line cfg)
 - #92899 (Mention std::iter::zip in Iterator::zip docs)
 - #93193 (Add test for stable hash uniqueness of adjacent field values)
 - #93325 (Introduce a limit to Levenshtein distance computation)
 - #93339 (rustdoc: add test case for multiple traits and erased names)
 - #93357 (Clarify the `usage-of-qualified-ty` error message.)
 - #93363 (`#[rustc_pass_by_value]` cleanup)
 - #93365 (More arena cleanups)

Failed merges:

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

More arena cleanups

A sequel to #90990.

r? `@oli-obk`

`#[rustc_pass_by_value]` cleanup

Clarify the `usage-of-qualified-ty` error message.

I found this message confusing when I encountered it. This commit makes
it clearer that you have to import the unqualified type yourself.

r? `@lcnr`

rustdoc: add test case for multiple traits and erased names

https://github.com/rust-lang/rust/pull/92339#discussion_r792805289

Introduce a limit to Levenshtein distance computation

Incorporate distance limit from `find_best_match_for_name` directly into
Levenshtein distance computation.

Use the string size difference as a lower bound on the distance and exit
early when it exceeds the specified limit.

After finding a candidate within a limit, lower the limit further to
restrict the search space.

Add test for stable hash uniqueness of adjacent field values

This PR adds a simple test to check that stable hash will produce a different hash if the order of two values that have the same combined bit pattern changes.

r? `@the8472`

Mention std::iter::zip in Iterator::zip docs

Closes https://github.com/rust-lang/rust/issues/91960

I'm not sure about the wording. I think it's alright, but happy to change.

Define c_char using cfg_if rather than repeating 40-line cfg

Libstd has a 40-line cfg that defines the targets on which `c_char` is unsigned, and then repeats the same cfg with `not(…)` for the targets on which `c_char` is signed.

This PR replaces it with a `cfg_if!` in which an `else` takes care of the signed case.

I confirmed that `x.py doc library/std` inlines the type alias because c_char_definition is not a publicly accessible path:

![Screenshot from 2021-12-07 13-42-07](https://user-images.githubusercontent.com/1940490/145110596-f1058406-9f32-44ff-9a81-1dfd19b4a24f.png)

It's simply a binary thing to allow different behaviour for `Copy` vs
`!Copy` types. The new code makes this much clearer; I was scratching my
head over the old code for some time.

[debuginfo] Fix and unify handling of fat pointers in debuginfo: Change doc comment so it is not interpreted as doc-test.