…ad for collecting iterators

and replace it with `extended_key_value_attributes` feature.

This also relaxes the bounds on some structs and moves them to the impl
block instead.

Unlike the other cases of this lint, there's no simple way to detect if
an old version of the relevant crate (`syn`) is in use. The `actix-web`
crate only depends on `pin-project` v1.0.0, so checking the version of
`actix-web` does not guarantee that a new enough version of
`pin-project` (and therefore `syn`) is in use.

Instead, we rely on the fact that virtually all of the regressed crates
are pinned to a pre-1.0 version of `pin-project`. When this is the case,
bumping the `actix-web` dependency will pull in the *latest* version of
`pin-project`, which has an explicit dependency on a newer v dependency
on a newer version of `syn`.

The lint message tells users to update `actix-web`, since that's what
they're most likely to have control over. We could potentially tell them
to run `cargo update -p syn`, but I think it's more straightforward to
suggest an explicit change to the `Cargo.toml`

The `actori-web` fork had its last commit over a year ago, and appears
to just be a renamed fork of `actix-web`. Therefore, I've removed the
`actori-web` check entirely - any crates that actually get broken can
simply update `syn` themselves.

One of the examples used to say “this leads to a possibly confusing situation,
where the type of the closure is a double reference” while _actually_ referring to
the type of the closure _argument_.

Reuse `std::sys::unsupported::pipe` on `hermit`

Pipes are not supported on `hermit` and `hermit/pipe.rs` is identical to `unsupported/pipe.rs`. This PR reduces duplication between the two by doing the following on `hermit`:

```rust
#[path = "../unsupported/pipe.rs"]
pub mod pipe;
```

…chenkov

Remove unwrap_none/expect_none from compiler/.

We're not going to stabilize `Option::{unwrap_none, expect_none}`. (See rust-lang#62633.) This removes the usage of those unstable methods from `compiler/`.

…n514

rustdoc: allow list syntax for #[doc(alias)] attributes

Fixes rust-lang#81205.

It now allows to have:

```rust
#[doc(alias = "x")]
// and:
#[doc(alias("y", "z"))]
```

cc ``@jplatte``
r? ``@jyn514``

Clarify docs for Read::read's return value

Right now the docs for `Read::read`'s return value are phrased in a way that makes it easy for the reader to assume that the return value is never larger than the passed buffer. This PR clarifies that this is a requirement for implementations of the trait, but that callers have to expect a buggy yet safe implementation failing to do so, especially if unchecked accesses to the buffer are done afterwards.

I fell into this trap recently, and when I noticed, I looked at the docs again and had the feeling that I might not have been the first one to miss this.

The same issue of trusting the return value of `read` was also present in std itself for about 2.5 years and only fixed recently, see rust-lang#80895.

I hope that clarifying the docs might help others to avoid this issue.

…enkov

Extend `proc_macro_back_compat` lint to `actix-web`

Unlike the other cases of this lint, there's no simple way to detect if
an old version of the relevant crate (`syn`) is in use. The `actix-web`
crate only depends on `pin-project` v1.0.0, so checking the version of
`actix-web` does not guarantee that a new enough version of
`pin-project` (and therefore `syn`) is in use.

Instead, we rely on the fact that virtually all of the regressed crates
are pinned to a pre-1.0 version of `pin-project`. When this is the case,
bumping the `actix-web` dependency will pull in the *latest* version of
`pin-project`, which has an explicit dependency on a newer v dependency
on a newer version of `syn`.

The lint message tells users to update `actix-web`, since that's what
they're most likely to have control over. We could potentially tell them
to run `cargo update -p syn`, but I think it's more straightforward to
suggest an explicit change to the `Cargo.toml`

The `actori-web` fork had its last commit over a year ago, and appears
to just be a renamed fork of `actix-web`. Therefore, I've removed the
`actori-web` check entirely - any crates that actually get broken can
simply update `syn` themselves.

…iplett

Move some test-only code to test files

Split out from rust-lang#83185.

Fix gitattibutes for old git versions

Deprecate std::os::haiku::raw, which accidentally wasn't deprecated

In early 2016, all `std::os::*::raw` modules [were deprecated](rust-lang@aa23c98) in accordance with [RFC 1415](https://github.com/rust-lang/rfcs/blob/master/text/1415-trim-std-os.md). However, at this same time support for Haiku was being added to libstd, landing shortly after the aforementioned commit, and due to some crossed wires a `std::os::haiku::raw` module was added and was not marked as deprecated.

I have been in correspondence with the author of the Haiku patch, ````@nielx,```` who has confirmed that this was simply an oversight and that the definitions from the libc crate should be preferred instead.

Remove unnecessary `forward_inner_docs` hack

and replace it with `extended_key_value_attributes` feature.

This is rust-lang#79150, but for compiler/.

Upgrade memmap to memmap2

memmap is no longer maintained. memmap2 is a fork that is still maintained. https://rustsec.org/advisories/RUSTSEC-2020-0077.html

The remaining use of memmap is through measureme.

…_doc, r=joshtriplett

Fix typo/inaccuracy in the documentation of Iterator::skip_while

One of the examples used to say “this leads to a possibly confusing situation, where the type of the closure is a double reference” while _actually_ referring to the type of the closure _argument_.

This PR just changes a single word in documentation.

`````@rustbot````` modify labels: A-iterators, T-doc, T-lang