During borrowchecking, we treat any free (early-bound) regions on
the 'defining type' as `RegionClassification::External`. According
to the doc comments, we should only have 'external' regions when
checking a closure/generator.

However, a plain function can also have some if its regions
be considered 'early bound' - this occurs when the region is
constrained by an argument, appears in a `where` clause, or
in an opaque type. This was causing us to incorrectly mark these
regions as 'external', which caused some diagnostic code
to act as if we were referring to a 'parent' region from inside
a closure.

This PR marks all instantiated region variables as 'local'
when we're borrow-checking something other than a
closure/generator/inline-const.

This provides the user with a helpful error message in case a key="value"
message was specified but couldn't be parsed.

Now, multipart suggestions are used instead of `span_to_snippet`, which
improves code quality, makes the suggestion work even without access to
source code, and, most importantly, improves the rendering of the
suggestion.

This should make it easier to read.

This code is sufficiently complex -- I'm guessing due to the very long
`match` guards -- that rustfmt doesn't format it.

Co-authored-by: David Wood <Q0KPU0H1YOEPHRY1R2SN5B5RL@david.davidtw.co>

A number of trait implementations incorrectly claimed to be zero cost.

…les.

For all table layouts, set overflow-wrap: break-word.

x.py has support for excluding some steps from the invocation, but
unfortunately that's not granular enough: some steps have the same name
in different modules, and that prevents excluding only *some* of them.

As a practical example, let's say you need to run everything in `./x.py
test` except for the standard library tests, as those tests require IPv6
and need to be executed on a separate machine. Before this commit, if
you were to just run this:

    ./x.py test --exclude library/std

...the execution would fail, as that would not only exclude running the
tests for the standard library, it would also exclude generating its
documentation (breaking linkchecker).

This commit adds support for an optional module annotation in --exclude
paths, allowing the user to choose which module to exclude from:

    ./x.py test --exclude test::library/std

This maintains backward compatibility, but also allows for more ganular
exclusion. More examples on how this works:

| `--exclude`         | Docs    | Tests   |
| ------------------- | ------- | ------- |
| `library/std`       | Skipped | Skipped |
| `doc::library/std`  | Skipped | Run     |
| `test::library/std` | Run     | Skipped |

Note that the new behavior only works in the `--exclude` flag, and not
in other x.py arguments or flags yet.

… r=Mark-Simulacrum

Add more granular `--exclude` in `x.py`

x.py has support for excluding some steps from the current invocation, but unfortunately that's not granular enough: some steps have the same name in different modules, and that prevents excluding only *some* of them.

As a practical example, let's say you need to run everything in `./x.py test` except for the standard library tests, as those tests require IPv6 and need to be executed on a separate machine. Before this commit, if you were to just run this:

    ./x.py test --exclude library/std

...the invocation would eventually fail, as that would not only exclude running the tests for the standard library (`library/std` in the `test` module), it would also exclude generating its documentation (`library/std` in the `doc` module), breaking linkchecker.

This commit adds support to the `--exclude` flag for prefixing paths with the name of the module their step is defined in, allowing the user to choose which module to exclude from:

    ./x.py test --exclude test::library/std

This maintains backward compatibility with existing invocations, while allowing more ganular exclusion. Examples of the behavior:

| `--exclude`         | Docs    | Tests   |
| ------------------- | ------- | ------- |
| `library/std`       | Skipped | Skipped |
| `doc::library/std`  | Skipped | Run     |
| `test::library/std` | Run     | Skipped |

Note that this PR only changes the `--exclude` flag, and not in other `x.py` arguments or flags yet.

In the implementation I tried to limit the impact this would have with rustbuild as a whole as much as possible. The module name is extracted from the step by parsing the result of `std::any::type_name()`: unfortunately that output can change at any point in time, but IMO it's better than having to annotate all the existing and future `Step` implementations with the module name. I added a test to ensure the parsing works as expected, so hopefully if anyone makes changes to the output of `std::any::type_name()` they'll also notice they have to update rustbuild.

r? `@Mark-Simulacrum`

…i-obk

Ensure that early-bound function lifetimes are always 'local'

During borrowchecking, we treat any free (early-bound) regions on
the 'defining type' as `RegionClassification::External`. According
to the doc comments, we should only have 'external' regions when
checking a closure/generator.

However, a plain function can also have some if its regions
be considered 'early bound' - this occurs when the region is
constrained by an argument, appears in a `where` clause, or
in an opaque type. This was causing us to incorrectly mark these
regions as 'external', which caused some diagnostic code
to act as if we were referring to a 'parent' region from inside
a closure.

This PR marks all instantiated region variables as 'local'
when we're borrow-checking something other than a
closure/generator/inline-const.

…espidf, r=yaahc

Set the allocation MIN_ALIGN for espidf to 4.

Closes esp-rs#99.

cc: `@ivmarkov`

…ror-message, r=nagisa

Improve error message for key="value" cfg arguments.

Hi, I ran into difficulties using the `--cfg` flag syntax, first hit when googling for the error was issue rust-lang#66450. Reading that issue, it sounded like the best way to improve the experience was to improve the error message, this is low risk and doesn't introduce any additional argument parsing.

The issue mentions that it is entirely dependent on the shell, while this may be true, I think guiding the the user into the realization that the quotes may need to be escaped is helpful. The two suggested escapings both work in Bash and in the Windows command prompt.

fyi `@ehuss`

Improve string concatenation suggestion

Before:

    error[E0369]: cannot add `&str` to `&str`
     --> file.rs:2:22
      |
    2 |     let _x = "hello" + " world";
      |              ------- ^ -------- &str
      |              |       |
      |              |       `+` cannot be used to concatenate two `&str` strings
      |              &str
      |
    help: `to_owned()` can be used to create an owned `String` from a string reference. String concatenation appends the string on the right to the string on the left and may require reallocation. This requires ownership of the string on the left
      |
    2 |     let _x = "hello".to_owned() + " world";
      |              ~~~~~~~~~~~~~~~~~~

After:

    error[E0369]: cannot add `&str` to `&str`
     --> file.rs:2:22
      |
    2 |     let _x = "hello" + " world";
      |              ------- ^ -------- &str
      |              |       |
      |              |       `+` cannot be used to concatenate two `&str` strings
      |              &str
      |
      = note: string concatenation requires an owned `String` on the left
    help: create an owned `String` from a string reference
      |
    2 |     let _x = "hello".to_owned() + " world";
      |                     +++++++++++

…avidtwco

Implement tuple array diagnostic

Fixes rust-lang#92089

Use let_else in even more places

Followup of rust-lang#89933, rust-lang#91018, rust-lang#91481.

Improve `Arc` and `Rc` documentation

This makes two changes (I can split the PR if necessary, but the changes are pretty small):
 1. A bunch of trait implementations claimed to be zero cost; however, they use the `Arc<T>: From<Box<T>>` impl which is definitely not free, especially for large dynamically sized `T`.
 2.  The code in deferred initialization examples unnecessarily used excessive amounts of `unsafe`. This has been reduced.

delete `Stdin::split` forwarder

Part of rust-lang#87096. Delete the `Stdin::split` forwarder because it's seen as too niche to expose at this level.

`@rustbot` label T-libs-api A-io

rustdoc: fix overflow-wrap for table layouts

For all table layouts, set overflow-wrap: break-word.

Fixes rust-lang#93135

Demo: https://rustdoc.crud.net/jsha/fix-wrapped-names/std/intrinsics/index.html#functions

(Compare vs https://doc.rust-lang.org/nightly/std/intrinsics/index.html - you may have to make your browser narrower to see the effect)

r? `@Nemo157`