…pin_loop_hint

…e path.

- libarena
- librustc_allocator
- librustc_borrowck
- librustc_codegen_ssa
- librustc_codegen_utils
- librustc_driver
- librustc_errors
- librustc_incremental
- librustc_metadata
- librustc_passes
- librustc_privacy
- librustc_resolve
- librustc_save_analysis
- librustc_target
- librustc_traits
- libsyntax
- libsyntax_ext
- libsyntax_pos

- libfmt_macros
- librustdoc

When using the `rustfix-coverage` flag, some tests currently fail
because they define a different error-format than `json`.

The current implementation crashes when encountering those tests. Since
we don't care about non-json test output when collecting the coverage
data, we handle those tests by returning an empty `Vec` instead.

…li-obk

Internal lints take 2

cc rust-lang#58701
cc rust-lang#49509

TODO: Add `#![warn(internal)]` to crates (and fix violations)

Crates depending on `rustc_data_structures`

- [x] librustc_resolve
- [x] librustc_driver
- [x] librustc_passes
- [x] librustc_metadata
- [x] librustc_interface
- [x] librustc_save_analysis
- [x] librustc_lint
- [x] librustc
- [x] librustc_incremental
- [x] librustc_codegen_utils
- [x] libarena
- [x] librustc_target
- [x] librustc_allocator
- [x] librustc_privacy
- [x] librustc_traits
- [x] librustc_borrowck
- [x] libsyntax
- [x] librustc_codegen_ssa
- [x] libsyntax_ext
- [x] librustc_errors
- [x] librustc_mir
- [x] libsyntax_pos
- [x] librustc_typeck

Crates with `feature(rustc_private)`
Excluding crates, which are already in the list above. Also excluding tools and tests.

- [ ] ~~libstd~~
- [x] libfmt_macros
- [x] librustdoc

r? @oli-obk

Be more direct about borrow contract

I always was confused by the difference between Borrow and AsRef, despite the fact that I've read all available docs at least a dozen of times.

I finally grokked the difference between the two when I realized the Borrow invariant:

> If you implement Borrow, you **must** make sure that Eq, Ord and Hash implementations are equivalent for borrowed and owned data

My problem was that this invariant is not stated explicitly in documentation, and instead some  vague and philosophical notions are used.

So I suggest to mention the requirements of `Borrow` very explicitly: instead of "use Borrow when X and use AsRef when Y", let's phrase this as `Borrow` differs from `AsRef` in `W`, so that's why `Borrow` is for `X` and `AsRef` is for `Y`.

Note that this change could be seen as tightening contract of the Borrow. Let's say Alice has written the following code:

```rust
#[derive(PartialEq, Eq, Hash, PartialOrd, Ord)]
struct Person {
    first_name: String,
    last_name: String,
}

impl Borrow<str> for Person {
      fn borrow(&self) -> &str { self.first_name.as_str() }
}
```

Now Bob uses this `Person` struct, puts it into `HashMap` and tries to look it up using `&str` for the first name. Bob's code naturally fails.

The question is, who is to blame: Alice, who has written the impl, or Bob, who uses the HashMap. If I read the current docs literally, I would say that `Bob` is to blame: `Eq` and `Hash` bounds appear on HashMap, so it is the HashMap which requires that they are consistent. By using a type for which the `Borrow` impl does not yield well-behaved `Eq`, Bob is violating contract of HashMap.

If, as this PR proposes, we unconditionally require that Eq & friends for borrow should be valid, then the blame shifts to Alice, which I think is more reasonable.

closes rust-lang#44868

… r=alexcrichton

Updated the documentation of spin_loop and spin_loop_hint

# Description

- Updated the description of `core::hints::spin_loop`
- Updated the description of `core::async::spin_loop_hint`

Both documentation is rewritten to better reflect when one should prefer using a busy-wait spin-loop (and the `spin_loop` and `spin_loop_hint` functions) over `yield_now`. It also dives a little bit deeper on what the function actually does.

closes rust-lang#55418

…criptions, r=GuillaumeGomez

Updated the environment description in rustc.

# Description

- Updated the "environment" description in the `rustc` man pages

The old wording suggested that all the mentioned flags influenced the output of the compiler,
where this was not the case.

closes rust-lang#59504

Reduce repetition in librustc(_lint) wrt. impl LintPass by using macros

r? @oli-obk
cc @Zoxc

…er_error_formats, r=oli-obk

rustfix coverage: Skip UI tests with non-json error-format

When using the `rustfix-coverage` flag, some tests currently fail
because they define a different error-format than `json`.

The current implementation crashes when encountering those tests. Since
we don't care about non-json test output when collecting the coverage
data, we handle those tests by returning an empty `Vec` instead.

r? @oli-obk