`std::os::fd` defines types like `OwnedFd` and `RawFd` and is common
between Unix and non-Unix platforms that share a basic file-descriptor
concept. Rust currently uses this internally to simplify its own code,
but it would be useful for external users in the same way, so make it
public.

This means that `OwnedFd` etc. will all appear in three places, for
example on unix platforms:
 - `std::os::fd::OwnedFd`
 - `std::os::unix::io::OwnedFd`
 - `std::os::unix::prelude::OwnedFd`

Add `#[unstable(feature = "os_fd", issue = "98699")]` to the new
`pub use` declarations.

Fixes a regression caused by 8846c08, where
a header's top margin used to be collapsed, but isn't any more.

These rules were copied from normalize.css 3, and are mostly redundant.

* `optgroup` isn't used in rustdoc at all
* `textarea` is only used for the "copy" button, so it's not visible
* The remaining buttons and inputs mostly have styles set anyway.
* We should never be setting `color` without also setting the
  background to something. Otherwise, you get white-on-gray
  text. That seems to be [the reason] why `normalize.css` changed this.

[the reason]: necolas/normalize.css#502

This line was added in c494a06, because at
the time, the headers had these classes on them. Now, the headers are
children of the `<section>` with the class on it.

This commit also adds a test case, to make sure the srclink font weight does
not regress again.

More cleanup for 8846c08, this time in trait
layouts when things are collapsed.

…r=joshtriplett

Make `std::os::fd` public.

`std::os::fd` defines types like `OwnedFd` and `RawFd` and is common
between Unix and non-Unix platforms that share a basic file-descriptor
concept. Rust currently uses this internally to simplify its own code,
but it would be useful for external users in the same way, so make it
public.

This means that `OwnedFd` etc. will all appear in three places, for
example on unix platforms:
 - `std::os::fd::OwnedFd`
 - `std::os::unix::io::OwnedFd`
 - `std::os::unix::prelude::OwnedFd`

r? ```@joshtriplett```

Code refactoring smart_resolve_report_errors

`smart_resolve_report_errors` https://github.com/rust-lang/rust/blob/4ecfdfac51b159f68fce608792affb34a70e6f73/compiler/rustc_resolve/src/late/diagnostics.rs#L143
is almost 600 lines of code, we should do some code refactoring.

Add a niche to `Duration`, unix `SystemTime`, and non-apple `Instant`

As the nanoseconds fields is always between `0` and `(NANOS_PER_SEC - 1)` inclusive, use the `rustc_layout_scalar_valid_range` attributes to create a niche in the nanosecond field of `Duration` and `Timespec` (which is used to implement unix `SystemTime` and non-apple unix `Instant`; windows `Instant` is implemented with `Duration` and therefore will also benefit). This change has the benefit of making `Option<T>` the same size as `T` for the previously mentioned types. Also shrinks the nanoseconds field of `Timespec` to a `u32` as nanoseconds do not need the extra range of an `i64`, shrinking `Timespec` by 4 bytes on 32-bit platforms.

r? `@joshtriplett`

…issue-94923, r=JohnTitor

Add regression test for issue 94923

Fixes rust-lang#94923

Account for use of index-based lifetime names in print of binder

Fixes rust-lang#102374

r? `@lcnr`

cc `@steffahn`

…ler-errors

remove FIXME, improve documentation

r? types

env::temp_dir: fix a typo

…, r=GuillaumeGomez

rustdoc: clean up "normalize.css 8" input override CSS

These rules were copied from normalize.css 3, and are mostly redundant.

* `optgroup` isn't used in rustdoc at all
* `textarea` is only used for the "copy" button, so it's not visible
* The remaining buttons and inputs mostly have styles set anyway.
* We should never be setting `color` without also setting the background to something. Otherwise, you get white-on-gray text. That seems to be [the reason] why `normalize.css` changed this.

[the reason]: necolas/normalize.css#502

… r=jsha

rustdoc: cut margin-top from first header in docblock

Fixes a regression caused by 8846c08, where a header's top margin used to be collapsed, but isn't any more.

## Before

![image](https://user-images.githubusercontent.com/1593513/192893092-8e158bf7-ae18-41ef-8f11-6f34c724d345.png)

## After

![image](https://user-images.githubusercontent.com/1593513/192893139-d6ee06bf-9c0b-4194-bd5d-636312c89367.png)

… r=GuillaumeGomez

rustdoc: remove bad CSS font-weight on `.impl`, `.method`, etc

This line was added in c494a06, because at the time, the headers had these classes on them. Now, the headers are children of the `<section>` with the class on it.

This commit also adds a test case, to make sure the srclink font weight does not regress again.

… r=jsha

rustdoc: add method spacing to trait methods

More cleanup for 8846c08, this time in trait layouts when things are collapsed.

This PR makes two changes to the appearance of trait pages:

* It adds the `method-toggle` class to method toggles on traits, making the DOM more consistent with type pages (which already have this class).

  ## Before

  ![image](https://user-images.githubusercontent.com/1593513/192914353-ed17e1eb-df1d-480b-9998-3b5e8283b0ee.png)

  ## After

  ![image](https://user-images.githubusercontent.com/1593513/192914570-bdd0f2e1-5254-4e2e-9576-a797b82b3b3b.png)

* It adds a bottom margin to docblocks nested directly in the implementors list, giving it a similar appearance to if it was nested within a toggle.

  ## Before

  ![image](https://user-images.githubusercontent.com/1593513/192914503-1c3f39d5-690f-44ec-8f11-385302477d04.png)

  ## After

  ![image](https://user-images.githubusercontent.com/1593513/192914702-cbce4b3b-5cc6-49dc-b7f8-73be9e76791c.png)