This should cover a mostly cross-platform subset of supported exit codes.

Previous efforts to ignore partially consumed values meant we were also
not considering borrows of a projection. This led to cases where we'd
miss borrowed types which MIR expected to be there, leading to ICEs.

The W3C Web Content Accessibility Guidelines specify a minimum line
spacing of 1.5 and a minimum paragraph spacing of 1.5 times the line
spacing. Our current line spacing (implemented by line-height) is 1.4,
so it's a small bump to go up to 1.5. Similarly, we have a paragraph
spacing of 0.6em. Bump that to 0.75em (which is 1.5 times the 0.5em
distance between lines).

Also, fix all the font sizes so instead of being round-ish numbers in
rem (like 1.1rem, 1.2rem), they are round numbers in pixels. Ensure each
font size is at least 2 pixels different than the nearest other font
size, so distinctions can be clearly seen. Overall the font-sizes are
mostly staying the same, being rounded up or down as appropriate.

Remove a few unused styles.

Simplify the display of the mobile-topbar location, by setting its
margins to auto rather than trying to size it exactly to the topbar.

Co-authored-by: Oli Scherer <github35764891676564198441@oli-obk.de>

Add From<u8> for ExitCode

This should cover a mostly cross-platform subset of supported exit codes.

We decided to stick with `u8` initially since its the common subset between all platforms that we support (excluding wasm which I think only works with `true` or `false`). Posix is supposed to take i32s, but in practice many unix platforms mask out all but the low 8 bits or in some cases the 8-15th bits. Windows takes a u32 instead of an i32. Bourne-compatible shells also report signals as exitcode 128 + `signal_no`, so there's some ambiguity there when returning exit codes > 127, but it is possible to disambiguate them on the other side so we decided against restricting the possible codes further than to `u8`.

## Related

- Detailed analysis of exit code support on various platforms: https://internals.rust-lang.org/t/mini-pre-rfc-redesigning-process-exitstatus/5426
- rust-lang#48711
- rust-lang#43301
- https://rust-lang.zulipchat.com/#narrow/stream/219381-t-libs/topic/Termination.2FExit.20Status.20Stabilization

…eGomez

rustdoc: tweak line spacing and paragraph spacing for accessibility

The [W3C Web Content Accessibility Guidelines](https://www.w3.org/WAI/WCAG21/Understanding/visual-presentation.html) specify a minimum line spacing of 1.5 and a minimum paragraph spacing of 1.5 times the line spacing. Our current line spacing (implemented by line-height) is 1.4, so it's a small bump to go up to 1.5. Similarly, we have a paragraph spacing of 0.6em. Bump that to 0.75em (which is 1.5 times the 0.5em distance between lines).

Also, fix all the font sizes so instead of being round-ish numbers in rem (like 1.1rem, 1.2rem), they are round numbers in pixels: 16px, 18px, 20px, 22px, 24px. Ensure each font size is at least 2 pixels different than the nearest other font size, so distinctions can be clearly seen. Overall the font-sizes are mostly staying the same, being rounded up or down as appropriate. This will make reasoning about consistent layout sizes much easier.

Remove a few unused styles.

Simplify the display of the mobile-topbar location, by setting its margins to auto rather than trying to size it exactly to the topbar.

Part of rust-lang#59845.

Demo: https://rustdoc.crud.net/jsha/font-sizes-spacing/std/string/struct.String.html

r? `@GuillaumeGomez`

…oshtriplett

Stabilize int_abs_diff in 1.60.0.

FCP finished here: rust-lang#89492 (comment)

Remove defaultness from ImplItem.

This information is not really used anywhere, except HIR pretty-printing. This makes ImplItem and TraitItem more similar.

rustc_query_impl: reduce visibility of some modules/fn's

Locally this reduces number of exported functions from 15221 -> 14952 and size a little.

Perf run please?

…jection, r=tmiasko

Drop tracking: track borrows of projections

Previous efforts to ignore partially consumed values meant we were also not considering borrows of a projection. This led to cases where we'd miss borrowed types which MIR expected to be there, leading to ICEs.

This PR also includes the `-Zdrop-tracking` flag from rust-lang#93313. If that PR lands first, I'll rebase to drop the commit from this one.

Fixes rust-lang#93648

update `ty::TyKind` documentation

slightly unsure about `ty::Opaque` and `ty::Bound`/`ty::Placeholder`.

r? `@jackh726` `@nikomatsakis` `@oli-obk`