…ls/alloc.rs` nicer

- Use `.addr()` instead of `as`-cast
- Use `add` instead of `offset` and remove some `as isize` casts by doing that
- Remove some casts

…rminal

The UNIX and WASI implementations use `isatty`. The Windows
implementation uses the same logic the `atty` crate uses, including the
hack needed to detect msys terminals.

Implement this trait for `File` and for `Stdin`/`Stdout`/`Stderr` and
their locked counterparts on all platforms. On UNIX and WASI, implement
it for `BorrowedFd`/`OwnedFd`. On Windows, implement it for
`BorrowedHandle`/`OwnedHandle`.

Based on rust-lang#91121

Co-authored-by: Matt Wilkinson <mattwilki17@gmail.com>

If a process has no console, it'll have NULL in place of a console
handle, so return early with `false` in that case without making any OS
calls.

Rather than referencing a slice's pointer and then creating a new slice
with a longer length, offset from the base structure pointer instead.
This makes some choices of Rust semantics happier.

…n allocations

This rule became redundant in 07e3f99.
When `#source-sidebar` became nested below `.sidebar`, it went from being
`position: fixed` to `position: static`, and according to MDN's [z-index]
documentation, this means it has no effect.

[z-index]: https://developer.mozilla.org/en-US/docs/Web/CSS/z-index

This rule became redundant in 07e3f99.
When `#source-sidebar` became nested below `.sidebar`, it went from being
`position: fixed` to `position: static`, and according to MDN's [z-index]
documentation, this means it has no effect.

[z-index]: https://developer.mozilla.org/en-US/docs/Web/CSS/z-index

Fixes rust-lang#101065

… r=thomcc

Add `IsTerminal` trait to determine if a descriptor or handle is a terminal

The UNIX implementation uses `isatty`. The Windows implementation uses
the same logic the `atty` crate uses, including the hack needed to
detect msys terminals.

Implement this trait for `Stdin`/`Stdout`/`Stderr`/`File` on all
platforms. On Unix, implement it for `BorrowedFd`/`OwnedFd`. On Windows,
implement it for `BorrowedHandle`/`OwnedHandle`.

Based on rust-lang#91121

Co-authored-by: Matt Wilkinson <mattwilki17@gmail.com>

Refactor some `std` code that works with pointer offstes

This PR replaces `pointer::offset` in standard library with `pointer::add` and `pointer::sub`, [re]moving some casts and using `.addr()` while we are at it.

This is a more complicated refactor than all other sibling PRs, so take a closer look when reviewing, please 😃  (though I've checked this multiple times and it looks fine).

r? ```@scottmcm```

_split off from rust-lang#100746, continuation of #100822_

Fix wrongly refactored Lift impl

see rust-lang#101858 (comment)

r? `@bjorn3`

…=fee1-dead

Add const_closure, Constify Try trait

Adds a struct for creating const `FnMut` closures (for now just copy pasted form my [const_closure](https://crates.io/crates/const_closure) crate).
I'm not sure if this way is how it should be done.
The `ConstFnClosure` and `ConstFnOnceClosure` structs can probably also be entirely removed.

This is then used to constify the try trait.

Not sure if i should add const_closure in its own pr and maybe make it public behind a perma-unstable feature gate.

cc ``@fee1-dead``  ``@rust-lang/wg-const-eval``

…, r=GuillaumeGomez

rustdoc: remove no-op CSS `#source-sidebar { z-index }`

This rule became redundant in 07e3f99. When `#source-sidebar` became nested below `.sidebar`, it went from being `position: fixed` to `position: static`, and according to MDN's [z-index] documentation, this means it has no effect.

[z-index]: https://developer.mozilla.org/en-US/docs/Web/CSS/z-index

…r=cjgillot

diagnostics: avoid syntactically invalid suggestion in if conditionals

Fixes rust-lang#101065