Co-authored-by: Andrew Hickman <andrew.hickman1@sky.com>

It is not always obvious that people could see the docs for `&`
especially for beginners, it also helps learnability.

first_ptr -> slice_as_ptr
first_ptr_mut -> slice_as_mut_ptr
slice_get_ref -> slice_assume_init_ref
slice_get_mut -> slice_assume_init_mut

…brary

Fixes 76271

To match better naming from proc-macro

These tests are about the standard library, not the compiler itself, thus should live in `library`, see rust-lang#76268.

Move:
 - `src\test\ui\consts\const-nonzero.rs` to `library\core`
 - `src\test\ui\consts\ascii.rs` to `library\core`
 - `src\test\ui\consts\cow-is-borrowed` to `library\alloc`

Part of rust-lang#76268

Add test for checking duplicated branch or-patterns

This adds a regression test for checking `or-patterns` in MIR as shown in rust-lang#75439.
This doesn't introduce a fix as I'm not sure where it would go(I suspect maybe here: src/librustc_mir_build/build/matches/mod.rs), and I'm not particularly able to fix it.

cc: @lzutao

Add a regression test for issue-72793

Adds a regression test for rust-lang#72793, which is fixed by rust-lang#75443. Note that this won't close the issue as the snippet still shows ICE with `-Zmir-opt-level=2`. But it makes sense to add a test anyway.

…ing_issues, r=steveklabnik

Unstable Book: add links to tracking issues for FFI features

`impl Rc::new_cyclic`

References rust-lang#75861

r? @Dylan-DPC

Link vec doc to & reference

It is not always obvious that people could see the docs for `&`
especially for beginners, it also helps learnability.

…odrAus

Use Arc::clone and Rc::clone in documentation

This PR replaces uses of `x.clone()` by `Rc::clone(&x)` (or `Arc::clone(&x)`) to better match the documentation for those types.

@rustbot modify labels: T-doc

rename MaybeUninit slice methods

The `first` methods conceptually point to the whole slice, not just its first element, so rename them to be consistent with the raw ptr methods on ref-slices.

Also, do the equivalent of rust-lang#76047 for the slice reference getters, and make them part of rust-lang#63569 (so far they somehow had no tracking issue).

* first_ptr -> slice_as_ptr
* first_ptr_mut -> slice_as_mut_ptr
* slice_get_ref -> slice_assume_init_ref
* slice_get_mut -> slice_assume_init_mut

Add missing link in README

Add regression test

This adds a regression test for rust-lang#75777, effectively closing it since it is solved on nightly and beta.

Move some Vec UI tests into alloc unit tests

A bit of work towards rust-lang#76268, makes a number of the Vec UI tests that are simply running code into unit tests. Ensured that they are being run when testing liballoc locally.

Allow try blocks as the argument to return expressions

Fixes rust-lang#76271

I don't think this needs to be edition-aware (phew) since `return try` in 2015 is also the start of an expression, just with a struct literal instead of a block (`return try { x: 4, y: 5 }`).

Rename IsJoint -> Spacing

Builds on rust-lang#76286 and might conflict with rust-lang#76285

r? @petrochenkov

Make `Ipv4Addr` and `Ipv6Addr` const tests unit tests under `library`

These tests are about the standard library, not the compiler itself, thus should live in `library`, see rust-lang#76268.

Address review comments on `Peekable::next_if`

r? @pickfire
See rust-lang#72310 (review) for context.

Link to `#capacity-and-reallocation` when using with_capacity

Follow up to rust-lang#76058 (comment).
r? @pickfire

Move various ui const tests to `library`

Move:
 - `src\test\ui\consts\const-nonzero.rs` to `library\core`
 - `src\test\ui\consts\ascii.rs` to `library\core`
 - `src\test\ui\consts\cow-is-borrowed` to `library\alloc`

Part of rust-lang#76268

r? @matklad