At first, you might think, "Why not just click through to the aliased
type?" But, if a type alias instantiates all of the generic parameters
of the aliased type, then it can show layout info even though the
aliased type cannot (because we can't compute layout for generic types).
So, I think it's useful to show layout info for type aliases.

This is a followup of 78d4b453ad2e19d44011b26fc55c949bff5dba3d
(originally part of rust-lang#83501).

This commit does the following.
- Expands on some of the things already mentioned in comments.
- Describes the uniqueness assumption, which is critical but wasn't
  mentioned at all.
- Rewrites `empty()` into a clearer form, as provided by Daniel
  Henry-Mantilla on Zulip.
- Reorders things slightly so that more important things
  are higher up, and incidental things are lower down, which makes
  reading the code easier.

Update library/core/src/iter/adapters/zip.rs

Co-authored-by: r00ster <r00ster91@protonmail.com>

Update library/core/src/iter/adapters/zip.rs

Co-authored-by: r00ster <r00ster91@protonmail.com>

the current target.

…y, r=lcnr

Improve the readability of `List<T>`.

This commit does the following.
- Expands on some of the things already mentioned in comments.
- Describes the uniqueness assumption, which is critical but wasn't
  mentioned at all.
- Rewrites `empty()` into a clearer form, as provided by Daniel
  Henry-Mantilla on Zulip.
- Reorders things slightly so that more important things
  are higher up, and incidental things are lower down, which makes
  reading the code easier.

r? ```@lcnr```

Simplify collection of in-band lifetimes

Split from rust-lang#91403

r? ```@oli-obk```

asm: Allow using r9 (ARM) and x18 (AArch64) if they are not reserved by the current target

This supersedes rust-lang#88879.

cc `@Skirmisher`

r? `@joshtriplett`

…, r=dtolnay

Use spare_capacity_mut instead of invalid unchecked indexing when joining str

This is a fix for rust-lang#91574

I think in general I'd prefer to see this code implemented with raw pointers or `MaybeUninit::write_slice`, but there's existing code in here based on copying from slice to slice, so converting everything from `&[T]` to `&[MaybeUninit<T>]` is less disruptive.

rustdoc: Show type layout for type aliases

Fixes rust-lang#91265.

At first, you might think, "Why not just click through to the aliased
type?" But, if a type alias instantiates all of the generic parameters
of the aliased type, then it can show layout info even though the
aliased type cannot (because we can't compute layout for generic types).
So, I think it's useful to show layout info for type aliases.

This is a followup of 78d4b453ad2e19d44011b26fc55c949bff5dba3d
(originally part of rust-lang#83501).

… r=Mark-Simulacrum

Improve `std::iter::zip` example

`println!` isn't great for doc comments / tests.