When constructing a MIR from a THIR field expression, introduce an
additional downcast projection before accessing a field of an enum.

When rebasing a place builder on top of a captured place, account for
the fact that a single HIR enum field projection corresponds to two MIR
projection elements: a downcast element and a field element.

The docs were saying something about "statically initializing" the
mutex, and it's not clear what this means. Remove that part to avoid
confusion.

Co-authored-by: Weiyi Wang <wwylele@gmail.com>

Namely, the two functions `from_ptr` and `from_bytes_with_nul_unchecked`.
Before, this functions didn't state the requirements clearly enough,
and I was not immediately able to find them like for other functions.

This doesn't change the content of the docs, but simply rewords them for
clarity.

… r=RalfJung

Improve the safety docs for `CStr`

Namely, the two functions `from_ptr` and `from_bytes_with_nul_unchecked`.
Before, these functions didn't state the requirements clearly enough,
and I was not immediately able to find them like for other functions.

This doesn't change the content of the docs, but simply rewords them for
clarity.

note: I'm not entirely sure about the '`ptr` must be valid for reads of `u8`.', there might be room for improvement for this (and maybe for the other docs as well 😄)

…-aman

Fix precise field capture of univariant enums

When constructing a MIR from a THIR field expression, introduce an
additional downcast projection before accessing a field of an enum.

When rebasing a place builder on top of a captured place, account for
the fact that a single HIR enum field projection corresponds to two MIR
projection elements: a downcast element and a field element.

Fixes rust-lang#95271.
Fixes rust-lang#96299.
Fixes rust-lang#96512.
Fixes rust-lang#97378.

r? ``@nikomatsakis`` ``@arora-aman``

…=lnicola

⬆️ rust-analyzer

r? ``@ghost``

Remove confusing sentence from `Mutex` docs

The docs were saying something about "statically initializing" the
mutex, and it's not clear what this means. Remove that part to avoid
confusion.

…fo, r=Dylan-DPC

Add more information for rustdoc-gui tests

It was missing `--no-sandbox` in the `--help` message and the README was a bit outdated.

cc `@jsha` (I recall you asking some questions about passing arguments to the rustdoc gui tester so here it).

r? `@notriddle`