Searching for `chdir` in the Rust documentation produces no useful
results.

Fix rust-lang#84769, follow up to rust-lang#84499, rust-lang#83667.

Clippy: Decreases indentation and improves readability

Signed-off-by: wcampbell <wcampbell1995@gmail.com>

This updates the documentation since `ptr::addr_of!` and
`ptr::addr_of_mut!` are now stable. One might remove the distinction
between the sections `# On packed structs` and `# Examples`, as the old
section on packed structs was primarily to prevent users of doing unde-
fined behavior, which is not necessary anymore.
There is also a new section in "how to obtain a pointer", which referen-
ces the `ptr::addr_of!` macros.

This commit contains squashed commits from code review.

Co-authored-by: Joshua Nelson <joshua@yottadb.com>
Co-authored-by: Mara Bos <m-ou.se@m-ou.se>
Co-authored-by: Soveu <marx.tomasz@gmail.com>
Co-authored-by: Ralf Jung <post@ralfj.de>

…items

When encountering a path that can't have generics, do not call
`generics_of`. This would happen when writing something like
`path::this_is_a_mod<const_val>`.

Fix rust-lang#84831.

…, r=pnkfelix

Improve diagnostic for when field is never read

Related to (but does not close) rust-lang#81658

This completes the first step of ````````@pnkfelix's```````` [mentoring instructions](rust-lang#81658 (comment)) but does not actually improve the diagnostics (yet!). The two tests are heavily reduced versions of code from the original bug report.

I've confirmed that the reduced `field-used-in-ffi` test [fails on nightly](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=f0862c89ddca028c55c20a5ed05e679a) but [passes on stable](https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=f0862c89ddca028c55c20a5ed05e679a). This confirms that the regression is reproduced correctly. The `drop-only-field` test is a case that ````````@pnkfelix```````` mentioned in his mentoring instructions. It is not a regression, but will come in handy when we make the diagnostic smarter by looking at whether the field type implements `Drop`.

Per the [rustc-dev-guide](https://rustc-dev-guide.rust-lang.org/tests/adding.html), each test includes a comment summarizing what it is about.

Update `ptr` docs with regards to `ptr::addr_of!`

This updates the documentation since `ptr::addr_of!` and `ptr::addr_of_mut!` are now stable. One might remove the distinction between the sections `# On packed structs` and `# Examples`, as the old section on packed structs was primarily to prevent users of doing undefined behavior, which is not necessary anymore.

Technically there is now wrong/outdated documentation on stable, but I don't think this is worth a point release 😉

Fixes rust-lang#83509.

````````@rustbot```````` modify labels: T-doc

…albini

Update RELEASES.md for 1.52.0

### [Rendered](https://github.com/rust-lang/rust/blob/relnotes-1.52.0/RELEASES.md)

r? ``````@Mark-Simulacrum``````
cc ``````@rust-lang/release``````

…lnay

Add doc alias for `chdir` to `std::env::set_current_dir`

Searching for `chdir` in the Rust documentation produces no useful
results.

I wrote some code recently that called `libc::chdir` and manually
handled errors, because I didn't realize that the safe
`std::env::set_current_dir` existed. I searched for `chdir` and
`change_dir` and `change_directory` (the latter two based on the
precedent of unabbreviating set by `create_dir`), and I also read
through `std::fs` expecting to potentially find it there. Given that
none of those led to `std::env::set_current_dir`, I think that provides
sufficient justification to add this specific alias.

…nkov

Reduce duplication in `impl_dep_tracking_hash` macros

Cherry-picked from rust-lang#84234 since it will be a while until it lands.

Account for unsatisfied bounds in E0599

Fix rust-lang#84769, follow up to rust-lang#84499, rust-lang#83667.

…olnay

use else if in std library

Decreases indentation and improves readability

…riplett

Clarify documentation for `[T]::contains`

Change the documentation to correctly characterize when the suggested alternative to `contains` applies, and correctly explain why it works.

Fixes rust-lang#84877

…tting, r=Dylan-DPC

platform-support: Center the contents of the `std` and `host` columns

Minor formatting improvement.

…RalfJung

Remove `rustc_middle::mir::interpret::CheckInAllocMsg::NullPointerTest`

Removing it per rust-lang#84842 (comment): it's a dead enum variant.

Note that `PointerArithmeticTest` also seems dead:
```
$ rg -F PointerArithmeticTest -C5
compiler/rustc_middle/src/mir/interpret/error.rs
169-
170-/// Details of why a pointer had to be in-bounds.
171-#[derive(Debug, Copy, Clone, TyEncodable, TyDecodable, HashStable)]
172-pub enum CheckInAllocMsg {
173-    MemoryAccessTest,
174:    PointerArithmeticTest,
175-    InboundsTest,
176-}
177-
178-impl fmt::Display for CheckInAllocMsg {
179-    /// When this is printed as an error the context looks like this
--
182-        write!(
183-            f,
184-            "{}",
185-            match *self {
186-                CheckInAllocMsg::MemoryAccessTest => "memory access",
187:                CheckInAllocMsg::PointerArithmeticTest => "pointer arithmetic",
188-                CheckInAllocMsg::InboundsTest => "inbounds test",
189-            }
190-        )
191-    }
192-}
```
Not sure if that is also desirable to be removed, however.

Do not ICE on invalid const param

When encountering a path that can't have generics, do not call
`generics_of`. This would happen when writing something like
`path::this_is_a_mod<const_val>`.

Fix rust-lang#84831.