…n global scope

Rebasing off master

…om the globally reachable change

Update doc comments to make the guarantee explicit. However, some
implementations does not have the statement though.

* `HashMap`, `HashSet`: require guarantees on hashbrown side.
* `PathBuf`: simply redirecting to `OsString`.

Fixes rust-lang#99606.

Currently `Vec::new()` is guaranteed to not allocate until elements are
pushed onto the `Vec`, but such a guarantee is missing for `Vec`'s
implementation of `Default::default`. This adds such a guarantee for
`Vec::default()` to the API reference.

Expand potential inner `Or` pattern for THIR

Code assumed there wouldn't be a deeper `Or` pattern inside expanded `PatStack` this fixes it by looking for the `Or` pattern inside expanded `PatStack`.

A more ideal solution would be recursively doing this but I haven't found a good way to do that.
_fixes #97898_

…-obk

Make some const prop mir-opt tests `unit-test`s

Most of these have no or only tiny diffs beyond line numbers being changed (would it make sense to not have line numbers in mir-opt tests?). Some things changed a bit, but I think it should all be fine, not sure though.

…se, r=Mark-Simulacrum

Rework Ipv6Addr::is_global to check for global reachability rather than global scope - rebase

Rebasing of pull request rust-lang#86634 off of master to try and get the feature "ip" stabilized.

I also found a test failure in the rebase that is_global was considering the benchmark space to be globally reachable.

This is related to my other rebasing pull request rust-lang#99947

…ilure, r=thomcc

Guarantee `try_reserve` preserves the contents on error

Update doc comments to make the guarantee explicit. However, some
implementations does not have the statement though.

* `HashMap`, `HashSet`: require guarantees on hashbrown side.
* `PathBuf`: simply redirecting to `OsString`.

Fixes rust-lang#99606.

…it, r=oli-obk

Fix two const_trait_impl issues

r? ``@oli-obk``

Fixes rust-lang#100222.
Fixes rust-lang#100543.

…stics, r=estebank

Convert diagnostics in parser/expr to SessionDiagnostic

This migrates all the easy cases in `rustc_parse::parser::expr` to `SessionDiagnostic`s, I've left things such as `multipart_suggestion`s out for now in the hopes of a derive API being developed soon.

…thods, r=scottmcm

Use pointer `is_aligned*` methods

This PR replaces some manual alignment checks with calls to `pointer::{is_aligned, is_aligned_to}` and removes a useless pointer cast.

r? `@scottmcm`

_split off from #100746_

…=fee1-dead

Add guarantee that Vec::default() does not alloc

Currently `Vec::new()` is guaranteed to not allocate until elements are pushed onto the `Vec`, but such a guarantee is missing for `Vec`'s implementation of `Default::default`.

This adds such a guarantee for `Vec::default()` to the API reference.

See also [this discussion on URLO](https://users.rust-lang.org/t/guarantee-that-vec-default-does-not-allocate/79903).