When encountering code like

```rust
fn foo() -> i32 {
    match 0 {
        1 => return 0,
        2 => "",
        _ => 1,
    }
}
```

Point at the return type and not at the prior arm, as that arm has type
`!` which isn't influencing the arm corresponding to arm `2`.

Fix rust-lang#78124.

This lets us put a version on the impl, too.

…m-ou-se

Improve docs for impl Default for ExitStatus

This addresses a review comment in rust-lang#106425 (which is on the way to being merged I think).

Some of the other followup work is more complicated so I'm going to do individual MRs.

~~Note this branch is on top of rust-lang#106425~~

Fix pthread_attr_union layout on Wasi

Fixes rust-lang#114608

Ran the tests as described in https://github.com/rust-lang/rust/blob/master/src/doc/rustc/src/platform-support/wasm32-wasi-preview1-threads.md?plain=1#L125

Point out expectation even if we have `TypeError::RegionsInsufficientlyPolymorphic`

just a minor tweak, since saying "one type is more general than the other" kinda sucks if we don't actually point out two types.

…trochenkov

Deny `FnDef` in patterns

We can only see these via `const { .. }` patterns, which are unstable.

cc rust-lang#76001 (tracking issue for inline const pats)

Fixes rust-lang#114658
Fixes rust-lang#114659

…rrors

Point at return type when it influences non-first `match` arm

When encountering code like

```rust
fn foo() -> i32 {
    match 0 {
        1 => return 0,
        2 => "",
        _ => 1,
    }
}
```

Point at the return type and not at the prior arm, as that arm has type `!` which isn't influencing the arm corresponding to arm `2`.

Fix rust-lang#78124.

Fix typos

add missing feature(error_in_core)

Needed to fix feature gate errors in https://github.com/rust-lang/miri-test-libstd/actions/runs/5862810459/job/15895203359. I don't know how doctests are passing in-tree without this feature gate...

…lor-33, r=notriddle

Migrate GUI colors test to original CSS color format

Follow-up of rust-lang#111459.

r? ``@notriddle``