In the code sample for the `finish` method on `DebugList`,
`DebugMap`, and `DebugSet`, refer to finishing the list, map, or
set, rather than struct as it did.

This reverts commit 171f541.

…ions

…lidation

typos

…zed, r=GuillaumeGomez

rustdoc: fix cross-crate `impl Sized` & `impl ?Sized`

Previously, cross-crate impl-Trait (APIT, RPIT, etc.) that only consists of a single `Sized` bound (modulo outlives-bounds) and ones that are `?Sized` were incorrectly rendered. To give you a taste (before vs. after):

```diff
- fn sized(x: impl ) -> impl
+ fn sized(x: impl Sized) -> impl Sized

- fn sized_outlives<'a>(x: impl 'a) -> impl 'a
+ fn sized_outlives<'a>(x: impl Sized + 'a) -> impl Sized + 'a

- fn maybe_sized(x: &impl ) -> &impl
+ fn maybe_sized(x: &impl ?Sized) -> &impl ?Sized

- fn debug_maybe_sized(x: &impl Debug) -> &impl ?Sized + Debug
+ fn debug_maybe_sized(x: &(impl Debug + ?Sized)) -> &(impl Debug + ?Sized)
```

Moreover, we now surround impl-Trait that has multiple bounds with parentheses if they're the pointee of a reference or raw pointer type. This affects both local and cross-crate docs. The current output isn't correct (rustc would emit the error *ambiguous `+` in a type* if we fed the rendered code back to it).

---

Best reviewed commit by commit :)

`@rustbot` label A-cross-crate-reexports

Bump syn dependency

r? `@davidtwco` because this affects diagnostics derive diagnostics (yes this sentence is grammatically correct)

…ents, r=GuillaumeGomez

docs: fmt::Debug*: Fix comments for finish method.

In the code sample for the `finish` method on `DebugList`, `DebugMap`, and `DebugSet`, refer to finishing the list, map, or set, rather than struct as it did.

…illaumeGomez

Docs: Fix URL for `rmatches`

This PR fixes a link to `str::rmatches()` by pointing it to the correct URL.

…lcnr

Restore region uniquification in the new solver 🎉

All of the bugs that were "due" to uniquification have been settled via other means (e.g. bidirectional alias-relate, param-env incompleteness, etc).

Firstly, revert the functional changes in rust-lang#110180. 😸

Secondly, we need to ignore regions when considering if a goal has changed (the "has_changed" boolean returned from `evaluate_goal`) -- otherwise, because we're doing region uniquification, we may perpetually consider a goal to be changed. See the UI test I committed for an explanation.

Turns out opaque types can have hidden types registered during mir validation

See the newly added test's documentation for an explanation.

fixes rust-lang#114121