…uaranteed

Hide repr attribute from doc of types without guaranteed repr

Rustdoc has an undesirable behavior of blindly copying `repr` into the documentation of structs and enums, even when there is no particular repr that the type guarantees to its users. This is a source of confusion for standard library users who assume the fact that a repr is documented means it must be something the standard library promises they can rely on (in transmutes, or FFI).

Some issues on the topic of rustdoc's incorrect handling of `repr`:

- rust-lang#66401
- rust-lang#90435

In places, the standard library currently works around this confusing rustdoc behavior by just omitting `repr(transparent)` altogether even where it should be required if equivalent code were being written outside of the standard library. See rust-lang#61969.

IMO that is even more confusing, even for standard library maintainers — see rust-lang#105018 (comment). It's also not something that works for other reprs like `C` or `u8` which cannot just be omitted even in standard library code.

This PR tries a different approach for some types that are being currently incorrectly documented with a repr.

> **Warning**
> This PR does not imply that every type that still has a `repr` attribute in its docs after this PR is now public for users to rely on. This PR only tries to reduce harm from this longstanding rustdoc issue.

Use error term in projection if missing associated item in new solver

We were previously delaying a bug but not bailing, leading to an ICE in the `tcx.type_of(assoc_def.item.def_id)` call below.

…li-obk

Handle error body in generator layout

Fixes rust-lang#111468

I feel like making this query return `Option<GeneratorLayout>` might be better but had some issues with that approach

…WaffleLapkin

Erase `ReError` properly

Fixes rust-lang#111341

Since we check whether a type has free regions before erasing (to short circuit unnecesary folding), we need to consider `ReError` as a free region, or else we'll skip it when erasing a type that only mentions `ReError`.

cc `@nnethercote`

… r=joshtriplett

Change Vec examples to not assert exact capacity except where it is guaranteed

It was [brought up on discord](https://discord.com/channels/273534239310479360/818964227783262209/1107633959329878077) that the `Vec::into_boxed_slice` example contradicted the `Vec::with_capacity` docs in that the returned `Vec` might have _more_ capacity than requested.

So, to reduce confusion change all the `assert_eq!(vec.capacity(), _)` to `assert!(vec.capacity() >= _)`, except in 4 examples that have guaranteed capacities: `Vec::from_raw_parts`, `Vec::from_raw_parts_in`, `Vec::<()>::with_capacity`,`Vec::<(), _>::with_capacity_in`.

fix(diagnostic): wrap parens for ref impl trait param

Fixes rust-lang#99597

When parameters are an `impl_trait` which it needed to add trait, and it is a reference, add parentheses to the type of the parameter in the suggestion

…es, r=notriddle

[rustdoc] Only keep impl blocks from bodies

Fixes rust-lang#111415.

The problem was that we kept everything inside bodies whereas only impl blocks are actually accessible from outside bodies.

r? `@notriddle`