… to raise errors

Signed-off-by: Yuki Okushi <jtitor@2k36.org>

Arms are about TAIT and RPIT, as the variants clearly show.

lub: don't bail out due to empty binders

allows for the following to compile. The equivalent code using `struct Wrapper<'upper>(fn(&'upper ());` already compiles on stable.
```rust
let _: fn(&'upper ()) = match v {
    true => lt_in_fn::<'a>(),
    false => lt_in_fn::<'b>(),
};
```
see https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=7034a677190110941223cafac6632f70 for a complete example

r? ```@rust-lang/types```

…li-obk

interpret: convert_tag_add_extra: allow tagger to raise errors

Needed for rust-lang/miri#2234

r? `@oli-obk`

Move some tests to more reasonable directories

r? `@petrochenkov`

…rrors

Add a full regression test for rust-lang#73727

Closes rust-lang#73727

This also moves a test to the `issues` directory as it's also tested on the adt_const_params feature.

r? ```@compiler-errors```

Signed-off-by: Yuki Okushi <jtitor@2k36.org>

…t, r=GuillaumeGomez

Remove the unused-`#[doc(hidden)]` logic from the `unused_attributes` lint

Fixes rust-lang#96890.

It was found out that `#[doc(hidden)]` on trait impl items does indeed have an effect on the generated documentation (see the linked issue). In my opinion and the one of [others](https://rust-lang.zulipchat.com/#narrow/stream/266220-rustdoc/topic/Validy.20checks.20for.20.60.23.5Bdoc.28hidden.29.5D.60/near/281846219), rustdoc's output is actually a bit flawed in that regard but that should be tracked in a new issue I suppose (I will open an issue for that in the near future).

The check was introduced in rust-lang#96008 which is marked to be part of version `1.62` (current `beta`). As far as I understand, this means that **this PR needs to be backported** to `beta` to fix rust-lang#96890 on time. Correct me if I am wrong.

CC `@dtolnay` (in case you would like to agree or disagree with my decision to fully remove this check)

`@rustbot` label A-lint T-compiler T-rustdoc

r? `@rust-lang/compiler`

…t, r=oli-obk

This comment is out dated and misleading, the arm is about TAITs

r? ```@oli-obk```

```@oli-obk``` unsure if you want to add a different comment of some sort.

```@bors``` rollup=always