rustdoc/clean: Fix lowering of fn params (fixes correctness & HIR vs. middle parity regressions)
**(0)** PR #136411 aimed to stop rendering unnamed params of fn ptr types as underscores in the common case (e.g., `fn(_: i32)` → `fn(i32)`) to make the rendered output stylistically more conventional.
**(0.a)** However, since the cleaning fn that the PR modified is also used for lowering the HIR params of foreign fns and required assoc fns in traits, it accidentally butchered the rendering of the latter two:
```rs
pub trait Trait { fn assoc_fn(_: i32); } // as well as (Rust 2015 only): fn assoc_fn(i32);
unsafe extern "C" { pub fn foreign_fn(_: i32); }
// Since 1.86 the fns above gets mis-rendered as:
pub fn assoc_fn(: i32) // <-- BUTCHERED
pub unsafe extern "C" fn foreign_fn(: i32) // <-- BUTCHERED
```
**(0.b)** Furthermore, it broke parity with middle cleaning (which includes inlined cross-crate re-exports) re-regressing parts of #44306 I once fixed in PR #103885.
**(1)** Lastly, PR #139035 introduced an ICE triggered by the following input file:
```rs
trait Trait { fn anon(()) {} } // internal error: entered unreachable code
```
---
This PR fixes all of these regressions and in the first commit renames several types and fns to be more ~~correct~~ descriptive and legible.
~~It also refactors `Param.name` to be of type `Option<Symbol>` instead `Symbol` (where `None` ~ `kw::Empty`), so rendering mistakes like that can no longer creep in like that (ignoring tests). CC #137978.~~ Independently done in PR #139846 a day prior.
[rustdoc] Show enum discrimant if it is a C-like variant
Fixes https://github.com/rust-lang/rust/issues/101337.
We currently display values for associated constant items in traits:
And we also display constant values like [here](file:///home/imperio/rust/rust/build/x86_64-unknown-linux-gnu/doc/std/f32/consts/constant.E.html).
I think that for coherency, we should display values of C-like enum variants.
With this change, it looks like this:
As for the display of the constant value itself, I used what we already have to keep coherency.
We display the C-like variants value in the following scenario:
1. It is a C-like variant with a value set => all the time
2. It is a C-like variant without a value set: All other variants are C-like variants and at least one them has its value set.
Here is the result in code:
```rust
// Ax and Bx value will be displayed.
enum A {
Ax = 12,
Bx,
}
// Ax and Bx value will not be displayed
enum B {
Ax,
Bx,
}
// Bx value will not be displayed
enum C {
Ax(u32),
Bx,
}
// Bx value will not be displayed, Cx value will be displayed.
#[repr(u32)]
enum D {
Ax(u32),
Bx,
Cx = 12,
}
```
r? `@notriddle`
[rustdoc] If re-export is private, get the next item until a public one is found or expose the private item directly
Fixes#81141.
If we have:
```rust
use Private as Something;
pub fn foo() -> Something {}
```
Then `Something` will be replaced by `Private`.
r? `@notriddle`
This class originated in the very first commit of `rustdoc_ng`, and was used
to add a color border around the item decl based on its kind.
4fd061c426/src/rustdoc_ng/html/static/main.css (L102-L106)
The item decl no longer has a border, and there aren't any
kind-specific styles in modern rustdoc's rendering of this UI item.
Most of this commit is updating test cases so that they use `item-decl` to
find the `<pre>` tag instead of relying on the fact that the class name
had `rust {kind}` in it while other `<pre>` tags only had class `rust`.
