Rollup merge of #103885 - fmease:rustdoc-various-cross-crate-reexport-fixes, r=cjgillot,GuillaumeGomez

rustdoc: various cross-crate reexport fixes

Fixes for various smaller cross-crate reexport issues.
The PR is split into several commits for easier review. Will be squashed after approval.

Most notable changes:

* We finally render late-bound lifetimes in the generic parameter list of cross-crate functions & methods.
  Previously, we would display the re-export of `pub fn f<'s>(x: &'s str) {}` as `pub fn f(x: &'s str)`
* We now render unnamed parameters of cross-crate functions and function pointers as underscores
  since that's exactly what we do for local definitions, too. Mentioned as a bug in #44306.
* From now on, the rendering of cross-crate trait-object types is more correct:
  * `for<>` parameter lists (for higher-ranked lifetimes) are now shown
  * the return type of `Fn{,Mut,Once}` trait bounds is now displayed

Regarding the last list item, here is a diff for visualization (before vs. after):

```patch
- dyn FnOnce(&'any str) + 'static
+ dyn for<'any> FnOnce(&'any str) -> bool + 'static
```

The redundant `+ 'static` will be removed in a follow-up PR that will hide trait-object lifetime-bounds if they coincide with [their default](https://doc.rust-lang.org/reference/lifetime-elision.html#default-trait-object-lifetimes) (see [Zulip discussion](https://rust-lang.zulipchat.com/#narrow/stream/266220-rustdoc/topic/clean_middle_ty.3A.20I.20need.20to.20add.20a.20parameter/near/307143097)). `FIXME(fmease)`s were added.

``@rustbot`` label A-cross-crate-reexports
r? ``@GuillaumeGomez``

1 files changed, 4 insertions, 7 deletions

diff --git a/src/librustdoc/html/format.rs b/src/librustdoc/html/format.rs
index 06db3fb0ec4..a5c3d35b1b5 100644
--- a/src/librustdoc/html/format.rs
+++ b/src/librustdoc/html/format.rs
@@ -1232,9 +1232,8 @@ impl clean::Arguments {
     ) -> impl fmt::Display + 'a + Captures<'tcx> {
         display_fn(move |f| {
             for (i, input) in self.values.iter().enumerate() {
-                if !input.name.is_empty() {
-                    write!(f, "{}: ", input.name)?;
-                }
+                write!(f, "{}: ", input.name)?;
+
                 if f.alternate() {
                     write!(f, "{:#}", input.type_.print(cx))?;
                 } else {
@@ -1367,10 +1366,8 @@ impl clean::FnDecl {
                     args.push_str("const ");
                     args_plain.push_str("const ");
                 }
-                if !input.name.is_empty() {
-                    write!(args, "{}: ", input.name);
-                    write!(args_plain, "{}: ", input.name);
-                }
+                write!(args, "{}: ", input.name);
+                write!(args_plain, "{}: ", input.name);
 
                 if f.alternate() {
                     write!(args, "{:#}", input.type_.print(cx));