rustdoc: Increased impl header size makes section icon cramped

[camelid]

Also, the increased font size looks a little too big for the trait impls section, since there are a lot of impls and their items are not expanded by default. The new font size looks good for inherent impls though, since the items cause the headers to be spaced apart.

Before

After

cc #90155
cc @jsha @GuillaumeGomez

[jsha]

I agree the section icon looks cramped now. It's not because of the font size, though: It's because previously the impl had a 15px indent, which I removed in #90155 for two reasons: the size of the indent was inconsistent (should have been 24px like other indents), and having an indent at all under an underlined prose header is inconsistent with what we do in other places, e.g.:

Also contributing to crampedness is the presence of the [+].

One possible quick fix would be to re-indent the impls but do it by 24px this time. Another fix would be to move the [+] further left into the gutter. That would probably make it look more awkward though. At a fundamental level, the [+] and § are competing for space: both want to be immediately to the left of a heading.

Another possibility would be to remove the § for impls. It's already the case that methods don't have §. See for instance https://doc.rust-lang.org/nightly/std/string/struct.String.html#method.new - the method name (like new) serves as the click target. If we could pick something within impl (or the whole impl heading) to be the click target, we could omit the §.

[camelid]

One possible quick fix would be to re-indent the impls but do it by 24px this time.

Yeah, I also thought of that, but it's possible it'll look funny. We could definitely try it though.

At a fundamental level, the [+] and § are competing for space: both want to be immediately to the left of a heading.

Agreed, that "competition" unfortunately adds more UI clutter.

If we could pick something within impl (or the whole impl heading) to be the click target, we could omit the §.

The problem with making the whole heading be the click target is that there are already links within the header. I think it'd be confusing and might not even be valid HTML.