rustdoc: Use the concrete type of `self` in the search-index

[camelid]

See the discussion starting at #90630 (comment).

EDIT (@GuillaumeGomez): For example:

pub struct Foo;

impl Foo {
    pub fn something(&self) -> PathBuf { ... }
}

For the example above, if you use Foo -> PathBuf in the search, something won't show up because &self isn't "recognized"/"generated" in the search index as Foo.

[GuillaumeGomez]

I don't really have an opinion on this: it seems a bit counter-intuitive for me to look for Foo (from the example above) inside the arguments of its methods but I can see the value of it too. A bit tricky.

[camelid]

I think it's really bizarre for vec -> usize to not return Vec::capacity. Many uses of a type are in its methods; if we don't make this change, those will just be ignored.

[GuillaumeGomez]

I'm strongly biased here because it's how it's always been. But I think it'd be a good change. 👍

[jsha]

I agree, this would be a good change. I would expect a search for vec -> usize to return Vec::capacity.

[GuillaumeGomez]

Just to keep everyone updated here: once #90630 is merged, I'll work on this.