Show resolved type when hovering over underscore

[dbeckwith]

It would be great if when you have something like a function call foo::<_, Bar> and you hover over the _, RA would show a popup filling in the type based what it resolves to in the given context. Currently, hovering over foo shows its definition, hovering over Bar shows its definition, hovering over ::< shows the resolved types of the whole function signature, and hovering over _ shows the same. I was expecting hovering over _ to just show me its resolved type, but it shows the whole resolved type of the function, so it takes a bit longer to search through that visually and match up the type parameters to find what I'm looking for.

[srikarplus]

Another example from "The Book"

fn main() {
    use std::collections::HashMap;

    let teams = vec![String::from("Blue"), String::from("Yellow")];
    let initial_scores = vec![10, 50];

    let mut scores: HashMap<_, _> =
        teams.into_iter().zip(initial_scores.into_iter()).collect();
}

It would be great if it looked like HashMap<_: String, _: i32>. Ofcourse, hovering over scores shows the resolved type HashMap<String, i32>.

[idanarye]

I'd like to BUMP this feature request and add that if rust-lang/rfcs#3444 gets implemented - and if _ is indeed chosen as the syntax - then having rust analyzer able to show the type of the _ will be very helpful.