Trait suggestions should use outermost candidates

[AndiDog]

Beginning with issue #21405, Rust combines multiple identical candidates into one (in some way). Since crates typically pub use the traits on the outermost level (e.g. module::TheTrait instead of module::inner::detail::TheTrait), the outermost candidate should be displayed as suggestion.

Here's a real-life example:

main.rs:44:21: 44:62 error: no method named `json_as` found for type `&'r mut nickel::request::Request<'mw, 'conn, _>` in the current scope
main.rs:44                let dir = request.json_as::<BlaBla>().unwrap().dir;
                                                          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<nickel macros>:24:12: 24:42 note: in this expansion of as_block! (defined in <nickel macros>)
<nickel macros>:10:1: 10:60 note: in this expansion of _middleware_inner! (defined in <nickel macros>)
main.rs:43:47: 48:3 note: in this expansion of middleware! (defined in <nickel macros>)
main.rs:44:21: 44:62 help: items from traits can only be used if the trait is in scope; the following trait is implemented but not in scope, perhaps add a `use` for it:
main.rs:44:21: 44:62 help: candidate #1: use `nickel::json_body_parser::JsonBody`

However the trait "JsonBody" can be imported with just use nickel::JsonBody.

[Aatch]

I'm not sure what the code is doing there, but using the shortest path version might be acceptable.

[steveklabnik]

Triage: I can't reproduce this because there aren't good enough instructions; could you provide some example code that triggers this? Thanks!

[Dylan-DPC]

Closing this as this issue is vague and there's no further updates on it.