clippy::redundant_closure suggestion unnecessarily complicated

Clippy rightfully suggests to simplify a map with a as_str () in the closure to us as_str directly. However the given suggestion is a bit too complicated and verbose given that the String module is always imported:

warning: redundant closure found
   --> src/main.rs:317:30
    |
317 |         version.as_ref().map(|v| v.as_str()),
    |                              ^^^^^^^^^^^^^^ help: remove closure as shown: `std::string::String::as_str`
    |
    = note: #[warn(clippy::redundant_closure)] on by default
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#redundant_closure

It would be gread if the lint would say:

^^^^^^^^^^^^^^ help:  remove closure as shown: `String::as_str`

instead.

The version is:

clippy 0.0.212 (1fac3808 2019-02-20)

Start by locating the redundant_closure lint implementation and its suggestion-generation entry point. Reproduce the reported map(|v| v.as_str()) case, then add or update coverage so the help text uses String::as_str rather than std::string::String::as_str.