default_field_values

[kouhe3]

fix #19780

Add enum and field to track = and ..

Create a new function to determine match and missing msg

behavior

#![feature(default_field_values)]
fn main() {
    let u1 = UserInfo { id: 10, $0 ,.. }; // trigger suggestion: age,email
               ^^^^^^ 💡 missing field 
                    | -email
}

struct UserInfo {
    id: i32,
    age: f32 = 1.0,
    email: String,
}

[ChayimFriedman2]

LGTM. Just rebase, and also please squash with a useful commit message.

[ChayimFriedman2]

Thanks!