It's really nice to see this RFC progress

I think this would be a nice improvement to reduce boiler plate.

Hmmm... I guess I don't see why not?

This is really great and would solve the problem that led me to create constructor-lite.

With this RFC, its usage could be replaced with

#[derive(Debug, PartialEq)]
struct Movie {
    title: String,
    year: Option<u16> = None,
}

assert_eq!(
    Movie { title: "Star Wars".to_owned(), .. },
    Movie { title: "Star Wars".to_owned(), year: None },
)