#[derive(Default, Debug)]
struct SomeOptions {
    foo: i32,
    bar: f32,
}

fn main() {
    let options: SomeOptions = Default::default();
    println!("{:?}", options)
}

https://doc.rust-lang.org/std/default/trait.Default.html

Rust implements Default for various primitives types.

If you want to override a particular option, but still retain the other defaults:

fn main() {
let options = SomeOptions { foo: 42, ..Default::default() };
}

#[derive(Default, Debug)]
struct SomeOptions {
    foo: i32,
    bar: f32,
}

fn main() {
    let options = SomeOptions { foo: 42, ..Default::default()};
    println!("{:?}", options)
}