Crate option_constructor_derive

Example:

#[macro_use]
extern crate option_constructor_derive;

#[derive(OptionConstructor, Debug, PartialEq)]
struct Example {
    field1: bool,
    field2: Option<bool>,
    field3: Option<bool>,
}

fn main() {
    let x = Example::new(true).field2(false);
    assert_eq!(x, Example {
        field1: true,
        field2: Some(false),
        field3: None,
    });
}