extern crate serde;
#[macro_use]
extern crate serde_derive;
extern crate toml;

#[derive(Serialize)]
struct BigInt {
    val: i128,
}

fn main() {
    let o = BigInt { val: std::i128::MAX };
    let ser = toml::to_string(&o).unwrap(); //Err
    println!("{}", ser);

    deser(); //comment the serialzing code in order to use that
}

fn deser() {
    let t = r#"
    val = 28828373726
    "#

    let o: BigInt = toml::from_str(&t).unwrap();
    println!("{}", o);
}