fn main() {
    let mut safety = &String::from("hello");
    println!("address of safety {:p}: {}", &safety, safety);
    {
        let name = "xfy".to_string();
        let name = expand(&name);
        println!("address of name {:p}: {}", &name, name);
        safety = &name;
    }
    println!("address of safety {:p}: {}", &safety, safety);
}

pub const fn lifetime_translator<'a, 'b, T>(_val_a: &'a &'b (), _val_b: &'b T) -> &'a T {
    _val_b
}

pub fn lifetime_translator_mut<'a, 'b, T>(_val_a: &'a &'b (), _val_b: &'b mut T) -> &'a mut T {
    _val_b
}

pub fn expand<'a, 'b, T>(x: &'a T) -> &'b T {
    // lifetime_translator(STATIC_UNIT, x)
    let f: fn(_, &'a T) -> &'b T = lifetime_translator;
    f(STATIC_UNIT, x)
}

pub fn expand_mut<'a, 'b, T>(x: &'a mut T) -> &'b mut T {
    let f: fn(_, &'a mut T) -> &'b mut T = lifetime_translator_mut;
    f(STATIC_UNIT, x)
}

const STATIC_UNIT: &&() = &&();