Code shared from the Rust Playground

playground.rs

#[derive(Default)]
struct X {
    a: String,
    b: String,
    c: String,
}

macro_rules! reject_empty {
    ($obj:ident, $first_field:tt, $($field:tt),*) => {
        {
           if $obj.$first_field.is_empty() {
               Err(format!("{}.{} is empty", stringify!($obj), stringify!($first_field)))
           } 
           $(
               else if $obj.$field.is_empty() {
                   Err(format!("{}.{} is empty", stringify!($obj), stringify!($field)))
               }
           )*
           else {
               Ok(())
           }
        }
        
    };
}

fn main() {
    {
        let x = X::default();
        println!("Checked?: {:?}", reject_empty!(x, a, b));
    }
    
    {
        let x =  X { a: "One".to_string(), b: "".to_string(), c: "x".to_string() }; 
        println!("Checked?: {:?}", reject_empty!(x, a, b));
    }
    
    {
        let x =  X { a: "One".to_string(), b: "Two".to_string(), c: "x".to_string() }; 
        println!("Checked?: {:?}", reject_empty!(x, a, b));
    }
}