Get matched expression inside match block

Question

Is it possible to access the matched expression inside a match block?

Considering this example, with what should I replace HERE?

fn fetch_u32(args: &mut Vec<&str>) -> Result<u32,String> {
    match args.remove(0).parse::<u32>() {
        Ok(result) => Ok(result),
        Err(_) => Err("Argument '" + HERE + "' is not of type uint32".to_string())
    };
}

Answer 1

I would simply extract the expression before, and reuse the binding in the error message.

fn fetch_u32(args: &mut Vec<&str>) -> Result<u32, String> {
    let a = args.remove(0);
    match a.parse::<u32>() {
        Ok(result) => Ok(result),
        Err(_) => Err(format!("Argument '{}' is not of type uint32", a)),
    }
}

fn main() {
    let mut args = vec!["123", "bla", "456", "hop"];
    while !args.is_empty() {
        let r = fetch_u32(&mut args);
        println!("{:?}", r);
    }
}
/*
Ok(123)
Err("Argument 'bla' is not of type uint32")
Ok(456)
Err("Argument 'hop' is not of type uint32")
*/