Unused variable ... conundrum

challenge4.rs

pub fn wc_single_char_xor_encrypted_line(hex_line_60: &str) -> usize {
    let mut best: usize = 0;

    for x in 0..255 {
        let hexkey = format!("{:02x}",x);
        let bigkey = iter::repeat(hexkey).take(30).collect::<String>();
        let result = xor(hex_line_60,&bigkey);
		let utf8_error = "UTF-8 Error".to_string();
         let s = match String::from_utf8(result) {
           Ok(v) => v,
	       Err(e) => utf8_error,
         };
	 let wc = word_count(&s);
	 if wc > best {
	   best = wc;
	 }

    }

    return best; // highest word count using any error 
}