1 use std::{error, fmt}; 2 3 /// Error returned if the inner [`Service`] has not been set. 4 /// 5 /// [`Service`]: crate::Service 6 #[derive(Debug)] 7 pub struct None(()); 8 9 impl None { new() -> None10 pub(crate) fn new() -> None { 11 None(()) 12 } 13 } 14 15 impl fmt::Display for None { fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result16 fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result { 17 write!(fmt, "None") 18 } 19 } 20 21 impl error::Error for None {} 22