Rust Programming By Example

Displaying the error

Since we want to print the error to the terminal, we'll implement the Display trait for our Error type:

use std::fmt::{self, Display, Formatter};

use self::Error::*;

impl Display for Error {
    fn fmt(&self, formatter: &mut Formatter) -> fmt::Result {
        match *self {
            FromUtf8(ref error) => error.fmt(formatter),
            Io(ref error) => error.fmt(formatter),
            Utf8(ref error) => error.fmt(formatter),
            Msg(ref msg) => write!(formatter, "{}", msg),
        }
    }
}

For the three cases where we wrap an error from another type, we just call the corresponding fmt() method of these errors. In the case that it is a Msg, we write the string using the write! macro. This macro is a bit similar to print!, but needs a parameter to specify where to write the ...