main.rs

extern crate failure;
#[macro_use]
extern crate failure_derive;


use std::process;
use std::io::{self, Read};
use failure::Error;

#[derive(Debug, Fail)]
enum MainErr {
    #[fail(display = "No Harrys allowed")]
    NoHarrys
}

fn get_name() -> Result<String, Error> {
    let mut buffer = String::new();
    io::stdin().read_to_string(&mut buffer)?;
    let name = buffer.trim_right();
    match name {
        "Harry" => Err(MainErr::NoHarrys),
        _ => Ok(String::from(name))
    }
}

fn run() -> Result<(), Error> {
    let name = get_name()?;
    println!("Hello, {}!", name);
    Ok(())
}

fn main() {
    match run() {
        Ok(_) => (),
        Err(e) => {
            eprintln!("{}\n\n {}", e, e.backtrace());
            process::exit(1);
        }
    }
}

out.txt

$ cargo run
   Compiling hellostdin v0.1.0 (file:///Users/emoritz/Data/Projects/hellostdin)
error[E0308]: mismatched types
  --> src/main.rs:21:24
   |
21 |         "Harry" => Err(MainErr::NoHarrys),
   |                        ^^^^^^^^^^^^^^^^^ expected struct `failure::Error`, found enum `MainErr`
   |
   = note: expected type `failure::Error`
              found type `MainErr`

error: aborting due to previous error

error: Could not compile `hellostdin`.

To learn more, run the command again with --verbose.

I'm doing something wrong with the failure crate. I'm not sure what.