failure2.rs

#[macro_use]
extern crate failure;

use failure::Error;

#[derive(Fail, Debug)]
enum MyEnumError {
    #[fail(display = "An error occurred.")]
    Variant1,
    #[fail(display = "A different error occurred.")]
    Variant2(#[cause] ::std::io::Error),
}

fn err1() -> Result<(), Error> {
    bail!(MyEnumError::Variant1)
}

impl From<::std::io::Error> for MyEnumError {
    fn from(e: ::std::io::Error) -> Self {
        MyEnumError::Variant2(e)
    }
}

fn io_err() -> Result<(), MyEnumError> {
    let _ = std::fs::File::open("/lolwut")?;
    Ok(())
}

fn io_err2() -> Result<(), Error> {
    let _ = std::fs::File::open("/lolwut")?;
    Ok(())
}

fn main() -> Result<(), Error> {
    let _ = err1()?;
    let _ = io_err()?;
    let _ = io_err2()?;
    Ok(())
}