derive-enum-error 0.0.1

Derive macro for `std::error::Error`
Documentation 
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use derive_enum_error::Error;
use std::error::Error;

#[derive(Debug, Error)]
#[error(display = "An error has occurred.")]
struct UnitError;

#[test]
fn unit_struct() {
    let s = format!("{}", UnitError);
    assert_eq!(&s[..], "An error has occurred.");
}

#[derive(Debug, Error)]
#[error(display = "Error code: {}", code)]
struct RecordError {
    code: u32,
}

#[test]
fn record_struct() {
    let s = format!("{}", RecordError { code: 0 });
    assert_eq!(&s[..], "Error code: 0");
}

#[derive(Debug, Error)]
#[error(display = "Error code: {}", _0)]
struct TupleError(i32);

#[test]
fn tuple_struct() {
    let s = format!("{}", TupleError(2));
    assert_eq!(&s[..], "Error code: 2");
}

#[derive(Debug, Error)]
enum EnumError {
    #[error(display = "Error code: {}", code)]
    StructVariant { code: i32 },
    #[error(display = "Error: {}", _0)]
    TupleVariant(&'static str),
    #[error(display = "An error has occurred.")]
    UnitVariant,
}

#[test]
fn enum_error() {
    let s = format!("{}", EnumError::StructVariant { code: 2 });
    assert_eq!(&s[..], "Error code: 2");
    let s = format!("{}", EnumError::TupleVariant("foobar"));
    assert_eq!(&s[..], "Error: foobar");
    let s = format!("{}", EnumError::UnitVariant);
    assert_eq!(&s[..], "An error has occurred.");
}

#[derive(Debug, Error)]
enum ErrorWithSource {
    #[error(display = "tuple error")]
    A(#[error(source)] TupleError),
}

#[test]
fn error_with_source() {
    let e = ErrorWithSource::A(TupleError(1));

    assert!(e.source().is_some());
}