macron-impl-error 0.1.2

The implementation of trait Error
Documentation 
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extern crate macron_impl_error;  use macron_impl_error::Error;

#[test]
fn error_struct() {
    #[derive(Debug, Error)]
    struct Error {
        source: Option<Box<dyn std::error::Error>>
    }

    impl ::std::fmt::Display for Error {
        fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
            write!(f, "it's my custom error")
        }
    }

    let err = Error { source: None };

    assert_eq!(format!("{err}"), "it's my custom error");
}

#[test]
fn error_enum() {
    #[derive(Debug, Error)]
    enum Error {
        WithAnySource { source: Option<Box<dyn std::error::Error>>, msg: String },

        WithCertainSource(#[source] SourceError),
        
        WithoutSource,

        WithoutSource2(String, String),
    }

    impl ::std::fmt::Display for Error {
        fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
            match &self {
                Self::WithAnySource { source, msg } => write!(f, "the error with a message: '{msg}' and a source: '{src}'", src = if let Some(src) = source.as_deref() { src.to_string() }else { "no source".to_owned() }),
                Self::WithCertainSource(src) => write!(f, "the error with the source: '{src}'"),
                Self::WithoutSource => write!(f, "the error without a source"),
                Self::WithoutSource2(_, _) => write!(f, "the error without source"),
            }
        }
    }

    #[derive(Debug, Error)]
    enum SourceError {
        Error
    }

    impl ::std::fmt::Display for SourceError {
        fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
            match &self {
                Self::Error => write!(f, "the source of error"),
            }
        }
    }

    let err = Error::WithAnySource { source: Some(Box::new(SourceError::Error)), msg: "the message of error".to_owned() };
    let err2 = Error::WithCertainSource( SourceError::Error );
    let err3 = Error::WithoutSource;

    assert_eq!(format!("{err}"), "the error with a message: 'the message of error' and a source: 'the source of error'");
    assert_eq!(format!("{err2}"), "the error with the source: 'the source of error'");
    assert_eq!(format!("{err3}"), "the error without a source");
}