Derive Macro ErrorKind 

#[derive(ErrorKind)]
{
    // Attributes available to this derive:
    #[error_kind]
}

Create a kind method for struct

Examples

use derive_error_kind::ErrorKind;
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
enum ErrorType {
    A,
    B,
    C,
}

#[derive(ErrorKind)]
#[error_kind(ErrorType)]
enum CacheError {
    #[error_kind(ErrorType, A)]
    Poisoned,

    #[error_kind(ErrorType, B)]
    Missing,
}

#[derive(ErrorKind)]
#[error_kind(ErrorType)]
enum ServiceError {
    #[error_kind(transparent)]
    Cache(CacheError),

    #[error_kind(ErrorType, C)]
    Db,
}

assert_eq!(ServiceError::Cache(CacheError::Missing).kind(), ErrorType::B);
assert_eq!(ServiceError::Db.kind(), ErrorType::C);