solana/sdk/program/src/decode_error.rs

use num_traits::FromPrimitive;

/// Allows custom errors to be decoded back to their original enum
pub trait DecodeError<E> {
    fn decode_custom_error_to_enum(custom: u32) -> Option<E>
    where
        E: FromPrimitive,
    {
        E::from_u32(custom)
    }
    fn type_of() -> &'static str;
}

#[cfg(test)]
mod tests {
    use super::*;
    use num_derive::FromPrimitive;

    #[test]
    fn test_decode_custom_error_to_enum() {
        #[derive(Debug, FromPrimitive, PartialEq)]
        enum TestEnum {
            A,
            B,
            C,
        }
        impl<T> DecodeError<T> for TestEnum {
            fn type_of() -> &'static str {
                "TestEnum"
            }
        }
        assert_eq!(TestEnum::decode_custom_error_to_enum(0), Some(TestEnum::A));
        assert_eq!(TestEnum::decode_custom_error_to_enum(1), Some(TestEnum::B));
        assert_eq!(TestEnum::decode_custom_error_to_enum(2), Some(TestEnum::C));
        let option: Option<TestEnum> = TestEnum::decode_custom_error_to_enum(3);
        assert_eq!(option, None);
    }
}