Fails to deserialize f64 inside tagged enum

[bheisler]

Hello! I encountered this while exploring the use of CBOR as an alternative to JSON for something I'm working on. My project will require moving around a bunch of floating point numbers, and if I can I'd prefer to avoid the precision loss of converting them to text and back as JSON does. Unfortunately, I also can't guarantee that the two sides of the communication will be running the same code, so I need some flexibility to evolve the messages without breaking things. CBOR seems to fit that bill quite nicely!

However, I did find something odd:

#[derive(Debug, serde_derive::Serialize, serde_derive::Deserialize)]
#[serde(tag = "event")]
pub enum EnumMessage {
    Message { value: f64 },
}
#[derive(Debug, serde_derive::Serialize, serde_derive::Deserialize)]
struct Message {
    value: f64,
}

#[test]
fn test_roundtrip_cbor_enum() {
    let val = EnumMessage::Message { value: 3f64 };

    let bytes = serde_cbor::to_vec(&val).unwrap();
    let new_val: EnumMessage = serde_cbor::from_slice(&bytes).unwrap();
}

#[test]
fn test_roundtrip_cbor_struct() {
    let val = Message { value: 3f64 };

    let bytes = serde_cbor::to_vec(&val).unwrap();
    let new_val: Message = serde_cbor::from_slice(&bytes).unwrap();
}

The enum test fails with this error message:

thread 'test_roundtrip_cbor_enum' panicked at 'called `Result::unwrap()` on an `Err` value: ErrorImpl { code: Message("invalid type: floating point `3`, expected f64"), offset: 0 }', tests/criterion_tests.rs:559:32

As a workaround, removing the tag from the enum allows it to deserialize just fine.

[jzrake]

I am encountering the same bug, but the workaround might not be possible for my case. I hope this bug gets fixed.