Serializing simple enum leads to UnsupportedType

[soywod]

Sorry if the answer is obvious, but I cannot understand why toml is not able to serialize this struct (but serde_json can):

#[derive(Debug, serde::Serialize, serde::Deserialize)]
struct Struct {
    field: Enum,
}

#[derive(Debug, serde::Serialize, serde::Deserialize)]
enum Enum {
    Variant(u8),
}

let ser = Struct {
    field: Enum::Variant(21),
};

println!("json: {:?}", serde_json::to_string(&ser));

println!("toml: {:?}", toml::to_string(&ser));

json: Ok("{\"field\":{\"Variant\":21}}")
toml: Err(Error { inner: UnsupportedType(Some("Enum")) })

Even mor surprising, the same struct can be deserialized without any problem:

let de: Result<Struct, toml::de::Error> = toml::from_str("[field]\nVariant = 21");

println!("toml: {:?}", de);

toml: Ok(Struct { field: Variant(21) })

[soywod]

May be linked to #534.

[epage]

All in one reproduction case:

#!/usr/bin/env rust-script

//! ```cargo
//! [dependencies]
//! toml = "0.7.3"
//! serde = { version = "1", features = ["derive"] }
//! serde_json = "1"
//! ```

#[derive(Debug, serde::Serialize, serde::Deserialize)]
struct Struct {
    field: Enum,
}

#[derive(Debug, serde::Serialize, serde::Deserialize)]
enum Enum {
    Variant(u8),
}

fn main() {
    let ser = Struct {
        field: Enum::Variant(21),
    };
    println!("json: {:?}", serde_json::to_string(&ser));
    println!("toml: {:?}", toml::to_string(&ser));

    let de: Result<Struct, toml::de::Error> = toml::from_str("[field]\nVariant = 21");
    println!("toml: {:?}", de);
}

[epage]

New release out with newtype variant support

[soywod]

Awesome, thank you!