gistfile1.txt

# This macro is annoying
macro_rules! try_conv {
    ($expr:expr) => (match $expr {
        Ok(val) => val,
        Err(err) => {
            return Err(SerdeError::custom(err.description()))
        }
    })
}

impl serde::Deserialize for Foo {
    fn deserialize<D>(deserializer: &mut D) -> Result<Self, D::Error>
        where D: serde::Deserializer
    {
        let value: Value = try!(Value::deserialize(deserializer));

        // XXX find a solution to get rid of this clone
        if let Some(ref s) = value.clone().find("classtype") {
            use serde_json::from_value;
            if !s.is_string() {
                return Err(SerdeError::custom("non-string 'classtype'"))
            }
            match s.as_string().unwrap() {
                "stuff" =>
                    Ok(Foo(try_conv!(from_value(value)))),
                _ => Err(SerdeError::custom("invalid"))
            }
        } else {
            Err(SerdeError::missing_field("classtype"))
        }
    }
}