Rust code shared from the playground

playground.rs

extern crate rustc_serialize;

use rustc_serialize::{ Decodable, Decoder };

#[derive(Debug)]
pub enum CallbackQueryData {
    String(String),
    GameShortName(String),
}

impl Decodable for CallbackQueryData {
    fn decode<D: Decoder>(d: &mut D) -> Result<CallbackQueryData, D::Error> {
        if let Some(data) = d.read_struct_field("data", 0, Decodable::decode)? {
            return Ok(CallbackQueryData::String(data));
        }

        if let Some(game_short_name) = d.read_struct_field("game_short_name", 0, Decodable::decode)? {
            return Ok(CallbackQueryData::GameShortName(game_short_name));
        }

        unreachable!()
    }
}

// {"id":32,"chat_instance":"3986534","data":"Foo"}
// {"id":32,"chat_instance":"3986534","game_short_name":"My Game"}
#[derive(Debug)]
pub struct CallbackQuery {
    id: u32,
    chat_instance: String,
    data: CallbackQueryData,
}

impl Decodable for CallbackQuery {
    fn decode<D: Decoder>(d: &mut D) -> Result<CallbackQuery, D::Error> {
        d.read_struct("CallbackQuery", 5, |d| {
            let id = d.read_struct_field("id", 0, Decodable::decode)?;
            let chat_instance = d.read_struct_field("chat_instance", 4, Decodable::decode)?;
            let data = Decodable::decode(d)?;

            Ok(CallbackQuery { id, chat_instance, data })
        })
    }
}

fn main () {}