Rust code shared from the playground

playground.rs

extern crate serde;
#[macro_use]
extern crate serde_derive;
extern crate serde_json;

use std::collections::HashMap;
use serde::{Serialize, Serializer};

fn main() {
    let mut map: HashMap<String, String> = HashMap::new();
    map.insert("hello".into(), "world".into());

    let data = ApiResult::Success(map.keys());

    println!("{}", serde_json::to_string(&data).unwrap());
}

#[derive(Serialize)]
#[serde(bound(serialize = "T: Clone + Iterator, T::Item: Serialize"))]
pub enum ApiResult<'a, T> {
    Failure { code: u32, errors: Vec<&'a str> },
    Success(#[serde(serialize_with = "serialize_iter")] T),
}

fn serialize_iter<T, S>(iter: &T, serializer: S) -> Result<S::Ok, S::Error>
    where T: Clone + Iterator,
          T::Item: Serialize,
          S: Serializer
{
    serializer.collect_seq(iter.clone())
}