JSON deserialization of empty HashMap results corrupted object

[alexbers]

This code(saving an emtpy map as json file and loading it):

extern mod std;

use core::path::Path;
use core::hashmap::HashMap;

use std::serialize::{Encodable, Decodable};


fn save_db(queues: &HashMap<~str,~str>) {
    match io::buffered_file_writer(&Path("db.json")) {
        Ok(wr) => {
            let enc = ~std::json::Encoder(wr);
            queues.encode(enc);
        }
        Err(e) => {
            println(e);
        }
    }
}

fn load_db() -> HashMap<~str,~str> {
    match io::file_reader(&Path("db.json")) {
        Ok(rd) => {
            match std::json::from_reader(rd) {
                Ok(json) => {
                    let dec = ~std::json::Decoder(json);
                    return Decodable::decode(dec);
                },
                Err(_) => {
                    println("Db file is bad, using empty db");
                    return HashMap::new();
                }
            }
        }
        Err(e) => {
            println(e);
            return HashMap::new();
        }
    }
}

fn main() {
    let mut map : HashMap<~str,~str> = HashMap::new();

    save_db(&map);
    let mut map = load_db();

    map.insert(~"key", ~"val");
}

Gives on insert operation:

rust: task failed at 'modulo zero', json.rs:1

I think it is because the internal structure of map is wrong after loading.

[alexcrichton]

Closed as part of #6851