error error fun time

code.rs

// the offending code:

pub fn populate_world(world: &mut World<Agent>) -> Uuid {
    let zone_a_id = world.new_zone(24, setup_zone);
    // ....
}

/*
the error:

14:52 error: cannot determine a type for this bounded type parameter: unconstrained type
/.../builder.rs:14     let zone_a_id = world.new_zone(24, setup_zone);
                                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/

// here's the impl for World, along w/ its constraints:
impl<D: Decoder, E: Encoder, TPayload: Send + Payloadable + Decodable<D> + Encodable<E>> World<TPayload> {
  // ...
  pub fn new_zone(&mut self, size: uint, cb: |&mut Zone<TPayload>|) -> uint {
      // ..
  }
}