You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: mod.rs
    path of file: ./repos/rustrogueliketutorial/chapter-64-curses/src/map_builders/prefab_builder
    
    the code of the file until where you have to start completion: use super::{InitialMapBuilder, MetaMapBuilder, BuilderMap, TileType, Position};
use rltk::RandomNumberGenerator;
pub mod prefab_levels;
pub mod prefab_sections;
pub mod prefab_rooms;
use std::collections::HashSet;

#[derive(PartialEq, Copy, Clone)]
#[allow(dead_code)]
pub enum PrefabMode {
    RexLevel{ template : &'static str },
    Constant{ level : prefab_levels::PrefabLevel },
    Sectional{ section : prefab_sections::PrefabSection },
    RoomVaults
}

#[allow(dead_code)]
pub struct PrefabBuilder {
    mode: PrefabMode
}

impl MetaMapBuilder for PrefabBuilder {
    fn build_map(&mut self, rng: &mut rltk::RandomNumberGenerator, build_data : &mut BuilderMap)  {
        self.build(rng, build_data);
    }
}

impl InitialMapBuilder for PrefabBuilder {
    #[allow(dead_code)]
    fn build_map(&mut self, rng: &mut rltk::RandomNumberGenerator, build_data : &mut BuilderMap) {
        self.build(rng, build_data);
    }
}

impl PrefabBuilder {
    #[allow(dead_code)]
    pub fn new() -> Box<PrefabBuilder> {
        Box::new(PrefabBuilder{
            mode : PrefabMode::RoomVaults,
        })
    }

    #[allow(dead_code)]
    pub fn rex_level(template : &'static str) -> Box<PrefabBuilder> {
        Box::new(PrefabBuilder{
            mode : PrefabMode::RexLevel{ template },
        })
    }

    #[allow(dead_code)]
    pub fn constant(level : prefab_levels::PrefabLevel) -> Box<PrefabBuilder> {
        Box::new(PrefabBuilder{
            mode : PrefabMode::Constant{ level },
        })
    }

    #[allow(dead_code)]
    pub fn sectional(section : prefab_sections::PrefabSection) -> Box<PrefabBuilder> {
        Box::new(PrefabBuilder{
            mode : PrefabMode:
    
    fn char_to_map(&mut self, ch : char, idx: usize, build_data : &mut BuilderMap) {
        match ch {
            ' ' => build_data.map.tiles[idx] = TileType::Floor,
            '#' => build_data.map.tiles[idx] = TileType::Wall,
            '≈' => build_data.map.tiles[idx] = TileType::DeepWater,
            '@' => {
                let x = idx as i32 % build_data.map.width;
                let y = idx as i32 / build_data.map.width;
                build_data.map.tiles[idx] = TileType::Floor;
                build_data.starting_position = Some(Position{ x:x as i32, y:y as i32 });
            }
            '>' => build_data.map.tiles[idx] = TileType::DownStairs,
            'g' => {
                build_data.map.tiles[idx] = TileType::Floor;
                build_data.spawn_list.push((idx, "Goblin".to_string()));
            }
            'o' => {
                build_data.map.tiles[idx] = TileType::Floor;
                build_data.spawn_list.push((idx, "Orc".to_string()));
            }
            'O' => {
                build_data.map.tiles[idx] = TileType::Floor;
                build_data.spawn_list.push((idx, "Orc Leader".to_string()));
            }
            '^' => {
                build_data.map.tiles[idx] = TileType::Floor;
                build_data.spawn_list.push((idx, "Bear Trap".to_string()));
            }
            '%' => {
                build_data.map.tiles[idx] = TileType::Floor;
                build_data.spawn_list.push((idx, "Rations".to_string()));
            }
            '!' => {
                build_data.map.tiles[idx] = TileType::Floor;
                build_data.spawn_list.push((idx, "Health Potion".to_string()));
            }
            '☼' => {
                build_data.map.tiles[idx] = TileType::Floor;
                build_data.spawn_list.push((idx, "Watch Fire".to_string()));
            }
            _ => {
                rltk::console::log(format!("Unknown glyph loading map: {}", (ch as u8) as char));
            }
        }
    }