use std::any::{Any, TypeId};
use std::cell::*;
use std::collections::hash_map::ValuesMut;
use std::collections::{HashMap, HashSet};

pub trait TypeErasedTrait: std::fmt::Debug + Any {

}

pub trait InsideType: std::fmt::Debug {}


#[derive(Debug)]
pub struct RealType(i32);
impl InsideType for RealType { }


#[derive(Debug)]
pub struct ConcreteObject<T> where T: InsideType {
    field: T,
}

impl<T> TypeErasedTrait for ConcreteObject<T> where T: InsideType + 'static {

}

#[derive(Debug)]
pub struct Builder {
    objects: HashMap<i32, RefCell<Box<dyn TypeErasedTrait>>>,
}

fn main() {
    let mut builder = Builder { objects: Default::default() };
    let obj = ConcreteObject { field: RealType(5) };
    builder.objects.insert(0, RefCell::new(Box::new( obj )) );
    {
        let ref_cell = builder.objects.get(&0).unwrap();
        let mut ref_mut = ref_cell.borrow_mut();
        let something = ref_mut.downcast_mut::<ConcreteObject<RealType>>().unwrap();
        println!("{:?}", something.field);


    }


}