use std::any::{Any, TypeId};
use std::collections::HashMap;
struct Fabrica {
    constructors: HashMap<TypeId, Box<Fn() -> Box<Any>>>,
}
impl Fabrica {
    fn new() -> Self {
        Fabrica {
            constructors: HashMap::new(),
        }
    }
    fn register<F: 'static, T: Any>(&mut self, func: F)
    where
        F: Fn() -> T,
    {
        let type_id = TypeId::of::<T>();
        let constructor = Box::new(move || Box::new(func()) as Box<Any>);

        assert!(self.constructors.insert(type_id, constructor).is_none())
    }

    fn create<T: Any>(&self) -> Option<T> {
        self.constructors
            .get(&TypeId::of::<T>())
            .map(|func| *func().downcast::<T>().unwrap())
    }
}

fn main() {
    let mut f = Fabrica::new();
    f.register(|| 1u32);
    println!("{}", f.create::<u32>().unwrap());
}