namespace App
{
    public class World
    {
        private readonly Dictionary<Type, object> Resources = new Dictionary<Type, object>();

        public void Insert<T>(T resource)
            where T : class
        {
            Resources.Add(typeof(T), resource);
        }

        public T Fetch<T>()
            where T : class
        {
            if (Resources.TryGetValue(typeof(T), out var resource))
                return (T) resource;
            return null;
        }

        public bool Contains<T>()
            where T : class
        {
            return Resources.ContainsKey(typeof(T));
        }
    }

    public static class WorldVal
    {
        private class ValueWrapper<T>
        {
            public T Val;
        }

        public static T Fetch<T>(this World world)
            where T : struct
        {
            return world.Fetch<ValueWrapper<T>>().Val;
        }

        public static void Insert<T>(this World world, T resource)
            where T : struct
        {
            world.Insert(new ValueWrapper<T> {Val = resource});
        }
    }
}