I’m trying to add a more derived type as value to a dictionary<…, base> but i get the following error:
Cannot convert from HandleIntegrationEvent to HandleIntegrationEvent

Example

using System.Threading.Tasks;
using System.Collections.Generic;

public interface IBaseEvent
{
    string Name { get; }
}

public class UserCreatedEvent: IBaseEvent
{
    public string Name { get; } = "UserCreatedEvent";
}

public delegate Task HandleIntegrationEvent<in TR>(TR @event) where TR: IBaseEvent;

public class IntegrationBus
{
  private readonly IDictionary<string, HandleIntegrationEvent<IBaseEvent>> _listeners = new Dictionary<string, HandleIntegrationEvent<IBaseEvent>>();

  public void RegisterEventListener<TR>(string @event, HandleIntegrationEvent<TR> listener) where TR: IBaseEvent
  {
   // ERROR: cannot convert from HandleIntegrationEvent<TR> to HandleIntegrationEvent<IBaseEvent>
    _listeners.Add(@event, listener);
  } 
}

I just can’t understand it and have been trying to understand the problem for some time now.
As I understand it, the generic constraint should ensure that an instance has implemented the IBaseEvent interface.

I just have a mental block in the meantime