'All ComponentType must be known at compile time...' error for a generic System

Entity Component System (ECS)
1

I’m updating my local copy of FPSSample2 (Unity sample) to use Entities v0.1.1 and I’m getting an error indicating that I have a generic component

that I need to register using [RegisterGenericComponentType] beforehand.

The error is generated by the line #15 in this snippet

[DisableAutoCreation]
[AlwaysUpdateSystem]
public abstract class InitializeComponentSystem<T> : BaseComponentSystem where T : MonoBehaviour
{
    struct SystemState : IComponentData { }
    EntityQuery IncomingGroup;
    string name;

    public InitializeComponentSystem(GameWorld world) : base(world) { }

    protected override void OnCreate()
    {
        base.OnCreate();
        name = GetType().Name;
        IncomingGroup = GetEntityQuery(typeof(T), ComponentType.Exclude<SystemState>());
    }

    protected override void OnUpdate()
    {
            // ...
    }

    protected abstract void Initialize(Entity entity, T component);
}

T is non-generic component in this case (RagdollOwner).

I assume that I have to register a type that would somehow combine whatever’s passed as T and SystemState, but how do I do that using RegisterGenericComponentType?

2

… and of course I found solution after a minute of posting the thread.
All I had to do is move SystemState declaration out of the generic InitializeComponentSystem class which was also making it generic.