Test

        private IEnumerable<INamedTypeSymbol> FindMessageHandlersFor(INamedTypeSymbol message,  IEnumerable<INamedTypeSymbol> messageHandlers)
        {
            foreach (INamedTypeSymbol handler in messageHandlers)
            {
                foreach(var iface in handler.AllInterfaces)
                {
                    foreach(var typeArgument in iface.TypeArguments) 
                    {
                        if (typeArgument.Equals(message))
                        {
                            yield return handler;
                            break;
                        }
                        
                    }
                    
                }
                
            }
        }