Hi Alexander,
sorry my initial example was maybe misleading. What I really what to do is to associate each event with an arbitrary data type. For example, consider the following events:
NewPlayer
NewRule
Message
User

I want to associate the following data types with each, to pass to there respective handlers:
NewPlayer ---> Player
NewRule ---> Rule
Message ---> String
User ---> String

Message and User have the same data type associated, that's why we can't use this type as a key to index the event...