HaloO, just to deepen your understanding of co- and contravariance you should digest <http://www.pps.jussieu.fr/~gc/papers/toplas95.pdf> The important point to get from it is that dispatch-relevant parameters are also covariant.
Regards, TSa. -- "The unavoidable price of reliability is simplicity" -- C.A.R. Hoare 1 + 2 + 3 + 4 + ... = -1/12 -- Srinivasa Ramanujan
