Invalid types in RPC signature does not fail at compile time

[Jand42]

Whenever using a class that is not appropriate for RPC argument or result (for example it is a delegate or a class with no default constructor), no compiler error is given, only at server runtime, when RPC handler tries to deserialize an object. RPC result is also too allowing, for example an F# function object is allowed to be returned, but will be seen on the client as an empty JS object (failing to be called at client runtime).