
Make the OperationCode overloads take the derived operation instead of the Operation base class instance. This makes them usable from visitors of "Expr<T>.u". Also, fix small bug: OperationCode(Constant<T>) shoud be "Constant".
Make the OperationCode overloads take the derived operation instead of the Operation base class instance. This makes them usable from visitors of "Expr<T>.u". Also, fix small bug: OperationCode(Constant<T>) shoud be "Constant".