Simple numbers with data constructor

[yjwen]

To translate

module MaybePlus where
maybe_plus :: Maybe Int -> Maybe Int -> Maybe Int
maybe_plus (Just a) (Just b) = Just (a + b)
maybe_plus _ _ = Nothing

to

typedef struct {
   logic ctor;
   logic [63 : 0] body;
} MaybeInt;

module maybe_plus(MaybeInt a, MaybeInt b, output MaybeInt o);
   assign o.ctor = a.ctor && b.ctor;
   assign o.body = o.ctor ? a.body + b.body : 'x;
endmodule