Fix a bug in printing of negative variables.

types/types.ml

@@ -1954,6 +1954,7 @@ struct
                   | [],l,[] ->  [ intersection (l @ rem) ]
                   | l1,l2,[] -> [ intersection ((union l1) :: (l2 @ rem)) ]
                   | [],[],l2 -> [ intersection ([ Neg (alloc [union l2]) ] @ rem)]
+                  | l1,[],l2 -> [ intersection ((union l1) :: [ Neg (alloc [union l2]) ] @ rem) ]
                   | l1,l2, l3 -> [ intersection ([ union l1; intersection [ intersection l2; Neg(alloc l3)]] @ rem) ]
               in
               if subtype any tt then print_topvars [] else