Combining Inclusion Polymorphism and Parametric Polymorphism

We show that the question whether a term is typable is decidable for type systems combining inclusion polymorphism with parametric polymorphism provided the type constructors are at most unary. To prove this result we first reduce the typability problem to the problem of solving a system of type inequations. The result is then obtained by showing that the solvability of the resulting system of type inequations is decidable.