context addable(type T) {
   T ?+?(T,T);
};

type List(type T | addable(T) ) | addable(T) = struct { T data; List(T) *next; } *;
typedef List(int) ListOfIntegers;
ListOfIntegers li;
int f( List(int) ((*g))(int) );
[int] h( * List(int) p ); // new declaration syntax

struct(type T | addable(T) ) node { T data; struct(T) node *next; };
type List(type T) = struct(T) node *;
List(int) my_list;

type Complex | addable(Complex);

int main() {
    (struct(int) node)my_list;
}