C lang Syntax Error missing ";" before "*"

Question

The error appears in the List* next line.

typedef struct {
    List* next;
    int data;
    int index;
} List;

Answer 1

As noted in comments, the type List is not known when you use it. There are two solutions to this.

The first is to simply use struct List *next:

typedef struct List {
   int n;
   struct List *next;
} List;

The other is to typedef List into existence before defining struct List.

typedef struct List List;

struct List {
   int n;
   List *next;
};

Which is better is opinion, and thus inappropriate for SO.