Thread: dereferencing pointer to incomplete type

Hello, I am making an application that implements doubly linked lists (each node has a pointer to the previous node and the next node), and I am am having trouble with the functions that service the list. I am getting a compiler error "dereferencing pointer to incomplete type", and I am unsure of how to proceed.

Here is the relevant code

In list.h

Code:

 /* linked list node */
typedef struct _lnode {

  struct lnode *prev;

  struct lnode *next;

  int data;

} lnode;

/* struct for list, contains a pointer to the head of the list */
typedef struct _llist {

  lnode *head;

} llist;

in list.c

Code:

/* adds a node to the front of the list given a pointer to the list and the node to add
* replaces current head.
*/

void add_front(llist* list, lnode* node) {
  /* new head needs to point to old head as its next.
   * new head needs to point to old tail as its prev.
   * old head needs to point to new head as its prev.
   * tail needs to point to new head as its next.
   * list needs to recognize new head as head.
   */
  
  node->next = (struct lnode *) list->head; 
  node->prev = list->head->prev;
  //ERROR OCCURS NEXT LINE
  list->head->prev->next = node;
  list->head->prev = (struct lnode *)node;
  list->head = node;
 
}

list.h is included, so the compiler can find everything okay, so I don't know what 'incomplete type'
is referring to. On a side note, if I change

Code:

typedef struct _llist {

  lnode *head;

} llist;

to

Code:

typedef struct _llist {

  struct lnode *head;

} llist;

I will get a lot of the same error on different statements in the add_front function. I am not sure why this happens either. Is there something fundamental about pointers/structs that I am not getting? Thanks in advance.