What happens if a structure property points to the structure itself?

The compiler will produce an error because a struct is a value type and is stored on the stack. The size of a struct must be known at compile time. Declaring a property of the same type within the struct will create an infinite recursive dependency of sizes.

struct Node {
    var value: Int
    var next: Node // Error: Value type 'Node' cannot have a stored property that references itself
}

To avoid this problem, you can use a reference type (class), which is stored on the heap and represents a fixed-size reference.

class Node {
    var value: Int
    var next: Node? // Optional to indicate the end of the list
}

Alternatively, you can use an enum with an indirect case, which allows recursive value types.

enum LinkedList {
    case node(Int, indirect LinkedList)
    case end
}