original.name="Reference_Valid_22"
======
>>> main.whiley
type Node is {
    int item,
    List next
} where !(next is null) ==> item < next->item

type List is null | &Node

public export method test():
    List l1 = null
    List l2 = new { item: 0, next: l1 }
    // List l3 = new { item: 1, next: l2 }
---