original.name="Old_Valid_17"
js.compile.ignore=true
boogie.ignore=true
Whiley2Boogie.issue=128
======
>>> main.whiley
type List is null|Node
type Node is &{ List next }
variant unchanged(List l)
where (l is Node) ==> (l->next == old(l->next))
where (l is Node) ==> unchanged(l->next)
method m(List l)
ensures unchanged(l):
skip
public export method test():
List l1 = new {next:null}
List l2 = new {next:l1}
//
m(l2)
assert l2->next == l1
assert l1->next == null
---