ATS version of https://github.com/graydon/rust/issues/1259

gistfile1.txt

fun foo {v:view} (pf: !v | b1: (!v | int) -<cloref> void):void = {
  val v = 5
  val () = b1(pf | v)
}

implement main () = {
  var x: int? with pf_x
  viewdef V = int? @ x
  val () = foo {V} (pf_x | lam (pf | newval) => x := newval)
  val () = printf("%d\n", @(x)) 
}