-- ?T narrowing, all four shipped forms: the if-guard, the early-return
-- (a diverging then-branch proves the false facts after the `if`), the
-- short-circuit `and` chain, and the while condition. Each narrows a LOCAL
-- from ?Int to Int; field places never narrow by design.
class Box {
  v: ?Int
}

fn guard(b: Box) -> Int {
  let x = b.v;
  if x != nil { return x + 1; }
  return -1
}

fn early(b: Box) -> Int {
  let x = b.v;
  if x == nil { return -1; }
  return x + 10
}

fn chain(b: Box) -> Bool {
  let x = b.v;
  return x != nil and x > 3
}

fn main() -> Int {
  let full = Box { v: 7 };
  let empty = Box { v: nil };
  print_int(guard(full));
  print_int(guard(empty));
  print_int(early(full));
  print_int(early(empty));
  if chain(full) { print("chain full: gt3"); }
  if chain(empty) == false { print("chain empty: no"); }
  return 0
}