-- Ownership suite (plan 2), as an end-user program: `bag.items[0]` passed
-- twice as a `mut` parameter in the same call is a *provable* alias --
-- same runtime index, same call -- so it fails at compile time. Contrast
-- with tests/corpus/trap/exclusive-borrow-alias, the same shape with a
-- runtime-variable index (i == j): the analysis can't prove that one
-- either way, so it becomes a residual check the VM traps BORROW on
-- instead. This is the hybrid boundary: provable violations fail here;
-- unprovable ones trap there. Mirrors the `same_index` case of
-- compiler/test/golden/owner-err/double-mut.wo.
class Item {
  n: Int
}

class Bag {
  items: multi Item
}

fn swap(mut a: Item, mut b: Item) -> Int {
  return a.n + b.n
}

fn main() {
  let bag = Bag { items: multi_new() }
  push(bag.items, Item { n: 1 })
  print_int(swap(bag.items[0], bag.items[0]))
}