type Holder { values: List<Int> }

identity(values: List<Int>) (result: List<Int>) { result = values }

measure(values: List<Int>) (result: Int) { result = length(values) }

compare(values: List<Int>, size: Int) (same: Bool) { same = length(values) == size }

selected(keep: true, values: List<Int>) (result: List<Int>) { result = values }
selected(keep: other, values: List<Int>) (result: List<Int>) { result = [] }

readField(holder: Holder) (result: List<Int>) {
  result = selected(true, holder.values)
}

verify() (valid: Bool) {
  values = [1, 2, 3]
  direct = compare(values, measure(values))
  holder = Holder { values = [4, 5] }
  field = compare(holder.values, measure(holder.values))
  items = [6]
  forwarded = compare(identity(items), measure(identity(items)))
  consumed = Holder { values = [7, 8, 9, 10] }
  moved = readField(consumed)
  reused = Holder { values = [11, 12] }
  borrowed = readField(reused)
  preserved = compare(reused.values, measure(borrowed))
  repeated = Holder { values = [13, 14, 15] }
  duplicated = compare(repeated.values, measure(selected(true, repeated.values)))
  valid = direct and field and forwarded and length(moved) == 4 and preserved and duplicated
}