How can we write to a parameter-pack tuple with the iteration syntax?

Using Swift
,
1 
func myFunction<each T: FixedWidthInteger>(_ t: repeat each T) -> (repeat each T) {
  for value in repeat each t {
    print(value)
  }

  var result = (repeat each t)
  for dummy in repeat each ??? {  // `result`, or `&result`, is in the ???
    dummy += 1
  }
  return result
}

How can I write to each member of result one at a time? (I can't use an all-at-once functional solution here.) The actual needs are more complicated, but I need to work with the above first before asking new questions.