How to prevent a function to be treated as an "option" type

Stream: lean4

[Oscar Matemb ⚛️]

I am unsure how to modify the function's type from an option to the expected type. I am getting a type mismatch error for it

def takeTurnAux (game : MancalaGame) (player : Nat) (cupIdx : Nat) : MancalaGame :=
  let newGame := distributeStones game player cupIdx
  newGame

partial def takeTurn (game : MancalaGame) (player : Nat) : IO MancalaGame := do
  let stdin ← IO.getStdin
  let stdout ← IO.getStdout
  stdout.putStrLn s!"Player {player + 1}, it's your turn. Select a cup from 1 to 6:\n"
  let input ← stdin.getLine -- /
  let trimmedInput := input.trim  -- /
  match parseNat trimmedInput with
  | some n =>
    if n >= 1 ∧ n <= 6 then
      let cupIdx := n - 1
      pure (takeTurnAux game player cupIdx) -- /
    else do
      IO.println "Invalid input. Please enter a number between 1 and 6."
      takeTurn game player -- /
  | none => do
    IO.println "Invalid input. Please enter a number between 1 and 6."
    takeTurn game player --/

[Kim Morrison]

What is the error? Without a #mwe it is hard to help.