Making a move on the tic tac toe game

GameMakeMove.kt

...
fun make(move: Move): Either<GameError, Game> = either {
  val (coord, symbol) = move
  ensure(symbol == nextPlayer) { raise(NotPlayersTurn(symbol)) }
  ensure(cell(move.coordinates) == BLANK) { raise(InvalidMove(move)) }
  state
    .mapIndexed { ri, row ->
      if (ri == coord.row) {
        row.mapIndexed { ci, cell -> if (ci == coord.col) symbol else cell }
      } else row
    }
    .toGame()
  }
...