Snippet from https://play.nim-lang.org

playground.nim

proc season(month: range[1..12]): string = 
  case month
  of 1, 2, 12: return "winter"
  of 4, 5, 6: return "spring"
  of 7, 8, 9: return "summer"
  of 10, 11: return "autumn"

echo season(5) # in.nim(2, 3) Error: not all cases are covered