Solution: The closest supertype of types

  • Int and Double -> Number
  • Double and Number -> Number
  • String and Nothing -> String
  • Float and Double? -> Number?
  • String and Float -> Any
  • Char and Nothing? -> Char?
  • Nothing and Any -> Any
  • Nothing? and Any -> Any?
  • Char? and Nothing? -> Char?
  • Nothing? and Any? -> Any?