Creating a method which returns one or two parameters generically

Question

I have a method

def foo(num: Int): String

Where I call some in some places in my code, and everything was good.
Lately, I encountered

Answer 1

Since the result space is cleanly split into two sides (disjointed) consider Either like so

def foo(i: Int): Either[(String, String), String] =
  if (i == 10) Left("one", "two") else Right("one")

val Left(Tuple2(x, y)) = foo(10)
val Right(a) = foo(2)

which is inspired by @Krzysztof's edit regarding "special container".