3 ms·

The zero would obviously be the zero value of one of the constituents. Coproducts in most of Go are easy: it's interfaces that make it hard.

• masklinn 2y ago
  > The zero would obviously be the zero value of one of the constituents. If interfaces are used for union types then the obvious zero is nil, not any constituent. Nil is the zero value of interfaces. It’s perfectly consistent and in line with the rest of the langage.
  • wbl 2y ago
    It's not clear to me that that would satisfy the categorical properties of coproduct that are wanted.
    • foldr 2y ago
      Nobody cares about the categorical properties of the coproduct. But in any case, there's no theoretical issue here, since it would be just as if every enum had a 'Nil' variant implicitly defined.