>that's what discriminated unions (aka product types aka algebraic data types)

Just an FYI, discriminated unions are not product types, they are sum types. It's named so because the total number of possibilities is the sum of the number of possibilities for each variant.

Ex. A sum type Color is a PrimaryColor (Red, Blue, Yellow) OR a SecondaryColor (Purple, Green, Orange), the total number of possibilities is 3 + 3 = 6.

For a product type, if a ColorPair is a PrimaryColor AND a SecondaryColor, the total number of possibilities is 3 * 3 = 9

Both sum types and product types are algebraic types, in the same way that algebra includes both sums and products.

For the standard library, I'm curious for the family of TryParse kind of functions, since those are well modeled by a sum type. Maybe adding an overload without an `out` argument would give you back a DU to `switch` on