How to define “type disjunction” (union types)?

Question

One way that has been suggested to deal with double definitions of overloaded methods is to replace overloading with pattern matching:

object Bar {
   def fo         


        

Answer 1

Adding to the already great answers here. Here's a gist that builds on Miles Sabin union types (and Josh's ideas) but also makes them recursively defined, so you can have >2 types in the union (def foo[A : UNil Or Int Or String Or List[String])

https://gist.github.com/aishfenton/2bb3bfa12e0321acfc904a71dda9bfbb

NB: I should add that after playing around with the above for a project, I ended up going back to plain-old-sum-types (i.e. sealed trait with subclasses). Miles Sabin union types are great for restricting the type parameter, but if you need to return a union type then it doesn't offer much.