[theseoafs]

Well, the happy birthday article has a section on "union types", and that code block has the comment "# Here a can be an Int32 or Float64". I just assumed that this meant a had the type Int32 | Float64. If the language doesn't actually have union types, then the article should probably be edited to reflect that (because it's very misleading on this issue).

[asterite]

It has union types. Right now if you do 1 || 1.5 it gives you Int32 | Float64. If you do Foo.new || Bar.new, and Foo and Bar are not related (except they both inherit from Reference), then you get Foo | Bar. If Foo and Bar are related by some superclass Super, then you get Super+.

If you do:

a = [1, 'a', 1.5, "hello"]

you get Array(Int32 | Char | Float64 | String)

In a way, the Super+ type is a union type of all the subtypes of Super, including itself, but just with a shorter name.