Modern swift makes this technically possible but so cluttered that it's effectively impossible, especially compared with typescript.
Swift distinguishes between inclusive and exclusive / exhaustive unions with enum vs protocols and provides no easy or simple way to bridge between the two. If you want to define something that typescript provides as easy as the vertical bar, you have to write an enum definition, a protocol bridge with a type identifier, a necessarily unchecked cast back (even if you can logically prove that the type enum has a 1:1 mapping), and loads of unnecessary forwarding code. You can try and elide some of it with (iirc, its been a couple years) @dynamicMemberLookup, but the compiler often chokes on this, it kills autocomplete, and it explodes compile times because Swift's type checker degrades to exponential far more frequently than other languages, especially when used in practice, such as in SwiftUI.
Swift distinguishes between inclusive and exclusive / exhaustive unions with enum vs protocols and provides no easy or simple way to bridge between the two. If you want to define something that typescript provides as easy as the vertical bar, you have to write an enum definition, a protocol bridge with a type identifier, a necessarily unchecked cast back (even if you can logically prove that the type enum has a 1:1 mapping), and loads of unnecessary forwarding code. You can try and elide some of it with (iirc, its been a couple years) @dynamicMemberLookup, but the compiler often chokes on this, it kills autocomplete, and it explodes compile times because Swift's type checker degrades to exponential far more frequently than other languages, especially when used in practice, such as in SwiftUI.