type classes sort of solve the same problem and in both rust and haskell they can sort of emulate union types (I have no idea about the details, I am not an expert of subtyping).
Still the usability feature of being able to quickly create arbitrary union types is undeniable (Julia uses something similar as a main source of polymorphism and personally I think it is amazing)
Still the usability feature of being able to quickly create arbitrary union types is undeniable (Julia uses something similar as a main source of polymorphism and personally I think it is amazing)