[masklinn]

> Doesn't the iota identifier solve it for you ?

They're talking about sum types (aka tagged unions aka variant record), where you have a proper type with a closed set of variants (which can be checked for completeness by the compiler) and optional associated data (possibly of different types for each variant).

Iota isn't even a step up from C's enums, it doesn't come close to what you can find in ML descendants (such as Rust or Swift for the most recent ones).