> But in the last 30 years this didn’t go mainstream.
It's started to in the last few years (last decade?). First OO languages started getting type-safe enums, which still suck but at least aren't as bad as C-style enums, then most recent languages got either actual sum types or something more or equivalent (type-safe unions, sealed classes / interfaces).
It's started to in the last few years (last decade?). First OO languages started getting type-safe enums, which still suck but at least aren't as bad as C-style enums, then most recent languages got either actual sum types or something more or equivalent (type-safe unions, sealed classes / interfaces).