Sum types are cool. Many languages implement enums which are not tagged union sum types (even when language has rich sum types)

https://en.cppreference.com/w/c/language/enum

https://learn.microsoft.com/en-us/dotnet/csharp/language-ref...

https://docs.python.org/3/library/enum.html

https://api.rubyonrails.org/v5.2.4.5/classes/ActiveRecord/En... https://sorbet.org/docs/tenum

https://docs.oracle.com/javase/tutorial/java/javaOO/enum.htm...

https://dart.dev/language/enums

https://www.postgresql.org/docs/current/datatype-enum.html

https://dev.mysql.com/doc/refman/8.4/en/enum.html

https://zig.guide/language-basics/enums

https://www.erlang.org/eeps/eep-0013

https://hackage.haskell.org/package/planet-mitchell-0.1.0/do...

https://www.ibm.com/docs/en/openxl-fortran-aix/17.1.1?topic=...

This. I find Swift and Rust enums, which are indeed very similar, to be incredibly good at modelling the real world. For example the standard geospatial vector types which are heterogeneous and even recursive in the case of GeometryCollections can be modelled and operated upon very cleanly.