The reason why I created this project is that I miss sum types in C all the time, literally everywhere I need a custom error type or just any other alternative

The reason why I created this project is that I miss sum types in C all the time, literally everywhere I need a custom error type or just any other alternative data representation. And I do think the implementation of datatype99 is straightforward -- only long names, all the dirty hacks are encapsulated into the underlying framework.