 a feature that you'll also find in Roc, but I actually [first heard of the idea on the Elm discourse](https://discourse.elm-lang.org/t/idea-extensible-union-types-and-benefits-they-bring-for-real-world-elm-code/6118) back in 2020. Of course, it probably exists in a few other languages as well.\\n\\nWhile on the topic of sum types, Gren will further limit them to 0 or 1 arguments. The reasons behind this overlaps with [why tuples where removed](https://youtu.be/Sl9HHo1qDk0?si=wiJjSEMyl0f6HqTn), but there's 