[dataflow]

I think we might be speaking past each other? How is enum in Rust a tree type? You might be able to use it to create a tree type, but that's no different from using struct to make struct Tree : std::vector<Tree> {}; in C++. That wouldn't mean C++ has a tree type, it just means it's not hard to create your own. Whereas std::list is actually a linked list type that's already there.

[eru]

Well, std::list is something you can create with C++ code (and likely is in most implementations of C++?), it doesn't need any special support. So I can see why someone might not treat std::list as any more special than a tree datastructure supplied by a different library?

However, algebraic data types really make your life easier, and more languages should have them.