It seems managing singly-linked lists with shared sub-lists using RAII can be tricky. While I experimented with Rust's reference counting, it led to stack overflows for lists above 300,000 elements. Memory arenas appear more suitable, but effectively handling arena lifetimes in nested lists with varying types is challenging.

You can check my library at the repository at Codeberg. Perhaps, you want to fork it, or even take over the project.