I am using this crate to show what parts of an assertion failed and why (see assert-rs/predicates-rs#7).

For simple nodes, it seems like the current API is great. Unfortunately, I have heterogeneous nodes for my expression tree. so with treelines current API, I have to copy this into a treeline specific tree and convert each of my nodes into a Box<Display> to conform to the API, making a lot of unnecessary work.