The author doesn't seem to have much experience in writing Rust.
For instance, passing RefCell<u32> by value as their code does makes no sense (just use u32...), and the code seems to have a lot of clones, most of which are probably unnecessary, while not having a single instance of the "mut" keyword.
In fact, I'm pretty sure it's completely broken, since their gensym doesn't do what they want, due to their wrong use of clones and refcells (it should take an &mut u32 and just increment it).
Comments
The author doesn't seem to have much experience in writing Rust.
For instance, passing RefCell<u32> by value as their code does makes no sense (just use u32...), and the code seems to have a lot of clones, most of which are probably unnecessary, while not having a single instance of the "mut" keyword.
In fact, I'm pretty sure it's completely broken, since their gensym doesn't do what they want, due to their wrong use of clones and refcells (it should take an &mut u32 and just increment it).
And definitely not idiomatic at all.