I really don't know what categories to pick, so I'm happy to change them.
I am working on a source-to-source compiler for rust. There are check_item/check_item_post and check_impl_item/check_impl_item_post pairs. But for check_trait_item, there is no _post partner. The pairs are really handy to write both an analysis (I need a full call graph) and for a transformation. In the pre method, I push a new empty entry for metadata to a stack and in the post method, I have it filled with what I collected in other check_ methods. Is there a design choice that doesn't allow this for trait items? Or did just nobody care, yet?