Just wanted to say that I also submitted an OCaml Outreachy project!
The goal of the project is to improve the error reporting in the PPXs ecosystem. This includes both modifying ppxlib’s behavior when catching an exception raised by a rewriter; and modify existing PPXs to better report error (by embedding them inside the AST when relevant, allowing for both multiple error reporting, and creation of a partial AST that contains all information that could be created).