The documentation provided by Rust’s cargo doc gives you a search bar in your browser. This feature is implemented in the client frontend rather than backend by sending the search index as a json object. This avoid having to package a server backend with the docs.
There seems to be some discussion about providing a similar feature here but nothing much subsequently. I was curious if that had been more conversation subsequently.
Even a basic ability to fuzzy search a function name or type name would be useful.