This was an issue where rustdoc changed how it laid out files in documentation, and docs.rs was not updated in time to handle it.
In https://github.com/rust-lang/rust/pull/59776, rustdoc was updated to add the “resource suffix” to the search index, so that the filename would change if a crate was rebuilt.
(This was a previous issue with in-doc search, where a crate was rebuilt to fix a visual issue in an older rustdoc, but the Cloudfront CDN had cached the old search index. Since the layout of the search index had also changed a while back, this caused issues when the search code expected the newer search index layout but received the old one. By changing the filename on each rebuild, Cloudfront would be able to load the proper file for the new version of docs.)
However, docs.rs had hard-coded a handful of paths to serve the search index, the aliases file, and the source file listing, which were now outdated, since the filenames were going to change each time rustdoc was updated. I had intended https://github.com/rust-lang/docs.rs/pull/329 to land before updating, but the PR did not work as intended the first time, and i ran out of time to fix it before we started building lots of new crates with the updated rustdoc. However, i was able to come back to it this morning, fix it up, and deploy it. New crates should be able to load their new search indexes now.