Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @alexcrichton (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. The way Github handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see CONTRIBUTING.md for more information.

The byte is actually quite important: it is designed to protect against trivial hash-collisions, e.g. without the byte, ("foo", "bar") and ("", "foobar") would feed the same sequence of bytes (b"foobar") into the hasher, likely resulting in the same hash. The 0xFF byte cannot ever occur in a str, and so ensures that cases like the above always result in different byte sequences (b"foo\xFFbar\xFF" vs b"\xFFfoobar\xFF").

Thanks for the PR, but unfortunately we can't accept it.