As of December 2023, most of #17128 - Migration: Replace DeprecatedString with String has been completed. DeprecatedString has been renamed and repurposed as ByteString: a string type for data that may or may not be utf-8.

While using utf-8 everywhere is convenient, this is not always enforceable: for example, filesystem paths may be in any arbitrary encoding. For those situations, we want to keep using ByteString. But for everywhere else, we want to migrate to using String (or in some cases FlyString) instead.

It's not trivial to find these cases, but look for uses of String::to_byte_string() and String::from_byte_string() to find places where we convert from one to the other. Often, this is a sign that the ByteString side should become String instead.

See #17128 for more guidance on how to perform the migration.