We discussed this a bunch in the wg-diagnostics Zulip
So there’s a larger roadmap for improving diagnostics, and a part of that is using diagnostic structs.
The Fluent work can actually piggyback on the diagnostic struct work. If we use a custom derive or other attribute for the diagnostic structs, the vast majority of them can be autoconverted to Fluent strings, and we can make it possible to seamlessly and automatically upgrade the custom derive to use Fluent ids. We’d still need some kind of text! macro for diagnostics with complex custom logic.
This means the next steps for this are to help out with that work (once the team has figured out the precise design). Once that’s trundling along, we can start integrating Fluent (we can also wait for it to be completed, either works).