This plan is spun out of #11370 (closed)
The immediate plan (for 8.0) is
- Remove warn-redundant-constraints from the default constraint set and the -Wall constraint set.
- Implement #11429 (closed) and make unrecognized -W flags a warning rather than compile error.
Having done so, we are in a position to further move on https://gitlab.haskell.org/trac/ghc/wiki/Design/Warnings in a future release. In the course of that we can settle on the proper flagset to include this warning in.