The added nix expression allows maintainers to check for regressions in
the configuration overlays employed by haskellPackages and friends. The
reasoning behind this is that, if we add an override for something, it
should also build. To test this fact, we extract all attributes touched
by a configuration and obtain all relevant derivations corresponding to
it which can then be thrown into nix-build --keep-going.
I've been using this expression to verify configuration-ghc-9.2.x.nix
for a week or so which works quite well. The amount of stale overrides
in other configuration makes it a bit more painful for other use cases
at the moment.
7e9d55f0c4