Port to GHC-9.8.2 (missing: dhall-{lsp-server,nix,nixpkgs})

[lucasdicioccio]

Starting something to upgrade to 9.8.2, taking baby-steps absent #2583 .

My goal is to compile with -Werror with 9.8.2 (I run cabal 3.10.3.0 but that shouldn't matter much) then pass tests (without -Werror then with).

• I've mainly replaced safe head calls to NonEmpty.head . NonEmpty.fromList except in dhall/src/Dhall/Tags.hs (a more human-friendly symbol is welcomed) and dhall-openapi/src/Dhall/Kubernetes/Types.hs (we may expect the parser to occur at a boundary where human-readable errors are paramount)
• upgrade some package bounds here and there
• CPP-guard liftA2 imports
• pass tests
• same for dhall-{lspt-server,nix,nixpkgs}) (tbc: blocked on hnix)

I'm struggling to find cycles to feel free to take over the pull-request.

[ysangkok]

I think these look like sensible changes. Given that GHC 9.8.3 will be out in a few days, and the Stackage LTS after that, I think it would be good to merge and release this, so we can keep Dhall in Stackage LTS.

Any reason this is still 'draft' @lucasdicioccio ?

[ysangkok]

I am not sure how much of the work here is still pending on the default branch, but basic GHC 9.8 usage should already work since

• Fix TyVar BndrVis #2622

[lucasdicioccio]

I am not sure how much of the work here is still pending on the default branch, but basic GHC 9.8 usage should already work since

* [Fix TyVar BndrVis #2622](https://github.com/dhall-lang/dhall-haskell/pull/2622)

I think we can close this PR. Sorry the time I can allocate for open-source contribs is pretty narrow since a while ago.