Support GHC 9.2

[sjakobi]

Some dependencies aren't compatible yet, so I'm currently using this incantation:

cabal build all -O0 -w ghc-9.2 --allow-newer=basement:base,aeson:ghc-prim,aeson:template-haskell,modern-uri:template-haskell,relude:base,relude:ghc-prim,aeson-yaml:aeson,hnix:template-haskell,hnix:time,turtle:bytestring,tomland:base,validation-selective:base

…and this patch (due to #2270):

--- a/cabal.project
+++ b/cabal.project
@@ -1 +1 @@
-packages: ./dhall ./dhall-bash ./dhall-json ./dhall-yaml ./dhall-lsp-server ./dhall-nix ./dhall-docs ./dhall-openapi ./dhall-nixpkgs ./dhall-csv ./dhall-toml
+packages: ./dhall ./dhall-bash ./dhall-json ./dhall-yaml ./dhall-nix ./dhall-docs ./dhall-openapi ./dhall-nixpkgs ./dhall-csv ./dhall-toml

Blocked on:

• DRAFT Update basement for GHC 9.2 haskell-foundation/foundation#555
• Support GHC 9.2 haskell/aeson#885
• Support GHC 9.2 chrisdone/lucid#118
• Support GHC 9.2 mrkkrp/modern-uri#43 (via mmark via dhall-docs)
• Support GHC 9.2 kowainik/relude#388 (via hnix)
• Compatibility with aeson-2.0 clovyr/aeson-yaml#16 (comment)
• Compatibility with GHC 9.2 DanBurton/lens-family-th#19
• Compatibility with GHC 9.2 / bytestring 0.11 Gabriella439/turtle#410
• Compatibility with GHC 9.2 kowainik/tomland#395
• Build failure with GHC 9.2.1 Lysxia/generic-random#32

[Gabriella439]

Feel free to merge whenever this is ready

[sjakobi]

So I can already get a clean build with head.hackage (and --allow-newer). The one minor hurdle is https://gitlab.haskell.org/ghc/ghc/-/issues/20666, which prevents generic-random from building. I've worked around this by excluding that dependency and the Dhall.Test.QuickCheck module where generic-random is used.

Since no further changes in this project seem necessary, I'll merge and create a matching Hackage revision.

I hope it won't be too long until we can migrate CI to GHC 9.2 – the compiler perf benefits seem very promising. I haven't done any measurements yet though!