Update README to list 9.6 properly

[martijnbastiaan]

Plus, test on 9.6 on Windows/macOS CI

Still TODO:

• Write a changelog entry (see changelog/README.md)
• Check copyright notices are up to date in edited files

[martijnbastiaan]

@DigitalBrains1 Does it make sense to backport this? (Please remove label if you don't agree.)

[martijnbastiaan]

clash-cores    > build (lib)
clash-cores    > Preprocessing library for clash-cores-1.9.0..
clash-cores    > Building library for clash-cores-1.9.0..
clash-cores    > copy/register
clash-cores    > Installing library in /home/martijn/code/clash-compiler/.stack-work/install/x86_64-linux/9fc55fd213bf1b00ee7d515b087bcc74dbd56f765dd603b686bed78ef4aa535e/9.6.4/lib/x86_64-linux-ghc-9.6.4/clash-cores-1.9.0-CP0mYy2dyK4IziztwaWrhf
clash-cores    > Error: Cabal-simple_6HauvNHV_3.10.1.0_ghc-9.6.4:
clash-cores    > '/home/martijn/.ghcup/ghc/9.6.4/bin/ghc' exited with an error:
clash-cores    > <command line>: Could not find module ‘GHC.TypeLits.Extra.Solver’
clash-cores    > Use -v (or `:set -v` in ghci) to see a list of the files searched for.
clash-cores    > 
Progress 1/2

Error: [S-7282]
       Stack failed to execute the build plan.
       
       While executing the build plan, Stack encountered the error:
       
       [S-7011]
       While building package clash-cores-1.9.0 (scroll up to its section to see the error) using:
       /home/martijn/.stack/setup-exe-cache/x86_64-linux/Cabal-simple_6HauvNHV_3.10.1.0_ghc-9.6.4 --verbose=1 --builddir=.stack-work/dist/x86_64-linux/ghc-9.6.4 register
       Process exited with code: ExitFailure 1 

🤷

[DigitalBrains1]

It makes sense to backport because it adds CI stuff.

The weird error is reproducable under Linux (that's a good thing). I can't get it to work. Applying the Nix workaround here:

    -- It's absolutely grimy, but if we don't specify the `-package` flags here
    -- then when nix eventually calls `./Setup register` on the package it will
    -- still pass the `-fplugin` options to GHC and fail to create the package
    -- registation file needed to finish the `installPhase`.
    --
    -- These flags are something we NEVER want to manually specify in a normal
    -- build, since correctly configuring this kind of thing should be solely
    -- left to cabal as a build tool.
    ghc-options:
      -package ghc-typelits-extra
      -fplugin GHC.TypeLits.Extra.Solver
      -package ghc-typelits-knownnat
      -fplugin GHC.TypeLits.Normalise
      -package ghc-typelits-natnormalise
      -fplugin GHC.TypeLits.KnownNat.Solver

does not help (it'll just say cannot satisfy -package ghc-typelits-extra instead). Adding -v to the GHC invocation lists it though:

clash-cores    > *** initializing unit database:
clash-cores    > package flags [-package-id QuickCheck-2.14.3-51OWnOyIZZW6KHd0V3EO9x{unit QuickCheck-2.14.3-51OWnOyIZZW6KHd0V3EO9x True ([])},
[...]
clash-cores    >                -package-id ghc-typelits-extra-0.4.6-L6c8cgcuJuRHcCyvlVGpAw{unit ghc-typelits-extra-0.4.6-L6c8cgcuJuRHcCyvlVGpAw True ([])},
clash-cores    >                -package-id ghc-typelits-knownnat-0.7.10-fJlMrMNkyh9qGWAkYZ6O6{unit ghc-typelits-knownnat-0.7.10-fJlMrMNkyh9qGWAkYZ6O6 True ([])},
clash-cores    >                -package-id ghc-typelits-natnormalise-0.7.9-2LocrQy3VVV7lBggmw970k{unit ghc-typelits-natnormalise-0.7.9-2LocrQy3VVV7lBggmw970k True ([])},

I don't know what's up. And if the flags are even meant to be passed; I think it is running Setup.hs? The comments seem to imply this is a mistake Nix makes, but not Cabal. And Stack (2.13.1) up to GHC 9.4 works fine, but goes bad with 9.6.

[christiaanb]

Fixed by haskell/cabal#9384, which is backported to Cabal-3.10, https://github.com/haskell/cabal/blame/3.10/Cabal/src/Distribution/Simple/GHC.hs#L1864, so could in principle be included in a GHC 9.6.5 release.

[christiaanb]

As a work-around we can:

1. add the latest 3.10 branch of cabal to the extra-deps in our stack.yaml:

 - git: https://github.com/haskell/cabal.git
   commit: a3865991986361b3a736007f620b6a8878d178e3
   subdirs:
   - Cabal

2. Change the build-type of clash-cores.cabal file to Custom
3. Add a custom-setup stanza to clash-cores.cabal containing:

custom-setup
  setup-depends:
    base,
    Cabal >= 3.10.2.1

Very ugly, but it works.

I have requested that GHC 9.8.2 comes with a version of Cabal containing the fix: https://gitlab.haskell.org/ghc/ghc/-/issues/24079#note_547902

[christiaanb]

The same work-around could be applied to our starter projects in order to get them to work with GHC 9.6

[martijnbastiaan]

First, nice digging. Second, what a mess :(. I'll apply the three steps of the workaround.

Edit: If we apply the version constraint, older GHCs fail to build. Cabal syntax refuses if impl there. Luckily, the version constraint is already implied by the extra-deps, so we don't need it.

[martijnbastiaan]

I have requested that GHC 9.8.2 comes with a version of Cabal containing the fix: https://gitlab.haskell.org/ghc/ghc/-/issues/24079#note_547902

Okay, seems that we need to ask the Cabal maintainers to make a release in order for GHC to pick it up.

[martijnbastiaan]

I've asked on the Haskell Matrix.

[martijnbastiaan]