Build failure with GHC 9.8

[andreasabel]

Some types apparently have changed in template-haskell, there is now a mismatch between TyVarBndrUnit and TyVarBndr BndrVis.

src/Language/Haskell/TH/Datatype.hs:598:38: error: [GHC-83865]
    • Couldn't match type ‘BndrVis’ with ‘()’
      Expected: [TyVarBndrUnit]
        Actual: [TyVarBndr BndrVis]
    • In the first argument of ‘repairVarKindsWith’, namely ‘dvars’
      In a stmt of a 'do' block: ts' <- repairVarKindsWith dvars dk ts
      In the expression:
        do ts' <- repairVarKindsWith dvars dk ts
           return $ NewtypeInstD cx mbInstVars (foldl' AppT con ts') k c deriv
    |
598 |       = do ts' <- repairVarKindsWith dvars dk ts
    |                                      ^^^^^
...

Seems like the details behind this error have been reported in

• Adapt to TypeAbstractions in GHC 9.8 #103

A release on hackage compatible with the latest template-haskell / GHC would be nice.

[RyanGlScott]

I've prepared a fix for this issue (and #103, which is essentially the same issue) in #104, which is based on the corresponding head.hackage patch here. I've held off on releasing it pending a resolution to ghc-proposals/ghc-proposals#604 (which could impact how TypeAbstractions works in GHC 9.8), but upon a closer read, that proposal is unlikely to affect th-abstraction in particular.

I'll try to cut a new th-abstraction release soon.

[RyanGlScott]

I've uploaded th-abstraction-0.6.0.0 to Hackage, which contains the changes from #104. As such, I'll close this issue.

Do note that some downstream libraries that depend on th-abstraction will also need updates to support GHC 9.8. At a minimum, these include many of the libraries in this head.hackage patch. I'll get around to updating those libraries which I maintain in the coming days.