GHC2021 extensions not part of ghc9.2.5 on Windows 10

[salbeira]

Without specifying all the language extensions in the package.yaml that we had before some versions of stack seem unable to recognise the language: GHC2021 option.

src\Text\Decker\Filter\Footnotes.hs:16:45: error:
    * Ambiguous type variable `a0' arising from a use of `walkM'
      prevents the constraint `(Walkable a0 Block)' from being solved.
      Probable fix: use a type annotation to specify what `a0' should be.
      These potential instances exist:
        instance Walkable Block Block -- Defined in `Text.Pandoc.Walk'
        instance Walkable Inline Block -- Defined in `Text.Pandoc.Walk'
        instance Walkable [Block] Block -- Defined in `Text.Pandoc.Walk'
        ...plus one other
        (use -fprint-potential-instances to see them all)
    * In the first argument of `runState', namely
        `(walkM scan (Div nullAttr blocks))'
      In the expression:
        runState (walkM scan (Div nullAttr blocks)) (0, [])
      In a pattern binding:
        (Div _ noted, (_, notes))
          = runState (walkM scan (Div nullAttr blocks)) (0, [])
   |
16 |   let (Div _ noted, (_, notes)) = runState (walkM scan (Div nullAttr blocks)) (0, [])
   |                                             ^^^^^

src\Text\Decker\Filter\Footnotes.hs:20:5: error:
    * Non type-variable argument
        in the constraint: MonadState (a, [[Block]]) m
      (Use FlexibleContexts to permit this)
    * When checking the inferred type
        scan :: forall {m :: * -> *} {a}.
                (MonadState (a, [[Block]]) m, Num a, Show a) =>
                Inline -> m Inline
      In an equation for `renderFootnotes':
          renderFootnotes blocks
            = let
                (Div _ noted, (_, notes))
                  = runState (walkM scan (Div nullAttr blocks)) ...
                footnotes = Div ... ...
              in if not (null notes) then noted <> [footnotes] else noted
            where
                scan note@(Note blocks)
                  = do (n, notes) <- get
                       ....
                scan inline = return inline
   |
20 |     scan note@(Note blocks) = do
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^...

--  While building package decker-0.13.0 (scroll up to its section to see the error) using:
      C:\Users\Hauer\Git\github\decker\.stack-work\dist\8a54c84f\setup\setup --builddir=.stack-work\dist\8a54c84f build lib:decker exe:decker --ghc-options " -fdiagnostics-color=always"
    Process exited with code: ExitFailure 1
C:\Users\Hauer\Git\github\decker\package.yaml: Ignoring unrecognized field $.language

After recent updates to develop I am unable to build it using .\bin\build.ps1 -local

There are several more errors, all reporting certain options to be missing. Returning all the language extensions from before the ghc language version update fixes all errors.

[salbeira]

Solved by upgrading stack version to 2.9.3. Seems the 2.7.X version I had before did not recognize the language: GHC2021 tag.

We should add to the dependencies the smallest stack version that supports that compilation hint (as it was clearly not connected to the ghc version stack itself downloaded).

[monofon]

Yes, add this to the docs and close the issue.

[kno10]

Debian and Ubuntu currently only include haskell-stack 2.7.5.

[salbeira]

I put in a hint about upgrading your haskell-stack version with stack upgarde after installing from your package manager in the readme.