hw202207 / hello-haskell

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Unable to build with GHC

• This works

  cabal build
      

• This fails

  ghc --make Main.hs
      

• This fixes ghc build

  ghc --make -XHaskell2010 Main.hs
      

  GHC2021 is used by GHC if neither Haskell98 nor Haskell2010 is turned on explicitly.

  • GHC2021 enable StandaloneKindSignatures hence it supposes work.
  • Haskell2010 has CUSKs, which is legacy extension that fixes user specified kind signature.
  • GHC2021 is new feature since 9.2.1
  • Follow up this problem here.
• Reference
  • GHC guide - control extensions
• Tips
  • cabal build --verbose to see what being passed to GHC