GHC 8.12 (master) wants RankNTypes pragma in Distribution/Client/Sandbox.hs

[vdukhovni]

Distribution/Client/Sandbox.hs:713:7: error:
    • Illegal qualified type:
        GHC.Stack.Types.HasCallStack => IO WereDepsReinstalled
      Perhaps you intended to use RankNTypes
    • In the expansion of type synonym ‘Distribution.Compat.Stack.WithCallStack’
      In the expansion of type synonym ‘Cabal-3.3.0.0:Distribution.Compat.Prelude.IO’
      When checking the inferred type
        topHandler' :: Cabal-3.3.0.0:Distribution.Compat.Prelude.IO
                         WereDepsReinstalled
                       -> IO WereDepsReinstalled
    |       
713 |       topHandler' = topHandlerWith $ \_ -> do
    |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^...

Enabling the pragma resolves the issue (assuming not a GHC bug).

[phadej]

Please make a PR.

EDIT: as this is cabal-install (not Cabal) issue. This is not high-priority.