{-# LANGUAGE CPP #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE TypeOperators #-}
#if MIN_VERSION_template_haskell(2,12,0)
{-# LANGUAGE InstanceSigs #-}
{-# LANGUAGE TypeApplications #-}
{-# OPTIONS_GHC -Wno-unused-foralls #-} -- Due to GHC #13512. Sigh.
#endif
{-|
Module: GH27Spec
Copyright: (C) 2019 Ryan Scott
License: BSD-style (see the file LICENSE)
Maintainer: Ryan Scott
Portability: Template Haskell
A regression test for
https://github.com/haskell-compat/deriving-compat/issues/27.
We isolate this test case from the rest of "DerivingViaSpec" because
we have to disable @-Wunused-foralls@ due to
https://gitlab.haskell.org/ghc/ghc/issues/13512, and we would prefer not to
contaminate the rest of "DerivingViaSpec" with this hack.
-}
module GH27Spec where
import Prelude ()
import Prelude.Compat
import Test.Hspec
#if MIN_VERSION_template_haskell(2,12,0)
import Data.Deriving.Via
import Data.Functor.Const
newtype Age = MkAge Int
$(deriveVia [t| forall a. Show Age `Via` Const Int a |])
#endif
main :: IO ()
main = hspec spec
spec :: Spec
spec = pure ()