1 files changed, 40 insertions, 0 deletions
diff --git a/testsuite/tests/deriving/should_compile/T20375.hs b/testsuite/tests/deriving/should_compile/T20375.hs
new file mode 100644
index 0000000000..33a54a7c7c
--- /dev/null
+++ b/testsuite/tests/deriving/should_compile/T20375.hs
@@ -0,0 +1,40 @@
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE DerivingStrategies #-}
+{-# LANGUAGE MagicHash #-}
+{-# LANGUAGE UnliftedNewtypes #-}
+module T20375 where
+
+import Data.Data (Data)
+import Data.Ix (Ix)
+import GHC.Exts (Int#, RuntimeRep(..), TYPE)
+import GHC.Generics (Generic, Generic1)
+
+-- Test special-casing for unlifted types (e.g., Int#)
+data D1 (a :: TYPE IntRep) b = MkD1 a b
+deriving stock instance Eq (D1 Int# Int)
+deriving stock instance Ord (D1 Int# Int)
+deriving stock instance Generic (D1 Int# Int)
+deriving stock instance Generic1 (D1 Int#)
+deriving stock instance Show (D1 Int# Int)
+
+-- Test special-casing for tuples
+data D2 p a = MkD2 (p a Int)
+deriving stock instance Foldable (D2 (,))
+deriving stock instance Functor (D2 (,))
+deriving stock instance Traversable (D2 (,))
+
+-- Ensure that validity checks don't get tripped up by a runtime-polymorphic
+-- type that is instantiated to something runtime-monomorphic.
+newtype D3 (a :: TYPE r) = MkD3 a
+deriving stock instance Bounded (D3 Int)
+deriving stock instance Data (D3 Int)
+deriving stock instance Eq (D3 Int)
+deriving stock instance Foldable D3
+deriving stock instance Functor D3
+deriving stock instance Generic (D3 Int)
+deriving stock instance Generic1 D3
+deriving stock instance Ix (D3 Int)
+deriving stock instance Ord (D3 Int)
+deriving stock instance Read (D3 Int)
+deriving stock instance Show (D3 Int)
+deriving stock instance Traversable D3