1 files changed, 26 insertions, 0 deletions
diff --git a/testsuite/tests/polykinds/T11362.hs b/testsuite/tests/polykinds/T11362.hs
new file mode 100644
index 0000000000..945d68f825
--- /dev/null
+++ b/testsuite/tests/polykinds/T11362.hs
@@ -0,0 +1,26 @@
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE PolyKinds #-}
+{-# LANGUAGE KindSignatures #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE GADTs #-}
+
+module T11362 where
+-- this file when compiled with -dunique-increment=-1 made GHC crash
+
+data Sum a b = L a | R b
+
+data Sum1 (a :: k1 -> *) (b :: k2 -> *) :: Sum k1 k2 -> * where
+  LL :: a i -> Sum1 a b (L i)
+  RR :: b i -> Sum1 a b (R i)
+
+data Code i o = F (Code (Sum i o) o)
+
+-- An interpretation for `Code` using a data family works:
+data family In (f :: Code i o) :: (i -> *) -> (o -> *)
+
+data instance In (F f) r o where
+  MkIn :: In f (Sum1 r (In (F f) r)) o -> In (F f) r o
+
+-- Requires polymorphic recursion
+data In' (f :: Code i o) :: (i -> *) -> o -> * where
+  MkIn' :: In' g (Sum1 r (In' (F g) r)) t -> In' (F g) r t