5 files changed, 52 insertions, 0 deletions
diff --git a/testsuite/tests/deriving/should_fail/T14728a.hs b/testsuite/tests/deriving/should_fail/T14728a.hs
new file mode 100644
index 0000000000..28cf8e0ffc
--- /dev/null
+++ b/testsuite/tests/deriving/should_fail/T14728a.hs
@@ -0,0 +1,20 @@
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE StandaloneDeriving #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE TypeInType #-}
+module T14728a where
+
+import Data.Functor.Identity
+import Data.Kind
+
+class C (a :: Type) where
+  type T a (x :: a) :: Type
+  type U z :: a
+
+instance C () where
+  type T () '() = Bool
+
+deriving instance C (Identity a)
+
+f :: T (Identity ()) ('Identity '())
+f = True
diff --git a/testsuite/tests/deriving/should_fail/T14728a.stderr b/testsuite/tests/deriving/should_fail/T14728a.stderr
new file mode 100644
index 0000000000..b76d073645
--- /dev/null
+++ b/testsuite/tests/deriving/should_fail/T14728a.stderr
@@ -0,0 +1,7 @@
+
+T14728a.hs:17:1: error:
+    • Can't make a derived instance of ‘C (Identity a)’
+        (even with cunning GeneralizedNewtypeDeriving):
+        the associated type ‘T’ contains the last type variable
+          of the class ‘C’ in a kind, which is not (yet) allowed
+    • In the stand-alone deriving instance for ‘C (Identity a)’
diff --git a/testsuite/tests/deriving/should_fail/T14728b.hs b/testsuite/tests/deriving/should_fail/T14728b.hs
new file mode 100644
index 0000000000..7fdfcb3b5e
--- /dev/null
+++ b/testsuite/tests/deriving/should_fail/T14728b.hs
@@ -0,0 +1,16 @@
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE StandaloneDeriving #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE TypeInType #-}
+module T14728b where
+
+import Data.Functor.Identity
+import Data.Kind
+
+class C (a :: Type) where
+  type U z :: a
+
+instance C () where
+  type U z = '()
+
+deriving instance C (Identity a)
diff --git a/testsuite/tests/deriving/should_fail/T14728b.stderr b/testsuite/tests/deriving/should_fail/T14728b.stderr
new file mode 100644
index 0000000000..ee74f8b4da
--- /dev/null
+++ b/testsuite/tests/deriving/should_fail/T14728b.stderr
@@ -0,0 +1,7 @@
+
+T14728b.hs:16:1: error:
+    • Can't make a derived instance of ‘C (Identity a)’
+        (even with cunning GeneralizedNewtypeDeriving):
+        the associated type ‘U’ contains the last type variable
+          of the class ‘C’ in a kind, which is not (yet) allowed
+    • In the stand-alone deriving instance for ‘C (Identity a)’
diff --git a/testsuite/tests/deriving/should_fail/all.T b/testsuite/tests/deriving/should_fail/all.T
index c9b8469c3c..acd3486918 100644
--- a/testsuite/tests/deriving/should_fail/all.T
+++ b/testsuite/tests/deriving/should_fail/all.T
@@ -69,3 +69,5 @@ test('T12512', omit_ways(['ghci']), compile_fail, [''])
 test('T12801', normal, compile_fail, [''])
 test('T14365', [extra_files(['T14365B.hs','T14365B.hs-boot'])],
                multimod_compile_fail, ['T14365A',''])
+test('T14728a', normal, compile_fail, [''])
+test('T14728b', normal, compile_fail, [''])