testsuite/tests/polykinds/T17963.hs

+{-# Language DataKinds                #-}
+{-# Language PolyKinds                #-}
+{-# Language RankNTypes               #-}
+{-# Language StandaloneKindSignatures #-}
+{-# Language TypeApplications         #-}
+module T17963 where
+
+import GHC.Types (Constraint, Type, TYPE, RuntimeRep(..))
+
+type Cat :: forall (rep :: RuntimeRep). TYPE rep -> Type
+type Cat ob = ob -> ob -> Type
+
+type  Category' :: forall rep (ob :: TYPE rep). Cat @rep ob -> Constraint
+class Category' (cat :: Cat @rep ob) where
+ id' :: forall a. cat a a

testsuite/tests/polykinds/T17963.stderr

+
+T17963.hs:15:23: error:
+    • Couldn't match a lifted type with an unlifted type
+      ‘rep1’ is a rigid type variable bound by
+        the class declaration for ‘Category'’
+        at T17963.hs:13:27-29
+      When matching kinds
+        k0 :: *
+        ob :: TYPE rep1
+      Expected kind ‘ob’, but ‘a’ has kind ‘k0’
+    • In the first argument of ‘cat’, namely ‘a’
+      In the type signature: id' :: forall a. cat a a
+      In the class declaration for ‘Category'’

testsuite/tests/polykinds/all.T

@@ -216,3 +216,4 @@ test('T16263', normal, compile_fail, [''])
 test('T16902', normal, compile_fail, [''])
 test('CuskFam', normal, compile, [''])
 test('T17841', normal, compile_fail, [''])
+test('T17963', normal, compile_fail, [''])