Test Trac #12174

testsuite/tests/dependent/should_fail/T12174.hs

+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE ExistentialQuantification #-}
+{-# LANGUAGE KindSignatures #-}
+{-# LANGUAGE TypeInType #-}
+module T12174 where
+
+data V a
+data T = forall (a :: S). MkT (V a)
+data S = forall (a :: T). MkS (V a)

testsuite/tests/dependent/should_fail/T12174.stderr

+
+T12174.hs:9:23: error:
+    • Type constructor ‘T’ cannot be used here
+        (it is defined and used in the same recursive group)
+    • In the kind ‘T’
+      In the definition of data constructor ‘MkS’
+      In the data declaration for ‘S’

testsuite/tests/dependent/should_fail/all.T

@@ -14,3 +14,4 @@ test('InferDependency', normal, compile_fail, [''])
 test('KindLevelsB', normal, compile_fail, [''])
 test('T11473', normal, compile_fail, [''])
 test('T11471', normal, compile_fail, [''])
+test('T12174', normal, compile_fail, [''])