1 files changed, 16 insertions, 0 deletions
diff --git a/testsuite/tests/indexed-types/should_compile/T15122.hs b/testsuite/tests/indexed-types/should_compile/T15122.hs
new file mode 100644
index 0000000000..c05bd3a8a0
--- /dev/null
+++ b/testsuite/tests/indexed-types/should_compile/T15122.hs
@@ -0,0 +1,16 @@
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE TypeInType #-}
+module T15122 where
+
+import Data.Kind
+import Data.Proxy
+
+data IsStar (a :: k) where
+  IsStar :: IsStar (a :: Type)
+
+type family F (a :: k) :: k
+
+foo :: (F a ~ F b) => IsStar a -> Proxy b
+                   -> Proxy (F a) -> Proxy (F b)
+foo IsStar _ p = p