Test Trac #7804

testsuite/tests/indexed-types/should_compile/T7804.hs

+{-# LANGUAGE TypeFamilies, RankNTypes #-}
+
+module T7804 where
+
+type family F f a
+
+data Proxy a = P
+
+sDFMap :: (forall a. Proxy f -> Proxy a -> Proxy (F f a)) -> Int
+sDFMap _ = 3

testsuite/tests/indexed-types/should_compile/all.T

@@ -208,4 +208,5 @@ test('T7474', normal, compile, [''])
 test('T7489', normal, compile, [''])
 test('T7585', normal, compile, [''])
 test('T7282', normal, compile, [''])
+test('T7804', normal, compile, [''])