Test Trac #5719

testsuite/tests/indexed-types/should_run/T5719.hs

+{-# LANGUAGE ConstraintKinds, TypeFamilies, FlexibleInstances #-}
+module Main where
+
+import GHC.Prim (Constraint)
+
+import Prelude hiding (Functor, fmap)
+
+import           Data.Set (Set)
+import qualified Data.Set as S (map, fromList)
+
+class Functor f where
+    type C f a :: Constraint
+    type C f a = ()
+
+    fmap :: (C f a, C f b) => (a -> b) -> f a -> f b
+
+instance Functor Set where
+    type C Set a = Ord a
+    fmap = S.map
+
+instance Functor [] where
+    fmap = map
+--    type C [] a = ()
+
+testList = fmap (+1) [1,2,3]
+testSet  = fmap (+1) (S.fromList [1,2,3])
+
+main = do { print testList; print testSet }

testsuite/tests/indexed-types/should_run/T5719.stdout

+[2,3,4]
+fromList [2,3,4]

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

@@ -6,3 +6,4 @@ test('T4235', normal, compile_and_run, [''])
 
 test('GMapAssoc', normal, compile_and_run, ['-package containers'])
 test('GMapTop',   normal, compile_and_run, ['-package containers'])
+test('T5719', normal, compile_and_run, [''])