Test Trac #4497

testsuite/tests/ghc-regress/indexed-types/should_compile/T4497.hs

+{-# LANGUAGE FlexibleContexts, MultiParamTypeClasses, TypeFamilies #-}  
+
+module T4497 where
+
+norm2PropR a = twiddle (norm2 a) a
+
+twiddle :: Normed a => a -> a -> Double  
+twiddle a b = undefined
+
+norm2 :: e -> RealOf e
+norm2 = undefined
+
+class (Num (RealOf t)) => Normed t
+
+type family RealOf x

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

@@ -161,3 +161,4 @@ test('T4492', normal, compile, [''])
 test('T4494', normal, compile, [''])
 test('DataFamDeriv', normal, compile, [''])
 test('T1769', normal, compile, [''])
+test('T4497', normal, compile, [''])