Type families: Roman's test for normalisation of reduced dicts

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

+{-# LANGUAGE TypeFamilies, FlexibleContexts #-}
+{-# LANGUAGE EmptyDataDecls, FlexibleInstances #-}
+
+module InstContextNorm
+where
+
+data EX _x _y (p :: * -> *)
+data ANY
+
+class Base p
+
+class Base (Def p) => Prop p where
+ type Def p
+
+instance Base ()
+instance Prop () where
+ type Def () = ()
+
+instance (Base (Def (p ANY))) => Base (EX _x _y p)
+instance (Prop (p ANY)) => Prop (EX _x _y p) where
+ type Def (EX _x _y p) = EX _x _y p
+
+
+data FOO x
+
+instance Prop (FOO x) where
+ type Def (FOO x) = ()
+
+data BAR
+
+instance Prop BAR where
+ type Def BAR = EX () () FOO

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

@@ -95,6 +95,8 @@ test('InstEqContext2', if_compiler_lt('ghc', '6.9', expect_fail),
                        compile, [''])
 test('InstEqContext3', normal, compile, [''])
 
+test('InstContextNorm', if_compiler_lt('ghc', '6.9', expect_fail), compile, [''])
+
 test('HO', normal, compile, [''])
 
 test('GivenCheck', normal, compile, [''])