Test Trac #5776

testsuite/tests/simplCore/should_compile/Makefile

@@ -12,6 +12,10 @@ T5658b:
 	'$(TEST_HC)' $(TEST_HC_OPTS) -O -c T5658b.hs -ddump-simpl | grep --count indexIntArray
 # Trac 5658 meant that there were three calls to indexIntArray instead of two
 
+T5776:
+	$(RM) -f T5776.o T5776.hi 
+	'$(TEST_HC)' $(TEST_HC_OPTS) -O -c T5776.hs -ddump-rules | grep --count dEq
+
 T3772:
 	$(RM) -f T3772*.hi T3772*.o
 	'$(TEST_HC)' $(TEST_HC_OPTS) -c -O T3772_A.hs 

testsuite/tests/simplCore/should_compile/T5776.hs

+module T5776 where
+
+-- The point about this test is that we should get a rule like this:
+-- "foo" [ALWAYS]
+--    forall (@ a)
+--           ($dEq :: GHC.Classes.Eq a)
+--           ($dEq1 :: GHC.Classes.Eq a)
+--           (x :: a)
+--           (y :: a)
+--           (z :: a).
+--      T5776.f (GHC.Classes.== @ a $dEq1 x y)
+--              (GHC.Classes.== @ a $dEq y z)
+--      = GHC.Types.True
+--
+-- Note the *two* forall'd dEq parameters. This is important.
+-- See Note [Simplifying RULE lhs constraints] in TcSimplify
+
+{-# RULES "foo" forall x y z.
+      f (x == y) (y == z) = True
+ #-}
+
+f :: Bool -> Bool -> Bool
+{-# NOINLINE f #-}
+f a b = False
+
+blah :: Int -> Int -> Bool
+blah x y = f (x==y) (x==y)
+ 

testsuite/tests/simplCore/should_compile/T5776.stdout

+4

testsuite/tests/simplCore/should_compile/all.T

@@ -138,3 +138,7 @@ test('T5658b',
      normal,
      run_command,
      ['$MAKE -s --no-print-directory T5658b'])
+test('T5776',
+     normal,
+     run_command,
+     ['$MAKE -s --no-print-directory T5776'])