Test Trac #3155

testsuite/tests/ghc-regress/typecheck/should_fail/T3155.hs

+{-# LANGUAGE GADTs, TypeOperators #-}
+module T3155 where
+
+-- Test Trac #3155
+-- Gave bad error message in GHC 6.10
+
+data Any s where
+  Any :: s ix -> ix -> Any s
+
+data AnyR s r where
+  AnyR :: s ix -> r ix -> AnyR s r
+
+unR :: (forall ix. r ix -> ix) -> AnyR s r -> Any s
+unR f (AnyR ix rix) = Any ix (f rix)

testsuite/tests/ghc-regress/typecheck/should_fail/T3155.stderr

+
+T3155.hs:13:17:
+    Illegal symbol '.' in type
+    Perhaps you intended -XRankNTypes or similar flag
+    to enable explicit-forall syntax: forall <tvs>. <type>

testsuite/tests/ghc-regress/typecheck/should_fail/all.T

@@ -207,3 +207,4 @@ test('T2538', normal, compile_fail, [''])
 test('T2688', normal, compile_fail, [''])
 test('T2714', normal, compile_fail, [''])
 test('T2994', normal, compile_fail, [''])
+test('T3155', normal, compile_fail, [''])