Test for Trac #959

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

@@ -176,3 +176,4 @@ test('tcfail186',
      extra_clean(['Tcfail186_Help.hi', 'Tcfail186_Help.o']),
      multimod_compile_fail, ['tcfail186', '-v0'])
 test('tcfail187', normal, compile_fail, [''])
+test('tcfail188', normal, compile_fail, [''])

testsuite/tests/ghc-regress/typecheck/should_fail/tcfail188.hs

+{-# OPTIONS_GHC -Werror -fglasgow-exts #-}
+
+-- Trac #959
+
+module ShouldFail where
+
+data D (f :: (* -> *) -> * -> *) (af :: * -> *) (ax :: *) =
+  D (af (f af ax))
+
+data CList (f :: (* -> *) -> * -> *) (a :: *) =
+  RCons a (CList (D f) a)
+
+type CycleList a = forall f. CList f a
+
+chead :: CycleList a -> a
+chead ys = case ys of (RCons x xs) -> x

testsuite/tests/ghc-regress/typecheck/should_fail/tcfail188.stderr

+
+tcfail188.hs:13:26:
+    Warning: Inventing strangely-kinded Any TyCon
+               of kind `(* -> *) -> * -> *'
+               from an instantiation of type variable `f'
+             This warning can be suppressed by a type signature fixing `f'
+               but is harmless without -O (and usually harmless anyway).
+             See http://hackage.haskell.org/trac/ghc/ticket/959 for details