Fix Trac #3155: better error message when -XRankNTypes is omitted

This patch sligtly re-adjusts the way in which the syntax of types 
is handled:

 * In the lexer, '.' and '*' are always accepted in types
   (previously it was conditional).  This things can't mean
   anything else in H98, which is the only reason for doing things
   conditionally in the lexer.

 * As a result '.' in types is never treated as an operator.
   Instead, lacking a 'forall' keyword, it turns into a plain parse error.

 * Test for -XKindSignatures in the renamer when processing
     a) type variable bindings
     b) types with sigs (ty :: kind-sig)

 * Make -XKindSignatures be implied by -XTypeFamilies 
   Previously this was buried in the conditonal lexing of '*'

2 files changed, 21 insertions, 11 deletions

diff --git a/compiler/rename/RnEnv.lhs b/compiler/rename/RnEnv.lhs
index 72ec8c4708..56f18ab763 100644
--- a/compiler/rename/RnEnv.lhs
+++ b/compiler/rename/RnEnv.lhs
@@ -30,7 +30,7 @@ module RnEnv (
 	mapFvRn, mapFvRnCPS,
 	warnUnusedMatches, warnUnusedModules, warnUnusedImports, 
 	warnUnusedTopBinds, warnUnusedLocalBinds,
-	dataTcOccs, unknownNameErr, perhapsForallMsg,
+	dataTcOccs, unknownNameErr, kindSigErr, perhapsForallMsg,
 
 	checkM
     ) where
@@ -824,13 +824,15 @@ bindTyVarsRn :: SDoc -> [LHsTyVarBndr RdrName]
 	      -> RnM a
 -- Haskell-98 binding of type variables; e.g. within a data type decl
 bindTyVarsRn doc_str tyvar_names enclosed_scope
-  = let
-	located_tyvars = hsLTyVarLocNames tyvar_names
-    in
-    bindLocatedLocalsRn doc_str located_tyvars	$ \ names ->
-    enclosed_scope (zipWith replace tyvar_names names)
-    where 
-	replace (L loc n1) n2 = L loc (replaceTyVarName n1 n2)
+  = bindLocatedLocalsRn doc_str located_tyvars	$ \ names ->
+    do { kind_sigs_ok <- doptM Opt_KindSignatures
+       ; checkM (null kinded_tyvars || kind_sigs_ok) 
+       	 	(mapM_ (addErr . kindSigErr) kinded_tyvars)
+       ; enclosed_scope (zipWith replace tyvar_names names) }
+  where 
+    replace (L loc n1) n2 = L loc (replaceTyVarName n1 n2)
+    located_tyvars = hsLTyVarLocNames tyvar_names
+    kinded_tyvars  = [n | L _ (KindedTyVar n _) <- tyvar_names]
 
 bindPatSigTyVars :: [LHsType RdrName] -> ([Name] -> RnM a) -> RnM a
   -- Find the type variables in the pattern type 
@@ -1087,6 +1089,12 @@ dupNamesErr get_loc descriptor names
 	      | otherwise = ptext (sLit "Bound at:") <+> 
 			    vcat (map ppr (sortLe (<=) locs))
 
+kindSigErr :: Outputable a => a -> SDoc
+kindSigErr thing
+  = hang (ptext (sLit "Illegal kind signature for") <+> quotes (ppr thing))
+       2 (ptext (sLit "Perhaps you intended to use -XKindSignatures"))
+
+
 badQualBndrErr :: RdrName -> SDoc
 badQualBndrErr rdr_name
   = ptext (sLit "Qualified name in binding position:") <+> ppr rdr_name
diff --git a/compiler/rename/RnTypes.lhs b/compiler/rename/RnTypes.lhs
index d5fc150904..4f9672bb8c 100644
--- a/compiler/rename/RnTypes.lhs
+++ b/compiler/rename/RnTypes.lhs
@@ -148,9 +148,11 @@ rnHsType doc (HsListTy ty) = do
     ty' <- rnLHsType doc ty
     return (HsListTy ty')
 
-rnHsType doc (HsKindSig ty k) = do
-    ty' <- rnLHsType doc ty
-    return (HsKindSig ty' k)
+rnHsType doc (HsKindSig ty k)
+  = do { kind_sigs_ok <- doptM Opt_KindSignatures
+       ; checkM kind_sigs_ok (addErr (kindSigErr ty))
+       ; ty' <- rnLHsType doc ty
+       ; return (HsKindSig ty' k) }
 
 rnHsType doc (HsPArrTy ty) = do
     ty' <- rnLHsType doc ty