X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Frename%2FRnSource.lhs;h=606139b116b62824e4ed3a05f2fb4532d9d252cb;hb=202ac08f3e2afde0620e889cc81a95b2fd0ad9e1;hp=e29c2fefe200d572f66f100c2b9a843438d61c62;hpb=839a0880ea32b3ef2f0715957bfeec6e4bb3367b;p=ghc-hetmet.git

diff --git a/compiler/rename/RnSource.lhs b/compiler/rename/RnSource.lhs
index e29c2fe..606139b 100644
--- a/compiler/rename/RnSource.lhs
+++ b/compiler/rename/RnSource.lhs
@@ -43,7 +43,7 @@ import SrcLoc		( Located(..), unLoc, noLoc )
 import DynFlags	( DynFlag(..) )
 import Maybes		( seqMaybe )
 import Maybe            ( isNothing, isJust )
-import Monad		( liftM )
+import Monad		( liftM, when )
 import BasicTypes       ( Boxity(..) )
 \end{code}
 
@@ -280,7 +280,7 @@ rnSrcInstDecl (InstDecl inst_ty mbinds uprags ats)
 	-- The typechecker (not the renamer) checks that all 
 	-- the declarations are for the right class
     let
-	at_doc   = text "In the associated types in an instance declaration"
+	at_doc   = text "In the associated types of an instance declaration"
 	at_names = map (head . tyClDeclNames . unLoc) ats
     in
     checkDupNames at_doc at_names		`thenM_`
@@ -787,8 +787,11 @@ rnATs ats = mapFvRn (wrapLocFstM rn_at) ats
         rnTyClDecl tydecl
     rn_at _                      = panic "RnSource.rnATs: invalid TyClDecl"
 
-    lookupIdxVars _ tyvars cont = mappM lookupIdxVar tyvars >>= cont
-    --
+    lookupIdxVars _ tyvars cont = 
+      do { checkForDups tyvars;
+	 ; tyvars' <- mappM lookupIdxVar tyvars
+	 ; cont tyvars'
+	 }
     -- Type index variables must be class parameters, which are the only
     -- type variables in scope at this point.
     lookupIdxVar (L l tyvar) =
@@ -796,9 +799,27 @@ rnATs ats = mapFvRn (wrapLocFstM rn_at) ats
 	name' <- lookupOccRn (hsTyVarName tyvar)
 	return $ L l (replaceTyVarName tyvar name')
 
+    -- Type variable may only occur once.
+    --
+    checkForDups [] = return ()
+    checkForDups (L loc tv:ltvs) = 
+      do { setSrcSpan loc $
+	     when (hsTyVarName tv `ltvElem` ltvs) $
+	       addErr (repeatedTyVar tv)
+	 ; checkForDups ltvs
+	 }
+
+    rdrName `ltvElem` [] = False
+    rdrName `ltvElem` (L _ tv:ltvs)
+      | rdrName == hsTyVarName tv = True
+      | otherwise		  = rdrName `ltvElem` ltvs
+
 noPatterns = text "Default definition for an associated synonym cannot have"
 	     <+> text "type pattern"
 
+repeatedTyVar tv = ptext SLIT("Illegal repeated type variable") <+>
+		   quotes (ppr tv)
+
 -- This data decl will parse OK
 --	data T = a Int
 -- treating "a" as the constructor.