From 2962dc4a8a863c56faee53349cf79d4c7a175987 Mon Sep 17 00:00:00 2001
From: simonpj <unknown>
Date: Tue, 23 Apr 2002 08:55:47 +0000
Subject: [PATCH] [project @ 2002-04-23 08:55:47 by simonpj] Reject attempts
 to rebind built in syntax

---
 ghc/compiler/rename/RnEnv.lhs |   15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/ghc/compiler/rename/RnEnv.lhs b/ghc/compiler/rename/RnEnv.lhs
index c2c6762..1cb95da 100644
--- a/ghc/compiler/rename/RnEnv.lhs
+++ b/ghc/compiler/rename/RnEnv.lhs
@@ -211,7 +211,16 @@ lookupTopBndrRn rdr_name
 	-- The parser reads the special syntax and returns an Orig RdrName
 	-- But the global_env contains only Qual RdrNames, so we won't
 	-- find it there; instead just get the name via the Orig route
-  = lookupOrigName rdr_name
+	--
+  = 	-- This is a binding site for the name, so check first that it 
+	-- the current module is the correct one; otherwise GHC can get
+	-- very confused indeed.  This test rejects code like
+	--	data T = (,) Int Int
+	-- unless we are in GHC.Tup
+    getModuleRn				`thenRn` \ mod -> 
+    checkRn (moduleName mod == rdrNameModule rdr_name)
+	    (badOrigBinding rdr_name)	`thenRn_`
+    lookupOrigName rdr_name
 
   | otherwise
   = getModeRn	`thenRn` \ mode ->
@@ -1050,6 +1059,10 @@ unknownNameErr name
   where
     flavour = occNameFlavour (rdrNameOcc name)
 
+badOrigBinding name
+  = ptext SLIT("Illegal binding of built-in syntax:") <+> ppr (rdrNameOcc name)
+	-- The rdrNameOcc is because we don't want to print Prelude.(,)
+
 qualNameErr descriptor (name,loc)
   = pushSrcLocRn loc $
     addErrRn (vcat [ ptext SLIT("Invalid use of qualified name") <+> quotes (ppr name),
-- 
1.7.10.4