From 2c2509997743edeb63830b86c8ee910db2414c6b Mon Sep 17 00:00:00 2001
From: simonpj <unknown>
Date: Thu, 20 Sep 2001 08:47:13 +0000
Subject: [PATCH] [project @ 2001-09-20 08:47:13 by simonpj]
 ------------------------------ 	Fix a
 scoped-type-variable bug 
 ------------------------------

	MERGE WITH STABLE BRANCH

The bug caused an incorrect failure when the same type
variable was used more than once in a collection of patterns:

	f (x :: t) (y :: t) = e

On the way, I eliminated bindNakedTyVarsFVRn, which was only
called once.
---
 ghc/compiler/rename/RnEnv.lhs  |   29 +++++++++++++++++++++--------
 ghc/compiler/rename/RnExpr.lhs |   15 +--------------
 2 files changed, 22 insertions(+), 22 deletions(-)

diff --git a/ghc/compiler/rename/RnEnv.lhs b/ghc/compiler/rename/RnEnv.lhs
index ffcd10b..dda823b 100644
--- a/ghc/compiler/rename/RnEnv.lhs
+++ b/ghc/compiler/rename/RnEnv.lhs
@@ -11,7 +11,7 @@ module RnEnv where		-- Export everything
 import {-# SOURCE #-} RnHiFiles
 
 import HsSyn
-import RdrHsSyn		( RdrNameIE )
+import RdrHsSyn		( RdrNameIE, RdrNameHsType, extractHsTyRdrTyVars )
 import RdrName		( RdrName, rdrNameModule, rdrNameOcc, isQual, isUnqual, isOrig,
 			  mkRdrUnqual, mkRdrQual, lookupRdrEnv, foldRdrEnv, rdrEnvToList,
 			  unqualifyRdrName
@@ -607,15 +607,28 @@ bindTyVarsFV2Rn doc_str rdr_names enclosed_scope
     enclosed_scope names tyvars		`thenRn` \ (thing, fvs) ->
     returnRn (thing, delListFromNameSet fvs names)
 
-bindNakedTyVarsFVRn :: SDoc -> [RdrName]
-	            -> ([Name] -> RnMS (a, FreeVars))
-		    -> RnMS (a, FreeVars)
-bindNakedTyVarsFVRn doc_str tyvar_names enclosed_scope
-  = getSrcLocRn					`thenRn` \ loc ->
+bindPatSigTyVars :: [RdrNameHsType]
+		 -> ([Name] -> RnMS (a, FreeVars))
+	  	 -> RnMS (a, FreeVars)
+  -- Find the type variables in the pattern type 
+  -- signatures that must be brought into scope
+
+bindPatSigTyVars tys enclosed_scope
+  = getLocalNameEnv			`thenRn` \ name_env ->
+    getSrcLocRn				`thenRn` \ loc ->
     let
-	located_tyvars = [(tv, loc) | tv <- tyvar_names] 
+	forall_tyvars  = nub [ tv | ty <- tys,
+				    tv <- extractHsTyRdrTyVars ty, 
+				    not (tv `elemFM` name_env)
+			 ]
+		-- The 'nub' is important.  For example:
+		--	f (x :: t) (y :: t) = ....
+		-- We don't want to complain about binding t twice!
+
+	located_tyvars = [(tv, loc) | tv <- forall_tyvars] 
+	doc_sig        = text "In a pattern type-signature"
     in
-    bindLocatedLocalsRn doc_str located_tyvars	$ \ names ->
+    bindLocatedLocalsRn doc_sig located_tyvars	$ \ names ->
     enclosed_scope names			`thenRn` \ (thing, fvs) ->
     returnRn (thing, delListFromNameSet fvs names)
 
diff --git a/ghc/compiler/rename/RnExpr.lhs b/ghc/compiler/rename/RnExpr.lhs
index ce22f17..dba30bd 100644
--- a/ghc/compiler/rename/RnExpr.lhs
+++ b/ghc/compiler/rename/RnExpr.lhs
@@ -199,22 +199,9 @@ rnMatch ctxt match@(Match _ pats maybe_rhs_sig grhss)
     
     returnRn (Match sig_tyvars pats' maybe_rhs_sig' grhss', all_fvs)
 	-- The bindLocals and bindTyVars will remove the bound FVs
-
-
-bindPatSigTyVars :: [RdrNameHsType]
-		 -> ([Name] -> RnMS (a, FreeVars))
-	  	 -> RnMS (a, FreeVars)
-  -- Find the type variables in the pattern type 
-  -- signatures that must be brought into scope
-bindPatSigTyVars tys thing_inside
-  = getLocalNameEnv			`thenRn` \ name_env ->
-    let
-	forall_tyvars  = [ tv | ty <- tys, tv <- extractHsTyRdrTyVars ty, not (tv `elemFM` name_env)]
-	doc_sig        = text "In a pattern type-signature"
-    in
-    bindNakedTyVarsFVRn doc_sig forall_tyvars thing_inside
 \end{code}
 
+
 %************************************************************************
 %*									*
 \subsubsection{Guarded right-hand sides (GRHSs)}
-- 
1.7.10.4