From 0f098b75c81e884a445654b2fe097ee247436ee1 Mon Sep 17 00:00:00 2001
From: simonpj <unknown>
Date: Mon, 5 Apr 2004 10:26:28 +0000
Subject: [PATCH] [project @ 2004-04-05 10:26:28 by simonpj] Don't convert
 Exact RdrNames into Orig ones when comparing RdrNames. This
 implicit conversion (via nukeExact) was making the
 carefully-distinct RdrNames conjured up by Template Haskell
 into the same RdrName, and that in turn was reporting
 duplicate bindings.

I'm not 100% certain that the implicit conversion isn't needed
for some other purpose, but it seems unclean anyway, so I'm removing
it, and we'll see if anything else breaks.
---
 ghc/compiler/basicTypes/RdrName.lhs |   33 ++++++++++++++++++++-------------
 1 file changed, 20 insertions(+), 13 deletions(-)

diff --git a/ghc/compiler/basicTypes/RdrName.lhs b/ghc/compiler/basicTypes/RdrName.lhs
index d858dbc..e84a391 100644
--- a/ghc/compiler/basicTypes/RdrName.lhs
+++ b/ghc/compiler/basicTypes/RdrName.lhs
@@ -86,7 +86,7 @@ data RdrName
 	--  (b) when converting names to the RdrNames in IfaceTypes
 	--	Here an Exact RdrName always contains an External Name
 	--	(Internal Names are converted to simple Unquals)
-	--  (c) possibly, by the meta-programming stuff
+	--  (c) by Template Haskell, when TH has generated a unique name
 \end{code}
 
 
@@ -234,21 +234,28 @@ instance Ord RdrName where
     a >= b = case (a `compare` b) of { LT -> False; EQ -> True;  GT -> True  }
     a >	 b = case (a `compare` b) of { LT -> False; EQ -> False; GT -> True  }
 
-	-- Unqual < Qual < Orig
-	-- We always convert Exact to Orig before comparing
-    compare (Exact n1) (Exact n2) | n1==n2 = EQ	-- Short cut
-				  | otherwise = nukeExact n1 `compare` nukeExact n2
-    compare (Exact n1) n2	  	      = nukeExact n1 `compare` n2
-    compare n1	      (Exact n2)  	      = n1 `compare` nukeExact n2
-
-
-    compare (Qual m1 o1) (Qual m2 o2) = (o1 `compare` o2) `thenCmp` (m1 `compare` m2) 
-    compare (Orig m1 o1) (Orig m2 o2) = (o1 `compare` o2) `thenCmp` (m1 `compare` m2) 
+	-- Exact < Unqual < Qual < Orig
+	-- [Note: Apr 2004] We used to use nukeExact to convert Exact to Orig 
+	-- 	before comparing so that Prelude.map == the exact Prelude.map, but 
+	--	that meant that we reported duplicates when renaming bindings 
+	--	generated by Template Haskell; e.g 
+	--	do { n1 <- newName "foo"; n2 <- newName "foo"; 
+	--	     <decl involving n1,n2> }
+	--	I think we can do without this conversion
+    compare (Exact n1) (Exact n2) = n1 `compare` n2
+    compare (Exact n1) n2	  = LT
+
+    compare (Unqual _)   (Exact _)    = GT
     compare (Unqual o1)  (Unqual  o2) = o1 `compare` o2
- 
     compare (Unqual _)   _ 	      = LT
+
+    compare (Qual _ _)   (Exact _)    = GT
+    compare (Qual _ _)   (Unqual _)   = GT
+    compare (Qual m1 o1) (Qual m2 o2) = (o1 `compare` o2) `thenCmp` (m1 `compare` m2) 
     compare (Qual _ _)   (Orig _ _)   = LT
-    compare _		 _	      = GT
+
+    compare (Orig m1 o1) (Orig m2 o2) = (o1 `compare` o2) `thenCmp` (m1 `compare` m2) 
+    compare (Orig _ _)   _	      = GT
 \end{code}
 
 
-- 
1.7.10.4