From 435c21ed6a0f4be11e4e94055fc4b8bc3deff08f Mon Sep 17 00:00:00 2001
From: simonm <unknown>
Date: Fri, 7 May 1999 11:31:12 +0000
Subject: [PATCH] [project @ 1999-05-07 11:31:12 by simonm] Don't try to make
 a tag2con function if we're deriving Ix on a
 single-constructor datatype (it isn't needed, and will
 probably be type-incorrect anyway).

---
 ghc/compiler/typecheck/TcDeriv.lhs |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/ghc/compiler/typecheck/TcDeriv.lhs b/ghc/compiler/typecheck/TcDeriv.lhs
index 9e9a79a..fa51901 100644
--- a/ghc/compiler/typecheck/TcDeriv.lhs
+++ b/ghc/compiler/typecheck/TcDeriv.lhs
@@ -670,7 +670,8 @@ gen_taggery_Names inst_infos
     do_tag2con acc_Names tycon
       | isDataTyCon tycon &&
          (we_are_deriving enumClassKey tycon ||
-	  we_are_deriving ixClassKey   tycon)
+	  we_are_deriving ixClassKey   tycon
+	  && isEnumerationTyCon tycon)
       = returnTc ( (tag2con_RDR tycon, tycon, GenTag2Con)
 		 : (maxtag_RDR  tycon, tycon, GenMaxTag)
 		 : acc_Names)
-- 
1.7.10.4