[project @ 1997-06-05 19:55:57 by sof]

Only generate tag2con for data cons (not newtypes)

diff --git a/ghc/compiler/typecheck/TcDeriv.lhs b/ghc/compiler/typecheck/TcDeriv.lhs
index e54b7af..c3a7dc8 100644 (file)
--- a/ghc/compiler/typecheck/TcDeriv.lhs
+++ b/ghc/compiler/typecheck/TcDeriv.lhs
@@ -52,7 +52,7 @@ import Pretty         ( ($$), vcat, hsep, hcat,
                          ptext, text, char, hang, Doc )
 import SrcLoc          ( mkGeneratedSrcLoc, SrcLoc )
 import TyCon           ( tyConTyVars, tyConDataCons, tyConDerivings,
-                         tyConTheta, maybeTyConSingleCon,
+                         tyConTheta, maybeTyConSingleCon, isDataTyCon,
                          isEnumerationTyCon, isAlgTyCon, TyCon
                        )
 import Type            ( GenType(..), SYN_IE(TauType), mkTyVarTys, applyTyCon,
@@ -678,17 +678,18 @@ gen_taggery_Names inst_infos
     (tycons_of_interest, _) = removeDups cmp all_tycons
     
     do_con2tag acc_Names tycon
-      = if (we_are_deriving eqClassKey tycon
+      | isDataTyCon tycon &&
+        (we_are_deriving eqClassKey tycon
            && any isNullaryDataCon (tyConDataCons tycon))
-       || (we_are_deriving ordClassKey  tycon
+        || (we_are_deriving ordClassKey  tycon
            && not (maybeToBool (maybeTyConSingleCon tycon)))
-       || (we_are_deriving enumClassKey tycon)
-       || (we_are_deriving ixClassKey   tycon)
-       then
-         returnTc ((con2tag_RDR tycon, tycon, GenCon2Tag)
+        || (we_are_deriving enumClassKey tycon)
+        || (we_are_deriving ixClassKey   tycon)
+       
+      = returnTc ((con2tag_RDR tycon, tycon, GenCon2Tag)
                   : acc_Names)
-       else
-         returnTc acc_Names
+      | otherwise
+      = returnTc acc_Names
 
     do_tag2con acc_Names tycon
       = if (we_are_deriving enumClassKey tycon)