Extcore can now handle data types without constructors

compiler/coreSyn/MkExternalCore.lhs

@@ -64,7 +64,8 @@ collect_tdefs tcon tdefs
   where
     tdef | isNewTyCon tcon = 
                 C.Newtype (make_con_qid (tyConName tcon)) (map make_tbind tyvars) repclause 
-         | null (tyConDataCons tcon) = error "MkExternalCore died: can't handle datatype declarations with no data constructors"
+-- 20060420 GHC handles empty data types just fine. ExtCore should too! jds
+--         | null (tyConDataCons tcon) = error "MkExternalCore died: can't handle datatype declarations with no data constructors"
          | otherwise = 
                 C.Data (make_con_qid (tyConName tcon)) (map make_tbind tyvars) (map make_cdef (tyConDataCons tcon)) 
          where repclause | isRecursiveTyCon tcon = Nothing

compiler/parser/ParserCore.y

@@ -82,7 +82,7 @@ tdefs	:: { [TyClDecl RdrName] }
 	| tdef ';' tdefs	{$1:$3}
 
 tdef	:: { TyClDecl RdrName }
-	: '%data' q_tc_name tv_bndrs '=' '{' cons1 '}'
+	: '%data' q_tc_name tv_bndrs '=' '{' cons '}'
                 { mkTyData DataType (noLoc [], noLoc (ifaceExtRdrName $2), map toHsTvBndr $3) Nothing $6 Nothing }
 	| '%newtype' q_tc_name tv_bndrs trep 
 		{ let tc_rdr = ifaceExtRdrName $2 in
@@ -97,9 +97,9 @@ trep    :: { OccName -> [LConDecl RdrName] }
 			                in [noLoc $ ConDecl (noLoc dc_name) Explicit []
 					   (noLoc []) con_info ResTyH98]) }
 
-cons1	:: { [LConDecl RdrName] }
-	: con		{ [$1] }
-	| con ';' cons1	{ $1:$3 }
+cons	:: { [LConDecl RdrName] }
+	: {- empty -}	{ [] } -- 20060420 Empty data types allowed. jds
+	| con ';' cons	{ $1:$3 }
 
 con	:: { LConDecl RdrName }
 	: d_pat_occ attv_bndrs hs_atys