src/Pure/General/json.scala

   type S = String
 
   object Object
   {
     type T = Map[String, JSON.T]
-    val empty: T = Map.empty
+    val empty: Object.T = Map.empty
+
+    def apply(entries: (String, JSON.T)*): Object.T = Map(entries:_*)
 
     def unapply(obj: T): Option[Object.T] =
       obj match {
         case m: Map[_, _] if m.keySet.forall(_.isInstanceOf[String]) =>
           Some(m.asInstanceOf[Object.T])

 
   /* object values */
 
   def optional(entry: (String, Option[T])): Object.T =
     entry match {
-      case (name, Some(x)) => Map(name -> x)
+      case (name, Some(x)) => Object(name -> x)
       case (_, None) => Object.empty
     }
 
   def value(obj: T, name: String): Option[T] =
     obj match {