private <T> void processSet(Object impl) {
   Field f = builder.map.get(impl);
   if (f == null) {
       /* throw */
     throw new ClassHierarchyException(
         "Unknown Impl/Param when setting "
             + ReflectionUtilities.getSimpleName(impl.getClass())
             + ".  Did you pass in a field from some other module?");
   }
   if (!reqSet.contains(f)) {
     reqSet.add(f);
   }
 }