public static boolean processAddition(
     final MMenu menuModel,
     final ArrayList<MMenuElement> menuContributionsToRemove,
     MMenuContribution menuContribution,
     final HashSet<String> existingMenuIds,
     HashSet<String> existingSeparatorNames) {
   int idx = getIndex(menuModel, menuContribution.getPositionInParent());
   if (idx == -1) {
     return false;
   }
   for (MMenuElement item : menuContribution.getChildren()) {
     if (item instanceof MMenu && existingMenuIds.contains(item.getElementId())) {
       // skip this, it's already there
       continue;
     } else if (item instanceof MMenuSeparator
         && existingSeparatorNames.contains(item.getElementId())) {
       // skip this, it's already there
       continue;
     }
     MMenuElement copy = (MMenuElement) EcoreUtil.copy((EObject) item);
     if (DEBUG) {
       trace("addMenuContribution " + copy, menuModel.getWidget(), menuModel); // $NON-NLS-1$
     }
     menuContributionsToRemove.add(copy);
     menuModel.getChildren().add(idx++, copy);
     if (copy instanceof MMenu && copy.getElementId() != null) {
       existingMenuIds.add(copy.getElementId());
     } else if (copy instanceof MMenuSeparator && copy.getElementId() != null) {
       existingSeparatorNames.add(copy.getElementId());
     }
   }
   return true;
 }
 public MenuKey(MMenuContribution mc) {
   super(
       mc.getParentId(),
       mc.getPositionInParent(),
       mc.getTags(),
       (MCoreExpression) mc.getVisibleWhen(),
       mc.getTransientData().get(FACTORY));
   this.contribution = mc;
   mc.setWidget(this);
 }