protected boolean preprocessUsages(Ref<UsageInfo[]> refUsages) {
    final MultiMap<PsiElement, String> conflicts = new MultiMap<PsiElement, String>();

    checkExistingMethods(conflicts, true);
    checkExistingMethods(conflicts, false);
    final Collection<PsiClass> classes = ClassInheritorsSearch.search(myClass).findAll();
    for (FieldDescriptor fieldDescriptor : myFieldDescriptors) {
      final Set<PsiMethod> setters = new HashSet<PsiMethod>();
      final Set<PsiMethod> getters = new HashSet<PsiMethod>();

      for (PsiClass aClass : classes) {
        final PsiMethod getterOverrider =
            myDescriptor.isToEncapsulateGet()
                ? aClass.findMethodBySignature(fieldDescriptor.getGetterPrototype(), false)
                : null;
        if (getterOverrider != null) {
          getters.add(getterOverrider);
        }
        final PsiMethod setterOverrider =
            myDescriptor.isToEncapsulateSet()
                ? aClass.findMethodBySignature(fieldDescriptor.getSetterPrototype(), false)
                : null;
        if (setterOverrider != null) {
          setters.add(setterOverrider);
        }
      }
      if (!getters.isEmpty() || !setters.isEmpty()) {
        final PsiField field = fieldDescriptor.getField();
        for (PsiReference reference : ReferencesSearch.search(field)) {
          final PsiElement place = reference.getElement();
          if (place instanceof PsiReferenceExpression) {
            final PsiExpression qualifierExpression =
                ((PsiReferenceExpression) place).getQualifierExpression();
            final PsiClass ancestor;
            if (qualifierExpression == null) {
              ancestor = PsiTreeUtil.getParentOfType(place, PsiClass.class, false);
            } else {
              ancestor = PsiUtil.resolveClassInType(qualifierExpression.getType());
            }

            final boolean isGetter = !PsiUtil.isAccessedForWriting((PsiExpression) place);
            for (PsiMethod overridden : isGetter ? getters : setters) {
              if (InheritanceUtil.isInheritorOrSelf(myClass, ancestor, true)) {
                conflicts.putValue(
                    overridden,
                    "There is already a "
                        + RefactoringUIUtil.getDescription(overridden, true)
                        + " which would hide generated "
                        + (isGetter ? "getter" : "setter")
                        + " for "
                        + place.getText());
                break;
              }
            }
          }
        }
      }
    }
    return showConflicts(conflicts, refUsages.get());
  }