@Contract(pure=true)
  public @NotNull LookupElementBuilder appendTailText(@NotNull String tailText, boolean grayed) {
    final LookupElementPresentation presentation = copyPresentation();
    presentation.appendTailText(tailText, grayed);
    return cloneWithUserData(myLookupString, myObject, myInsertHandler, null, myExpensiveRenderer, presentation, myPsiElement,
                             myAllLookupStrings, myCaseSensitive);
  }
@Contract(pure=true)
  public @NotNull LookupElementBuilder appendTailText(@NotNull String tailText, boolean grayed)