static @Nullable PsiReferenceExpression createMockReference(PsiElement place, @NotNull PsiType qualifierType, LookupElement qualifierItem, String separator) {
    PsiElementFactory factory = JavaPsiFacade.getElementFactory(place.getProject());
    if (qualifierItem.getObject() instanceof PsiClass) {
      final String qname = ((PsiClass)qualifierItem.getObject()).getQualifiedName();
      if (qname == null) return null;

      String text = qname + separator + "xxx";
      try {
        final PsiExpression expr = factory.createExpressionFromText(text, place);
        if (expr instanceof PsiReferenceExpression) {
          return (PsiReferenceExpression)expr;
        }
        return null; // ignore ill-formed qualified names like "org.spark-project.jetty" that can't be used from Java code anyway
      }
      catch (IncorrectOperationException e) {
        LOG.info(e);
        return null;
      }
    }

    return (PsiReferenceExpression) factory.createExpressionFromText("xxx" + separator + "xxx", JavaCompletionUtil
      .createContextWithXxxVariable(place, qualifierType));
  }
static @Nullable PsiReferenceExpression createMockReference(PsiElement place, @NotNull PsiType qualifierType, LookupElement qualifierItem, String separator)