virtual bool Equals(const ParamIteratorInterface<ParamType>& other) const {
      // Having the same base generator guarantees that the other
      // iterator is of the same type and we can downcast.
      GTEST_CHECK_(BaseGenerator() == other.BaseGenerator())
          << "The program attempted to compare iterators "
          << "from different generators." << std::endl;
      const Iterator* typed_other =

  // like writing 'WithParamInterface<bool>::GetParam()' for a test that
  // uses a fixture whose parameter type is int.
  const ParamType& GetParam() const {
    GTEST_CHECK_(parameter_ != NULL)
        << "GetParam() can only be called inside a value-parameterized test "
        << "-- did you intend to write TEST_P instead of TEST_F?";
    return *parameter_;
  }

 private:

  // like writing 'WithParamInterface<bool>::GetParam()' for a test that
  // uses a fixture whose parameter type is int.
  const ParamType& GetParam() const {
    GTEST_CHECK_(parameter_ != NULL)
        << "GetParam() can only be called inside a value-parameterized test "
        << "-- did you intend to write TEST_P instead of TEST_F?";
    return *parameter_;
  }

 private: