Example of use of default specifier that fails to compile.

defaulted_stuff.cc

/**
 * \brief Class to represent a feature track.
 */
class FeatureTrack final {
 public:
  explicit FeatureTrack(const uint32_t id = 0, const uint32_t img_idx = 0,
                        const cv::Point2f& feat = cv::Point2f()) :
    id(id),
    pos(1, feat),
    img(1, img_idx) {}

  ~FeatureTrack() = default;

  FeatureTrack(const FeatureTrack& rhs) = default;
  FeatureTrack& operator=(const FeatureTrack& rhs) = default;

  FeatureTrack(const FeatureTrack&& rhs) = default;
  FeatureTrack& operator=(const FeatureTrack&& rhs) = default;

  uint32_t id; // Track id.
  std::vector<uint32_t> img; // Image indices.
  std::vector<cv::Point2f> pos; // Feature positions.
};

Compiler output:

/home/wng/Projects/rrg/rrg/src/perception/depthest/src/depthest/feature_track.h:27:3: error: defaulted declaration ‘depthest::FeatureTrack::FeatureTrack(const depthest::FeatureTrack&&)’
   FeatureTrack(const FeatureTrack&& rhs) = default;
   ^
/home/wng/Projects/rrg/rrg/src/perception/depthest/src/depthest/feature_track.h:27:3: error: does not match expected signature ‘depthest::FeatureTrack::FeatureTrack(depthest::FeatureTrack&&)’
/home/wng/Projects/rrg/rrg/src/perception/depthest/src/depthest/feature_track.h:28:17: error: defaulted declaration ‘depthest::FeatureTrack& depthest::FeatureTrack::operator=(const depthest::FeatureTrack&&)’
   FeatureTrack& operator=(const FeatureTrack&& rhs) = default;
                 ^
/home/wng/Projects/rrg/rrg/src/perception/depthest/src/depthest/feature_track.h:28:17: error: does not match expected signature ‘depthest::FeatureTrack& depthest::FeatureTrack::operator=(depthest::FeatureTrack&&)’
In file included from /home/wng/Projects/rrg/rrg/src/perception/depthest/src/depthest/feature_tracker.h:10:0,
                 from /home/wng/Projects/rrg/rrg/src/perception/depthest/src/depthest/klt_feature_tracker.h:13,
                 from /home/wng/Projects/rrg/rrg/src/perception/depthest/src/depthest/klt_feature_tracker.cc:3:
/home/wng/Projects/rrg/rrg/src/perception/depthest/src/depthest/feature_track.h:27:3: error: defaulted declaration ‘depthest::FeatureTrack::FeatureTrack(const depthest::FeatureTrack&&)’
   FeatureTrack(const FeatureTrack&& rhs) = default;
   ^
/home/wng/Projects/rrg/rrg/src/perception/depthest/src/depthest/feature_track.h:27:3: error: does not match expected signature ‘depthest::FeatureTrack::FeatureTrack(depthest::FeatureTrack&&)’
/home/wng/Projects/rrg/rrg/src/perception/depthest/src/depthest/feature_track.h:28:17: error: defaulted declaration ‘depthest::FeatureTrack& depthest::FeatureTrack::operator=(const depthest::FeatureTrack&&)’
   FeatureTrack& operator=(const FeatureTrack&& rhs) = default;
                 ^
/home/wng/Projects/rrg/rrg/src/perception/depthest/src/depthest/feature_track.h:28:17: error: does not match expected signature ‘depthest::FeatureTrack& depthest::FeatureTrack::operator=(depthest::FeatureTrack&&)’

For future reference this fails because the arguments to the move constructor and assignment operator are const (which doesn't make any sense given what they're supposed to do).