C++ version of PackedRtree violates rule of three

[district10]

I'm using PackedRTree as spatial index, demo code:

struct GeojsonWithAutoSpatialIndex {
	std::vector<int> query_by_bbox(double xmin, double ymin, double ymin, double ymax) const {
		auto &tree = this->tree(); // rebuild spatial index if needed
		auto hits = tree.search(...); // not working, always empty hits
		...
	}

	void add_feature(...) {
		// ...
		tree_.reset(); // reset spatial index
	}
	void remove_feature(...);

private:
	FeatureCollection features;
	// auto spatial index
	mutable std::optional<PackedRtree> tree_;
	PackedRtree &tree() const {
		if (!tree_) {
			// code to build rtree from features here
			// ...
			tree_ = PackedRTree(nodes, extent); // BAD CODE HERE
		}
		return *tree_;
	}
};

I've already tested PackedRTree in other projects and it works well. But in this case, it's not working.

Strugged for a while, I find that PackedRTree violates rule of three.

PackedRTree should disable copy (like boost:noncopyable), or implement proper deepcopy (handle NodeItem *_nodeItems).

Or make it value semantic (cubao/headers#17).

[bjornharrtell]

Thanks for noticing @district10, I think prefer the value semantic fix.