breadth_first_visit substitues null BFS visitor

[jeffythedragonslayer]

breadth_first_visit ignores the visitor object passed in and uses a null one instead. To recreate:

#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/properties.hpp>
#include <boost/graph/breadth_first_search.hpp>
#include <iostream>
using namespace std;

typedef boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS, boost::property<boost::vertex_index_t, uint>, boost::property<boost::edge_index_t, uint>> Graph;
typedef boost::graph_traits<Graph>::vertex_descriptor                       vertex_t;
typedef boost::graph_traits<Graph>::edge_descriptor                         edge_t;
typedef boost::graph_traits<Graph>::vertex_descriptor                       vertex_t;


struct CollectBFSVisitor : public boost::default_bfs_visitor
{
        virtual void initialize_vertex(vertex_t v, Graph const& g) {cout << "init vertex\n";};
        virtual void discover_vertex(vertex_t v, Graph const& g) {};
        virtual void examine_vertex(vertex_t v, Graph const& g) {};
        virtual void finish_vertex(vertex_t v, Graph const& g) {};
        virtual void black_target(edge_t, Graph const& g) {};
        virtual void gray_target(edge_t, Graph const& g) {};
        virtual void tree_target(edge_t, Graph const& g) {};
        virtual void tree_edge(edge_t, Graph const& g) {};
        virtual void non_tree_edge(edge_t, Graph const& g) {};
};

struct VertBuffer : boost::queue<vertex_t>
{
};

int main()
{
        Graph g;
        vertex_t x = add_vertex(g);
        auto indexmap = boost::get(boost::vertex_index, g);
        auto colormap = boost::make_vector_property_map<boost::default_color_type>(indexmap);

        VertBuffer q;

        CollectBFSVisitor v;
        breadth_first_visit(g, x, q, v, colormap); // the cout doesn't run, but if you change it to breadth_first_search it does
}

Problem line in boost/graph/breadth_first_search.hpp

breadth_first_visit
  (ng, s,
   choose_param(get_param(params, buffer_param_t()), boost::ref(Q)).get(),
   choose_param(get_param(params, graph_visitor),
                make_bfs_visitor(null_visitor())),
   choose_pmap(get_param(params, vertex_color), ng, vertex_color)
   );

[jeffythedragonslayer]

My bad, I tried putting in a cout << "discover vertex\n"; and found that the visitor object is in fact not being ignored. The line from breadth_first_search.hpp I posted seems to choose a default visitor if none was provided.