Re: iterator problem

Here is graph.hh
#ifndef GRAPH_HH
#define GRAPH_HH 1

#include <list>
#include <vector>
#include <cstddef>

std::list<int>::iterator it;

template<class NodeData, class EdgeData, typename NodeIndex=size_t>
                                                       class Graph {
public:
     struct Edge {
         NodeIndex lo, hi;
         EdgeData *data;

         Edge() : lo(0), hi(0), data(0) {}
     } ;

     class Node {
         std::list<Edge> edges;
         NodeData *data;
     } ;

     std::list<int >::iterator works;

     int fred;

     std::list<Edge>::iterator help;

private:
     std::vector<Node> nodes;

public:
     Graph(NodeIndex nodesNum) : nodes(nodesNum) {}

     void setNodeData(NodeIndex ni, NodeData *nd)
                             { nodes[ni].data=nd; }
     NodeData *getNodeData(NodeIndex ni) const
                      { return nodes[ni].data; }

} ; // Graph

#endif

Here is the error message when graph-test.cc #includes it
In file included from graph-test.cc:1:
graph.hh:29: error: type ?std::list<Graph<NodeData, EdgeData, NodeIndex>::Edge, std::allocator<Graph<NodeData, EdgeData, NodeIndex>::Edge> >? is not derived from type ?Graph<NodeData, EdgeData, NodeIndex>?
graph.hh:29: error: expected ?;? before ?help?

Note that my first use of iterator works.
What is the matter with std::list<Edge>::iterator
that is not the matter with std::list<int >::iterator ?