message: Collapse A* visit/is_visited calls
diff: @@ -55,12 +55,10 @@ pub fn astar<G, F, H, K>(graph: G, start: G::NodeId, finish: G::NodeId,
  // Don't visit the same node several times, as the first time it was visited it was using
  // the shortest available path.
  - if visited.is_visited(&node) {
  + if !visited.visit(node) {
  continue
  }
  - visited.visit(node);
  -
  // This lookup can be unwrapped without fear of panic since the node was necessarily scored
  // before adding him to `visit_next`.
  let node_score = *scores.get(&node).unwrap();
  