Improve a few cases of collecting to an FxHash(Map/Set)

1 files changed, 1 insertions, 4 deletions

diff --git a/src/librustc/infer/lexical_region_resolve/graphviz.rs b/src/librustc/infer/lexical_region_resolve/graphviz.rs
index 3b92d032bdc..a210d63f129 100644
--- a/src/librustc/infer/lexical_region_resolve/graphviz.rs
+++ b/src/librustc/infer/lexical_region_resolve/graphviz.rs
@@ -230,10 +230,7 @@ impl<'a, 'gcx, 'tcx> dot::GraphWalk<'a> for ConstraintGraph<'a, 'gcx, 'tcx> {
     type Node = Node;
     type Edge = Edge<'tcx>;
     fn nodes(&self) -> dot::Nodes<'_, Node> {
-        let mut set = FxHashSet::default();
-        for node in self.node_ids.keys() {
-            set.insert(*node);
-        }
+        let set = self.node_ids.keys().cloned().collect::<FxHashSet<_>>();
         debug!("constraint graph has {} nodes", set.len());
         set.into_iter().collect()
     }