message: Replace hashmap with hashset
  Better code
diff: @@ -234,27 +234,26 @@ impl<'a> Graph<'a> {
  let mut dupes: Vec<(&Node, usize)> = packages
  .into_iter()
  .filter(|(_name, indexes)| {
  - let mut pkg_map = HashMap::new();
  indexes
  .into_iter()
  - .filter(|(node, _)| {
  - // Do not treat duplicates on the host or target as duplicates.
  - let ignore_kind_package = match node {
  + .map(|(node, _)| {
  + match node {
  Node::Package {
  package_id,
  features,
  ..
  - } => Node::Package {
  + } => {
  + // Do not treat duplicates on the host or target as duplicates.
  + Node::Package {
  package_id: package_id.clone(),
  features: features.clone(),
  kind: CompileKind::Host,
  - },
  + }
  + }
  _ => unreachable!(),
  - };
  - !pkg_map.contains_key(&ignore_kind_package)
  - && pkg_map.insert(ignore_kind_package, ()).is_none()
  + }
  })
  - .collect::<Vec<&(&Node, usize)>>()
  + .collect::<HashSet<_>>()
  .len()
  > 1
  })
  