Suspicious invocation of the 'IEnumerable<T>.Union' method

[VasilievSerg]

Hi,
I found the suspicious code via the PVS-Studio analyzer.

Here is the code:

...
case ShardId shardId:
  _shards.Add(shardId); // <=
  return true;
case SnapshotOffer offer when (offer.Snapshot is ShardCoordinator.CoordinatorState state):
  _shards.UnionWith(state.Shards.Keys.Union(state.UnallocatedShards)); // <=
  return true;
case SnapshotOffer offer when (offer.Snapshot is State state):
  _shards.Union(state.Shards); // <=
...

Here is the link to the sources.

Several methods were called for the _shards variable. The last invocation looks suspicious.

Add and UnionWith are methods of the HashSet<T> type. They change the _shards object state. But Union is the extension method which does not change the _shards state. The result of this invocation is not used as well.

[Aaronontheweb]

Ah, so this is on the brand new 1.5 code - interesting, we'll take a look.

[Aaronontheweb]

cc @zbynek001 - is this something I overlooked during the PR review on the sharding storage update?