fix: address SubList code review findings

src/NATS.Server/Subscriptions/SubList.cs

@@ -6,16 +6,17 @@ namespace NATS.Server.Subscriptions;
 /// interested subscribers. Subscribers can have wildcard subjects to
 /// match multiple published subjects.
 /// </summary>
-public sealed class SubList
+public sealed class SubList : IDisposable
 {
     private const int CacheMax = 1024;
     private const int CacheSweep = 256;
 
     private readonly ReaderWriterLockSlim _lock = new();
     private readonly TrieLevel _root = new();
-    private Dictionary<string, SubListResult>? _cache = new();
+    private Dictionary<string, SubListResult>? _cache = new(StringComparer.Ordinal);
     private uint _count;
-    private ulong _genId;
+
+    public void Dispose() => _lock.Dispose();
 
     public uint Count
     {
@@ -84,7 +85,6 @@ public sealed class SubList
             }
 
             _count++;
-            _genId++;
             AddToCache(subject, sub);
         }
         finally
@@ -131,7 +131,9 @@ public sealed class SubList
 
                 var tokenStr = token.ToString();
                 pathList.Add((level, node, tokenStr, isPwc, isFwc));
-                level = node.Next ?? new TrieLevel();
+                if (node.Next == null)
+                    return; // corrupted trie state
+                level = node.Next;
             }
 
             if (node == null) return;
@@ -156,7 +158,6 @@ public sealed class SubList
             if (!removed) return;
 
             _count--;
-            _genId++;
             RemoveFromCache(sub.Subject);
 
             // Prune empty nodes (walk backwards)
@@ -216,9 +217,13 @@ public sealed class SubList
             }
             else
             {
+                var queueSubsArr = new Subscription[queueSubs.Count][];
+                for (int i = 0; i < queueSubs.Count; i++)
+                    queueSubsArr[i] = queueSubs[i].ToArray();
+
                 result = new SubListResult(
                     plainSubs.ToArray(),
-                    queueSubs.Select(q => q.ToArray()).ToArray());
+                    queueSubsArr);
             }
 
             if (_cache != null)
@@ -498,7 +503,7 @@ public sealed class SubList
 
     private sealed class TrieLevel
     {
-        public readonly Dictionary<string, TrieNode> Nodes = new();
+        public readonly Dictionary<string, TrieNode> Nodes = new(StringComparer.Ordinal);
         public TrieNode? Pwc; // partial wildcard (*)
         public TrieNode? Fwc; // full wildcard (>)
     }
@@ -507,7 +512,7 @@ public sealed class SubList
     {
         public TrieLevel? Next;
         public readonly HashSet<Subscription> PlainSubs = [];
-        public readonly Dictionary<string, HashSet<Subscription>> QueueSubs = new();
+        public readonly Dictionary<string, HashSet<Subscription>> QueueSubs = new(StringComparer.Ordinal);
 
         public bool IsEmpty => PlainSubs.Count == 0 && QueueSubs.Count == 0 &&
                                (Next == null || (Next.Nodes.Count == 0 && Next.Pwc == null && Next.Fwc == null));