Corrected freeze

Author: papafe

src/MongoDB.Bson/Serialization/BsonClassMap.cs

@@ -405,24 +405,24 @@ internal class FreezeContext
         {
             public int FreezeNestingLevel { get; set; } = 0;
             public Queue<Type> KnownTypesQueue { get; set; } = new();
-            public IBsonSerializationDomain SerializationDomain { get; set; }
+            public IBsonSerializationDomainInternal SerializationDomain { get; set; }
         }
 
         /// <summary>
         /// Freezes the class map.
         /// </summary>
         /// <returns>The frozen class map.</returns>
-        public BsonClassMap Freeze() => Freeze(BsonSerializer.DefaultSerializationDomain);
+        public BsonClassMap Freeze() => Freeze(BsonSerializer.DefaultSerializationDomain as IBsonSerializationDomainInternal);
 
-        internal BsonClassMap Freeze(IBsonSerializationDomain domain)
+        internal BsonClassMap Freeze(IBsonSerializationDomainInternal domain)
         {
             var freezeContext = new FreezeContext { SerializationDomain = domain };
             return Freeze(freezeContext);
         }
 
         private BsonClassMap Freeze(FreezeContext context)  //TODO This is not completely correct, because LookupClassMap calls freeze
         {
-            var configLock = (context.SerializationDomain as IBsonSerializationDomainInternal)!.ConfigLock;  //TODO This is ugly
+            var configLock = context.SerializationDomain!.ConfigLock;
             configLock.EnterReadLock();
             try
             {

src/MongoDB.Bson/Serialization/BsonClassMapDomain.cs

@@ -100,7 +100,7 @@ public BsonClassMap LookupClassMap(Type classType)
                 classMap = newClassMap;
             }
 
-            return classMap.Freeze();
+            return classMap.Freeze(_serializationDomain);
         }
         finally
         {