Address warnings and (some) nullables (#2013)

src/Microsoft.SqlTools.ManagedBatchParser/BatchParser/BatchParserWrapper.cs

@@ -408,7 +408,7 @@ namespace Microsoft.SqlTools.ServiceLayer.BatchParser
         /// <summary>
         /// Internal implementation class to implement IBatchEventHandlers
         /// </summary>
-        internal class BatchEventNotificationHandler : IBatchEventsHandler
+        internal sealed class BatchEventNotificationHandler : IBatchEventsHandler
         {
             public void OnBatchError(object sender, BatchErrorEventArgs args)
             {
@@ -477,7 +477,7 @@ namespace Microsoft.SqlTools.ServiceLayer.BatchParser
         }
         #endregion
 
-        private class BatchInfo
+        private sealed class BatchInfo
         {
             public BatchInfo(int startLine, int startColumn, string batchText, SqlCmdCommand sqlCmdCommand, int repeatCount = 1)
             {

src/Microsoft.SqlTools.ManagedBatchParser/Microsoft.SqlTools.ManagedBatchParser.csproj

@@ -32,7 +32,7 @@
 		<Version>$(VersionPrefix)</Version>
 		<FileVersion>$(VersionPrefix)</FileVersion>
 		<InformationalVersion>$(VersionPrefix)</InformationalVersion>
-		<!-- TODO FIX THESE WARNINGS ASAP -->
+		<!-- Disable CA1852 (Seal internal types) as it depends on SrGen Tool -->
 		<NoWarn>$(NoWarn);CA1852</NoWarn>
 	</PropertyGroup>
 	<ItemGroup>

src/Microsoft.SqlTools.ManagedBatchParser/ReliableConnection/AmbientSettings.cs

@@ -374,7 +374,7 @@ namespace Microsoft.SqlTools.ServiceLayer.Connection.ReliableConnection
         /// <summary>
         /// This class is used as value in the dictionary to ensure that the type of value is correct.
         /// </summary>
-        private class AmbientValue
+        private sealed class AmbientValue
         {
             private readonly Type _type;
             private readonly bool _isTypeNullable;

src/Microsoft.SqlTools.ManagedBatchParser/ReliableConnection/CachedServerInfo.cs

@@ -45,7 +45,7 @@ namespace Microsoft.SqlTools.ServiceLayer.Connection.ReliableConnection
         }
 
         #region CacheKey implementation
-        internal class CacheKey : IEquatable<CacheKey>
+        internal sealed class CacheKey : IEquatable<CacheKey>
         {
             private string dataSource;
             private string dbName;

src/Microsoft.SqlTools.ManagedBatchParser/ReliableConnection/RetryPolicy.cs

@@ -407,7 +407,7 @@ namespace Microsoft.SqlTools.ServiceLayer.Connection.ReliableConnection
             }
         }
 
-        internal class ExponentialDelayRetryPolicy : RetryPolicy
+        internal sealed class ExponentialDelayRetryPolicy : RetryPolicy
         {
             private readonly int _maxRetryCount;
             private readonly double _intervalFactor;