Make callbackTarget required parameter.

src/EditorFeatures/Core.Wpf/SymbolSearch/SymbolSearchUpdateEngineFactory.cs

@@ -28,7 +28,7 @@ internal static partial class SymbolSearchUpdateEngineFactory
             if (client != null)
             {
                 var callbackObject = new CallbackObject(logService, progressService);
-                var session = await client.TryCreateKeepAliveSessionAsync(WellKnownServiceHubServices.RemoteSymbolSearchUpdateEngine, cancellationToken, callbackObject).ConfigureAwait(false);
+                var session = await client.TryCreateKeepAliveSessionAsync(WellKnownServiceHubServices.RemoteSymbolSearchUpdateEngine, callbackObject, cancellationToken).ConfigureAwait(false);
                 if (session != null)
                 {
                     return new RemoteUpdateEngine(workspace, session);

src/EditorFeatures/TestUtilities/Diagnostics/TestDiagnosticAnalyzerDriver.cs

@@ -145,6 +145,7 @@ private async Task SynchronizeGlobalAssetToRemoteHostIfNeededAsync(Workspace wor
                 nameof(IRemoteHostService.SynchronizeGlobalAssetsAsync),
                 workspace.CurrentSolution,
                 new[] { (object)checksums },
+                callbackTarget: null,
                 CancellationToken.None).ConfigureAwait(false);
         }
 

src/Features/Core/Portable/AddImport/AbstractAddImportFeatureService.cs

@@ -71,8 +71,8 @@ internal abstract partial class AbstractAddImportFeatureService<TSimpleNameSynta
                         searchReferenceAssemblies,
                         packageSources
                     },
-                    cancellationToken,
-                    callbackTarget).ConfigureAwait(false);
+                    callbackTarget,
+                    cancellationToken).ConfigureAwait(false);
 
                 if (result.HasValue)
                 {

src/Features/Core/Portable/Completion/Providers/ImportCompletionProvider/ExtensionMethodImportCompletionHelper.cs

@@ -50,6 +50,7 @@ async Task<(ImmutableArray<SerializableImportCompletionItem>, StatisticCounter)>
                         nameof(IRemoteExtensionMethodImportCompletionService.GetUnimportedExtensionMethodsAsync),
                         project.Solution,
                         new object[] { document.Id, position, SymbolKey.CreateString(receiverTypeSymbol), namespaceInScope.ToArray(), forceIndexCreation },
+                        callbackTarget: null,
                         cancellationToken).ConfigureAwait(false);
 
                     if (result.HasValue)

src/Features/Core/Portable/DesignerAttributes/AbstractDesignerAttributeService.cs

@@ -46,6 +46,7 @@ public async Task<DesignerAttributeResult> ScanDesignerAttributesAsync(Document
                         nameof(IRemoteDesignerAttributeService.ScanDesignerAttributesAsync),
                         document.Project.Solution,
                         new[] { document.Id },
+                        callbackTarget: null,
                         cancellationToken).ConfigureAwait(false);
 
                     if (result.HasValue)

src/Features/Core/Portable/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer.InProcOrRemoteHostAnalyzerRunner.cs

@@ -110,6 +110,7 @@ private async Task FireAndForgetReportAnalyzerPerformanceAsync(Project project,
                             // +1 for project itself
                             project.DocumentIds.Count + 1
                         },
+                        callbackTarget: null,
                         cancellationToken).ConfigureAwait(false);
                 }
                 catch (Exception ex) when (FatalError.ReportWithoutCrashUnlessCanceled(ex))
@@ -139,7 +140,7 @@ private async Task FireAndForgetReportAnalyzerPerformanceAsync(Project project,
                     forcedAnalysis, analyzerDriver.AnalysisOptions.ReportSuppressedDiagnostics, analyzerDriver.AnalysisOptions.LogAnalyzerExecutionTime,
                     project.Id, optionAsset.Checksum, analyzerMap.Keys.ToArray());
 
-                using var session = await client.TryCreateSessionAsync(WellKnownServiceHubServices.CodeAnalysisService, solution, cancellationToken).ConfigureAwait(false);
+                using var session = await client.TryCreateSessionAsync(WellKnownServiceHubServices.CodeAnalysisService, solution, callbackTarget: null, cancellationToken).ConfigureAwait(false);
                 if (session == null)
                 {
                     // session is not available

src/Features/Core/Portable/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer_IncrementalAnalyzer.cs

@@ -540,6 +540,7 @@ private async Task ReportAnalyzerPerformanceAsync(Document document, Compilation
                     WellKnownServiceHubServices.CodeAnalysisService,
                     nameof(IRemoteDiagnosticAnalyzerService.ReportAnalyzerPerformance),
                     new object[] { pooledObject.Object.ToAnalyzerPerformanceInfo(AnalyzerService), /* unit count */ 1 },
+                    callbackTarget: null,
                     cancellationToken).ConfigureAwait(false);
             }
             catch (Exception ex) when (FatalError.ReportWithoutCrashUnlessCanceled(ex))

src/Features/Core/Portable/DocumentHighlighting/AbstractDocumentHighlightsService.cs

@@ -40,6 +40,7 @@ internal abstract partial class AbstractDocumentHighlightsService : IDocumentHig
                         position,
                         documentsToSearch.Select(d => d.Id).ToArray()
                     },
+                    callbackTarget: null,
                     cancellationToken).ConfigureAwait(false);
 
                 if (result.HasValue)

src/Features/Core/Portable/NavigateTo/AbstractNavigateToSearchService.cs

@@ -41,6 +41,7 @@ internal abstract partial class AbstractNavigateToSearchService : INavigateToSea
                     nameof(IRemoteNavigateToSearchService.SearchDocumentAsync),
                     solution,
                     new object[] { document.Id, searchPattern, kinds.ToArray() },
+                    callbackTarget: null,
                     cancellationToken).ConfigureAwait(false);
 
                 if (result.HasValue)
@@ -66,6 +67,7 @@ internal abstract partial class AbstractNavigateToSearchService : INavigateToSea
                     nameof(IRemoteNavigateToSearchService.SearchProjectAsync),
                     solution,
                     new object[] { project.Id, priorityDocuments.Select(d => d.Id).ToArray(), searchPattern, kinds.ToArray() },
+                    callbackTarget: null,
                     cancellationToken).ConfigureAwait(false);
 
                 if (result.HasValue)

src/Features/Core/Portable/TodoComments/AbstractTodoCommentService.cs

@@ -51,7 +51,9 @@ public async Task<IList<TodoComment>> GetTodoCommentsAsync(Document document, IL
                         WellKnownServiceHubServices.CodeAnalysisService,
                         nameof(IRemoteTodoCommentService.GetTodoCommentsAsync),
                         document.Project.Solution,
-                        new object[] { document.Id, commentDescriptors }, cancellationToken).ConfigureAwait(false);
+                        new object[] { document.Id, commentDescriptors },
+                        callbackTarget: null,
+                        cancellationToken).ConfigureAwait(false);
 
                     if (result.HasValue)
                     {

src/VisualStudio/Core/Def/Implementation/CodeLens/RemoteCodeLensReferencesService.cs

@@ -42,6 +42,7 @@ public RemoteCodeLensReferencesService()
                         nameof(IRemoteCodeLensReferencesService.GetReferenceCountAsync),
                         solution,
                         new object[] { documentId, syntaxNode.Span, maxSearchResults },
+                        callbackTarget: null,
                         cancellationToken).ConfigureAwait(false);
 
                     if (result.HasValue)
@@ -88,6 +89,7 @@ public RemoteCodeLensReferencesService()
                         nameof(IRemoteCodeLensReferencesService.FindReferenceMethodsAsync),
                         solution,
                         new object[] { documentId, syntaxNode.Span },
+                        callbackTarget: null,
                         cancellationToken).ConfigureAwait(false);
 
                     if (result.HasValue)
@@ -118,6 +120,7 @@ public RemoteCodeLensReferencesService()
                         nameof(IRemoteCodeLensReferencesService.GetFullyQualifiedName),
                         solution,
                         new object[] { documentId, syntaxNode.Span },
+                        callbackTarget: null,
                         cancellationToken).ConfigureAwait(false);
 
                     if (result.HasValue)
@@ -251,6 +254,7 @@ private static string GetLineTextOrEmpty(TextLineCollection lines, int index)
                     nameof(IRemoteCodeLensReferencesService.FindReferenceLocationsAsync),
                     solution,
                     new object[] { documentId, syntaxNode.Span },
+                    callbackTarget: null,
                     cancellationToken).ConfigureAwait(false);
 
                 if (result.HasValue)

src/VisualStudio/Core/Def/Implementation/Remote/RemoteHostClientServiceFactory.RemoteHostClientService.cs

@@ -210,6 +210,7 @@ private async Task<RemoteHostClient> EnableAsync(CancellationToken cancellationT
                         nameof(IRemoteHostService.SynchronizeGlobalAssetsAsync),
                         _workspace.CurrentSolution,
                         new[] { (object)checksums },
+                        callbackTarget: null,
                         cancellationToken).ConfigureAwait(false);
 
                     if (success)

src/VisualStudio/Core/Def/Implementation/Remote/RemoteHostClientServiceFactory.SolutionChecksumUpdater.cs

@@ -184,8 +184,11 @@ private void PushTextChanges(Document oldDocument, Document newDocument)
                     var state = await oldDocument.State.GetStateChecksumsAsync(CancellationToken).ConfigureAwait(false);
 
                     _ = await client.TryRunRemoteAsync(
-                        WellKnownRemoteHostServices.RemoteHostService, nameof(IRemoteHostService.SynchronizeTextAsync),
-                        new object[] { oldDocument.Id, state.Text, textChanges }, CancellationToken).ConfigureAwait(false);
+                        WellKnownRemoteHostServices.RemoteHostService,
+                        nameof(IRemoteHostService.SynchronizeTextAsync),
+                        new object[] { oldDocument.Id, state.Text, textChanges },
+                        callbackTarget: null,
+                        CancellationToken).ConfigureAwait(false);
 
                 }, CancellationToken).CompletesAsyncOperation(token);
             }

src/VisualStudio/Core/Def/Implementation/Remote/ServiceHubRemoteHostClient.cs

@@ -40,7 +40,7 @@ private enum GlobalNotificationState
         /// stop prior to hearing about the relevant start).
         /// </summary>
         private readonly object _globalNotificationsGate = new object();
-        private readonly Task<GlobalNotificationState> _globalNotificationsTask = Task.FromResult(GlobalNotificationState.NotStarted);
+        private Task<GlobalNotificationState> _globalNotificationsTask = Task.FromResult(GlobalNotificationState.NotStarted);
 
         public static async Task<ServiceHubRemoteHostClient?> CreateAsync(Workspace workspace, CancellationToken cancellationToken)
         {

src/VisualStudio/Core/Test.Next/Remote/RemoteHostClientServiceFactoryTests.cs

@@ -157,7 +157,7 @@ public async Task TestSessionWithNoSolution()
             var mock = new MockLogAndProgressService();
             var client = await service.TryGetRemoteHostClientAsync(CancellationToken.None);
 
-            var session = await client.TryCreateKeepAliveSessionAsync(WellKnownServiceHubServices.RemoteSymbolSearchUpdateEngine, CancellationToken.None, mock);
+            var session = await client.TryCreateKeepAliveSessionAsync(WellKnownServiceHubServices.RemoteSymbolSearchUpdateEngine, callbackTarget: mock, CancellationToken.None);
             var result = await session.TryInvokeAsync(nameof(IRemoteSymbolSearchUpdateEngine.UpdateContinuouslyAsync), new object[] { "emptySource", Path.GetTempPath() }, CancellationToken.None);
 
             Assert.True(result);
@@ -185,7 +185,7 @@ public async Task TestSessionClosed()
             });
 
             // create session that stay alive until client alive (ex, SymbolSearchUpdateEngine)
-            var session = await client.TryCreateKeepAliveSessionAsync("Test", CancellationToken.None);
+            var session = await client.TryCreateKeepAliveSessionAsync("Test", callbackTarget: null, CancellationToken.None);
 
             // mimic unfortunate call that happens to be in the middle of communication.
             var task = session.TryInvokeAsync("TestMethodAsync", arguments: null, CancellationToken.None);

src/VisualStudio/Core/Test.Next/Services/LanguageServiceTests.cs

@@ -120,6 +120,7 @@ private async Task UpdatePrimaryWorkspace(InProcRemoteHostClient client, Solutio
                 nameof(IRemoteHostService.SynchronizePrimaryWorkspaceAsync),
                 solution,
                 new object[] { await solution.State.GetChecksumAsync(CancellationToken.None), _solutionVersion++ },
+                callbackTarget: null,
                 CancellationToken.None));
         }
 

src/VisualStudio/Core/Test.Next/Services/ServiceHubServicesTests.cs

@@ -106,6 +106,7 @@ public async Task TestRemoteHostTextSynchronize()
                     WellKnownRemoteHostServices.RemoteHostService,
                     nameof(IRemoteHostService.SynchronizeTextAsync),
                     new object[] { oldDocument.Id, oldState.Text, newText.GetTextChanges(oldText) },
+                    callbackTarget: null,
                     CancellationToken.None);
 
                 // apply change to solution
@@ -134,6 +135,7 @@ public async Task TestTodoComments()
                     nameof(IRemoteTodoCommentService.GetTodoCommentsAsync),
                     solution,
                     new object[] { solution.Projects.First().DocumentIds.First(), ImmutableArray.Create(new TodoCommentDescriptor("TODO", 0)) },
+                    callbackTarget: null,
                     CancellationToken.None);
 
                 Assert.Equal(1, comments.Value.Count);
@@ -157,6 +159,7 @@ class Test { }";
                     nameof(IRemoteDesignerAttributeService.ScanDesignerAttributesAsync),
                     solution,
                     new[] { solution.Projects.First().DocumentIds.First() },
+                    callbackTarget: null,
                     CancellationToken.None);
 
                 Assert.Equal("Form", result.Value.DesignerAttributeArgument);
@@ -177,6 +180,7 @@ public async Task TestRemoteHostSynchronizeGlobalAssets()
                     nameof(IRemoteHostService.SynchronizeGlobalAssetsAsync),
                     workspace.CurrentSolution,
                     new object[] { new Checksum[0] { } },
+                    callbackTarget: null,
                     CancellationToken.None));
 
                 var storage = client.AssetStorage;
@@ -377,6 +381,7 @@ private async Task UpdatePrimaryWorkspace(InProcRemoteHostClient client, Solutio
                 nameof(IRemoteHostService.SynchronizePrimaryWorkspaceAsync),
                 solution,
                 new object[] { await solution.State.GetChecksumAsync(CancellationToken.None), _solutionVersion++ },
+                callbackTarget: null,
                 CancellationToken.None));
         }
 

src/VisualStudio/Core/Test.Next/Services/VisualStudioDiagnosticAnalyzerExecutorTests.cs

@@ -179,6 +179,7 @@ void Method()
                     nameof(IRemoteHostService.SynchronizeGlobalAssetsAsync),
                     workspace.CurrentSolution,
                     new[] { new Checksum[] { asset.Checksum } },
+                    callbackTarget: null,
                     CancellationToken.None));
 
                 // set option
@@ -234,6 +235,7 @@ void Method()
                     nameof(IRemoteHostService.SynchronizeGlobalAssetsAsync),
                     workspace.CurrentSolution,
                     new[] { new Checksum[] { asset.Checksum } },
+                    callbackTarget: null,
                     CancellationToken.None));
 
                 // run analysis

src/VisualStudio/Razor/RazorLanguageServiceClient.cs

@@ -29,7 +29,7 @@ public async Task<Session> CreateSessionAsync(Solution solution, object callback
                 return null;
             }
 
-            var innerSession = await _client.TryCreateSessionAsync(_serviceName, solution, cancellationToken, callbackTarget).ConfigureAwait(false);
+            var innerSession = await _client.TryCreateSessionAsync(_serviceName, solution, callbackTarget, cancellationToken).ConfigureAwait(false);
             if (innerSession == null)
             {
                 return null;

src/VisualStudio/VisualStudioDiagnosticsToolWindow/OptionPages/PerformanceLoggersPage.cs

@@ -71,6 +71,7 @@ public static void SetLoggers(IGlobalOptionService optionService, IThreadingCont
                 WellKnownRemoteHostServices.RemoteHostService,
                 nameof(IRemoteHostService.SetLoggingFunctionIds),
                 new object[] { loggerTypes, functionIds },
+                callbackTarget: null,
                 CancellationToken.None));
         }
 

src/Workspaces/Core/Portable/ExternalAccess/UnitTesting/Api/UnitTestingRemoteHostClientWrapper.cs

@@ -16,13 +16,13 @@ internal UnitTestingRemoteHostClientWrapper(RemoteHostClient underlyingObject)
 
         public async Task<UnitTestingKeepAliveSessionWrapper> TryCreateUnitTestingKeepAliveSessionWrapperAsync(string serviceName, CancellationToken cancellationToken)
         {
-            var keepAliveSession = await UnderlyingObject.TryCreateKeepAliveSessionAsync(serviceName, cancellationToken).ConfigureAwait(false);
+            var keepAliveSession = await UnderlyingObject.TryCreateKeepAliveSessionAsync(serviceName, callbackTarget: null, cancellationToken).ConfigureAwait(false);
             return new UnitTestingKeepAliveSessionWrapper(keepAliveSession);
         }
 
         public async Task<UnitTestingSessionWithSolutionWrapper> TryCreateUnitingSessionWithSolutionWrapperAsync(string serviceName, Solution solution, CancellationToken cancellationToken)
         {
-            var session = await UnderlyingObject.TryCreateSessionAsync(serviceName, solution, cancellationToken).ConfigureAwait(false);
+            var session = await UnderlyingObject.TryCreateSessionAsync(serviceName, solution, callbackTarget: null, cancellationToken).ConfigureAwait(false);
             return new UnitTestingSessionWithSolutionWrapper(session);
         }
 

src/Workspaces/Core/Portable/FindSymbols/Declarations/DeclarationFinder_AllDeclarations.cs

@@ -44,6 +44,7 @@ internal static partial class DeclarationFinder
                     nameof(IRemoteSymbolFinder.FindAllDeclarationsWithNormalQueryAsync),
                     solution,
                     new object[] { project.Id, query.Name, query.Kind, criteria },
+                    callbackTarget: null,
                     cancellationToken).ConfigureAwait(false);
 
                 if (result.HasValue)

src/Workspaces/Core/Portable/FindSymbols/Declarations/DeclarationFinder_SourceDeclarations.cs

@@ -47,6 +47,7 @@ internal static partial class DeclarationFinder
                     nameof(IRemoteSymbolFinder.FindSolutionSourceDeclarationsWithNormalQueryAsync),
                     solution,
                     new object[] { name, ignoreCase, criteria },
+                    callbackTarget: null,
                     cancellationToken).ConfigureAwait(false);
 
                 if (result.HasValue)
@@ -85,6 +86,7 @@ internal static partial class DeclarationFinder
                     nameof(IRemoteSymbolFinder.FindProjectSourceDeclarationsWithNormalQueryAsync),
                     project.Solution,
                     new object[] { project.Id, name, ignoreCase, criteria },
+                    callbackTarget: null,
                     cancellationToken).ConfigureAwait(false);
 
                 if (result.HasValue)
@@ -119,6 +121,7 @@ internal static partial class DeclarationFinder
                     nameof(IRemoteSymbolFinder.FindSolutionSourceDeclarationsWithPatternAsync),
                     solution,
                     new object[] { pattern, criteria },
+                    callbackTarget: null,
                     cancellationToken).ConfigureAwait(false);
 
                 if (result.HasValue)
@@ -152,6 +155,7 @@ internal static partial class DeclarationFinder
                     nameof(IRemoteSymbolFinder.FindProjectSourceDeclarationsWithPatternAsync),
                     project.Solution,
                     new object[] { project.Id, pattern, criteria },
+                    callbackTarget: null,
                     cancellationToken).ConfigureAwait(false);
 
                 if (result.HasValue)

src/Workspaces/Core/Portable/FindSymbols/SymbolFinder_FindLiteralReferences.cs

@@ -32,8 +32,8 @@ public static partial class SymbolFinder
                         nameof(IRemoteSymbolFinder.FindLiteralReferencesAsync),
                         solution,
                         new object[] { value, typeCode },
-                        cancellationToken,
-                        serverCallback).ConfigureAwait(false);
+                        serverCallback,
+                        cancellationToken).ConfigureAwait(false);
 
                     if (success)
                     {

src/Workspaces/Core/Portable/FindSymbols/SymbolFinder_FindReferences_Current.cs

@@ -49,8 +49,8 @@ public static partial class SymbolFinder
                                 documents?.Select(d => d.Id).ToArray(),
                                 SerializableFindReferencesSearchOptions.Dehydrate(options),
                             },
-                            cancellationToken,
-                            serverCallback).ConfigureAwait(false);
+                            serverCallback,
+                            cancellationToken).ConfigureAwait(false);
 
                         if (success)
                         {

src/Workspaces/Core/Portable/Remote/RemoteHostClient.cs

@@ -102,7 +102,7 @@ public static string CreateClientId(string prefix)
         /// <summary>
         /// Creates <see cref="SessionWithSolution"/> for the <paramref name="serviceName"/> if possible, otherwise returns <see langword="null"/>.
         /// </summary>
-        public async Task<SessionWithSolution?> TryCreateSessionAsync(string serviceName, Solution solution, CancellationToken cancellationToken, object? callbackTarget = null)
+        public async Task<SessionWithSolution?> TryCreateSessionAsync(string serviceName, Solution solution, object? callbackTarget, CancellationToken cancellationToken)
         {
             var connection = await TryCreateConnectionAsync(serviceName, callbackTarget, cancellationToken).ConfigureAwait(false);
             if (connection == null)
@@ -116,7 +116,7 @@ public static string CreateClientId(string prefix)
         /// <summary>
         /// Creates <see cref="KeepAliveSession"/> for the <paramref name="serviceName"/>, otherwise returns <see langword="null"/>.
         /// </summary>
-        public async Task<KeepAliveSession?> TryCreateKeepAliveSessionAsync(string serviceName, CancellationToken cancellationToken, object? callbackTarget = null)
+        public async Task<KeepAliveSession?> TryCreateKeepAliveSessionAsync(string serviceName, object? callbackTarget, CancellationToken cancellationToken)
         {
             var connection = await TryCreateConnectionAsync(serviceName, callbackTarget, cancellationToken).ConfigureAwait(false);
             if (connection == null)
@@ -128,9 +128,9 @@ public static string CreateClientId(string prefix)
         }
 
         public async Task<bool> TryRunRemoteAsync(string serviceName, string targetName, Solution solution,
-            IReadOnlyList<object> arguments, CancellationToken cancellationToken, object? callbackTarget = null)
+            IReadOnlyList<object> arguments, object? callbackTarget, CancellationToken cancellationToken)
         {
-            using var session = await TryCreateSessionAsync(serviceName, solution, cancellationToken, callbackTarget).ConfigureAwait(false);
+            using var session = await TryCreateSessionAsync(serviceName, solution, callbackTarget, cancellationToken).ConfigureAwait(false);
             if (session == null)
             {
                 return false;
@@ -140,7 +140,7 @@ public static string CreateClientId(string prefix)
             return true;
         }
 
-        public async Task<bool> TryRunRemoteAsync(string serviceName, string targetName, IReadOnlyList<object> arguments, CancellationToken cancellationToken, object? callbackTarget = null)
+        public async Task<bool> TryRunRemoteAsync(string serviceName, string targetName, IReadOnlyList<object> arguments, object? callbackTarget, CancellationToken cancellationToken)
         {
             using var connection = await TryCreateConnectionAsync(serviceName, callbackTarget, cancellationToken).ConfigureAwait(false);
             if (connection == null)
@@ -152,9 +152,9 @@ public async Task<bool> TryRunRemoteAsync(string serviceName, string targetName,
             return true;
         }
 
-        public async Task<Optional<T>> TryRunRemoteAsync<T>(string serviceName, string targetName, Solution solution, IReadOnlyList<object> arguments, CancellationToken cancellationToken, object? callbackTarget = null)
+        public async Task<Optional<T>> TryRunRemoteAsync<T>(string serviceName, string targetName, Solution solution, IReadOnlyList<object> arguments, object? callbackTarget, CancellationToken cancellationToken)
         {
-            using var session = await TryCreateSessionAsync(serviceName, solution, cancellationToken, callbackTarget).ConfigureAwait(false);
+            using var session = await TryCreateSessionAsync(serviceName, solution, callbackTarget, cancellationToken).ConfigureAwait(false);
             if (session == null)
             {
                 return default;

src/Workspaces/Core/Portable/Remote/RemoteHostClientExtensions.cs

@@ -36,6 +36,7 @@ public static async Task SynchronizePrimaryWorkspaceAsync(this Workspace workspa
                     nameof(IRemoteHostService.SynchronizePrimaryWorkspaceAsync),
                     solution,
                     new object[] { checksum, solution.WorkspaceVersion },
+                    callbackTarget: null,
                     cancellationToken).ConfigureAwait(false);
             }
         }