Named parameter.

src/Features/Core/Portable/Completion/CompletionServiceWithProviders.cs

@@ -40,7 +40,7 @@ public abstract class CompletionServiceWithProviders : CompletionService, IEqual
         private IEnumerable<Lazy<CompletionProvider, CompletionProviderMetadata>> _importedProviders;
 
         protected CompletionServiceWithProviders(Workspace workspace)
-            : this(workspace, null)
+            : this(workspace, exclusiveProviders: null)
         {
         }