Microsoft.CodeAnalysis.Completion.CompletionService.GetCompletionsAsync(Microsoft.CodeAnalysis.Document, System.Int32, Microsoft.CodeAnalysis.Completion.CompletionOptions, Microsoft.CodeAnalysis.Options.OptionSet, Microsoft.CodeAnalysis.Completion.CompletionTrigger, System.Collections.Immutable.ImmutableHashSet<System.String>, System.Threading.CancellationToken)