private Task <Document> AddSummaryCommentAsync(Document document, BaseTypeDeclarationSyntax declaration, CancellationToken c)
        {
            var leadingTrivias  = declaration.GetLeadingTrivia();
            var whitespaceCount = leadingTrivias[leadingTrivias.Count - 1].Span.Length;
            var newDeclaration  = declaration.WithLeadingTrivia(
                AnalyzerUtil.GetNewLeadingTriviaWithSummary(leadingTrivias, summaryComments, whitespaceCount));

            return(AnalyzerUtil.ReplaceNode(declaration, newDeclaration, document));
        }