public async Task <Document> ApplyRefactoringAsync(Document document, CancellationToken token)
{
MethodDeclarationSyntax method = _selectedNode.AncestorsAndSelf().OfType <MethodDeclarationSyntax>().First();
Option <ExpressionStatementSyntax> lastRequires = await GetLastRequiresStatement(document, method, token);
SyntaxNode root = await document.GetSyntaxRootAsync(token);
SyntaxNode rootWithRequires = root.ReplaceNode(method, RequiresUtils.AddEnsures(method, _semanticModel, lastRequires));
SyntaxNode rootWithUsings = RequiresUtils.AddContractNamespaceIfNeeded(rootWithRequires);
return(document.WithSyntaxRoot(rootWithUsings));
}
