private static bool TrimEnd(IDocumentAccessor doc)
{
var line = doc.Text;
if (!char.IsWhiteSpace(line[line.Length - 1])) return false;
// one space after an empty comment is allowed
if (line.EndsWith("// ", StringComparison.Ordinal) || line.EndsWith("* ", StringComparison.Ordinal))
return false;
doc.Text = line.TrimEnd();
return true;
}