/// <summary>
/// Writes the diagnostic and the offending code.
/// </summary>
/// <returns>A string for use in assert exception</returns>
internal static async Task <string> ToStringAsync(this Diagnostic diagnostic, Solution solution)
{
var sources = await Task.WhenAll(solution.Projects.SelectMany(p => p.Documents).Select(d => CodeReader.GetStringFromDocumentAsync(d, Formatter.Annotation, CancellationToken.None)));
return(diagnostic.ToString(sources));
}