/// <summary>
/// Writes the diagnostic and the offending code.
/// </summary>
/// <returns>A string for use in assert exception.</returns>
internal string ToString(IReadOnlyList <string> sources)
{
if (this.HasPosition)
{
var path = this.HasPath ? this.Span.Path : CodeReader.FileName(sources.Single());
var match = sources.SingleOrDefault(x => CodeReader.FileName(x) == path);
var line = match != null?CodeReader.GetLineWithErrorIndicated(match, this.Span.StartLinePosition) : string.Empty;
return($"{this.Id} {this.Message}\r\n" +
$" at line {this.Span.StartLinePosition.Line} and character {this.Span.StartLinePosition.Character} in file {path} | {line.TrimStart(' ')}");
}
return($"{this.Id} {this.Message}");
}