public ISourceLocation GetSourceLocation(int position, int length)
//^^ requires 0 <= position && (position < this.Length || position == 0);
//^^ requires 0 <= length;
//^^ requires length <= this.Length;
//^^ requires position+length <= this.Length;
//^^ ensures result.SourceDocument == this;
//^^ ensures result.StartIndex == position;
//^^ ensures result.Length == length;
{
return this.GetPrimarySourceLocation(position, length);
}