public Void VisitSingleParameterSequence(SingleParameterSequence ast, FormalParameterSequence arg)
 {
     if (arg is SingleFormalParameterSequence formal)
     {
         ast.Parameter.Visit(this, formal.Formal);
     }
     else
     {
         ReportError("incorrect number of actual parameters", ast);
     }
     return(null);
 }
 public int VisitSingleParameterSequence(SingleParameterSequence ast, Frame frame)
 {
     return(ast.Parameter.Visit(this, frame));
 }