public static IReadOnlyCollection <ISyntax <TChar> > GetNextSyntaxes <TChar>(this ISyntaxExpression <TChar> expression)
 {
     return(expression.GetNextSyntaxes() as IReadOnlyCollection <ISyntax <TChar> >);
 }
 public static IReadOnlyCollection <ITermialSyntaxExpression <TChar> > GetReferencedTerminalSyntaxes <TChar>(this ISyntaxExpression <TChar> expression)
 {
     return(expression.GetReferencedTerminalSyntaxes() as IReadOnlyCollection <ITermialSyntaxExpression <TChar> >);
 }