[antlr-interest] RewriteEmptyStreamException

[Manu]

I'm using ANTLR v3.0.1 with C# templates.

The following grammar:

grammar Orders;

options
{
	language=CSharp;
	output=AST;
	ASTLabelType=CommonTree;
}

tokens
{
	CABECERA;
	DETALLE;
	RESUMEN;
	RESTO;
}

@header {
using System.Text;
}

@rulecatch {
}

s: mensajeORDER EOF -> mensajeORDER;

mensajeORDER: HEADER_ID CR LF linea* (CR | LF)* -> ^(HEADER_ID linea*);

linea: lineasCabecera;

restoLinea:	('|' an+=AN)* CR LF -> {($an != null) && ($an.Count > 0)}?
^(RESTO AN*)
								-> ;
lineasCabecera:	lineaORD -> ^(CABECERA lineaORD);

lineaORD: 'ORD' '|' numPedido=AN '|' tipoPedido=AN '|' funcion=AN
restoLinea -> ^('ORD' $numPedido $tipoPedido $funcion restoLinea);

HEADER_ID:	'ORDERS';
CR:	'\r';
LF:	'\n';

	
fragment CARACTER
	:	'a'..'z'
	|	'A'..'Z'
	;

fragment NUMERO: ('0'..'9');

AN: (CARACTER | NUMERO)+;
N: NUMERO+ ('.' NUMERO+)?;

Doesn't work when restoLinea is just CR LF. It gives me the exception:

Antlr.Runtime.Tree.RewriteEmptyStreamException was unhandled
  Message="rule restoLinea"
  Source="Antlr3.Runtime"
  StackTrace:
       en Antlr.Runtime.Tree.RewriteRuleElementStream._Next()
       en Antlr.Runtime.Tree.RewriteRuleElementStream.Next()
       ....


However, if I change restoLinea to:

restoLinea:	('|' an+=AN)* CR LF -> {($an != null) && ($an.Count > 0)}?
^(RESTO AN*)
								-> {(CommonTree)adaptor.GetNilNode()};

It works as expected.

I thought that using an empty rewrite rule (-> ;) returned an empty
AST. Am I wrong? If so, how can I do the same with a rewrite rule that
doesn't use custom code?

Thanks