[antlr-interest] tree construction : skip empty nodes

[Sébastien Kirche]

Hi,

I have the two following rules :

codeBlock : stmt+=compoundStatement* -> ^(STMT $stmt)* ;

compoundStatement
	:
	(
		(	/* empty */
			|	tryCatchBlock
			|	localVarDecl
	      		| 	ifStatement
			|	chooseCaseStatement
			|	forStatement
			|	loopStatement
			| 	embeddedSQL
			|	singleStatement
		) (Semi! | EOL! )
	)
	|	Label -> ^(LABEL Label)
	;

As the compoundStatement can match empty lines or null statements
(like ;;;) my parser sometimes emit empty STMT nodes.
I cannot figure the correct way to conditionaly emit STMT if only the
compoundStatement is not empty.

I have tried something like codeBlock : stmt+=compoundStatement* ->
{$stmt.tree != null} ^(STMT $stmt)* ;
but because of the += notation the $stmt is a list and I did not find
yet the proper way to test each item.

Could you give me some help ?
-- 
Sébastien Kirche