[antlr-interest] Tree parser eats up DOWN node when navigating optional child node

[Gerald Rosenberg]

  ------ Original Message (Wednesday, August 04, 2010 9:53:09 
AM) From: Junkman ------
Subject: Re: [antlr-interest] Tree parser eats up DOWN node when navigating
optional child node
>
>> parent: ^(parent_a B?) ;
>> parent_a: ^(PARENT A?) ;
>> --------------------------------------------
>

. . . is the same as

parent: ^( ^(PARENT A?) B? ) ;

which will not match ^(PARENT B), but will match ^( ^(PARENT) B).  BTW, 
a subtree match() will always properly consume the UP DOWN subtree 
delimiters.

You probably want

parent: ^(parent_a B?) ;
parent_a: PARENT A? ;