[antlr-interest] "Treeparser returns" question

[camiel at srxp.com]

Hope plain text will work better...:

Hi you all,
 
I have a question on the proper syntax of Treeparser methods. Suppose
that you want to parse "a=1" or just "a"
with the following parser rule:
 
class myparser extends Parser
 
statement: IDENTIFIER (EQUALS INT)? EOF!;
 
and we want to echo the evaluation via an extension of the treeparser, 
the following is not going to work:
 
class mytreeparser extends TreeParser
 
statement returns [String s]
{String a; int b; s=""}
            : # (IDENTIFIER a=identifier) {s=a"}
            | # (EQUALS a=identifier, b=integer) {s=a+b;};
 
where identifier and integer are defined in the lexer.
 
My question is: what would work? The answer possibly centers around
method overloading (with different sets of parameters) but how exactly
I cannot figure out from online sources. Maybe anybody has written some
elaborate tutorial piece on this functionality of Antlr !?? 
 
Thanks anyway,
 
Camiel