grammar t057autoAST40; options {language=JavaScript;output=AST;} a returns [result]: x+=b x+=b { t=$x[1] $result = "2nd x="+t.toStringTree()+','; }; b : ID; ID : 'a'..'z'+ ; INT : '0'..'9'+; WS : (' '|'\n') {$channel=HIDDEN;} ;