grammar t057autoAST42; options {language=JavaScript;output=AST;} a returns [result] : x+=b! x+=b { $result = "1st x="+$x[0].toStringTree()+','; } ; b : ID; ID : 'a'..'z'+ ; INT : '0'..'9'+; WS : (' '|'\n') {$channel=HIDDEN;} ;