DSL EXPRESSION:
$x = 2 * $a + $b . $c


AST:
* statement block
    * assignment "="
        * direct field value "x"
        * operator "+"
            * operator "*"
                * int literal "2"
                * direct field value "a"
            * dot operator "."
                * direct field value "b"
                * direct field value "c"

