DSL EXPRESSION:
$z = {"a":"1", "b":2,}


AST:
* statement block
    * assignment "="
        * direct field value "z"
        * map literal "{}"
            * map-literal key-value pair ":"
                * string literal "a"
                * string literal "1"
            * map-literal key-value pair ":"
                * string literal "b"
                * int literal "2"

