DSL EXPRESSION:
$x =  1 +  (2 ** 3)


AST:
"block" [tt:block] [nt:StatementBlock]
    "=" [tt:equals] [nt:Assignment]
        "$x" [tt:field_name] [nt:DirectFieldValue]
        "+" [tt:op_plus] [nt:Operator]
            "1" [tt:int_literal] [nt:int_literal]
            "**" [tt:op_pow] [nt:Parenthesized]
                "**" [tt:op_pow] [nt:Operator]
                    "2" [tt:int_literal] [nt:int_literal]
                    "3" [tt:int_literal] [nt:int_literal]

