DSL EXPRESSION:
$y = $a ** $b ** $c


AST:
"block" [tt:block] [nt:StatementBlock]
    "=" [tt:equals] [nt:Assignment]
        "$y" [tt:field_name] [nt:DirectFieldValue]
        "**" [tt:op_pow] [nt:Operator]
            "$a" [tt:field_name] [nt:DirectFieldValue]
            "**" [tt:op_pow] [nt:Operator]
                "$b" [tt:field_name] [nt:DirectFieldValue]
                "$c" [tt:field_name] [nt:DirectFieldValue]

