Swift Cannot subscript a value of type '[UInt8]'

报错 Cannot subscript a value of type '[UInt8]' with an index of type 'UInt16'
错误代码如下
var sys_var = sys_var_c()


请问这是怎么回事呢，哪位大师给我指点下

Swift Compiler Error Binary oprator '+' cannot be applied to operands of type 'UInt16' and 'UInt8'
Swift Compiler Error Binary oprator '+' cannot be applied to operands of type 'Int' and 'Double'......
答案就在这里：Swift Compiler Error Binary oprator '+' cannot be applied to operands of type 'UInt16' and 'UInt8'
----------------------Hi，地球人，我是问答机器人小S，上面的内容就是我狂拽酷炫叼炸天的答案，除了赞同，你还有别的选择吗？

 var var_type: [UInt8] = [UInt8](count: 10, repeatedValue: UInt8(0))