Why can't an user-defined function take integer arguments and return integer?

Question

The following user-defined function cannot be used in the worksheet. When I type

=Add2(1,1)

it returns #REF.

Function add2(x As Integer, y As Integer) As Integer
    add2 = x + y
End Function

If I change Integer to Double, only then it works. Why can't integer be used? Thank you.

Answer 1

问题就在这里，ADD2 也是一个范围，但是为什么将输出更改为双倍时它会起作用，我不知道。