Is there a way to implement this integer casting function with unsafe Pointer in golang?

Question

I was wondering if I could implement a less verbose version of this function. It would be great if it had better performance.

func AnyIntToInt(x interface{}) (int, error) {
    switch val := x.(type) {
    case int8:
        return int(val), nil
    case int16:
        return int(val), nil
    case int32:
        return int(val), nil
    case int64:
        return int(val), nil
    case uint8:
        return int(val), nil
    case uint16:
        return int(val), nil
    case uint32:
        return int(val), nil
    case uint64:
        return int(val), nil
    }
    return 0, ErrNotInteger
}

I have been trying with this one, however it yields unexpected results.

func AnyIntToInt(x interface{}) (int, error) {
    return *(*int)(unsafe.Pointer(&x))
}

Answer 1

The code in the question is the way to go, but you can reduce lines of code using the reflect package:

func AnyIntToInt(x interface{}) (int, error) {
    v := reflect.ValueOf(x)
    switch v.Kind() {
    case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
        return int(v.Int()), nil
    case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
        return int(v.Uint()), nil
    }
    return 0, ErrNotInteger
}

https://go.dev/play/p/gJ4ASo7AeyN