Yes, the *underlying type* of Class is `byte`, but the type-switch checks
if the dynamic type is *exactly* `byte`.
The only way, currently, to implement the kind of check you want is to use
reflect:
switch rv := reflect.ValueOf(v); rv.Kind() {
case reflect.Uint8: // byte
v := uint8(rv.Uint())
// ...
}
Though you might be interested in #45380
<https://github.com/golang/go/issues/45380>, which would be able to solve
this without reflect.
On Mon, Apr 8, 2024 at 11:04 AM Xiangrong Fang <xrf...@gmail.com> wrote:
> I wrote a TLV handling package: go.xrfang.cn/tlv
> <https://pkg.go.dev/go.xrfang.cn/tlv>, and encountered problem with type
> checking. Problematic code below:
>
> 1. The "Set" function in side tlv package:
>
> package tlv
>
> type (
> ValueType interface {
> string | []byte | ~float32 | ~float64 |
> ~int8 | ~int16 | ~int32 | ~int64 |
> ~uint8 | ~uint16 | ~uint32 | ~uint64
> }
> Prop map[byte][]byte
> )
>
> func Set[T ValueType](p Prop, tag byte, val T) Prop {
> ... ...
> switch v := any(val).(type) {
> case string:
> ... ...
> default:
> fmt.Printf("tlv.Set: '%T' not supported!\n", val)
> }
> ...
> }
>
> 2. event.go, which uses tlv:
>
> package event
>
> import (
> "go.xrfang.cn/tlv"
> )
>
> type (
> Class byte
> Event struct {
> tlv.Prop
> }
> )
>
> const (
> TagClass = 3
> )
>
> func (e *Event) WithClass(cls Class) *Event {
> (*e).Prop = tlv.Set((*e).Prop, TagClass, cls)
> return e
> }
>
> The problem is, while the Class type is based on "byte", it should be
> accepted by tlv.Set(), which is the case (there is no compiler error). But
> when the code is running, it printed error message: tlv.Set: 'event.Class'
> not supported!
>
> --
> You received this message because you are subscribed to the Google Groups
> "golang-nuts" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to golang-nuts+unsubscr...@googlegroups.com.
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/golang-nuts/b4786988-b9da-44c3-9070-ba718f3be5ban%40googlegroups.com
> <https://groups.google.com/d/msgid/golang-nuts/b4786988-b9da-44c3-9070-ba718f3be5ban%40googlegroups.com?utm_medium=email&utm_source=footer>
> .
>
--
You received this message because you are subscribed to the Google Groups
"golang-nuts" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to golang-nuts+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/golang-nuts/CAEkBMfHg007as7h5NNf-EPCTy8ZSv1sX%3D0pWO2dFjszswnvEwQ%40mail.gmail.com.
