On Mon, Aug 2, 2021 at 10:02 AM cpu...@gmail.com <cpui...@gmail.com> wrote:
> Consider this example: https://play.golang.org/p/16cU0kc8Lku, basically > > var Err = errors.New("sentinel") > err := errors.New("foo") > if errors.As(err, &Err) { > fmt.Println("why?") > } > > I'm wondering why this matches the sentinel error > Because both are of type `*errors.errorString`, so the types match and it copies over the value. Arguably, `errors.errorString` should implement `As()` and return `false`, unless the pointers match. I suggest filing an issue. > or rather how to properly use sentinel errors. > Use `errors.Is`, instead of `errors.As`. > However, if thats the case, how should I construct a sentinel error that > would be usable with errors.As? I don't want to rely on errors.Is as errors > could be wrapped. > And? They can be wrapped for `As` as well. `errors.As` is only useful if you want to get additional information out of the error (e.g. it's useful for use with `os.PathError`). By definition, it's pointless to use it with a sentinel error. > So to "break" the assignability- would that mean that I'd need to define > sentinel errors as e.g. struct types? > > Seem's I'm still lacking the level of understanding for go errors that I'd > aspire to :/ > > Cheers, > Andi > > -- > 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/4d8969b4-dd5a-4834-893b-3e01174570bfn%40googlegroups.com > <https://groups.google.com/d/msgid/golang-nuts/4d8969b4-dd5a-4834-893b-3e01174570bfn%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/CAEkBMfGyjtNg-vGCvS95Pt0_iy_-yVWhr8TcKixhyvvMVkf_0g%40mail.gmail.com.
