> 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.
Will do. It could also be a vet check to highlight errors.As used on sentinel errors which is most likely wrong as I demonstrated. On Monday, August 2, 2021 at 10:09:48 AM UTC+2 axel.wa...@googlemail.com wrote: > On Mon, Aug 2, 2021 at 10:02 AM cpu...@gmail.com <cpu...@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...@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/730c78dd-cd24-4377-b154-c1e238a2c929n%40googlegroups.com.
