BTW, in the std lib, half of error types use value receivers, half use pointer receivers: https://docs.go101.org/std/pkg/builtin.html#name-error
On Wednesday, June 4, 2025 at 10:36:41 PM UTC+8 tapi...@gmail.com wrote: > On Wednesday, June 4, 2025 at 10:33:07 PM UTC+8 Axel Wagner wrote: > > I guess we will just have to disagree. > > > Agree on this. :D > > > > On Wed, 4 Jun 2025 at 15:38, tapi...@gmail.com <tapi...@gmail.com> wrote: > > > > On Wednesday, June 4, 2025 at 12:18:26 PM UTC+8 Axel Wagner wrote: > > On Tue, 3 Jun 2025 at 22:17, tapi...@gmail.com <tapi...@gmail.com> wrote: > > Or better, use ErrType instead of *ErrType, so that no need to declare the > global error var. > > > Doing that is problematic. If the `Error` method is declared with a value > receiver, it is promoted to the pointer-type as well. At that point, it is > no longer a priori clear, whether you should type-assert to `ErrType` or > `*ErrType`. Or similarly, which to use with `errors.As`. Likewise, it is > possible to assign either to `error`, so it is easy to accidentally return > the wrong type. This can lead to very hard to find bugs, as error-paths > tend to not be well tested anyways. This doesn't happen with pointer > receivers, as they are not promoted to the value type. So any mixup gets > statically caught by the compiler. > > So, as a general rule, an often type-asserted interface like `error` > should be implemented using pointer-receivers. > > > As a basic rule, we should never use *ZeroSizeType as error types. Just > use ZeroSizeType as error types. > > > > > > > > On Tue, 3 Jun 2025 at 17:56, tapi...@gmail.com <tapi...@gmail.com> wrote: > > > > On Tuesday, June 3, 2025 at 8:58:10 PM UTC+8 Bushnell, Thomas wrote: > > Why do you think these are incorrect uses of errors.Is? If you are only > testing the Boolean value, Is is fine and the same as As; you should only > use As if you are actually going to use the identified error value in some > way. > > Because errors.Is mainly use == to compare errors. When the errors are > pointers to zero-size values, the comparison result is compiler dependent, > as the whole thread is talking about. > > Maybe using errors.As is also not a good idea for such cases. Such cases > just need an errors.OfType[ErrType]() alike function. > > > > > *From:* golan...@googlegroups.com <golan...@googlegroups.com> *On Behalf > Of *tapi...@gmail.com > *Sent:* Monday, June 2, 2025 3:14 PM > *To:* golang-nuts <golan...@googlegroups.com> > *Subject:* Re: [go-nuts] Comparison of pointers to distinct zero-sized > variables > > > > This message was sent by an external party. > > > > > > On Sunday, June 1, 2025 at 11:21:28 PM UTC+8 Oliver Eikemeier wrote: > > > Am 27.06.2024 um 05:17 schrieb Ian Lance Taylor <ia...@golang.org>: > > > > On Tue, Jun 25, 2024 at 9:37 PM 'Axel Wagner' via golang-nuts > > <golan...@googlegroups.com> wrote: > >> > >> you might be interested to learn that Ian has filed a CL adding an FAQ > entry. > > > > Now committed at https://go.dev/doc/faq#zero_size_types . > > > > Ian > > Thanks for that. I discovered that comparing pointers to ZSTs is pretty > popular in Go: > > - x/sync/singleflight: > https://cs.opensource.google/go/x/sync/+/refs/tags/v0.14.0:singleflight/singleflight_test.go;l=78 > > > - Delve: > https://github.com/go-delve/delve/blob/v1.24.2/service/debugger/debugger.go#L387 > > > - Grafana: > https://github.com/grafana/grafana/blob/v12.0.1/pkg/services/serviceaccounts/extsvcaccounts/service.go#L353 > > > - Skaffold: > https://github.com/GoogleContainerTools/skaffold/blob/v2.16.0/pkg/skaffold/hooks/render.go#L93 > > > - Coder: https://github.com/coder/coder/blob/v2.22.1/cli/ssh.go#L578 > > - quic-go: > https://github.com/quic-go/quic-go/blob/v0.52.0/connection_test.go#L1008 > > - SigStore Cosign: > https://github.com/sigstore/cosign/blob/v2.5.0/cmd/cosign/cli/attest/attest_blob_test.go#L60 > > > Seems like a classic example of Hyrum's Law, we now have a lot of code > that depends on runtime.zerobase. > > > > It looks all of bad code (using errors.Is) should use errors.As instead. > > This indeed reflects that the design of the errors APIs is prone to being > misused. > > > > An "errros/v2" is really needed to avoid such misuses. > > > > > > I’ve written a linter along with an accompanying blog post about the > subject: > > fillmore-labs.com/zerolint: https://github.com/fillmore-labs/zerolint > > “The Perils of Pointers in the Land of the Zero-Sized Type”: > https://blog.fillmore-labs.com/posts/zerosized-1/ > > > I would be interested whether I got the “default” level right. Or maybe > everything wrong. > > Thanks for the insight, again > Oliver > > -- > 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 visit > https://groups.google.com/d/msgid/golang-nuts/7750b85c-2e09-4e42-a290-480b81caf19dn%40googlegroups.com > > <https://groups.google.com/d/msgid/golang-nuts/7750b85c-2e09-4e42-a290-480b81caf19dn%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...@googlegroups.com. > > To view this discussion visit > https://groups.google.com/d/msgid/golang-nuts/06eef021-6d5b-496c-898f-bdd375453b35n%40googlegroups.com > > <https://groups.google.com/d/msgid/golang-nuts/06eef021-6d5b-496c-898f-bdd375453b35n%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...@googlegroups.com. > > To view this discussion visit > https://groups.google.com/d/msgid/golang-nuts/d9b53c59-1d53-49bc-98e0-5d0b587b5705n%40googlegroups.com > > <https://groups.google.com/d/msgid/golang-nuts/d9b53c59-1d53-49bc-98e0-5d0b587b5705n%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...@googlegroups.com. > > To view this discussion visit > https://groups.google.com/d/msgid/golang-nuts/39f6abe2-3cd9-4cd0-8998-44cf5157df8bn%40googlegroups.com > > <https://groups.google.com/d/msgid/golang-nuts/39f6abe2-3cd9-4cd0-8998-44cf5157df8bn%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. 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