They can just define a singleton sentinel of the error type. e.g. do
type errValue struct{}
func (e *errValue) Error() string { return "…" }
var valueErr = new(errValue)
if errors.Is(err, valueErr) { … }
No need to define new API, if this can just be solved by fixing the code.
Perhaps there should be a vet check (either for comparisons of pointers to
zero-sized values, or specifically for pointers to zero-sized error types).
On Tue, 3 Jun 2025 at 17:56, tapi...@gmail.com <tapir....@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
>
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