Sorry to revive this, but I'd like to add to conversation (without weighing in on correctness of the nil check) that it appears the CodeReview comments on interfaces ( https://go.dev/wiki/CodeReviewComments#interfaces ) and the FAQ nil error https://go.dev/doc/faq#nil_error give mutually exclusive guidance.
On Wednesday, September 2, 2020 at 6:09:51 PM UTC-6 Ian Lance Taylor wrote: > On Wed, Sep 2, 2020 at 3:45 AM targe...@gmail.com <targe...@gmail.com> > wrote: > > > > > Other people have said this too, but I want to emphasize that there > > are not 4 potential states of an interface value. There are 2 > > potential states: 1) interface does not hold any value, and is == nil; > > 2) interface holds a value, and is != nil. > > > > Indeed, there are 2 states of interface observable from outside. > Although one of these observable states gets expressed through 2 states > invisible to outer world. Which isn't a problem on its own. > > > > > When you start talking about an interface as a fat pointer you are > > talking about how those 2 states are implemented. There are other > > possible implementations > > > > Yes. And that's not an issue on its own. The issue is, such > implementation detail kind of "leaks" sometimes and bites you when you > don't expect. And it does so because the way it gets constructed omits one > specific detail of conversion from pointer to interface. > > I don't think that is correct. The implementation detail never leaks. > An interface always either holds a valid value (is != nil) or does not > hold a valid value (is == nil). > > I believe the confusion is due to the overloading of "nil". It means > both an invalid interface and an invalid pointer, but you are > permitted to store an invalid pointer in a valid interface. > > Ian > -- 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/00a87015-a09e-4529-8dfc-c547126524e1n%40googlegroups.com.
