On Sat, Jul 5, 2025 at 9:19 PM Ge <evergon...@gmail.com> wrote: > Thanks Ian and Dominik for the tips. I have checked the issue 72860 and > found randall77 posted a comment that > I couldn't confirm from golang spec(go.dev/ref/spec): > > //https://github.com/golang/go/issues/72860#issuecomment-2734549770 > ``` > > Where f returns a pointer and an error. f expects its callers to only use > the ptr result if the error is nil. And in particular, f returns a nil > pointer whenever it returns a non-nil error. > > This code is incorrect, in that it dereferences the ptr result before > checking the error. The Go spec says that it should nil pointer panic if f > returns > a nil pointer and non-nil error. > ``` > > I did a search in whole spec and did't find any descriptions about it. > From my understanding, `v, err := f()` is like `v1, v2 := f()` from > compiler's view, > checking error is user code's business logic and couldn't be assumed by > compiler. > If it's defined in spec, what about variants like `a, b, err := f()` or > `a, b, err1, err2 := f()`？ >
No, it is not defined in the spec. For the very reasons you mention (and probably others). But I would argue that commonsense suggests that unless a function explicitly says a returned non-error pointer is useful (i.e., non-nil) when an error is returned you should assume that pointer is likely to be nil if an error is indicated. Ideally this would be explicit in the documentation of every function that returns an error and non-error pointer. However, in the absence of the documentation stating that the non-error pointer value is useful if an error is indicated it seems reasonable to assume that pointer is not useful; even if it isn't nil. Even a non-pointer return value is unlikely to be meaningful if an error was indicated unless explicitly documented. If the called function returns the "zero value" when it also returns an error indicator what does it mean to ignore the error and use the "zero value"? That's obviously context dependent but it is unlikely, in my experience, to ignore the error and use the returned "zero value". -- Kurtis Rader Caretaker of the exceptional canines Junior and Hank -- 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 visit https://groups.google.com/d/msgid/golang-nuts/CABx2%3DD_mFGEOfhYLxV1gMMw%3DnX03CKfTGnpUFWQoF%2Bc4Bp%2B_Rw%40mail.gmail.com.
