You are right, I am wrong. I wasn't aware that the struct field would be named after the alias, I assumed it would be named after the type itself. I agree that this looks like a bug in the json-package and that it should look at the field name itself.
On Mon, Jan 22, 2018 at 4:47 PM, Josh Humphries <jh...@bluegosling.com> wrote: > I'm not trying to suggest that the example code makes sense or is > something that one *should* do. > > But it is surprising behavior that is not expected, even after reading > relevant parts of the language spec and the reflect and json package docs. > > It looks like this is a bug in the json package. When it encounters an > anonymous field, it looks directly at the name of the field's type, instead > of the name of the field itself, to decide whether the field is exported or > not: > https://golang.org/src/encoding/json/encode.go?s=6456:6499#L1097 > In this case, the StructField's indicate exported names (based on the type > alias names), but the field's type is simply int (which is not exported due > to starting with lower-case letter). > > > > ---- > *Josh Humphries* > jh...@bluegosling.com > > On Mon, Jan 22, 2018 at 3:12 AM, 'Axel Wagner' via golang-nuts < > golang-nuts@googlegroups.com> wrote: > >> On Mon, Jan 22, 2018 at 8:50 AM, dc0d <kaveh.shahbaz...@gmail.com> wrote: >> >>> Then the main question would be why is it possible to embed type aliases? >>> >> >> Because it is possible to embed types and an alias is simply another name >> for a type. >> >> For example, embedding an x/image/draw.Image >> <https://godoc.org/golang.org/x/image/draw#Image> makes 100% complete >> sense: It allows your type to be used as an Image itself, while adding or >> overwriting some methods. And the alias makes x/image/draw a drop-in >> replacement for image/draw, so you can use your embedding type also in >> functions that expect an image/draw. Also note, that even with unexported >> embedded types, you are *still* promoting fields and methods >> <https://play.golang.org/p/k-223vmcfNJ>. >> >> In the end, the issue here boils down to: Aliases are a purely >> compile-time feature. type Foo = Bar will *by definition* not introduce >> a new actual type, but just an identifier to refer to the same type - >> that's the point. Given that encoding/json works with reflection, so uses >> runtime type information, it can't possibly know about your alias and will >> have to assume you are embedding an int instead. And note, that embedding >> an int was always possible <https://play.golang.org/p/70jzEBzq5Ov> - but >> always sorta pointless. But why explicitly disallow it? If it ain't broke >> don't fix it. >> >> Why are you even using aliases in your example? It would seem that those >> things either shouldn't have a name at all (and instead be field names) or >> they should be actual types. Probably the former. >> >> >>> >>> >>> On Sunday, January 21, 2018 at 10:42:28 PM UTC+3:30, Kevin Malachowski >>> wrote: >>>> >>>> Given the last playground post, I'd guess that the aliased type (i.e. >>>> 'int' here) is being used for visibility rather than the alias's new name. >>>> >>>> It's also a little weird to use embedded types that dont need to be >>>> (there's no method promotion here because 'int' has no methods), or seeing >>>> aliases to primitive types. Do you need to do both of those things? >>>> >>> -- >>> 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. >>> For more options, visit https://groups.google.com/d/optout. >>> >> >> -- >> 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. >> For more options, visit https://groups.google.com/d/optout. >> > > -- 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. For more options, visit https://groups.google.com/d/optout.
