Explained in proposal <https://go.googlesource.com/proposal/+/master/design/18130-type-alias.md>:
<https://go.googlesource.com/proposal/+/master/design/18130-type-alias.md#type-cycles>Type > cycles > > In a type alias declaration, in contrast to a type declaration, T2 must > never refer, directly or indirectly, to T1. For example type T = *T and type > T = struct { next *T } are not valid type alias declarations. In > contrast, if the equals signs were dropped, those would become valid > ordinary type declarations. The distinction is that ordinary type > declarations introduce formal names that provide a way to describe the > recursion. In contrast, aliases must be possible to “expand out”, and there > is no way to expand out an alias like type T = *T. > суббота, 8 декабря 2018 г., 20:33:48 UTC+3 пользователь Jan Mercl написал: > > This code compiles fine > > package main > > type node struct { > next *node > } > > func main() {} > > (https://play.golang.org/p/ZYg0EciQnOQ) > > This code does not > > package main > > type node = struct { > next *node > } > > func main() {} > > (https://play.golang.org/p/gWWX8ngPsS6) > > The error is > > prog.go:3:6: invalid recursive type alias node > prog.go:3:6: node uses <T> > prog.go:3:13: <T> uses node > > The specification remains silent about what is considered "invalid > recursive type alias" so I'm not sure, but it seems to me the first and > second programs should both compile fine. In both cases, so to say "the > pointer breaks the cycle" while type checking. But maybe/probably I'm > mistaken. > > Can anybody enlighten me please and explain if the compiler is right or if > it's a bug? > > Thanks in advance. > > -- > > -j > -- 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.
