Thanks for your explanation, that's very helpful :-) On Friday, March 12, 2021 at 3:03:00 PM UTC+8 axel.wa...@googlemail.com wrote:
> On Fri, Mar 12, 2021 at 4:55 AM messi...@gmail.com <messi...@gmail.com> > wrote: > >> Does it use for generics constraints only? > > > That is my understanding. > > >> As described at >> https://go.googlesource.com/proposal/+/refs/heads/master/design/go2draft-type-parameters.md#comparable-types-in-constraints >> >> . If so the type comparison and this interface is two unrelated things? >> > > They are related in the sense that `comparable` expresses exactly the > constraint of being able to compare values of a type. But the compiler > already knows how to compare values of the same type, if that type is > comparable. And the `comparable` interface won't be usable as an actual > type which can have a value (that would be useless - you need two values of > the same concrete type to actually compare, but there is, in general, no > guarantee that two values of an interface type are the same concrete type). > So there doesn't have to be a direct connection between the two. > > >> >> On Friday, March 12, 2021 at 11:42:07 AM UTC+8 messi...@gmail.com wrote: >> >>> Hi, >>> >>> I'm reading the new typechecker source code of go compiler(under >>> directory cmd/compile/internal/types2), during the initialization process, >>> universe.go registers an implicit interface "comparable" inside function >>> defPredeclaredComparable >>> <https://github.com/golang/go/blob/e8b82789cda6c9d9e3dfc9a652b4d7a823b834f2/src/cmd/compile/internal/types2/universe.go#L199>, >>> >>> I know it's supposed to be used for type comparison >>> <https://golang.org/ref/spec#Comparison_operators>but failed to find >>> where and how this interface and related method "==" is used. >>> >>> In predicates.go >>> <https://github.com/golang/go/blob/e8b82789cda6c9d9e3dfc9a652b4d7a823b834f2/src/cmd/compile/internal/types2/predicates.go#L86> >>> there's >>> a function 'Comparable" to check whether a type is comparable or not, but >>> seems there's nothing to do with the interface. >>> >>> And I don't understand the lookup logic for method "==" in type.go >>> <https://github.com/golang/go/blob/e8b82789cda6c9d9e3dfc9a652b4d7a823b834f2/src/cmd/compile/internal/types2/type.go#L465> >>> neither, >>> how could an Interface type have method named "=="? >>> >>> I searched a lot from the code base but failed to find the answer, could >>> anybody kindly give me some clue? >>> >>> Thanks a lot :-) >>> >> -- >> 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...@googlegroups.com. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/golang-nuts/50661f0e-289e-43f3-a9d7-a42feb77f7fbn%40googlegroups.com >> >> <https://groups.google.com/d/msgid/golang-nuts/50661f0e-289e-43f3-a9d7-a42feb77f7fbn%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- 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/14cc2521-a155-48db-b000-a5300c6711f1n%40googlegroups.com.
