Thanks for the reference document, and a compressed way of using it ! Cheers Nz
On Wed, 3 May 2023 at 11:20, Axel Wagner <[email protected]> wrote: > That's a well-known implementation restriction, mentioned in the release > notes of Go 1.18 <https://go.dev/doc/go1.18#generics>: > > The Go compiler only supports calling a method m on a value x of type >> parameter type P if m is explicitly declared by P's constraint interface. >> Similarly, method values x.m and method expressions P.m also are only >> supported if m is explicitly declared by P, even though m might be in the >> method set of P by virtue of the fact that all types in P implement m. We >> hope to remove this restriction in a future release. > > > So far, we haven't managed to remove this restriction. It's surprisingly > complicated. > I tend to spell that call as `P(&t).Bar()` for what it's worth. > > On Wed, May 3, 2023 at 5:48 PM Steve Heyns <[email protected]> wrote: > >> Ran into this and I was wondering if it was a bug or not. Assuming "Foo" >> is an interface with a function of "Bar", then the following function >> should have a type reference of T and a pointer reference of P that >> implements the Foo interface, and is bound to the Type of T ( >> https://gotipplay.golang.org/p/BKsA7-6MlHV). >> >> *type Foo interface {* >> >> * Bar() string }* >> >> >> >> >> *func Update[T any, P interface { Foo *T}]() {* >> >> Inside that function : >> *var t T; t.Bar()* // gives >> t.Bar undefined (type T has no field or method Bar) >> >> *var t T; i:= &t; i.Bar()* // Gives >> i.Bar undefined (type *T is pointer to type parameter, not type parameter) >> >> But the following passes compile, and creates a new instance of type T, >> with "i" being the pointer to it. >> *var t T; var i P; i= &t; i.Bar()* // Pass >> >> IMO all three ways should work, but curious as to why they don't >> >> Thanks >> Nz >> >> -- >> 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 [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/golang-nuts/205934b5-0b7e-4fe5-9912-402fdcb4db1fn%40googlegroups.com >> <https://groups.google.com/d/msgid/golang-nuts/205934b5-0b7e-4fe5-9912-402fdcb4db1fn%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 [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/CANDob0LX_zZV%3D6Ankc9HO4mUaGedhKvCLJtONcPOM6RSPOzxww%40mail.gmail.com.
