[generics] Embedding interfaces

[Viet Nguyen]

Hi,

I'm trying to convert this code to use generics:

type Cache interface {

GetIfPresent(interface{}) (interface{}, bool)

}

type LoadingCache interface {

Cache

Get(interface{}) (interface{}, error)

}

However, I couldn't find any way to include Cache[K, V] in LoadingCache[K, V]. (No similar use cases in the proposal? I must miss something here). The workaround is copying all methods over, like:

type Cache[K comparable, V any] interface {

GetIfPresent(K) (V, bool)

}

type LoadingCache[K comparable, V any] interface {

GetIfPresent(K) (V, bool) // FIXME: Embedding the Cache interface

Get(K) (V, error)

}

// See: https://go2goplay.golang.org/p/T7h15CdUEa3

// WIP: https://github.com/goburrow/cache/tree/go2

Is it possible to have something like "interface LoadingCache<K,V> extends Cache<K,V>" as in Java?

Regards,

Viet

[Ian Lance Taylor]

On Fri, May 7, 2021 at 11:08 AM Viet Nguyen <afe...@gmail.com> wrote:
>
> I'm trying to convert this code to use generics:
>
> type Cache interface {
> GetIfPresent(interface{}) (interface{}, bool)
> }
>
> type LoadingCache interface {
> Cache
> Get(interface{}) (interface{}, error)
> }
>
> However, I couldn't find any way to include Cache[K, V] in LoadingCache[K, V]. (No similar use cases in the proposal? I must miss something here). The workaround is copying all methods over, like:
>
> type Cache[K comparable, V any] interface {
> GetIfPresent(K) (V, bool)
> }
>
> type LoadingCache[K comparable, V any] interface {
> GetIfPresent(K) (V, bool) // FIXME: Embedding the Cache interface
> Get(K) (V, error)
> }
>
> // See: https://go2goplay.golang.org/p/T7h15CdUEa3
> // WIP: https://github.com/goburrow/cache/tree/go2

The go2go tool is an experiment and it does not support all valid
code. It's particularly bad at embedding. In the real release it
should work to write

type LoadingCache[K comparable, V any] interface {

Cache[K, V]
Get(K) (V, error)
}

Ian

[Viet Nguyen]

Awesome. Thanks muchly