Can not convert a generic struct type to a generic interface type in golang

[Log4bob]

Given there's a generic interface:

type Packet interface { Content() int } type Recycler[T any] interface { Get() *T }

and their implementation:

type packet struct { content int } type BaseRecycler[T any] struct { t T }

its impossible to convert the implementation to the interface:

r := &BaseRecycler[packet]{} r1 := r.(Recycler[Packet]) fmt.Println(r3.Get().Content()) // compile error: Unresolved reference 'Content'

here is a live code example: https://go.dev/play/p/qbnYfyDd22A

The error is because the Packet interface align with the *packet instead of packet. Could anyone suggest how to handle this?

[Marvin Renich]

* Log4bob <qdon...@gmail.com> [241028 08:47]:

If you uncomment line 39 (assignment to r3), add «_ = r3» to avoid
"unused variable" error, and run it, you get a runtime panic. Your
primary problem is related to this FAQ:

https://go.dev/doc/faq#convert_slice_of_interface

because BaseRecycler[packet] is "struct { t packet }" not "struct { t
Packet }" so r is *struct { t packet }, which has a different, and
differently sized, internal representation.

What are you really trying to do?

...Marvin

[Jason Phillips]

The Go FAQ has another, perhaps slightly more applicable, entry:

https://go.dev/doc/faq#t_and_equal_interface

Basically, even though *packet satisfies the Packet interface,

    interface {

        Get() *packet

    }

Is different than

    interface {

        Get() Packet

    }

And one isn't directly convertible into the other. In Go, interface signatures must match _exactly_ in order to satisfy an interface.

Jason

[Jason Phillips]

And by "interface signatures" I of course meant method signatures in the corresponding interface method sets.

[noreply_...@shipt.com]

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