[go-nuts] How can i implement a "generic" base interface/struct hierarchy?

I want to do something like this http://play.golang.org/p/eIVIE_wP67
(pasted below) but i get

cannot use newAny() (type any) as type all in field value: need type
assertion


"all" is allowed to be an "any" in "newAny" but isn't allowed to be an
"any" when embedded in "allThing"?


package main

import "fmt"

type any interface{}
type all struct{}

func newAny() any {
  return all{}
}

type anyThing interface {
  any
}
type allThing struct {
  all
}

func newThing() anyThing {
  return allThing{all: newAny()} // This is not allowed
}

func main() {
  n := newThing()
  fmt.Printf("%T %+v", n, n)
}


Thanks