Seems like bug in the translation tool

type Nat interface {
	type Zero, Succ
}

type Zero struct{}
type Succ struct{ Nat }

becomes

type Zero struct{}
type Succ struct{ Nat }

type Importable୦ int

where Nat is not defined.

This shouldn't pass the type checker. You aren't allowed to embed an interface with a type list into a struct. An interface with a type list can only be used as a type constraint, not as a general type.

So, yes, the translation tool mishandles it, but this code shouldn't get to the translation tool at all.

var _ map[A]struct{}
var _ map[int]A
var _ []A
var _ chan A

https://go2goplay.golang.org/p/TKaDmb6jrop
passes the type checker too

Change https://golang.org/cl/251718 mentions this issue: [dev.go2go] go/types: interfaces with type lists cannot be embedded in structs

Fixed on dev.go2go branch.