Is it necessary to import interface definition package?

[binbai]

I’m learning Golang, the design is pretty.
But while I try separating interface definition and implementation, I meet compile error:

.\main.go:16: cannot use new(dog.Dog) (type *dog.Dog) as type animal.Animal in assignment:
*dog.Dog does not implement animal.Animal (wrong type for Born method)
have Born() *dog.Dog
want Born() animal.Runner

While, if the “iface/animal” is imported in dog.go, and the Run function return type is animal.Runner, everything is fine, but it’s ugly.

Is it necessary to import interface definition package?

Source code:

// animal.go
package animal

type Animal interface {
Born() Runner
}

type Runner interface {
Run()
}

// dog.go
package dog

type Dog struct {
}

func (d *Dog) Born() *Dog {
dd := new(Dog)
return dd
}

func (d *Dog) Run() {
}

// iface project main.go
package main

import (
“fmt”

"iface/animal"
"iface/dog"

)

var (
dd animal.Animal
)

func main() {
dd = new(dog.Dog)

fmt.Printf("%t %v\n", dd, dd)

}

[calmh (Jakob Borg)]

*dog.Dog does not implement animal.Animal (wrong type for Born method)
		have Born() *dog.Dog
		want Born() animal.Runner

In Go, method signatures must match precisely for an interface to be satisfied. That means that even though a type *dog.Dog may implement the animal.Runner interface on it’s own, a method func Born() *dog.Dog does not implement an interface expecting a func Born() animal.Runner.

[binbai]

Thanks Jakob.

It’s understandable that current method signature checking is not recursively.

I mean it still looks ugly, and violate the base Go design rule of avoid import explicitly.
It’s that possible to support implementation of interface implicitly recursively?