What version of Go are you using (go version)?

$ go version

What did you do?

type A1 []int

func (a A1) Len() int {
	return len(a)
}

type A2 A1

func main() {
	a1 := make(A1, 0)
	println(a1.Len()) // ok

	a2 := make(A2, 0)
	println(a2.Len()) // error
}

What did you expect to see?

0
0

What did you see instead?

a2.Len undefined (type A2 has no field or method Len)