Cannot implement interface methods for multiple structs placed in the same package

Question

I have three files:

node.go:

type Node interface {
    AMethod(arg ArgType) bool
    BMethod() bool
}

anode.go:

type aNode struct {}

func AMethod(aNode ANode, arg ArgType) bool {
    return true
}

func BMethod(aNode ANode) bool {
    return true
}

bnode.go:

type bNode struct {}

func AMethod(bNode BNode, arg ArgType) bool {
    return true
}

func BMethod(bNode BNode) bool {
    return true
}

But I'm getting the error:

Nodes/bnode.go:16:58: AMethod redeclared in this block
    previous declaration at Nodes/anode.go:15:58
Nodes/bnode.go:20:60: BMethod redeclared in this block
    previous declaration at Nodes/anode.go:19:60

How do I validly implement an interface here?

That's not how you declare methods. See the Tour of Go #Methods, Effective Go, or any other documentation — Mr_Pink
– Mr_Pink, Commented Sep 1, 2017 at 13:50

score 3 · Accepted Answer · 2017-09-01 13:56:47Z

3

Declaring a function that accepts a certain type does not make that function part of the type's method set (meaning it does not help the type satisfy a particular interface).

Instead, you need to use the proper syntax to declare a function as a method, like so:

type BNode struct {}

func (ANode) AMethod(arg ArgType) bool {
    return true
}

func (ANode) BMethod() bool {
    return true
}

type BNode struct {}

func (BNode) AMethod(arg ArgType) bool {
    return true
}

func (BNode) BMethod() bool {
    return true
}

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