关于golang规范中方法值的部分中的“非接口方法”是什么意思？

Question

The Go Programming Language Specification says:

As with selectors, a reference to a non-interface method with a value receiver using a pointer will automatically dereference that pointer: pt.Mv is equivalent to (*pt).Mv.

and:

As with method calls, a reference to a non-interface method with a pointer receiver using an addressable value will automatically take the address of that value: t.Mp is equivalent to (&t).Mp.

So, what is non-interface method in the given context?

Answer 1

Interface method means the method you refer to (you call) is a call on an interface value (whose method set contains the method). Similarly, non-interface method means the method you refer to (you call) is not a call on an interface value (but on a concrete type).

For example:

var r io.Reader = os.Stdin
r.Read(nil) // Interface method: type of r is an interface (io.Reader)

var p image.Point = image.Point{}
p.String() // Non-interface method, p is a concrete type (image.Point)

To demonstrate the auto-dereferencing and address taking, see this example:

type myint int

func (m myint) ValueInt() int { return int(m) }

func (m *myint) PtrInt() int { return int(*m) }

func main() {
    var m myint = myint(1)

    fmt.Println(m.ValueInt()) // Normal
    fmt.Println(m.PtrInt())   // (&m).PtrInt()

    var p *myint = new(myint)
    *p = myint(2)

    fmt.Println(p.ValueInt()) // (*p).ValueInt()
    fmt.Println(p.PtrInt())   // Normal
}

It outputs (try it on the Go Playground):

1
1
2
2