type someInterface interface { someFunc() } type A struct { } func(a A) someFunc() { } type B struct { A } type C struct { some A }

The provided Go code demonstrates interfaces and structures with embedding.

1. The someInterface interface defines the method someFunc().
2. The A struct implements the someFunc() method, so A satisfies the someInterface interface.
3. The B struct embeds A anonymously, meaning it inherits all methods of A and also satisfies someInterface through embedding.
4. The C struct contains a field some of type A with a named field, so the methods of A are not automatically promoted to C. Therefore, C does not implement someInterface unless it explicitly implements someFunc().

Example:

package main

import "fmt"

type someInterface interface {
    someFunc()
}

type A struct {}

func (a A) someFunc() {
    fmt.Println("A's someFunc")
}

type B struct {
    A // anonymous embedding
}

type C struct {
    some A // named field
}

func main() {
    var i someInterface

    a := A{}
    b := B{}
    c := C{}

    i = a // OK
    i.someFunc()

    i = b // OK, through embedding
    i.someFunc()

    // i = c // Compilation error: C does not implement someInterface
    
    // To make C implement the interface, explicitly define:
    // func (c C) someFunc() { c.some.someFunc() }
}

Thus, anonymous embedding allows a struct to automatically implement interfaces if the embedded type does, whereas named fields do not.