What is the correct syntax for inner struct literals in Go?

Question

I would like to initialize A with all its inner structs in a literal form.

package main

import "fmt"

type A struct {
    B struct {
        C struct {
            D string
        }
    }
}

func main() {
    x := A{B{C{D: "Hello"}}}
    y := A{B.C.D: "Hello"}

    fmt.Println(a)
}

What is the correct syntax?

I need this to build structs for XML marshaling.

Answer 1

You must declare the literal type for structs when building Composite literals.

This makes it rather tedious if using only anonymous types. Instead, you should consider declaring each struct separately:

package main

import "fmt"

type A struct {
    B B
}

type B struct {
    C C
}

type C struct {
    D string
}

func main() {
    x := A{B: B{C: C{D: "Hello"}}}
    // x := A{B{C{"Hello"}}} // Without using keys

    fmt.Println(x)
}

Edit:

Initializing the struct with anonymous types as shown in your example, would look like this:

x := A{struct{ C struct{ D string } }{struct{ D string }{"Hello"}}}