recursion - Swift struct type recursive value

Question

Structs can't have recursive value types in Swift. So the follow code can't compile in Swift

struct A {
    let child: A
}

A value type can not be recursive, because it would have infinite size.But I wonder why the follow code can compile?

struct A {
    let children: [A]
}

Answer 1

I think it's about the required space.

Infinite space

To create a value of this type

struct A {
    let child: A
}

we need

• the space for the current struct
• the space for the child
• the space for the child's child
• ...

So we need infinite space.

Finite space

On the other hand to create a value of this

struct A {
    let children: [A]
}

we only need

• the space for A
• the space for an empty Array.