How to copy const object?

[Mitacha]

I've a const struct object and I'd like to make a mutable copy of 
it.
Struct definition contains string and an array of structs.
```
struct A {
     string a;
     B[] b;
}

struct B {
     string a;
     string b;
}
```
As far as I can tell copy constructor isn't generated for struct 
`A` because it contains an array. Correct?

Is there an idiomatic way to create copy of a const object?