Declaring constant references in struct members

[David Zhang via Digitalmars-d-learn]

On Thursday, 16 February 2017 at 00:49:45 UTC, Adam D. Ruppe 
wrote:
> On Thursday, 16 February 2017 at 00:43:30 UTC, David  Zhang 
> wrote:
>> struct S {
>>     O object;
>> }
>
> import std.typecons;
>
> Rebindable!O object;
>
> http://dpldocs.info/experimental-docs/std.typecons.Rebindable.html

Is there a similar mechanism for one struct holding another? 
Otherwise, you get a cannot modify X with immutable members error.

eg:

struct A {
     B b;
}

struct B {
     const size_t something;
}

A a = A(B(16));

//attempt to replace a.b with new B
a.b = B(32); //error: cannot modify struct a.b B with immutable 
members