Has the ban on returning function nested structs been lifted?

[Andrej Mitrovic]

This seems to work with classes as well. The TDPL has an example of a
class that subclasses a class definition in module scope. But this one
is defined in function scope, doesn't derive, and still works:

void main()
{
    auto local = foo(0);
    assert(local.sum() == 30);
}

auto foo(int a)
{
    int z = a + 10;

    class Local
    {
        int x = 10;
        int y = 10;

        int sum()
        {
            return x + y + z;
        }
    }
    return new Local();
}