c++ - is there a way to have "inline" structs (similar to inline namespaces)

Question

If I have two structs:

struct Base {
    int a;
};

struct Derived : Base {
    int b;
};

then with an instance Derived d, I can directly access a and b as d.a and d.b.

However with this setup, Derived isn't a standard layout type.

If I wanted to make it standard layout, I could do something like:

struct Derived {
    Base base;
    int b;
};

but then to access a I'd have to use d.base.a instead of d.a as before.

Can I can declare the Derived struct in a way that lets me access a and b as in the first example, while keeping it a standard layout type?