D2 Pointer confusion

[A Bothe]

Hey guys,
I got a problem with the following code:

void main()
{
        struct SomeStruct
        {
                int aa;
        }
        
        class SomeClass
        {
                int a;
                
                SomeStruct foo()
                {
                        SomeStruct m;
                        m.aa=a;
                        return m;
                }
        }
        
        SomeClass inst=new SomeClass();
        inst.foo.aa=20;
        
        assert(inst.a==20);
}


How can I make D set the member variable 'a' of SomeClass via this construction 
to another value?
And what's with using "ref SomeStruct foo() {}"?

Thanks in advance!

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