alias can't find symbol or can't use symbol

[Carl Sturtivant via Digitalmars-d-learn]

Consider the following.

struct member
{
     int n;
}

struct outer
{
     member x;
     alias x this;
     alias n2 = n;
}

This does not compile: alias n2 = n;
Error: undefined identifier 'n'

On the other hand if change that into
     alias n2 = x.n;
then it does compile.

void main()
{
     outer o;
     o.n2 = 5;
}

Now this code doesn't compile: o.n2 = 5;
Error: need 'this' for 'n' of type 'int'

Given that one struct inside another is a static situation, this 
seems unnecessarily strict. It's getting in the way of some name 
management with `alias this`. What's the rationale here?