Nested struct member has no access to the enclosing class data

[RivenTheMage]

Is it bug or feature? :)

------------
class Foo
{
     int i;

     struct Bar
     {
         int j;

         int foobar()
         {
             return i + j;
         }
     }
}
------------

main.d(ХХ): Error: this for i needs to be type Foo not type Bar