enum - auto

[so]

Auto and immutable.
Can we please put an end to this issue?
I remember a few discussions, never a complete answer, but many  
contradicting answers.

1. Is enum (its current usage) still a temporary hack to a technical  
limitation on immutable?
2. Can or Will immutable replace enum? (Not that i want such a change)
3. Isn't enum a higher order immutable, which is guarantied to be a  
compile time constant?

--

Another issue, auto.
I was thinking that it works like C++0x auto.
Now i realize they are not that alike. Can anyone show me the D equivalent  
of the code below?

struct test {
     int a;
};

void main() {
     test tmp;
     auto& a = tmp.a;
}

Thanks.