Walter's second axiom

[Walter Bright]

Janice Caron wrote:
> This is not a feature request as such. I'm just mentioning - from a
> purely theoretical standpoint - a violation of Walter's second axiom,
> and a possible remedy.

That axiom didn't really exist until Andrei started pointing out to me 
all the advantages of being able to wrap types in a struct. So we can 
expect some historical problems with it.

But it is a very useful one going forward with changes to the language, 
as it keeps us from making things worse. I suspect that the closer we 
can adhere to that axiom, the better generic programming will work.

Other axioms in D have been there from the beginning, and have helped 
keep the language on track. For example:

1) D can be lexed with no syntactic information
2) D can be parsed with no semantic information
3) Modules can be imported in any order without affecting their meaning
4) The meaning of imported declarations is not affected by the context 
of where they are imported