AA key conversion woes

[SomeDude]

On Wednesday, 18 April 2012 at 05:09:55 UTC, H. S. Teoh wrote:

> - Built-in reference types (pointers, refs, arrays) must be 
> either
>   tail-immutable, or the tail must be a struct or class (i.e., 
> the user
>   is allowed to use arrays of unqualified objects with custom 
> toHash and
>   opEquals as AA keys).
>
> This should allow the "nice" properties we can get from having 
> the type
> system enforce key immutability, for simple key types, and 
> still allow
> users to do complex stuff (define their own toHash/opEquals 
> that ignore
> parts of the object) when they need to.
>
> T

I'm not sure I got that part.

But for the rest, I tend to agree.
Actually, it's how it's done in Java: the Object class from which 
derive all the other classes, has an equals() and an hashCode() 
method. Of course these methods can be overriden.
http://docs.oracle.com/javase/6/docs/api/java/lang/Object.html