More magical AA semantics

[monarch_dodra]

On Friday, 11 January 2013 at 09:50:18 UTC, deadalnix wrote:
> On Friday, 11 January 2013 at 08:55:55 UTC, Bernard Helyer 
> wrote:
>> I completely agree. Doesn't the spec say that relying on
>> the order of assignment evaluation is undefined?
>
> After a long discussion with Andrei, it seems that it is left 
> to right.

This seems wrong to me.

In particular, if you define an opIndexAssign, then the RHS *has* 
to be evaluated first (from a "visual" point of view, since LHS 
is pretty much "this").

//----
a[0] = a[0]
//----
Becomes
//----
a.opIndexAssign(a[0], 0);
//----

On a related note, I don't know how AA's are actually 
implemented, but it sounds like giving them opIndexXXX would 
solve a lot of our problems:
* Initialization to T.init if RHS throws
* a[0] = a[0]; runs if there is no a[0].

Or even code such as this:
//----
     int[int] a;
     ++a[0];
//----
In what universe do we actually expect this to work? It shouldn't.