Bug in the spec or implementation?

[simendsjo]

On 05.08.2010 20:53, Steven Schveighoffer wrote:
> On Thu, 05 Aug 2010 14:45:18 -0400, simendsjo
> <simen.endsjo at pandavre.com> wrote:
>
>> This is only tested on dmd 2.047 on win7.
>>
>> According to the spec at http://digitalmars.com/d/2.0/arrays.html:
>> "Concatenation always creates a copy of its operands, even if one of
>> the operands is a 0 length array"
>>
>> But this doesn't seem like the case:
>>
>> auto a = [0];
>> auto oldPtr = a.ptr;
>> assert(a.length == 1);
>> assert(a.capacity == 3);
>> a ~= 1;
>> assert(a.ptr != oldPtr); // Fails - Still the same array
>
> Concatenation is this:
>
> a ~ 1
>
> appending is this:
>
> a ~= 1
>
> Two separate operations, two separate semantics. It might not be easy to
> determine that from the spec, but I believe the spec is clear.
>
> -Steve

Hmm... Doing "a = a ~ 1", and it works like specified.
I always assumed that composite operators would mean the same..
That "a += 1" is the same as "a = a + 1" etc.
I cannot find this behavior explained in the spec though..

 From the Expression spec, I found that "a op= b" is the same as "a = a 
op b" - see "Assignment Operator Expressions".
No mention of a CatAssignExpression behaving differently. Array doesn't 
mention anything either.