Bug in the spec or implementation?

[Don]

simendsjo wrote:
> On 05.08.2010 22:24, Steven Schveighoffer wrote:
>> On Thu, 05 Aug 2010 16:00:35 -0400, simendsjo
>> <simen.endsjo at pandavre.com> wrote:
>>
>>> On 05.08.2010 21:41, Steven Schveighoffer wrote:
> (...)
>>> Seems there are plenty of errors in the spec though...
>>> It will be very difficult to learn the language if the spec and
>>> implementation is different. Spec or compiler bug?
>>>
>>>
>>> char[] a = new char[20];
>>> char[] b = a[0..10];
>>> assert(a.ptr == b.ptr); // hmm.. does slice has a offset property or
>>> something?
>>>
>>> // In the spec on arrays#Setting Dynamic Array Length,
>>> // this is the example, but it doesn't work as in the spec...
>>>
>>> char[] c = a[10..20];
>>> // The spec says expanding b.length should expand
>>> // in place as a has enough memory and thus overlapping a, but...
>>> assert(b.capacity == 0); // capacity is 0, so...
>>> b.length = 15;
>>> assert(b.capacity == 15); // .. setting length removed it from a..
>>> assert(a.ptr == b.ptr); // fails...
>>> b[11] = 'x'; // Says a[11] and c[1] should also change..
>>> assert(a[11] == 'x'); // fails
>>> assert(c[1] == 'x'); // fails
>>>
>>
>> Yep, I noticed that too when going to file the bug :)
>>
>> see here: http://d.puremagic.com/issues/show_bug.cgi?id=4590
>>
>> I should take responsibility for not fixing this sooner since the
>> runtime used to work this way, but does not since a patch I added in
>> 2.041 or 2.042.
>>
>> Sorry.
>>
>> -Steve
> 
> Thanks again!
> Hope spec bugs have high priorities as it's difficult to learn the 
> language otherwise. Are the compiler pretty stable, so I can assume most 
> bugs are in the spec, or is it the other way around?
> 
> 

Rule of thumb:
If the code compiles, but behaves differently to what the spec says, you 
can be pretty sure it's a spec bug. If the spec says it should work, but 
the compiler rejects it, it's most likely a compiler bug.