if(arr) now a warning

[Iain Buclaw via Digitalmars-d]

On 30 April 2015 at 04:41, Steven Schveighoffer via Digitalmars-d
<digitalmars-d at puremagic.com> wrote:
> On 4/29/15 4:29 AM, Iain Buclaw via Digitalmars-d wrote:
>>
>> On 29 April 2015 at 06:38, Steven Schveighoffer via Digitalmars-d
>> <digitalmars-d at puremagic.com> wrote:
>>>
>>> FYI, Andrei and Walter are reversing this change barring any new evidence
>>> it's helpful to people. Please speak up if you disagree.
>>>
>>>
>>> https://github.com/D-Programming-Language/dmd/pull/2885#issuecomment-97299912
>>>
>>
>> I disagree, and I would extend my thoughts to say that I don't think
>> that the change is enough.  We should also be warning on delegates and
>> associative arrays too!
>>
>> if (arr)  // Implicitly converted to (arr.ptr | arr.length) != 0
>
> if(arr) simply means if(arr.ptr) != 0. Length does not come into play.
>

https://github.com/D-Programming-Language/dlang.org/pull/981#commitcomment-10918439

The two mov's followed by an 'or' suspiciously look like (.ptr | .length) to me.

>> if (dg)  // Implicitly converted to (dg.ptr | dg.funcptr) != 0
>
>
> I don't know if I've ever expected that, you sure that's true? I would
> actually expect if(dg) to be equivalent to if(dg.funcptr). I have no idea
> how a dg would have a null pointer but valid funcptr.
>

Yes, it does (it emits the same assembly as arrays).

>> if (aa)  // Implicitly converted to (aa.ptr != null)
>
>
> This is easily fixed when we fix aa to be a library type. We don't need
> compiler help to fix this issue (we do need compiler help to remove AA
> specialty code from the compiler, but once it's out, we can fix this without
> effort).
>

It's still annoying to have to special-case non-scalar types in
boolean contexts.  The front-end should do this lowering. :-)

https://github.com/D-Programming-GDC/GDC/blob/e9bfc0332e42d01402aeb2063d38fc5ea4e12fea/gcc/d/d-codegen.cc#L605

Iain.