if(arr) now a warning

[via Digitalmars-d]

On Friday, 10 April 2015 at 10:09:18 UTC, jkpl wrote:
> Then, imagine that the syntactic shortcut is accepted, this 
> would lead to the following confusion:
> ---
> char[] * arr;
> if(arr)
> ---
> Here the test is really about the array being null or not.

`arr` is a pointer, not an array. I don't understand what you're 
arguing here.

>
> It's like in the topic from yesterday:
>
> ---
> void a(uint p, string a = null){}
> ---
>
> Totally wrong, the guy should write:
>
> ---
> void a(uint p, string a = ""){}
> ---
>

I don't know what that topic was about, but there is nothing 
obviously wrong with either version. The language mostly treats 
both the same way:

     string nullstr = null;
     assert(nullstr == "");
     assert(nullstr.length == 0);

The only difference is that "" has a non-null address:

     assert(!nullstr.ptr);
     assert("".ptr);

OTOH, maybe the programmer in question actually wants to make a 
distinction between the two, and there's nothing wrong with doing 
that either.

> because if you pass a struct as param, the param is never null !

So what? An array isn't a struct.

>
> I'm against the shortcut...it doesn't help to understand how it 
> works. It's a useless and confusing shortcut. Warning about the 
> amibuous usage was the right
> to do.

I don't think it's confusing. Also note that the shortcut (=> 
length) is much more likely to be correct. There are lots of 
non-null empty arrays, but I don't know a non-contrived way to 
accidentally end up with a non-empty null array.