Why is &array[0] @safer than array.ptr?

[Atila Neves via Digitalmars-d-learn]

On Tuesday, 24 January 2017 at 11:32:47 UTC, TheFlyingFiddle 
wrote:
> On Tuesday, 24 January 2017 at 11:28:17 UTC, Atila Neves wrote:
>> void main() {
>>     foo;
>> }
>>
>> void foo() @safe {
>>     int[] array;
>>     auto ptr = array.ptr;
>> }
>>
>>
>> foo.d(7): Deprecation: array.ptr cannot be used in @safe code, 
>> use &array[0] instead
>>
>>
>> &array[0] is incredibly ugly and feels like an unnecessary 
>> hack, and I'm wondering why it's @safe.
>>
>> Atila
>
> Just a speculative guess.
>
> unittest @safe
> {
>    int[] array;
>
>    auto ptr  = array.ptr; //could be null
>    auto ptr2 = &array[0]; //Does a bounds check?
>    auto ptr3 = &array[5]; //Should do a bounds check.
> }

&array[5] makes sense to bounds check, and I guess then the issue 
is I could instead do `array.ptr + 5` which would be bad. But 
it's still annoying to have to do &array[0] just to pass it to a 
C function, since `my_c_func(array.ptr)` isn't going to screw up 
anything.

BTW, in that example above array.ptr is null even though array is 
null. It doesn't crash.

Atila