Deprecation: foreach: loop index implicitly converted from size_t to int

[user1234]

On Friday, 3 May 2024 at 14:59:57 UTC, BoQsc wrote:
> On Friday, 3 May 2024 at 13:18:02 UTC, user1234 wrote:
>> On Friday, 3 May 2024 at 10:50:03 UTC, BoQsc wrote:
>>> [...]
>>
>> **You can specify the index type, just choose the right one.** 
>> For now there's a deprecation message but after some while 
>> you'll get a proper error message, e.g _"index type for arr 
>> must be of type T because arr.length type is T"_.
>>
>> What's is happening now is to help people updating their code 
>> and prevent abrupt breakages.
>
>
>
>
> So how would you update this example, what is the right index 
> type here to choose?
>
> ```
> import std.stdio : writefln;
>
> void main() {
>     auto arr = [
>         [5, 15],      // 20
>         [2, 3, 2, 3], // 10
>         [3, 6, 2, 9], // 20
>     ];
>
>     foreach (i, row; arr)
>     {
>         double total = 0.0;
>         foreach (e; row)
>             total += e;
>
>         auto avg = total / row.length;
>         writefln("AVG [row=%d]: %.2f", i, avg);
>     }
> }
> ```
>
> Example taken from https://tour.dlang.org/tour/en/basics/foreach

Isn't that obvious ?

```d
foreach (const size_t i, row; arr)
```

`arr` is not a static array, it is a dynamic one, consequently 
its `.length` type is `size_t`, even if you have the feeling 
that, in the present situation, `int` bitwidth would be 
sufficient.