This is not supported in D and to concatenate string literals an explicit ‘~’ operator is required. I’m in two minds as to whether that is a good thing, and am not settling either way. I would be interested to know what the arguments were for and against, when this design aspect was chosen.

This use to work.

It was removed a few years ago.

On Sunday, 25 June 2023 at 21:22:49 UTC, Richard (Rikki) Andrew Cattermole wrote:
> This use to work.
>
> It was removed a few years ago.

I think so too. I recently had to rework a lot of old code because of it, a real nuisance. Was it thought that null concat was dangerous somehow? A recipe for potential for some kind of mistakes? I presume that reinstating it would be safe enough? If there’s any reason to.

On Sunday, 25 June 2023 at 21:39:13 UTC, Dave P. wrote:
> On Sunday, 25 June 2023 at 21:30:52 UTC, Cecil Ward wrote:
>> On Sunday, 25 June 2023 at 21:22:49 UTC, Richard (Rikki) Andrew Cattermole wrote:
>>> This use to work.
>>>
>>> It was removed a few years ago.
>>
>> I think so too. I recently had to rework a lot of old code because of it, a real nuisance. Was it thought that null concat was dangerous somehow? A recipe for potential for some kind of mistakes? I presume that reinstating it would be safe enough? If there’s any reason to.
>
> It’s easy to make this mistake:
>
> ```d
> const x = [
>      "foo"
>      "bar",
>      "baz"
> ];
> ```
>
> `x` only has 2 elements, when it looks like it has 3.

An excellent point. I now fall in with the new status quo. :-)

On Sunday, 25 June 2023 at 21:47:01 UTC, Cecil Ward wrote:
>>
>> `x` only has 2 elements, when it looks like it has 3.
>
> An excellent point. I now fall in with the new status quo. :-)

And it's exactly the reasoning behind the deprecation.
You can find it in the changelog for 2.072, where this deprecation was introduced: https://dlang.org/changelog/2.072.0.html#deprecated_implicit_cat

Note that using the concat operator gives you exactly the same behavior: Concatenation happens at compile time, there is no runtime cost / GC allocation.