https://issues.dlang.org/show_bug.cgi?id=24570

--- Comment #1 from Steven Schveighoffer <schveiguy@gmail.com> ---
A further note is that an array of arrays is not consumed when printed -- because formatValue has a specialized case for that.

--

https://issues.dlang.org/show_bug.cgi?id=24570

Salih Dincer <salihdb@hotmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |salihdb@hotmail.com

--- Comment #2 from Salih Dincer <salihdb@hotmail.com> ---
(In reply to Steven Schveighoffer from comment #1)
> A further note is that an array of arrays is not consumed when printed -- because formatValue has a specialized case for that.

If you do the following instead of `auto save() => return this;`, the problem
is solved:

```
struct R
{
  wchar* ptr;
  size_t len;

  this(T)(T[] range)
  {
    ptr = cast(wchar*)range.ptr;
    len = range.length;
  }

  auto empty() => len == 0;
  auto front() => *ptr++;
  auto popFront() => len--;
  auto save()
  {
    auto r = R([]);
    r.len = len;
    r.ptr = ptr;
    return r;
  }
}

void main()
{
  auto c = ['€', '₺', '₽'];
  auto r = R(c);
  auto arr = [r, r, r];

  assert(!arr.empty);

  import std.conv : text;
  auto str = arr.text; // "€₺₽"

  assert(!arr.empty);
}
```

--

https://issues.dlang.org/show_bug.cgi?id=24570

--- Comment #3 from Salih Dincer <salihdb@hotmail.com> ---
There's no reason why this issue can't be easily fixed. Because when you include narrow string or wchar, there is no problem of not being able to save(): https://forum.dlang.org/post/qgtrcupsniezqgazkztd@forum.dlang.org

--

https://issues.dlang.org/show_bug.cgi?id=24570

--- Comment #4 from Steven Schveighoffer <schveiguy@gmail.com> ---
(In reply to Salih Dincer from comment #2)

> If you do the following instead of `auto save() => return this;`, the
> problem is solved:
> 
> ```
> struct R
> {
>   wchar* ptr;
>   size_t len;
> 
>   this(T)(T[] range)
>   {
>     ptr = cast(wchar*)range.ptr;
>     len = range.length;
>   }
> 
>   auto empty() => len == 0;
>   auto front() => *ptr++;

this is an invalid implementation. Using `front` more than once is supported.

>   auto popFront() => len--;
>   auto save()
>   {
>     auto r = R([]);
>     r.len = len;
>     r.ptr = ptr;
>     return r;
>   }
> }
> 
> void main()
> {
>   auto c = ['€', '₺', '₽'];
>   auto r = R(c);
>   auto arr = [r, r, r];
> 
>   assert(!arr.empty);
> 
>   import std.conv : text;
>   auto str = arr.text; // "€₺₽"
> 
>   assert(!arr.empty);

But it was never arr that was empty. It's just an array of empty ranges at this point.

But the difference here is that you are using wchar and not short. format treats character data differently (as evidenced by the printout, it's not an array of items, but a string).

Yet another reason why this bug has gone undetected for so long.

--