[Issue 24570] printing a range of ranges consumes sub-ranges

[d-bugmail at puremagic.com]

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

Salih Dincer <salihdb at hotmail.com> changed:

           What    |Removed                     |Added
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                 CC|                            |salihdb at hotmail.com

--- Comment #2 from Salih Dincer <salihdb at 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);
}
```

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