Seeking help with opend std

[Dennis]

On Monday, 13 January 2025 at 12:26:07 UTC, Anton Pastukhov wrote:
> My uninformed opinion is that shouldn't cause too much trouble? 
> popFront and popBack currently return void, so it's safe to 
> assume there are no places in the existing code that expect a 
> return value, so it's just going to be discarded.

It would break this mini implementation of `map`:

```D
private struct MapResult(alias func, R)
{
     R r;
     auto front() => func(r.front);
     bool empty() => r.empty;
     void popFront() => r.popFront();
}
```