[Issue 22359] joiner over an empty forward range object liable to segfault

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=22359

--- Comment #2 from Adam D. Ruppe <destructionator at gmail.com> ---
A patched function that can fix the issue:


        static if (isForwardRange!RoR && isForwardRange!(ElementType!RoR))
        {
                @property auto save()
                {
                        static if(is(typeof(null) : typeof(_current))) {
                                auto r = Result(_items.save, _current is null ?
                                null : _current.save);
                        } else
                                auto r = Result(_items.save, _current.save);
                        static if (isBidirectional)
                        {
                                static if(is(typeof(null) :
                                typeof(_currentBack))) {
                                        r._currentBack = _currentBack is null ?
                                        null : _currentBack.save;
                                } else {
                                        r._currentBack = _currentBack.save;

                                }
                                r.reachedFinalElement = reachedFinalElement;
                        }
                        return r;
                }
        }

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