[Issue 13805] Nested struct initialization error

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=13805

Kenji Hara <k.hara.pg at gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|DMD                         |Phobos
           Hardware|x86                         |All
                 OS|Windows                     |All

--- Comment #1 from Kenji Hara <k.hara.pg at gmail.com> ---
This would be a Phobos bug in GroupByImpl struct.

    static if (isForwardRange!Range)
    {
        private Range _prev;
        private void savePrev() { _prev = r.save; }
        private @property ElementType!Range prev() { return _prev.front; }
    }
    else
    {
        private ElementType!Range _prev;
        private void savePrev() { _prev = r.front; }
        private alias prev = _prev;
    }

    this(Range _r)
    {
        r = _r;
        if (!empty)
        {
            // Check reflexivity if predicate is claimed to be an equivalence
            // relation.
            assert(!equivRelation || pred(r.front, r.front),
                   "predicate " ~ pred.stringof ~ " is claimed to be "~
                   "equivalence relation yet isn't reflexive");
            savePrev();   // <---- here
        }
    }

As error message says, the _prev field is not correctly initialized inside
constructor. Indeed, it's assigned in savePrev member function, but compiler
cannot handle the assignment as the initialization.

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