`__rvalue` is not working on Windows

[limepoutine]

Only when the struct has a move constructor will the program have expected behavior (no double free) on Windows. The two examples in DIP draft do not work.

struct MockAllocator
{
    enum size_t count = 100;
    enum void* baseAddr = cast(void*)0xc0ffee;
    static bool[count] freed;
    static size_t index;

    static void* alloc()
    {
        void* p = baseAddr + index;
        index++;
        return index <= count ? p : null;
    }

    static void free(void* p)
    {
        if (!p) return;
        ptrdiff_t d = p - baseAddr;
        assert(d >= 0 && d < count && !freed[d]);
        freed[d] = true;
    }
}

// Test argument passing

struct S1
{
    ubyte* p;
    ~this()
    {
        MockAllocator.free(p);
        p = null;
    }
}

void aggh(S1 s)
{
}

void testArgument()
{
    S1 s;
    s.p = cast(ubyte*)MockAllocator.alloc();
    aggh(__rvalue(s));
}

// Test move assignment

struct S2
{
    ubyte* p;
    ~this()
    {
        MockAllocator.free(p);
        p = null;
    }
    void opAssign(S2 s)
    {
        this.p = s.p;
        s.p = null;
    }
}

void testMoveAssign()
{
    S2 s;
    s.p = cast(ubyte*)MockAllocator.alloc();
    S2 t;
    t = __rvalue(s);
}