[Issue 22552] New: moveEmplace wipes context pointer of nested struct contained in non-nested struct

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=22552

          Issue ID: 22552
           Summary: moveEmplace wipes context pointer of nested struct
                    contained in non-nested struct
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: druntime
          Assignee: nobody at puremagic.com
          Reporter: stanislav.blinov at gmail.com

import core.lifetime;

void main()
{
    int i;

    struct Nested
    {
        ~this() { ++i; }
    }

    static struct NotNested
    {
        Nested n;
    }

    auto a = NotNested(Nested()); // when this is destructed things go boom...

    NotNested b = void;
    moveEmplace(a, b); // ...because this wipes context pointer in a.n
} // segmentation fault

---

That's because moveEmplace simply blits NotNested.init into a. Instead it
probably should move things fieldwise and avoid wiping context pointers in
fields that are nested structs.

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