[Issue 22966] New: Inconsistent `shared`attribute for generated destructor

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=22966

          Issue ID: 22966
           Summary: Inconsistent `shared`attribute for generated
                    destructor
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: kinke at gmx.net

The `shared` attribute for a generated destructor seems NOT to depend on the
aggregate alone:

```
struct WithDtor {
    int x;
    ~this() {}
}

struct A {
    WithDtor withDtor;
}

struct B {
    version (Shared)
        shared A a;
    else
        A a;
}

struct C {
    A a;
}

void main() {
    B b;
    pragma(msg, A.__xdtor.mangleof);
}
```

With DMD v2.099:
```
$ dmd -o- foo.d
_D3mod1A11__fieldDtorMFZv
$ dmd -o- foo.d -version=Shared
_D3mod1A11__fieldDtorMOFZv
```

This leads to linker errors in real-world code.

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