Use-after-scope bug in Phobos unittest, how to fix?

[Johan]

Hi all,
   I found a bug in Phobos typecons unittest:
https://github.com/ldc-developers/phobos/blob/6c83b490f7d6c66bf430e5249dae608848d3ac2c/std/typecons.d#LL7088C1-L7108C46
```d
pure @system unittest
{
     foreach (MyRefCounted; AliasSeq!(SafeRefCounted, RefCounted))
     {
         MyRefCounted!int* p;
         {
             auto rc1 = MyRefCounted!int(5);
             p = &rc1; // assigns reference to variable in inner 
scope...
             assert(rc1 == 5);
             assert(rc1._refCounted._store._count == 1);
             auto rc2 = rc1;
             assert(rc1._refCounted._store._count == 2);
             // Reference semantics
             rc2 = 42;
             assert(rc1 == 42);
             rc2 = rc2;
             assert(rc2._refCounted._store._count == 2);
             rc1 = rc2;
             assert(rc1._refCounted._store._count == 2);
         }
         assert(p._refCounted._store == null);  // use after scope!
```

The bug is uncovered when optimization and variable lifetime are 
considered with LDC.
I see that the test is trying to prove that the MyRefCounted 
dtors are run correctly when the scope ends. However, the way 
that this is tested is technically UB as far as I understand the 
D lang spec (although I cannot find explicit mention of variable 
lifetimes, please help...).
I can simply disable optimization for this unittest function 
(ldc.attributes.optStrategy), but would rather not.

Ideas?

thanks,
   Johan