fix(variant): support non-trivially destructable types

Author: Nerixyz

lldb/source/Plugins/Language/CPlusPlus/MsvcStlVariant.cpp

@@ -69,14 +69,18 @@ std::optional<int64_t> GetIndexValue(ValueObject &valobj) {
 }
 
 ValueObjectSP GetNthStorage(ValueObject &outer, int64_t index) {
-  // We need to find the std::_Variant_storage base class.
-
-  // -> std::_SMF_control (typedef to std::_Variant_base)
-  ValueObjectSP container_sp = outer.GetSP()->GetChildAtIndex(0);
-  if (!container_sp)
+  // navigate "down" to std::_SMF_control/std::_Variant_base
+  // by finding the holder of "_Which". This might be down a few levels if a
+  // variant member isn't trivally destructible/copyable/etc.
+  ValueObjectSP which_sp = outer.GetChildMemberWithName("_Which");
+  if (!which_sp)
     return nullptr;
-  // -> std::_Variant_storage
-  container_sp = container_sp->GetChildAtIndex(0);
+  ValueObject *parent = which_sp->GetParent();
+  if (!parent)
+    return nullptr;
+
+  // Now go to std::_Variant_storage
+  ValueObjectSP container_sp = parent->GetChildAtIndex(0);
   if (!container_sp)
     return nullptr;