[clang] [Clang][Interp] Fix the location of uninitialized base warning (PR #100761)

[Timm Baeder via cfe-commits]

================
@@ -122,19 +124,21 @@ static bool CheckFieldsInitialized(InterpState &S, SourceLocation Loc,
   }
 
   // Check Fields in all bases
-  for (const Record::Base &B : R->bases()) {
+  for (auto [I, B] : llvm::enumerate(R->bases())) {
     Pointer P = BasePtr.atField(B.Offset);
     if (!P.isInitialized()) {
       const Descriptor *Desc = BasePtr.getDeclDesc();
-      if (Desc->asDecl())
-        S.FFDiag(BasePtr.getDeclDesc()->asDecl()->getLocation(),
-                 diag::note_constexpr_uninitialized_base)
+      if (const auto *CD = dyn_cast_or_null<CXXRecordDecl>(R->getDecl())) {
----------------
tbaederr wrote:

```suggestion
      if (const auto *CD = dyn_cast_if_present<CXXRecordDecl>(R->getDecl())) {
```

https://github.com/llvm/llvm-project/pull/100761