[clang] [Clang][C++23] Implement P2448R2: Relaxing some constexpr restrictions (PR #77753)

[via cfe-commits]

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@@ -1722,12 +1722,19 @@ static bool CheckConstexprDestructorSubobjects(Sema &SemaRef,
       return true;
 
     if (Kind == Sema::CheckConstexprKind::Diagnose) {
-      SemaRef.Diag(DD->getLocation(), diag::err_constexpr_dtor_subobject)
+      SemaRef.Diag(DD->getLocation(),
+                   SemaRef.getLangOpts().CPlusPlus23
+                       ? diag::warn_cxx23_compat_constexpr_dtor_subobject
+                       : diag::ext_constexpr_dtor_subobject)
           << static_cast<int>(DD->getConstexprKind()) << !FD
           << (FD ? FD->getDeclName() : DeclarationName()) << T;
       SemaRef.Diag(Loc, diag::note_constexpr_dtor_subobject)
           << !FD << (FD ? FD->getDeclName() : DeclarationName()) << T;
     }
+
+    if (SemaRef.getLangOpts().CPlusPlus23)
+      return true;
+
     return false;
----------------
cor3ntin wrote:

```suggestion
return SemaRef.getLangOpts().CPlusPlus23;
```

https://github.com/llvm/llvm-project/pull/77753