[clang] [clang] Allow class with anonymous union member to be const-default-constructible even if a union member has a default member initializer (#95854) (PR #96301)

[Rajveer Singh Bharadwaj via cfe-commits]

================
@@ -1392,7 +1392,8 @@ class CXXRecordDecl : public RecordDecl {
   bool allowConstDefaultInit() const {
     return !data().HasUninitializedFields ||
            !(data().HasDefaultedDefaultConstructor ||
-             needsImplicitDefaultConstructor());
+             needsImplicitDefaultConstructor()) ||
+           hasInClassInitializer();
----------------
Rajveer100 wrote:

> This is a language extension so we get to choose its semantics, but I think the most logical choice is to reject because the union member is not _fully_ initialized.

At the moment, this gets accepted.

https://github.com/llvm/llvm-project/pull/96301