[clang] [Clang] [Sema] Error on reference types inside a union with msvc 1900+ (PR #102851)

[Max Winkler via cfe-commits]

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@@ -619,6 +616,20 @@ template<typename T> struct A {};
 template<typename T> struct B : A<A<T>> { A<T>::C::D d; }; // expected-warning {{implicit 'typename' is a C++20 extension}}
 }
 
+#elif TEST4
+
+union u {
+    int *i1;
+    int &i2;  // expected-warning {{union member 'i2' has reference type 'int &', which is a Microsoft extension}}
+};
+
+#elif TEST5
+
+union u {
+    int *i1;
+    int &i2;  // expected-error {{union member 'i2' has reference type 'int &'}}
+};
+
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MaxEW707 wrote:

The more you know. Putting this into my notes. I'll get this cleaned up :).

https://github.com/llvm/llvm-project/pull/102851