[clang] [Clang][Sema] Diagnosis for constexpr constructor not initializing a union member (PR #81225)

[Mariya Podchishchaeva via cfe-commits]

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@@ -149,9 +149,10 @@ Improvements to Clang's diagnostics
   prints.
 
 - Clang now diagnoses member template declarations with multiple declarators.
+- Clang now diagnoses use of the ``template`` keyword after declarative nested name specifiers.
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Fznamznon wrote:

I don't think this release note is about this patch, isn't it?
```suggestion
```

https://github.com/llvm/llvm-project/pull/81225