[clang] [Clang] Minimal support for availability attributes on partial specializations (PR #138426)

[Erich Keane via cfe-commits]

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@@ -586,6 +586,9 @@ Bug Fixes to Attribute Support
   ``__attribute__((unused))`` are still ignored after the definition, though
   this behavior may be relaxed in the future). (#GH135481)
 
+- Clang will warn if a completete type specializes a deprecated partial specialization.
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erichkeane wrote:

```suggestion
- Clang will warn if a complete type specializes a deprecated partial specialization.
```

https://github.com/llvm/llvm-project/pull/138426