[clang] [clang] Improve `_Alignas` on a `struct` declaration diagnostic (PR #65638)

[Erich Keane via cfe-commits]

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@@ -192,6 +192,13 @@ class AttributeCommonInfo {
 
   bool isC23Attribute() const { return SyntaxUsed == AS_C23; }
 
+  bool isAlignas() const {
+    // In the current state of code, IsAlignas is only configured to return
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erichkeane wrote:

This comment is immediately stale once we commit this, right?  Also, it refers to `IsAlignas`, but the function name is `isAlignas`. 

https://github.com/llvm/llvm-project/pull/65638