[clang] [Clang] Improve diagnostics to show the correct position for `[[maybe_unused]]` before a using-alias (PR #223910)

[Alexsander Borges Damaceno via cfe-commits]

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@@ -740,7 +749,10 @@ Parser::DeclGroupPtrTy Parser::ParseUsingDeclaration(
       return nullptr;
     }
 
-    ProhibitAttributes(PrefixAttrs);
+    SourceLocation MisplacedAttrFixItLoc;
+    if (PrefixAttrs.hasAttribute(ParsedAttr::AT_Unused))
+      MisplacedAttrFixItLoc = Tok.getLocation();
+    ProhibitAttributes(PrefixAttrs, MisplacedAttrFixItLoc);
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AlexsanderDamaceno wrote:

ok, gonna change it, I had put that because I thought about only apply for the `maybe_unused`

https://github.com/llvm/llvm-project/pull/223910