[clang] Raise an error on namespace aliases with qualified names. (PR #86122)

[via cfe-commits]

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@@ -140,6 +140,11 @@ Parser::DeclGroupPtrTy Parser::ParseNamespace(DeclaratorContext Context,
       SkipUntil(tok::semi);
       return nullptr;
     }
+    if (!ExtraNSs.empty()) {
+      Diag(IdentLoc, diag::err_unexpected_qualified_namespace_alias);
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Sirraide wrote:

If you want to, you could also consider adding a fix-it hint to remove the extra `::`+*nested-name-specifier*, but I doubt that this would be a common error (seeing as this bug has been in Clang for a long time w/o anyone noticing), so I don’t think it’s really that necessary here. Just the error would also be enough imo.

https://github.com/llvm/llvm-project/pull/86122