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

[Daniel M. Katz via cfe-commits]

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@@ -268,6 +268,8 @@ def err_expected_semi_after_namespace_name : Error<
   "expected ';' after namespace name">;
 def err_unexpected_namespace_attributes_alias : Error<
   "attributes cannot be specified on namespace alias">;
+def err_unexpected_qualified_namespace_alias : Error<
+  "unexpected nested name specifier in namespace alias definition">;
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katzdm wrote:

Sounds good - I was trying to think of the right phrasing and had found some references to "nested name specifiers" in other diagnostics. But I like your suggested phrasing 👍 

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