[clang-tools-extra] fix usr rhs (PR #68329)

[Sam McCall via cfe-commits]

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@@ -1070,6 +1063,24 @@ void USRGenerator::VisitMSGuidDecl(const MSGuidDecl *D) {
   D->NamedDecl::printName(Out);
 }
 
+void USRGenerator::VisitBaseUsingDecl(const BaseUsingDecl *D) {
+  // Add the filename when needed to disambiguate using decls from different
+  // files.
+  if (ShouldGenerateLocation(D) && GenLoc(D, /*IncludeOffset=*/false))
+    return;
+  VisitDeclContext(D->getDeclContext());
+  Out << "@UD";
+
+  // When the using-decl is resolved also print the context of the first target
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sam-mccall wrote:

what does "when the using-decl is resolved" mean?
I guess "when" just means "if", but UnresolvedUsing{Value,Typename}Decl aren't BaseUsingDecls, so what kind of "unresolved" are we talking about?

If it's just broken code, I think the comment isn't needed, the intent to defensively not-crash is clear. 

https://github.com/llvm/llvm-project/pull/68329