[clang] [Clang] Profile the NNS of UnresolvedUsingType correctly in concept hashing (PR #199617)

[Corentin Jabot via cfe-commits]

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@@ -399,6 +399,16 @@ class HashParameterMapping : public RecursiveASTVisitor<HashParameterMapping> {
     return true;
   }
 
+  bool TraverseUnresolvedUsingType(UnresolvedUsingType *T,
+                                   bool TraverseQualifier) {
+    // Sometimes the written type doesn't contain a qualifier which contains
+    // necessary template arguments, whereas the declaration does.
+    if (NestedNameSpecifier NNS = T->getDecl()->getQualifier();
+        TraverseQualifier && NNS)
+      return inherited::TraverseNestedNameSpecifier(NNS);
+    return true;
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cor3ntin wrote:

we should probably call `inherited::TraverseUnresolvedUsingType` - which visits the type

https://github.com/llvm/llvm-project/pull/199617