[clang-doc] fix conversion names of dependent types

Fixes llvm#59812

The names of conversion functions of template type parameters were
being emitted as "type-parameter-N-M". Now we check if the conversion
type is a TemplateTypeParmType and reconstruct the source name.

Author: evelez7

clang-tools-extra/clang-doc/Serialize.cpp

@@ -525,7 +525,13 @@ template <typename T>
 static void populateInfo(Info &I, const T *D, const FullComment *C,
                          bool &IsInAnonymousNamespace) {
   I.USR = getUSRForDecl(D);
-  I.Name = D->getNameAsString();
+  auto ConversionDecl = dyn_cast_or_null<CXXConversionDecl>(D);
+  if (ConversionDecl && ConversionDecl->getConversionType()
+                            .getTypePtr()
+                            ->isTemplateTypeParmType())
+    I.Name = "operator " + ConversionDecl->getConversionType().getAsString();
+  else
+    I.Name = D->getNameAsString();
   populateParentNamespaces(I.Namespace, D, IsInAnonymousNamespace);
   if (C) {
     I.Description.emplace_back();