Template Parameters Duplicator

class TemplateParamDuplicator {
public:
    TemplateParamDuplicator(
            clang::Parser &parser,
            bool bypassLocation = true)
    : Parser(parser),
      BypassLocation(bypassLocation),
      AttrFactory(parser.getAttrFactory()),
      Actions(parser.getActions()) {}

    NamedDecl *GetCopyOf(NamedDecl *D) {
      if (auto *NonTypeTPD = dyn_cast_or_null<NonTypeTemplateParmDecl>(D)) {
        return Copy(NonTypeTPD);
      } else if (auto *TemplateTypePD = dyn_cast_or_null<TemplateTypeParmDecl>(D)) {
        return Copy(TemplateTypePD);
      } else if (auto *TemplateTemplatePD = dyn_cast_or_null<TemplateTemplateParmDecl>(D)) {
        return Copy(TemplateTemplatePD);
      } else {
        llvm_unreachable("Invalid template parameter declaration");
      }
    }

protected:

    // TODO: May be we should clone identifier as well.
    // auto *OldIdentifier = D->getIdentifier();

    // TODO: May be use CreateDeserialized?

    NonTypeTemplateParmDecl *Copy(const NonTypeTemplateParmDecl *D) {

      auto &Context = Actions.getASTContext();

      NonTypeTemplateParmDecl *Param = NonTypeTemplateParmDecl::Create(
          Context, Context.getTranslationUnitDecl(),
          BypassLocation ? D->getBeginLoc() : SourceLocation(),
          BypassLocation ? D->getLocation() : SourceLocation(),
          D->getDepth(),
          D->getPosition(),
          D->getIdentifier(),
          D->getType(),
          D->isParameterPack(),
          D->getTypeSourceInfo()
      );

      Param->setAccess(D->getAccess());

      // Add the template parameter into the current scope.
      Actions.getCurScope()->AddDecl(Param);
      Actions.IdResolver.AddDecl(Param);

      if (D->isInvalidDecl())
        Param->setInvalidDecl();
      else {
        Param->setDefaultArgument(D->getDefaultArgument());
      }

      return Param;
    }

    TemplateTypeParmDecl *Copy(const TemplateTypeParmDecl *D) {
      auto &Context = Actions.getASTContext();
      auto *TypeForDecl = cast<TemplateTypeParmType>(D->getTypeForDecl());

      TemplateTypeParmDecl *Param = TemplateTypeParmDecl::Create(
          Context,
          Context.getTranslationUnitDecl(),
          BypassLocation ? D->getBeginLoc() : SourceLocation(),
          BypassLocation ? D->getLocation() : SourceLocation(),
          D->getDepth(),
          TypeForDecl->getIndex(),
          D->getIdentifier(),
          D->wasDeclaredWithTypename(),
          D->isParameterPack()
      );

      Param->setAccess(D->getAccess());

      // Add the template parameter into the current scope.
      Actions.getCurScope()->AddDecl(Param);
      Actions.IdResolver.AddDecl(Param);

      if (D->isInvalidDecl())
        Param->setInvalidDecl();
      else {
        Param->setDefaultArgument(D->getDefaultArgumentInfo());
      }

      return Param;
    }

    TemplateTemplateParmDecl *Copy(const TemplateTemplateParmDecl *D) {
      auto &Context = Actions.getASTContext();

      TemplateParameterList *NewTemplateTemplateParametersList;
      {
        auto *OldParams = D->getTemplateParameters();

        Parser::ParseScope TemplateParmScope(&Parser, clang::Scope::TemplateParamScope);
        SmallVector<NamedDecl *, 4> ParamsVector;

        for (auto *OldP : OldParams->asArray()) {
          ParamsVector.push_back(GetCopyOf(OldP));
        }

        // Note, there is no requires clause for template template params,
        // even in C++20
        NewTemplateTemplateParametersList = Actions.ActOnTemplateParameterList(
            OldParams->getDepth(),
            SourceLocation(),
            OldParams->getTemplateLoc(),
            OldParams->getLAngleLoc(),
            ParamsVector,
            OldParams->getRAngleLoc(),
            nullptr
        );
      }

      TemplateTemplateParmDecl *Param = TemplateTemplateParmDecl::Create(
          Context,
          Context.getTranslationUnitDecl(),
          BypassLocation ? D->getLocation() : SourceLocation(),
          D->getDepth(),
          D->getPosition(),
          D->isParameterPack(),
          D->getIdentifier(),
          NewTemplateTemplateParametersList
      );

      Param->setAccess(D->getAccess());

      // Add the template parameter into the current scope.
      Actions.getCurScope()->AddDecl(Param);
      Actions.IdResolver.AddDecl(Param);

      if (D->isInvalidDecl())
        Param->setInvalidDecl();
      else {
        Param->setDefaultArgument(Context, D->getDefaultArgument());
      }

      return Param;
    }

    clang::Parser &Parser;
    bool BypassLocation;

    AttributeFactory &AttrFactory;
    Sema &Actions;
};