Is there a way to ignore redefinition with clang?

Question

I am getting a Clang compiler error when compiling ROOT script:

~/root_install/include/ROOT/RStringView.hxx:32:4: error: redefinition of 'basic_string_view' as different kind of symbol using basic_string_view = ::std::experimental::basic_string_view<_CharT,_Traits>;
/usr/include/c++/9/string_view:90:11: note: previous definition is here
class basic_string_view

This is the problematic code in ROOT library:

namespace std {

   template<class _CharT, class _Traits = std::char_traits<_CharT> >
   using basic_string_view = ::std::experimental::basic_string_view<_CharT,_Traits>;

   // basic_string_view typedef names
   typedef basic_string_view<char> string_view;
   typedef basic_string_view<char16_t> u16string_view;
   typedef basic_string_view<char32_t> u32string_view;
   typedef basic_string_view<wchar_t> wstring_view;

//   template<class _CharT, class _Traits = std::char_traits<_CharT> >
//   basic_string_view<_CharT,_Traits>
//   &operator=(basic_string_view<_CharT,_Traits> &lhs, const TString &rsh) {
//      *lhs = basic_string_view<_CharT,_Traits>(rsh);
//      return *lhs;
//   }

#ifndef R__HAS_STOD_STRING_VIEW
   inline double stod(std::string_view str, size_t *pos)
   {
      return std::stod(std::string(str.data(), str.size()),pos);
   }
#endif

}

Is there a way to avoid this error without changing the library? Compiling it with g++ with following command works just fine:\

g++ -std=c++2a file.cpp `root-config --cflags --libs`

Edit: Clang compile command:
clang -std=c++20 --include-directory ~/root_install/include file.cpp

Answer 1

ROOT can be compiled with clang++ (but not with clang) using the following command:

clang++ file.C `root-config --cflags --libs`

This also works with the -std=c++20 flag.