Using Legacy Header in C++20 Modules with Clang Compiler - c++

Question

I am trying to write some codes in c++20 standard. I write some simple code in c++ module way. And I write '#include <iostream>' because 'import <iostream>' can not be compiled in clang-15.0.2 compiler. Then I meet compile error.
The code is:
// md.ixx
module;
#include <iostream>
export module md;
export int func() {
return 114514;
}
// main.cpp
#include <iostream>
import md;
using namespace std;
int main() {
auto val = func();
cout<<val<<endl;
return 0;
}
Compile error is:
error: main.cpp:10:5: error: missing '#include <iostream>'; 'cout' must be declared before it is used
cout<<val<<endl;
^
C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.32.31326\include\iostream:40:57: note: declaration here is not visible
__PURE_APPDOMAIN_GLOBAL extern _CRTDATA2_IMPORT ostream cout;
^
main.cpp:10:16: error: missing '#include <ostream>'; 'endl' must be declared before it is used
cout<<val<<endl;
^
C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.32.31326\include\ostream:1000:51: note: declaration here is not visible
basic_ostream<_Elem, _Traits>& __CLRCALL_OR_CDECL endl(
^
C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.32.31326\include\ostream:269:9: error: missing '#include <xiosbase>'; 'ios_base' must be declared before it is used
ios_base::iostate _State = ios_base::goodbit;
^
C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.32.31326\include\xiosbase:170:28: note: declaration here is not visible
class _CRTIMP2_PURE_IMPORT ios_base : public _Iosb<int> { // base class for ios
And If I delete #include<iostream> in file md.ixx. It can be successfully compiled.
So is there any solution to using <iostream> in both main.cpp and md.ixx?
Thank you a lot.