[Bug c++/99611] New: Code compilation issue using templates

["asif_bahrainwala at hotmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99611

            Bug ID: 99611
           Summary: Code compilation issue using templates
           Product: gcc
           Version: 9.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: asif_bahrainwala at hotmail dot com
  Target Milestone: ---

Hi,
a minimalist re-pro is available at
https://stackoverflow.com/questions/66641646/c-code-compilation-usage-of-fstream-ostream

The below code compiles in Clang but not in GCC (and VS2015):

#include <iostream>
#include <fstream>
using namespace std;


struct A
{
    int z=0;

    template<typename T>
    void func(T &y)
    {
        //cout<<typeid(T).name()<<endl;
        y<<z<<endl;
    }
};


template<typename T,typename T1>
T& operator<<(T &y,T1 &y1)
{
    y1.func(y);
    return y;
}

int main()
{
    A a;
    a.z=10;
    fstream fs("a.txt",ios::out);

    fs<<a; //this doesnt compile ????  ( I do have a walk around, but curious)
    cout<<a; //this works
    return 0;
}