Clang rejects valid program involving explict object member function

[ranaanoop]

The following valid program is rejected by clang and gcc but accepted by msvc. Demo

#include <iostream>

struct C{
   int f(this int);
};

decltype(C::f) func; //msvc accepts but clang and gcc rejects
  
int func(int j)
{
   std::cout << "called with: " << j << std::endl;
   return 5;
}

For future reference, the bug was discovered here.

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: Anoop Rana (ranaanoop)

The following [valid](https://stackoverflow.com/questions/78739117/explicit-this-member-function-use-accepted-by-msvc-but-rejected-by-clang-and-gcc) program is rejected by clang and gcc but accepted by msvc. [Demo](https://godbolt.org/z/a3vz3TW8q)

#include <iostream>

struct C{
   int f(this int);
};

decltype(C::f) func; //msvc accepts but clang and gcc rejects
  
int main()
{ 
     func(3);    
}
int func(int j)
{
   std::cout << "called with: " << j << std::endl;
   return 5;
}

For future reference, the bug was discovered here.

[cor3ntin]

Clang matches the intent. See https://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#2902