[clang++][frontend] clang++ can't treat `&` in `std::forward<void(int)>(&test<int>);` like g++

[eastB233]

source code

#include <utility>

template<typename T>
void test(T a) {}

int main() {
  std::forward<void(int)>(&test<int>);
  return 0;
}

clang fails with

<source>:7:3: error: no matching function for call to 'forward'
    7 |   std::forward<void(int)>(&test<int>);
      |   ^~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/arm64/gcc-12.2.0/aarch64-unknown-linux-gnu/lib/gcc/aarch64-unknown-linux-gnu/12.2.0/../../../../aarch64-unknown-linux-gnu/include/c++/12.2.0/bits/move.h:77:5: note: candidate function template not viable: no overload of 'test' matching 'typename std::remove_reference<void (int)>::type &' (aka 'void (&)(int)') for 1st argument
   77 |     forward(typename std::remove_reference<_Tp>::type& __t) noexcept
      |     ^       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/arm64/gcc-12.2.0/aarch64-unknown-linux-gnu/lib/gcc/aarch64-unknown-linux-gnu/12.2.0/../../../../aarch64-unknown-linux-gnu/include/c++/12.2.0/bits/move.h:89:5: note: candidate function template not viable: no overload of 'test' matching 'typename std::remove_reference<void (int)>::type &&' (aka 'void (&&)(int)') for 1st argument
   89 |     forward(typename std::remove_reference<_Tp>::type&& __t) noexcept
      |     ^       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.

https://godbolt.org/z/fTGz1PMfs

But gcc is okay
https://godbolt.org/z/d3971PWWM

[frederick-vs-ja]

Isn't this a bug of GCC? &test<int> is of type void(*)(int) and thus shouldn't be passed to std::forward<void(int)>.

Reported https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118354.

Update: Resolved as duplicate of
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91082.

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: None (eastB233)

source code ```c++ #include <utility>

template<typename T>
void test(T a) {}

int main() {
std::forward<void(int)>(&test<int>);
return 0;
}

clang fails with
```console
<source>:7:3: error: no matching function for call to 'forward'
    7 |   std::forward<void(int)>(&test<int>);
      |   ^~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/arm64/gcc-12.2.0/aarch64-unknown-linux-gnu/lib/gcc/aarch64-unknown-linux-gnu/12.2.0/../../../../aarch64-unknown-linux-gnu/include/c++/12.2.0/bits/move.h:77:5: note: candidate function template not viable: no overload of 'test' matching 'typename std::remove_reference<void (int)>::type &' (aka 'void (&)(int)') for 1st argument
   77 |     forward(typename std::remove_reference<_Tp>::type& __t) noexcept
      |     ^       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/compiler-explorer/arm64/gcc-12.2.0/aarch64-unknown-linux-gnu/lib/gcc/aarch64-unknown-linux-gnu/12.2.0/../../../../aarch64-unknown-linux-gnu/include/c++/12.2.0/bits/move.h:89:5: note: candidate function template not viable: no overload of 'test' matching 'typename std::remove_reference<void (int)>::type &&' (aka 'void (&&)(int)') for 1st argument
   89 |     forward(typename std::remove_reference<_Tp>::type&& __t) noexcept
      |     ^       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.

https://godbolt.org/z/fTGz1PMfs

But gcc is okay
https://godbolt.org/z/d3971PWWM

[EugeneZelenko]

@shafik: Could you please elaborate?

[shafik]

@shafik: Could you please elaborate?

Maybe I misunderstood the previous comment but this is a gcc not a clang bug?

[EugeneZelenko]

If so, invalid label should be added.