Wrong processing of overloaded set within requires-expression

[Fedr]

This program

void f();
void f(int);

template<typename T>
concept C = sizeof(T) == 42;

// accepted by Clang, but why?
static_assert( requires {{ &f } -> C;} );

looks ill formed because &f is an address of overloaded function. And the program is rejected by GCC and MSVC, but Clang accepts it. Online demo: https://gcc.godbolt.org/z/99q9M5afY

[to268]

CC: @shafik

[llvmbot]

@llvm/issue-subscribers-c-20

Author: Fedor Chelnokov (Fedr)

This program ``` void f(); void f(int);

template<typename T>
concept C = sizeof(T) == 42;

// accepted by Clang, but why?
static_assert( requires {{ &f } -> C;} );

looks ill formed because `&f` is an address of overloaded function. And the program is rejected by GCC and MSVC, but Clang accepts it. Online demo: https://gcc.godbolt.org/z/99q9M5afY
</details>

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: Fedor Chelnokov (Fedr)

This program ``` void f(); void f(int);

template<typename T>
concept C = sizeof(T) == 42;

// accepted by Clang, but why?
static_assert( requires {{ &f } -> C;} );

looks ill formed because `&f` is an address of overloaded function. And the program is rejected by GCC and MSVC, but Clang accepts it. Online demo: https://gcc.godbolt.org/z/99q9M5afY
</details>

[shafik]

This kind of looks like a regression from clang-17: https://gcc.godbolt.org/z/ovz6YWhxE

CC @cor3ntin @AaronBallman

[MitalAshok]

Looks like it's incorrectly being marked as dependent and waiting for a template instantiation to evaluate https://godbolt.org/z/ETr55a8b5:

void f();
void f(int);

template<typename T>
concept C = false;

static_assert(!requires {{ &f } -> C;} );
static_assert( requires {{ &f } -> C;} );

template<typename>
void g() {
  static_assert(!requires {{ &f } -> C;} );
  static_assert( requires {{ &f } -> C;} );  // This one fails
}

int main() {
  g<void>();  // (Only if the function is instantiated)
}

[cor3ntin]

Fixed by #162618