Bug in GCC when using string literal as const char(&)[N] through functor in templated function?

I created simple string class with construct from only constant strings (literal or const char[])

template<typename T> struct const_lit; template<unsigned N> struct const_lit<const char(&)[N]>{ inline static constexpr unsigned Count = N; }; struct str { const char* ptr; unsigned len; template<typename T> requires (const_lit<T>::Count > 0) str(T&& s) : ptr(s), len(const_lit<T>::Count - 1) { std::cout << "ctor from literal " << ptr << "\n"; } };

When I use it as function param, it work well:

void check_func(str s) {} ... int main() { check_func("test1"); const char fff[] = "test2"; check_func(fff); ...

But when I pass a function to a template function, no matter as a template parameter or as a function argument, then the GCC cannot use it inside function.

template<typename Func> void check_func_templ(const Func& f) { f("test3"); } template<auto f> void check_func_templ1() { f("test4"); } void check_func_templ2(auto&& f) { f("test5"); } template<auto f> void check_func_templ3() { const char tt[] = "test6"; f(tt); } ... check_func_templ(check_func); check_func_templ1<check_func>(); check_func_templ2(check_func); check_func_templ3<check_func>();

But Сlang can (link to godbolt).

If remove line #if !defined(__GNUC__) || defined(__clang__), GCC produce errors:

error: could not convert '(const char*)"test3"' from 'const char*' to 'str'

etc.

Why is GCC trying to convert the type to const char* in this case?

Is this a bug in GCC (sad) or Clang (even sadder)?