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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/102045] constructor is not being instantiated
Date: Tue, 24 Aug 2021 15:22:09 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102045

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Reduced:

template<typename T>
struct span
{
  template<unsigned long N>
  constexpr span(T (&a)[N]) : data(a), len(N) { }

  constexpr bool empty() const { return len =3D=3D 0; }

  T* data;
  unsigned long len;
};


struct byte_writer: span<char> {
        //byte_writer(auto && arg): std::span<char>{arg} { }
        constexpr void do_something() noexcept {
                (void)this->empty();
        }
};

int main() {
        char array[1];
        auto writer =3D byte_writer{array};
        writer.do_something();
}=