message: Initialize temporaries in optional's inspect
diff: @@ -287,8 +287,8 @@ template <class Inspector, class T>
  typename std::enable_if<Inspector::writes_state,
  typename Inspector::result_type>::type
  inspect(Inspector& f, optional<T>& x) {
  - bool flag;
  - typename optional<T>::type tmp;
  + bool flag = false;
  + typename optional<T>::type tmp{};
  optional_inspect_helper<T> helper{flag, tmp};
  auto guard = detail::make_scope_guard([&] {
  if (flag)
  @@ -299,7 +299,6 @@ inspect(Inspector& f, optional<T>& x) {
  return f(flag, helper);
  }
  -
  /// @relates optional
  template <class T>
  std::string to_string(const optional<T>& x) {
  