Proposed resolution:

This wording is relative to N5014.

1. Modify [func.wrap.ref.class] as indicated:

   namespace std {
     template<class R, class... ArgTypes>
     class function_ref<R(ArgTypes...) cv noexcept(noex)> {
     public:
       using result_type = R;
   
       // [func.wrap.ref.ctor], constructors and assignment operators
       template<class F> function_ref(F*) noexcept;
       […]
     };
   
   }
   

[ 2025-10-03; Hewill comments ]

Additionally, given that some third-party implementations also provide a mechanism for extracting the return type, for example, `type_safe::function_ref` provides a public member type alias return_type, and `llvm::function_ref` can work with llvm::function_traits to obtain the return type, providing such a member type alias for `std::function_ref` meets user potential demands.

Currently, `function`, `move_only_function`, and `copyable_function` all have a type member `result_type`, but `function_ref` does not:

static_assert(is_same_v<          function    <int(int)>::result_type, int>);
static_assert(is_same_v<move_only_function    <int(int)>::result_type, int>);
static_assert(is_same_v< copyable_function    <int(int)>::result_type, int>);
static_assert(is_same_v<          function_ref<int(int)>::result_type, int>); // error

It seems worthwhile to also provide it for the latter, as it is consistent with the other wrappers and allows the user to easily extract the return type.