Proposed resolution:

This wording is relative to N4981.

1. Modify [rand.synopsis], header <random> synopsis, as indicated:

   #include <initializer_list>     // see [initializer.list.syn]
   
   namespace std {
     […]
     namespace ranges {
       […]
       template<class R, class G, class D>
         requires output_range<R, invoke_result_t<D&, G&>> && invocable<D&, G&> &&
                  uniform_random_bit_generator<remove_cvref_t<G>> &&
                  is_arithmetic_v<invoke_result_t<D&, G&>>
       constexpr borrowed_iterator_t<R> generate_random(R&& r, G&& g, D&& d);
   
       template<class G, class D, output_iterator<invoke_result_t<D&, G&>> O, sentinel_for<O> S>
         requires invocable<D&, G&> && uniform_random_bit_generator<remove_cvref_t<G>> &&
                  is_arithmetic_v<invoke_result_t<D&, G&>>
       constexpr O generate_random(O first, S last, G&& g, D&& d);
     }
     […]
   }
   

2. Modify [alg.rand.generate] as indicated:

   template<class R, class G, class D>
     requires output_range<R, invoke_result_t<D&, G&>> && invocable<D&, G&> &&
              uniform_random_bit_generator<remove_cvref_t<G>> &&
              is_arithmetic_v<invoke_result_t<D&, G&>>
   constexpr borrowed_iterator_t<R> ranges::generate_random(R&& r, G&& g, D&& d);
   

   -5- Effects:

   […]

   template<class G, class D, output_iterator<invoke_result_t<D&, G&>> O, sentinel_for<O> S>
     requires invocable<D&, G&> && uniform_random_bit_generator<remove_cvref_t<G>> &&
              is_arithmetic_v<invoke_result_t<D&, G&>>
   constexpr O ranges::generate_random(O first, S last, G&& g, D&& d);
   

   -8- Effects: Equivalent to:

   […]

[ 2024-10-09; LWG telecon: Move to Ready ]

[ 2024-08-02; Reflector poll ]

Set priority to 2 after reflector poll.

[ 2024-05-12, Hewill Kang provides improved wording ]

The non-specialized case of generate_random(r, g, d) would call ranges::generate(r, [&d, &g] { return invoke(d, g); }). However, the lambda does not explicitly specify the return type, which leads to a hard error when invoke returns a reference to the object that is not copyable or R is not the output_range for decay_t<invoke_result_t<D&, G&>>.