fail with the following concept code

[Watson Romero via Gcc-help <gcc-help@xxxxxxxxxxx>]

I was trying to learn how concepts work and for some reason the following
lines of code:

#include <cstddef>
#include <cstdio>
#include <type_traits>

template <typename T>
concept Averageable = std::is_default_constructible<T>::value &&
        std::is_copy_constructible<T>::value &&
        requires(T a, T b) {
        { a + b }->T;
        { a / b }->T;
  };
}

template <Averageable T>
T mean(const T* values, size_t length) {
  T result{};
  for(size_t i{}; i < length; i++) {
    result += values[i];
  }
  return result / length;
}

int main() {
  const double nums_d[]{ 1.0f, 2.0f, 3.0f, 4.0f };
  const auto result1 = mean(nums_d, 4);
  printf("double: %f\n", result1);

  const float nums_f[]{ 1.0, 2.0, 3.0, 4.0 };
  const auto result2 = mean(nums_f, 4);
  printf("float: %f\n", result2);

  const char nums_c[]{ 1, 2, 3, 4 };
  const auto result3 = mean(nums_c, 4);
  printf("char: %d\n", result3);
}

produces the following error while running g++ like so:
g++ listing_6_21.cpp -std=c++20 -o a.out


listing_6_21.cpp:9:20: error: return-type-requirement is not a
type-constraint
    9 |         { a + b }->T;
      |                    ^
listing_6_21.cpp:10:20: error: return-type-requirement is not a
type-constraint
   10 |         { a / b }->T;
      |                    ^
listing_6_21.cpp:12:1: error: expected declaration before ‘}’ token
   12 | }

I'm not sure if this is consistent with what should happen but I figured
I'd inform you guys about it.

Sincerely,
Watson