C++20 factorial function

factorial.cpp

#include <algorithm>
#include <cassert>
#include <concepts>
#include <ranges>

[[nodiscard]] constexpr auto factorial(std::integral auto n) {
    assert(n >= 0);
    if (n == 0) {
        return 1;
    }
    return std::ranges::fold_left(std::ranges::iota_view(1, n), n,
                                  std::multiplies{});
}

static_assert(factorial(0) == 1);
static_assert(factorial(1) == 1);
static_assert(factorial(2) == 2);
static_assert(factorial(3) == 6);
static_assert(factorial(4) == 24);
static_assert(factorial(5) == 120);
static_assert(factorial(6) == 720);
static_assert(factorial(7) == 5'040);