<numeric>: std::reduce is missing static_assert for Mandates

[hewillk]

#include <vector>
#include <string>
#include <numeric>
#include <execution>

struct Op {
  int operator()(int, std::string);
};

int main() {
  std::vector<std::string> v;
  return std::reduce(v.begin(), v.end(), 0, Op{});
}

https://godbolt.org/z/5T4cn95nv

According to the current wording, the above should be rejected as std::reduce has the following Mandates ([reduce]):

Mandates: All of
(5.1) - binary_op(init, *first),
(5.2) - binary_op(*first, init),
(5.3) - binary_op(init, init), and
(5.4) - binary_op(*first, *first)
are convertible to T.

Not sure if std::transform_reduce has the same issue.

[frederick-vs-ja]

Duplicate of #4573 and #891?

[hewillk]

Duplicate of #4573 and #891?

Yap, I think you are correct.