<algorithm>: lexicographical_compare_three_way missing _Mandates_ check #4877
Description
There is a Mandates in [alg.three.way], which seems to be missing in the MSVC-STL implementation:
Mandates:
decltype(comp(*b1, *b2))is a comparison category type.
#include <algorithm>
struct Hack {
Hack(auto);
bool operator==(int) const;
};
struct Cmp {
Hack operator()(const auto&, const auto&) const;
};
int main() {
int x[] = {42};
auto r = std::lexicographical_compare_three_way(x, x+1, x, x+1, Cmp{}); // only ok in MSVC-STL
}