set/map equal_range bug in libc++, C++ (clang)

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#include <set>
#include <iostream>
#include <iterator>

struct comparator {
    using range_t = std::pair<int, int>;
    using is_transparent = std::true_type;
    bool operator()(int lhs, int rhs) const
    {
        return lhs < rhs;
    }
    bool operator()(int lhs, range_t rhs) const
    {
        return lhs < rhs.first;
    }
    bool operator()(range_t lhs, int rhs) const
    {
        return lhs.second < rhs;
    }
};

using range_set = std::set<int, comparator>;

int main()
{
    range_set set = { 1, 3, 6, 10 };
    auto range = comparator::range_t{2, 7};
    auto eq = set.equal_range(range);
    auto low = set.lower_bound(range);
    auto high = set.upper_bound(range);
    std::cout << "equal_range returned " << std::distance(eq.first, eq.second) << " elem(s): ";
    std::copy(eq.first, eq.second, std::ostream_iterator<int>(std::cout, " "));
    std::cout << "\nlower/upper returned " << std::distance(low, high) << " elem(s): ";
    std::copy(low, high, std::ostream_iterator<int>(std::cout, " "));
    std::cout << '\n';
    return 0;
}

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Compilation time: 0.83 sec, absolute running time: 0.07 sec, cpu time: 0.02 sec, memory peak: 3 Mb, absolute service time: 0,92 sec