[Bug c++/100330] New: operator bool() is used when operator<() is available to do comparison

[yin.li at bytedance dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100330

            Bug ID: 100330
           Summary: operator bool() is used when operator<() is available
                    to do comparison
           Product: gcc
           Version: 10.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: yin.li at bytedance dot com
  Target Milestone: ---

code:
#include <iostream>
#include <map>

class vertex_descriptor {
public:
        vertex_descriptor() : p(nullptr) {}
        vertex_descriptor(void *pp) : p(pp) {}

        operator bool() const {
                std::cout << __func__ << std::endl;
                return p;
        }

        bool operator<(const vertex_descriptor b) const {
                std::cout << __func__ << std::endl;
                return p < b.p;
        }
private:
        void *p;
};

int main()
{
        std::map<std::pair<vertex_descriptor, int>, vertex_descriptor> vs;
        vertex_descriptor v1(nullptr), v2((void *)1);

        vs[std::make_pair(v1, 0)] = v1;
        vs[std::make_pair(v2, 0)] = v2;
        return 0;
}

result:
~ $ g++ --std=c++17 1.cpp && ./a.out
operator<
operator<
operator<
operator<
~ $ g++ --std=c++20 1.cpp && ./a.out
operator bool
operator bool
operator bool
operator bool
operator bool
operator bool
~ $ g++ --version
g++ (Ubuntu 10.2.0-13ubuntu1) 10.2.0
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This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.