[Bug libstdc++/85040] New: [8 Regression] std::less<void> fails when operator< is overloaded

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85040

            Bug ID: 85040
           Summary: [8 Regression] std::less<void> fails when operator< is
                    overloaded
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Keywords: rejects-valid
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org
  Target Milestone: ---

#include <functional>

struct string { } s;
bool operator<(const string&, const string&) { return false; }

std::less<> lt;
bool b = lt(s, s);

This fails since the fix for PR 78420