[Bug libstdc++/80564] New: bind on SFINAE unfriendly generic lambda

[columbo@gmx-topmail.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80564

            Bug ID: 80564
           Summary: bind on SFINAE unfriendly generic lambda
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: columbo@gmx-topmail.de
  Target Milestone: ---

Related to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=49058

---
#include <functional>

int main() {
    int i;
    std::bind([] (auto& x) {x = 1;}, i)();
}

---

This is rejected because, during overload resolution, _Bind::operator() const's
default template argument is spuriously instantiated.