[Bug c++/122100] New: -Wunused-but-set-variable false positive of static variable used by a generic lambda

[olaf.krzikalla at dlr dot de via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122100

            Bug ID: 122100
           Summary: -Wunused-but-set-variable false positive of static
                    variable used by a generic lambda
           Product: gcc
           Version: 15.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: olaf.krzikalla at dlr dot de
  Target Milestone: ---

Very probably related to #114450, but more generalized: bogus warning about
unused static variable inside generic lambda:
```
#include <iostream>

void bar(auto&& fn)
{
    fn(std::cout);
}

int main()
{
    static const int i = 11;

    bar([&](auto& stream) { stream << i; });
}
```
https://godbolt.org/z/78TrqzGz3

Happens in all versions up to trunk.