[Bug c++/105195] New: spurious warning label defined but not used with if constexpr

[barry.revzin at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105195

            Bug ID: 105195
           Summary: spurious warning label defined but not used with if
                    constexpr
           Product: gcc
           Version: 11.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: barry.revzin at gmail dot com
  Target Milestone: ---

Similar to other "if constexpr" related warnings, gcc warns on this example:

void g();
void h();

template <bool B>
void f() {
    if constexpr (B) {
        goto label;
    }

    g();

label:
    h();
}

int main() {
    f<false>();
}

<source>:12:1: warning: label 'label' defined but not used [-Wunused-label]
   12 | label:
      | ^~~~~

But the label is used, just not in this particular instantiation.