[Bug c++/124324] New: [reflection] is_function reject static template operator

[mpolacek at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124324

            Bug ID: 124324
           Summary: [reflection] is_function reject static template
                    operator
           Product: gcc
           Version: 16.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mpolacek at gcc dot gnu.org
  Target Milestone: ---

```
#include <meta>

consteval std::meta::info worst_sizeof_p1(std::meta::info ty) {
    static constexpr auto lam = []<class T>() static { return sizeof(T); };
    return substitute(^^decltype(lam)::template operator(), {ty});
}

constexpr std::meta::info ws = worst_sizeof_p1(^^int);
static_assert([: ws :]() == 4);                 // ok
static_assert(is_function(ws));                 // ok
static_assert(is_static_member(ws));            // ok

using F = size_t();
constexpr F* f = extract<F*>(ws);
```

Here we think that ws is a function template rather than a function, so the
extract fails.