[Bug c++/110999] New: GCC rejects static variable with constexpr storage from inline method definition

["danakj at orodu dot net" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110999

            Bug ID: 110999
           Summary: GCC rejects static variable with constexpr storage
                    from inline method definition
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: danakj at orodu dot net
  Target Milestone: ---

Godbolt: https://godbolt.org/z/srvhxjqqz

GCC will accept it if the method definition comes after the `constexpr` storage
definition. But it rejects it if the method definition is inline in the class.

```
struct OutOfLine {
    static const OutOfLine kConstant;
    constexpr int f();
    int i = 2;
};
inline constexpr OutOfLine OutOfLine::kConstant;
// Accepted.
constexpr int OutOfLine::f() { return kConstant.i; }

struct InLine {
    static const InLine kConstant;
    // Rejected.
    constexpr int f() { return kConstant.i; }
    int i = 2;
};
inline constexpr InLine InLine::kConstant;

int main() {
    constexpr int x = OutOfLine().f();
    constexpr int y = InLine().f();
}
```