[Bug c++/126970] New: function wrongly regarded immediate-escalating

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126970

            Bug ID: 126970
           Summary: function wrongly regarded immediate-escalating
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mpolacek at gcc dot gnu.org
  Target Milestone: ---

I think this should fail:

```
using info = decltype(^^void);
struct M { info i = ^^int; M(); };
M::M() = default;
```

because https://cplusplus.github.io/CWG/issues/3153.html added
"non-user-provided", and a function defaulted on a declaration other than its
first is user-provided.