[Bug c++/123398] [13/14/15/16 Regression] ICE: Segmentation fault in tsubst_expr

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123398

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2026-01-06
            Summary|ICE: Segmentation fault in  |[13/14/15/16 Regression]
                   |tsubst_expr                 |ICE: Segmentation fault in
                   |                            |tsubst_expr
     Ever confirmed|0                           |1
           Keywords|                            |needs-bisection
   Target Milestone|---                         |13.5
             Status|UNCONFIRMED                 |NEW

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.

Reduced testcase:
```
int main() {
    extern void target_func(int);
    auto func = [](auto arg) -> decltype(target_func(arg)) {};
    func(5);
}
```

The ICE only happens with --enable-checking=yes . Also GCC 11.5.0 used to
reject the code while GCC 12.1.0 started to ICE with --enable-checking=yes but
does not ICE with --enable-checking=release.

Also the ICE does not happen if target_func declaration moved out to the global
scope.