[Bug c++/123970] ICE in lto_write_tree: tree code 'decltype_type' is not supported in LTO streams

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123970

--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Reduced from the dup bug:
```
struct a{int i;};
template<int=0>
int f()
{
  auto [... j] = a{};
  return j...[0];
}
int x = f();
```