[Bug c++/123237] [reflection] ICE: in write_type, at cp/mangle.cc:2744

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123237

--- Comment #8 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Another, without requires:

```
#include <type_traits>

template <auto I>
struct X {};

struct Y {
  int name;
};

template <decltype(^^::) R>
constexpr auto foo (typename [:R:] s) {
  return X<^^[:R:]::name> {};
}

constexpr auto a = foo<^^Y> (Y { 42 });
static_assert (std::is_same_v <decltype (a), const X <^^Y::name>>);
```