https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99745
--- Comment #1 from 康桓瑋 <hewillk at gmail dot com> ---
Reduce a little:
template <int... Xs>
struct S {
int x : Xs;
};
S s;
<source>:3:7: internal compiler error: unexpected expression 'Xs' of kind
template_parm_index
3 | int x : Xs;
| ^
