https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67147
--- Comment #4 from Antony Polukhin <antoshkka at gmail dot com> ---
Shorter reproducer:
template<typename T, int = sizeof(T)> concept bool fn = true;
template <fn T> int test();
Above sample produces the following output:
<source>:1:28: internal compiler error: in tsubst, at cp/pt.c:14368
template<typename T, int = sizeof(T)> concept bool fn = true;
^~~~~~~~~
