[Bug c++/87269] [9 Regression] ICE in tsubst_copy, at cp/pt.c:15475 starting from r261802

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87269

--- Comment #1 from Martin Liška <marxin at gcc dot gnu.org> ---
Reduced test-case:

$ cat ice2.ii
namespace {
void  operator"" a(const char *, unsigned long);
}
inline namespace b {
void operator"" a(unsigned long long );
}
namespace c {
struct d {
    using e = bool ;
    e f;
};
struct g {
    d h;
}                        ;
template < class > class i  {
    static const g k;
    static bool f();
};
template < class j > bool i< j >::f() {
    ""a;
}                      template <> const g i< int >::k {                      
f};
}